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The pharmacokinetics of antipyrine following a single 1-g intravenous dose was determined in 63 healthy women. Subjects were divided into 4 groups as follows: 1) cigarette smokers using low-dose oral contraceptives (n = 15); 2) nonsmokers using low-dose oral contraceptives (n = 12); 3) cigarette smokers not using oral contraceptives (n = 10); and 4) controls, neither cigarette smokers nor oral contraceptive users. Plasma antipyrine concentrations during 24 to 48 hours after dosage were measured by high-performance liquid chromatography. Mean kinetic variables in the nonsmoking, non-oral contraceptive using control group were: volume of distribution, 37.7 L; elimination half-life, 13.2 hours; and clearance, 34.4 mL/min. In cigarette smoking, non-oral contraceptive users versus controls, elimination half-life was reduced (8.0 vs. 13.2 hours, P < 0.05) and clearance increased (56.0 vs. 34.4 mL/min, P < 0.05). In nonsmoker oral contraceptive users, the reverse was true (elimination half-life was significantly increased: 16.6 vs. 13.2 hours, P < 0.05; and clearance was significantly decreased: 24.8 vs. 34.4 mL/min, P < 0.05). In smokers who were using oral contraceptives, values were not significantly different from controls (elimination half-life, 11.2 hours; clearance, 39.5 mL/min). Volume of distribution did not differ among the four groups. Thus the opposing effects on antipyrine clearance of the induction of metabolism by cigarette smoking and the inhibition due to low dose oral contraceptive use in effect negate each other when combined in humans.

Single drug therapy for the treatment of hypertension has traditionally been a standard of practice. More recently combination therapy as first-line treatment has gained acceptance both by the medical practice community and the US Food and Drug Administration. The advantages of combinations may be a synergistic or additive antihypertensive effect, metabolic improvement, or both. The combination of a thiazide-type diuretic and a potassium-sparing diuretic has been quite useful in the past to prevent the need for potassium supplementation. The combination of beta-adrenoceptor blockade and a thiazide diuretic results in an additive antihypertensive effect that permits the effective use of very low thiazide doses. The mechanism of antihypertensive effects of each member of the combination are complimentary with increased sympathetic outflow and renin-angiotensin axis activation induced by the diuretic being blunted by beta1-adrenergic blockade. Combinations not used as first-line therapy, such as angiotensin converting enzyme inhibitors or angiotensin receptor blockade and a thiazide diuretic, have complimentary antihypertensive mechanisms and have been useful in treating patient groups who do not respond well to converting enzyme inhibitor monotherapy. The combination of a calcium antagonist with diuretic therapy has an additive hypertensive effect as well; however, the complimentary mechanisms are less obvious. Finally, the combination of angiotensin converting enzyme inhibition and calcium antagonist therapy has been useful in selected patients, but again the complimentary mechanisms are less obvious. As first-line therapy, combinations for diuretics and beta1-receptor blockers have been useful for achieving increased antihypertensive effect with decreased adverse drug effect.

Background: Orthostatic hypotension is a dangerous problem in elderly patients, often exacerbated by vasodilator medications. Age- and disease-related impairments in cardioacceleration and diastolic ventricular function may make older patients particularly vulnerable to the hypotensive effects of these drugs. Therefore we aimed to determine mechanisms of postural blood pressure regulation in elderly patients with coronary artery disease and to compare the effects of isosorbide dinitrate and nicardipine hydrochloride on postural blood pressure homeostasis in these patients., Methods: Twenty elderly subjects with stable coronary artery disease (age, 76 +/- 4 [SD] years) underwent a baseline evaluation followed by a double-blind, randomized crossover comparison of nicardipine (20 mg by mouth t.i.d.) versus isosorbide (20 mg by mouth t.i.d.). Doppler echocardiography and a 15-minute 60-degree head-up tilt test were conducted on no study medications and then after successive 3-week treatment periods with nicardipine or isosorbide. Blood pressure, heart rate, vascular resistance, cardiac output, and spectral characteristics of heart rate and blood pressure variability were measured before and during each tilt., Results: Isosorbide treatment was associated with a higher prevalence of symptoms of cerebral hypoperfusion and a failure to increase systemic vascular resistance during tilt. While taking isosorbide subjects were able to preserve cardiac output and maintain upright blood pressure through enhanced cardioacceleration. During nicardipine treatment systemic vascular resistance and low-frequency blood pressure variability were reduced, but the ability to increase systemic vascular resistance during tilt was preserved., Conclusions: Although nicardipine may decrease vascular responsiveness to sympathetic activation, the baroreflex-mediated vasoconstrictor response to upright tilt remains intact. In contrast, isosorbide impairs the systemic vascular response to orthostatic stress in elderly patients with stable coronary artery disease.

We describe here an improved method of encapsulating doxorubicin in liposomes using phosphatidylcholine, cholesterol and synthetic tetramyristoyl cardiolipin. With this new composition of lipids the entrapment of doxorubicin was found to be > 90%. Cytotoxicity studies using vincristine-resistant HL-60/VCR leukaemia cells showed that liposome-encapsulated doxorubicin reverses multidrug resistance 5-fold compared with conventional doxorubicin and at levels equivalent to that obtained using liposomes with natural cardiolipin. In normal mice, liposome-encapsulated doxorubicin was much less toxic than the conventional drug. A dose of 25 mg kg-1 i.v. of conventional doxorubicin produced 100% mortality in mice by day 14, whereas liposomal doxorubicin exhibited only 10% mortality by day 60. Liposomal doxorubicin demonstrated enhanced anti-tumour activity against murine ascitic L1210 leukaemia compared with conventional doxorubicin. At a dose of 15 mg kg-1, liposomal doxorubicin increased the median life span with 12 of 18 long-term (60 days) survivors compared with only 3 of 18 with conventional drug. Mice injected i.v. with liposomal doxorubicin had plasma levels 44-fold higher than conventional doxorubicin, producing significantly higher (P < 0.02) area under the plasma concentration curve. An altered tissue distribution was also observed with liposomal doxorubicin; cardiac tissue demonstrating at least 2-fold lower levels with liposomal doxorubicin probably accounting for its lower toxicity. This altered pharmacokinetics of liposome-encapsulated doxorubicin, providing enhanced therapeutic advantage and the ability to modulate multidrug resistance, could be useful in a clinical setting.

Over the last decade, the number of pharmaceutical benefits managers has increased, and their influence has expanded rapidly. These managers now provide prescription drug coverage to more than 100 million Americans. The effect of pharmaceutical benefits managers on health care delivery remains unclear. We review the development of these organizations, their current role in the delivery of pharmaceutical therapies to patients, and their relationship with pharmaceutical manufacturers. We discuss potential advantages and disadvantages of pharmaceutical benefits manager practices and suggest ways in which these organizations can be made more accountable to the employer groups that hire them.

The growth response of aortic vascular smooth muscle cells (VSMCs) to chronic hypertension includes vascular hypertrophy. We have shown previously that angiotensin II positively regulates the expression of the human vascular smooth muscle (SM) alpha-actin gene. To further expand our understanding of vasoactive peptide-induced vascular hypertrophy, we studied endothelin-1 (ET-1) regulation of total protein synthesis and cytoskeletal gene expression in VSMCs. In a concentration-dependent manner ET-1 increased [3H] leucine incorporation by VSMCs (122.4 +/- 5.5%, mean +/- SEM, n = 5). ET-1 (0.1 microM) induced expression of SM alpha-actin mRNA as detected by Northern blot analysis. Also, ET-1 in a concentration-dependent manner (0.1 nM-0.1 microM) induced expression of the chloramphenicol acetyl transferase gene driven by 896 bp of the human SM alpha-actin promoter when transiently transfected into rat aortic VSMCs by the calcium phosphate method (141.2 +/- 9.8%, mean +/- SEM, n = 10). These data suggest that part of ET-1-induced increase in protein synthesis is achieved through transcriptional regulation of the SM alpha-actin gene via activation of cis-acting element(s) in the promoter. Such findings help elucidate the role of ET-1 in regulation of vascular growth.

Objective: The physiologic role of endothelin-1 is not well established; however, it may have a role in modulation of peripheral vascular tone complimentary to angiotensin II. In vitro and animal studies suggested an interrelationship between angiotensin II and endothelin-1 vasoconstriction. We hypothesized that local vascular or systemic renin-angiotensin II systems must be intact for endothelin-1-mediated vasoconstriction in humans., Methods: To test this hypothesis, responses to brachial artery infusion of endothelin-1 alone and endothelin-1 plus local low-dose infusion of enaliprilat were studied in seven healthy male and seven healthy female volunteers., Results: In these subjects, baseline forearm vascular resistance (mean +/- SEM; 24 +/- 3.5 mm Hg.ml/dl forearm vol/min) increased with a 38.2 ng/min endothelin-1 infusion (61.8 +/- 6.8 mm Hg.ml/dl forearm vol/min; p < 0.01). Forearm vascular resistance decreased when 38.2 ng/min endothelin-1 was infused concomitantly with a local 5 micrograms/min infusion of enaliprilat (45.5 +/- 5.9 mm Hg.ml/dl forearm vol/min; p < 0.01 compared with endothelin-1 alone)., Conclusions: These data indicate that an endothelin-1-induced increase in forearm vascular resistance is inhibited by local forearm angiotensin-converting enzyme inhibition.

To compare and contrast the antihypertensive efficacy of an angiotensin-converting enzyme (ACE) inhibitor to a calcium antagonist, 88 and 90 patients with essential hypertension were randomly assigned to receive moexipril and verapamil, respectively. At the end of the first 6 weeks of active therapy, sitting diastolic blood pressure decreased by 11 mmHg in patients receiving moexipril and by 9 mmHg in patients receiving verapamil. The 24-week treatment period was completed by 72 patients who received moexipril and 71 patients who received verapamil. Mean decreases in sitting diastolic blood pressure of 10 mmHg and 11 mmHg were observed in the respective intent-to-treat moexipril and verapamil groups. At doses of 7.5 mg and 15 mg once daily, moexipril had an antihypertensive effect comparable to that of sustained-release verapamil at doses of 180 mg and 240 mg once daily.

A human case of infection by Trichinella pseudospiralis has recently been described. Some morphologic anomalies of the muscle larvae, however, raise the possibility of an incorrect taxonomic attribution. A molecular taxonomic approach has therefore been applied for the identification of the parasite. Random amplified polymorphic DNAs were obtained from a single larva extracted from a muscle biopsy of the suspected case of T. pseudospiralis infection, and compared with those derived from 27 reference strains of Trichinella spp. Nearly identical amplification patterns were obtained from the suspected larva and from reference strains of T. pseudospiralis, thus supporting the original morphology-based identification. An enzyme-linked immunosorbent assay and Western blots carried out on pretreatment and post-treatment sera provided further confirmation.

Extracts of liver and spleen were used to isolate opossum adenosine deaminase isoenzymes (ADA1 and ADA2) and to determine their activities with adenosine and 2'-deoxyadenosine as substrates. Km values (microM) for adenosine and 2'-deoxyadenosine, respectively, as substrates for partially purified opossum liver adenosine deaminase isoenzymes were ADA1: 57 +/- 7 vs. 26 +/- 4 and ADA2: 285 +/- 25 vs. 580 +/- 92. In crude spleen extract, ADA2 activity was stable at 56 degrees C during 40 min of incubation. ADA1 activity declined in a linear fashion under the above conditions with an apparent T1/2 of 80 min. Sephadex G-150 column chromatography of crude spleen extract showed the apparent molecular weight of the ADA activity not inhibited by (+/-)-EHNA (i.e. ADA2) to be 170 kDa; ADA activity fully inhibited by (+/-)-EHNA (i.e. ADA1) eluted in the fractions corresponding to a molecular weight of 35 kDa.

It is known that regenerating axons emerging from the proximal stump of a transected nerve are attracted towards the distal stump. It is not certain whether this neurotropic effect is on the axons themselves or whether it is on supporting cells such as Schwann cells that the axons then follow. In order to investigate this question in rats, segments of the sciatic nerve were either isolated or removed and reinserted as grafts, and then sutured into the opposing ends of double-Y silicone tubes. In these tubes, a central conduit was formed by connecting the centrally facing limb of each Y tube. The nerve segments were sutured into one of the limbs at either end. The third limbs of the Y tubes formed side arms, one of which was left open; a plug of mobilised fatty connective tissue was sutured into the other. A gap of 6 mm was left between the cut ends and the fat pads (or openings from the side arms). After 2-3 wk a significantly greater outgrowth (P < 0.001) was found to link the nerve segments than to invade the side arms. The major cell component in the outgrowth was Schwann cells, supported by fibroblasts and capillaries and surrounded by a lamellated layer of flattened fibroblasts. The growth into the side arms had a looser cellular architecture and contained considerably fewer Schwann cells. The results strongly suggest the existence of mutual attraction between emigrant Schwann cells, or possibly endoneurial fibroblasts, from the 2 cut ends of transected nerves. This conclusion has implications for the guidance of axons across gaps in nerves. It does not exclude an additional neurotropic effect from the distal stump on axons.

The first known human case of Trichinella pseudospiralis myositis is described. A 33 years old woman reported 5 years of relatively mild symptoms of tiredness, muscle fatigue and muscle pain after exercise. She had minimal proximal weakness. Creatinine kinase was significantly elevated, and muscle biopsy showed polymyositis and Trichinella larvae. Steroid treatment dramatically worsened the weakness. Treatment with albendazole led to complete resolution of symptoms and laboratory abnormalities. Diagnosis and identification of the parasite were based on the distinctive appearance of the unencapsulated larvae and their movement in fresh muscle, plus clinical and laboratory findings.

Pharmacokinetic and pharmacodynamic data were compared between elderly and young patients with hypertension who received single intravenous doses of amlodipine, a dihydropyridine calcium antagonist, followed by oral administration of amlodipine up to 10 mg once daily for 12 weeks. After intravenous administration, elderly patients had prolonged elimination half-life values (58 +/- 11 vs 42 +/- 8 hr; p < 0.05) caused by decreased clearance (19 +/- 5 vs 7 liters/hr; p < 0.05). Systolic and diastolic blood pressures were significantly decreased from baseline throughout the 3-month treatment period in both groups. After long-term oral administration, elderly and young patients had comparable decreases in mean blood pressure at a given drug plasma concentration. The antihypertensive effect of amlodipine is well correlated with plasma concentration and, at a given concentration, is similar in both elderly and young patients.

To determine if clinically used doses of the calcium antagonist verapamil measurably alter intracellular transduction mechanisms associated with the phosphatidylinositol pathway, lymphocyte protein kinase C activity was determined in subjects in a drug-free state, after 1 week of verapamil treatment (120 mg three times daily) and after a second week of verapamil treatment (240 mg sustained-release preparation once daily). Nine healthy male volunteers were studied and in these subjects baseline protein kinase C activity (mean +/- SEM; 5.07 +/- 0.76 pmol/microgram protein/min) tended to decrease after 1 week (3.50 +/- 0.20 pmol/micrograms protein/min) and was significantly decreased after 2 weeks (3.14 +/- 0.27 pmol/micrograms protein/min; p < 0.05 from baseline) of verapamil treatment. These data indicate that verapamil, at usual clinical doses, decreases protein kinase C activity in a marker tissue, the circulating lymphocyte. If protein kinase C activity in this tissue is a surrogate for other verapamil target tissues, such as vascular smooth muscle and heart muscle, these findings may provide insight into the in vivo mechanism by which verapamil decreases protein synthesis, limits cell growth, and reverses cellular hypertrophy in these tissues.

Angiotensin II (AII) has been shown to induce vascular smooth muscle cell (VSMC) hypertrophy and increased expression of vascular cytoskeletal proteins. We have studied basal and AII-induced expression of the chloramphenicol acetyl transferase (CAT) gene driven by three fragments of the human vascular smooth muscle (SM) alpha-actin promoter. We show basal CAT expression driven by the three fragments of the promoter when the constructs are transiently transfected into rat aortic VSMCs. AII in a concentration-dependent manner (1.0 nM to 10 microM) increased expression of the CAT gene driven by 896 bp fragment. When comparing the 896 bp fragment to fragments successively deleted at the 5' end (674 bp and 258 bp respectively), AII markedly stimulated CAT expression driven by the 896 bp fragment (257 +/- 31% over control, p < 0.01), stimulated CAT expression driven by 674 bp fragment to an apparently lesser degree (189 +/- 20% over control, p < 0.01), and tended to stimulate CAT expression driven by the 258 bp fragment, though not significantly greater than baseline (157 +/- 28% of control). These data suggest that AII exerts transcriptional regulation of human SM alpha-actin gene through activation of cis-acting element(s) in an upstream area localized between positions -258 and -896 of the SM alpha-actin promoter. Such findings help establish the role of AII in enhancement of expression of components of the contractile apparatus.

Calcium antagonists have been shown to induce a decrease in peripheral vascular resistance as well as a decrease in synthesis of vascular-wall matrix proteins. It has been shown previously that calcium antagonists decrease RNA synthesis of cultured, vascular, smooth-muscle cells. Here, these findings are extended to the investigation of whether calcium antagonists produce their vascular effects through their action on vascular, smooth-muscle cells only or whether they regulate fibroblast cells as well. It is demonstrated that in a concentration-dependent manner verapamil, diltiazem, and nifedipine each induced a decrease in RNA synthesis of quiescent and serum-stimulated NIH 3T3 cells, a fibroblast cell line shown to express voltage-dependent Ca2+ channels. Verapamil and nifedipine (10(-5)M) and diltiazem (10(-4)M) caused a marked decrease of basal and serum-induced increase in [3H]uridine uptake of NIH 3T3 cells. This is the first report to demonstrate that calcium antagonists have a direct effect on a fibroblast cell line leading to a decrease of RNA synthesis. Such findings suggest that calcium-antagonist vascular effects extend beyond vascular smooth muscle cells to connective tissues associated with extracellular-matrix protein production.

Stereoselective verapamil disposition and dynamics were evaluated after racemic verapamil administration of single i.v. doses, simulated steady-state intravenous infusions, chronic (1 week) administration of oral immediate-release tablets (120 mg three times daily) and chronic (1 week) administration of oral sustained-release tablets (240 mg once daily) to 15 young (mean +/- S.E.M. age 22 +/- 1 year) and 15 older (69 +/- 1 year) healthy male volunteers. After single i.v. doses S-verapamil clearance (young, 102 +/- 6 vs. older, 77 +/- 6 l/hr; P < .01) and R-verapamil clearance (young, 61 +/- 3 vs. older, 45 +/- 3 l/hr; P < .01) were similarly decreased. Electrocardiographic P-R prolongation using S-verapamil concentrations and an Emax model (young Emax, 69 +/- 8 vs. older, 42 +/- 6 msec; P < .05: young EC50, 15 +/- 1 vs. older, 23 +/- 3 ng/ml; P < .05) was greater in the young. Simulated steady-state i.v. S-verapamil clearance (young, 76 +/- 3 vs. older, 49 +/- 2 l/hr; P < .01) and R-verapamil clearance (young, 47 +/- 2 vs. older, 28 +/- 1 l/hr; P < .01) were similarly less in older subjects and this was unrelated to infusion rate. Qualitatively similar findings were observed during chronic oral (immediate release) treatment and chronic oral (sustained release) treatment. Plasma protein binding of S-verapamil was less in both groups (young, 8.5 +/- 0.4 and older, 8.0 +/- 0.5% unbound) than that of R-verapamil (young, 5.4 +/- 0.2 and older, 5.1 +/- 0.3% unbound) and not different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Fourteen antimitochrodrial antibody-positive patients (13 women, 1 man) with biopsy-proven primary biliary cirrhosis, aged 40 to 71 years (mean, 57 years) weighing 43 to 102 kg (mean, 63 kg), along with 14 age- and sex-matched healthy controls, received a single 1.0- to 1.2-g dose of intravenous antipyrine. Plasma antipyrine levels were determined during a 12- to 24-hour period. Patients' mean serum chemistry values were: albumin, 3.9 g/dL (range, 3.1-4.4) and total bilirubin, 1.9 mg/dL (range, 0.3-10.9). Seven of the fourteen patients had cirrhosis. Mean kinetic variables for antipyrine in controls and primary biliary cirrhosis patients were: Vd, .54 versus .49 L/kg; half-life, 12.0 versus 15.1 hours (P < .07); clearance, .55 versus .41 mL/min/kg (P < .04). Within the primary biliary cirrhosis group, there was no correlation between total bilirubin and clearance (r = .09), nor did clearance vary significantly among histologic categories. Clearance of antipyrine in primary biliary cirrhosis patients is reduced by an average of 25%, but the clinical prognosticators of serum bilirubin levels and histologic grade do not correlate with or predict the degree of clearance impairment.

A large number of studies have been reported on the genotoxicity of styrene in vitro and in vivo and the potential effects on humans of occupational exposure. Because of a variety of technical problems and difficulties in data interpretation, it has not been clearly established whether styrene can induce chromosomal aberrations and/or sister chromatid exchange (SCE) in vivo in animals or humans. The importance of clarifying this situation led to the development of the study described in this paper. Male Fischer 344 rats were exposed to styrene at concentrations of 150, 500 or 1000 ppm for 6 h/day on 5 days/week for 4 weeks. A negative control (air) was included. An additional control (ethylene oxide, 150 ppm) group was included in an attempt to establish the usefulness of rat lymphocytes for cytogenetic analysis in this protocol of long-term exposure by inhalation. The choice of agent and of exposure was based on the expectation that they would produce a positive response for SCE and/or chromosomal aberrations under the assay conditions used. Peripheral blood samples were drawn at 1, 2, 3 and 4 weeks of exposure and at 4 weeks after the end of exposure. Cultures were established, and SCE (second mitosis) and chromosomal aberrations (first mitosis) were analysed. The frequency of chromosomal aberrations was not increased over that in the air controls in the animals exposed to styrene or ethylene oxide at any of the sampling times. Styrene did not induce SCE at any of the concentrations or sampling times; however, the frequency of SCE was increased following exposure to ethylene oxide at all sampling times, with a positive exposure-response relationship with time of exposure as the variable. The data are compared with other, similar sets reported in the literature, and their significance for predicting responses in people occupationally exposed to styrene is discussed.

The capacity of three vasodilators that act by distinct mechanisms to reverse endothelin-I-mediated vasoconstriction was studied in 11 healthy nonsmoking male subjects (mean age +/- SEM, 26 +/- 2 years; mean weight +/- SEM, 74 +/- 2 kg) by use of brachial artery infusion and forearm strain-gauge plethysmography. Isoproterenol (cyclic adenosine monophosphate-mediated vasodilation), sodium nitroprusside (cyclic guanosine monophosphate-mediated vasodilation), and verapamil (L-type calcium channel blocker) were compared for capacity to reverse endothelin-I-mediated increase in forearm vascular resistance (FVR). Endothelin-I infusion increased FVR 1.9-fold in the control state. Isoproterenol infusion decreased FVR with or without concurrent endothelin-I infusion; however, at comparable isoproterenol infusion rates, endothelin-I increased FVR similar to the control state (for 5 ng/min isoproterenol, endothelin-I increased FVR 1.85-fold; for 12.5 ng/min isoproterenol, endothelin-I increased FVR 2.03-fold). Similarly, sodium nitroprusside infusion decreased FVR with or without concurrent endothelin-I infusion; however, at comparable sodium nitroprusside infusion rates the endothelin-I increase in FVR was similar to control (for 0.48 micrograms/min sodium nitroprusside, endothelin-I increased FVR 1.89-fold; for 0.96 micrograms/min sodium nitroprusside, endothelin-I increased FVR 2.36-fold). In contrast, verapamil infusion decreased FVR with or without endothelin-I infusion. At a verapamil infusion rate of 19.1 microns/min, endothelin-I increase in FVR was comparable to control (for 19.1 microns/min verapamil, endothelin-I increased FVR 1.36-fold, less than the 1.0-fold increase in the control state; p < 0.05). Isoproterenol and sodium nitroprusside decreased FVR during concurrent endothelin-I infusion but did not reverse the endothelin-I effect. In contrast, verapamil reversed endothelin-I--induced vasoconstriction to control FVR, suggesting a specific antagonism of endothelin-I--mediated increase in FVR.

Observations have been made on the growth of regenerating axons from transected rat sciatic nerve through Y-shaped silicone tubes. When the distal stump of the nerve was sutured into 1 distal limb of the tube and a fat pad into the other, a clear preference for the axons to regenerate towards the distal stump was found. In other experiments regenerating axons from the peroneal or tibial divisions of the sciatic nerve were given the choice of growing towards either the peroneal or tibial nerves, each being inserted into 1 of the 2 distal limbs of the Y-tube. No significant preference of the proximal stump to regenerate towards its appropriate distal stump was detected. A neurotropic influence of the distal stump on the nerve has therefore been confirmed, but topographic specificity of regeneration at the level of the nerve trunk has not been established.

Calcium antagonists are known to decrease peripheral vascular resistance in vivo in humans. The mechanism of this vascular relaxation has not been clearly elucidated. Vascular tone is maintained by several endogenous neurohumoral systems including sympathetic nervous system activity and angiotensin II. We compared and contrasted the capacity of calcium antagonist drugs to prevent angiotensin II and phenylephrine-induced alpha-1 adrenergic vasoconstriction using brachial artery infusion and measurement of forearm blood flow by strain gauge plethysmography. In a dose-dependent manner, calcium antagonists blocked angiotensin II-induced vasoconstriction. The rank order of this blockade was nifedipine greater than verapamil greater than diltiazem. Nifedipine and verapamil, but not diltiazem blocked alpha-1 adrenergic (phenylephrine-induced) vasoconstriction. At 7.64 and 19.1 micrograms/min infusion rates for nifedipine and verapamil, respectively, they abolished the angiotensin II effect; however, the phenylephrine effect was incompletely blocked. Calcium antagonist-induced vascular relaxation in vivo in humans is in part explained by their capacity to block angiotensin II-mediated vasoconstriction. In addition, two calcium antagonists (nifedipine and verapamil) may inhibit alpha-1 adrenergic vasoconstriction.

We evaluated VER effect on RNA synthesis of quiescent and angiotensin II (AII)- stimulated cultured rat aortic vascular smooth muscle cells (VSMC). In a dose-dependent manner, VER decreased [3H]uridine uptake by quiescent VSMCs (ED50 7 x 10(-6)M), an effect that was shared by other calcium antagonists, but to a variable degree. VER caused a significant effect within 3 hours and attained a maximal effect at 7 hours. In addition VER caused a 22 +/- 2% decrease in [3H]uridine uptake by VSMCs stimulated with 10% fetal bovine serum, while it completely abolished [3H]uridine uptake by VSMCs induced by AII. We conclude that VER decreases basal and inhibits AII-induced increase in mRNA synthesis of VSMCs. These data may explain in part how VER causes a decrease in vascular resistance and alters the vasoconstrictor effect of AII.

Amlodipine is a low-clearance, dihydropyridine calcium antagonist. The slow rate of elimination (elimination half-life of 40-60 h) confers several pharmacokinetic characteristics that are not seen with other calcium-antagonist drugs. It has high oral bioavailability (60-80%) and accumulates to a steady-state with once-daily administration over a period of 1-1 1/2 weeks. Fluctuation of plasma drug concentration between doses is between 20 and 25% when once-daily dosing is used. Onset of effect is gradual after oral administration which is due, in part, to an intermediate rate of drug absorption (peak plasma drug concentration occurs 6-8 h after dosing) and perhaps also to the physicochemical characteristics of the drug-cell membrane-receptor interaction. The pharmacodynamic profile of the drug in hypertensive patients is consistent with the disposition of the drug. After single doses, blood pressure decreases gradually over 4-8 h and may slowly return to baseline over 24-72 h. No change in heart rate is noted after the dose as the onset is gradual and physiological reflexes are not activated. During chronic, oral, once-daily dosing blood pressure is decreased from pretreatment baseline with little fluctuation over the 24-hour dose interval. Discontinuation of amlodipine treatment results in a slow return of blood pressure to baseline over 7-10 days, with no evidence of a 'rebound' effect. Amlodipine is a low-clearance, dihydropyridine calcium antagonist which is effective for the treatment of hypertension and angina pectoris with once-daily dosing.

Plasma adenosine deaminase2 (ADA2) has recently been proposed to be a marker for human immunodeficiency virus-1 (HIV) infection. We measured ADA2 levels in plasma from two groups of white homosexual males at 6-month intervals for a total of 2.5 years. One group consisted of 6 subjects who seroconverted for HIV, and the other consisted of 8 HIV seropositive patients who progressed from asymptomatic (CDC Groups II/III) to symptomatic (CDC Group IV) disease. Seroconversion was associated with a significant increase in plasma ADA2 which persisted throughout follow-up of 1.5 years. However, disease progression in HIV seropositive patients was not associated with any significant change in plasma ADA2. In conclusion, ADA2 may represent a unique marker for HIV seroconversion which does not change with later progression to symptomatic disease.

Diethylaminoethyl-cellulose chromatography was used to separate the two isoenzymes of adenosine deaminase (EC3.5.4.4), adenosine deaminase1 (ADA1) and adenosine deaminase2 (ADA2), in human plasma. One hundred and fifteen purine base, nucleoside, and nucleotide analogs were tested as inhibitors of this partially purified preparation of ADA2. Coformycin and 2'-deoxycoformycin were by far the most potent inhibitors of this isoenzyme (apparent Ki values 20 and 19 nM, respectively). ADA2 was also inhibited by nebularine (apparent Ki 1.5 mM) but was resistant to the potent ADA1 inhibitor (+)-erythro-9(2-S-hydroxy-3-R-nonyl)adenine. alpha-D-Adenosine also inhibited ADA2, as did several halogenated purine and adenine base analogs. Structural requirements for the binding of purine analogs to ADA2 are presented which provide a general basis for the design of specific inhibitors of ADA2. Such inhibitors may be useful in studies designed to provide an understanding of the physiological role of ADA2 both in the normal state and in diseases such as human immunodeficiency virus-1 infection where levels in plasma are increased markedly.

Healthy men were administered i.v. racemic warfarin, S-warfarin or R-warfarin on two occasions, once in the drug-free state and once during concomitant administration of oral diltiazem 120 mg three times daily. Blood samples for determination of plasma warfarin and diltiazem concentrations, the prothrombin time and complete urine collections were obtained for determination of urinary excretion of dehydrowarfarin, 4'-hydroxywarfarin, 6-hydroxywarfarin, 7-hydroxywarfarin, 8-hydroxywarfarin and unchanged parent drug for 216 h after each dose. Concurrent diltiazem administration decreased total racemic warfarin clearance (+/- S.D.) [3.60 +/- 0.99 (control) versus 3.19 +/- 0.86 (diltiazem) ml/min; P less than .05]. Disposition of the more potent anticoagulant S-warfarin was not altered by diltiazem treatment. In contrast total clearance of R-warfarin was decreased [3.47 +/- 1.10 (control) versus 2.77 +/- 0.92 ml/min; P less than .05]. No change in the area under the prothrombin time versus time after warfarin administration curve was associated with diltiazem treatment for any warfarin trial. Inhibition of R-warfarin by diltiazem was regioselective for metabolites as determined by fractional clearance of urinary metabolites. R-6-hydroxywarfarin clearance (+/- S.E.) [29.5 +/- 7.2 (control) versus 15.7 +/- 2.8 ml/h; P less than 0.05] and R-8-hydroxywarfarin clearance [21.1 +/- 3.6 (control) versus 11.2 +/- 2.0 ml/h; P less than .05] were selectively decreased with no significant change in the urinary clearance of R-dehydro, R-4-hydroxy and R-7-hydroxywarfarin. Urinary clearance of unchanged R-warfarin was also decreased during diltiazem administration. Diltiazem inhibits warfarin disposition in humans in a stereospecific and regiospecific manner.

Plasma concentrations of the two isoenzymes of adenosine deaminase (ADA, E.C. 3.5.4.4), adenosine deaminase1 (ADA1) and adenosine deaminase2 (ADA2), were measured in a cohort of ambulatory patients infected with the human immunodeficiency virus (HIV) and controls. A sensitive isoenzyme-specific radioisotopic assay system was developed for these studies. Among 22 HIV-infected patients, plasma ADA2 was significantly elevated as compared with 16 control subjects (p less than 0.01) and 6 uninfected subjects having a risk factor for HIV infection (p less than 0.01). Plasma ADA2 was not associated with the stage of disease as defined by clinical status (p greater than 0.05) or helper (CD4) lymphocyte count (p greater than 0.05). Available evidence suggests that elevated plasma ADA2 could be a useful surrogate marker for HIV infection that occurs early in the disease process.

Structural features of amlodipine give the molecule physicochemical and pharmacokinetic properties that are unique among calcium antagonists. Amlodipine is absorbed gradually after oral administration (peak plasma levels 6-12 h postdose) and has an absolute bioavailability of 64%. Low clearance and a high volume of distribution give amlodipine a long elimination half-life, and mean effective plasma levels are maintained with once-daily doses. With repeated once-daily dosing, the steady state is achieved after the seventh to ninth dose. The pharmacokinetic properties of amlodipine avoid the sharp fluctuations in plasma level seen with other calcium antagonists that are associated with vasodilatation-induced side effects such as tachycardia, headache, and flushing. The pharmacokinetics of amlodipine are not significantly altered in elderly or renally impaired patients, but there is reduced clearance in patients with hepatic impairment. There are no pharmacokinetic interactions between amlodipine and cimetidine or digoxin.

Over the past decade, clinical pharmacokinetic studies in the elderly, both healthy subjects and patients, have burgeoned. This data base has provided a useful first approximation to the understanding of age-related changes in drug disposition. It is now appropriate to reflect on the approach for future studies. The most accessible population, healthy elderly who are otherwise drug-free, may not provide completely relevant data for extrapolation to the very elderly, concurrently medicated patient population. Similarly, the most straightforward study, single dose drug exposure, may provide an incomplete understanding of pharmacokinetics during multiple dose drug administration in the very elderly patient. With careful attention to details of the study and informed consent procedures, it is appropriate to obtain the needed data.

Pharmacodynamics and disposition of amlodipine, a dihydropyridine calcium antagonist, were compared between elderly and young patients with hypertension. Elderly (mean +/- SD; age, 68 +/- 3 years) and young (35 +/- 5 years) patients received single intravenous amlodipine doses followed by oral administration once daily for a total of 12 weeks. After intravenous administration, elderly patients had prolonged elimination half-life values (58 +/- 11 versus 42 +/- 8 hours; p less than 0.01) caused by decreased clearance (19 +/- 5 versus 25 +/- 7 L/hr; p less than 0.01). After a 3-months oral treatment washout period, half-life tended to be prolonged in the elderly patients (69 +/- 20 hours for the elderly patients versus 53 +/- 14 hours for the young patients; difference not significant) and was not markedly different from the short-term intravenous measurement. Both systolic and diastolic blood pressure were significantly decreased from baseline throughout the treatment period, with greater decreases in elderly patients for both systolic and diastolic pressure. When amlodipine plasma concentration was correlated to change in mean blood pressure after short-term intravenous doses, elderly patients had a greater decrease than young patients at a given drug concentration. However, after long-term oral administration, elderly and young patients had comparable decreases in mean blood pressure at a given drug concentration, and the increased antihypertensive effect in the elderly was associated with somewhat higher amlodipine plasma concentration. Amlodipine administered once daily is an effective antihypertensive agent in elderly patients and young patients with essential hypertension.

With use of direct brachial artery infusion and measurement of forearm blood flow and vascular resistance by strain gauge plethysmography, the effect of verapamil on phenylephrine-induced vasoconstriction was determined. Seven healthy men (age range, 19 to 47 years; weight range, 68 to 108 kg; mean blood pressure, 74 to 100 mm Hg; five nonsmokers) were systemically beta-blocked with intravenous administrations of 10 mg propranolol. Each subject then received ascending doses of phenylephrine (0.191 to 7.6 micrograms/min) alone and with concurrent verapamil (19.1 micrograms/min) by brachial arterial infusion. Dose-ratio during verapamil infusion compared with control was 8.1 (p less than 0.05). No change in slope of the phenylephrine dose-response curve was noted; however, consistent with the dose ratio, verapamil shifted the curve to the right with a decrease in the y intercept determined by linear regression (60.0 versus 40.3 mm Hg ml/100 ml forearm volume/min; p less than 0.05). Verapamil-induced attenuation of forearm vasoconstriction elicited by phenylephrine indicates that, in humans, in vivo verapamil forearm vasodilating effects are, in part, a result of alpha 1-adrenergic blockade.

To properly predict drug effects in elderly patients for cardiovascular drugs requires understanding of age-related and disease-related changes in tissues and organs which mediate the observed pharmacodynamic response. Linking this understanding with the known changes in drug pharmacokinetics permits more effective cardiovascular pharmacotherapy in the geriatric patient. At the present time only a limited number of drug classes have been studied in this manner. Although it may be intuitively obvious that human pathophysiology may impact on drug response, until recently we have relied solely on description of drug concentration or pharmacokinetics to predict expected responses. We can look forward to improved geriatric therapeutics when the patient as well as the drug is considered as a variable in clinical therapeutic responses.

Previously, we have demonstrated in vivo, in humans, nonlinear diltiazem disposition with an elimination half-life 50-100% greater after chronic diltiazem as compared to single-dose diltiazem administration. At least two metabolites, desmethyldiltiazem (MA) and desacetyldiltiazem (M1), accumulate significantly in human plasma during chronic diltiazem administration. To test the hypothesis that nonlinear diltiazem accumulation is associated with inhibition of biotransformation, we studied diltiazem disappearance during incubation with a number of its identified metabolites in an isolated rat hepatocyte system. Apparent kis for disappearance of diltiazem were: MA, 88.3 microM; M1, 608 microM; M2 (desacetyl N-desmethyldiltiazem), 495 microM; M4 (desacetyl O-desmethyldiltiazem), 152 microM; and M6 (desacetyl N,O-desmethyldiltiazem), 448 microM. These apparent ki values are similar to those derived for diltiazem-mediated inhibition of other drug substrates such as antipyrine, the clearance of which is inhibited by diltiazem in vivo in humans. Nonlinear diltiazem accumulation in vivo may be explained in part by progressive metabolite accumulation, particularly MA, which results in the inhibition of parent drug diltiazem biotransformation.

The aged are now viewed as a special population for the purposes of drug development. This has produced challenges for the investigator, in that separation of age- and disease-related changes in drug effect is only beginning to be defined. In addition, development of measurement tools for use in the elderly, particularly for central nervous system-active drugs, is an important ongoing process. As investigations proceed, we can look forward to an improved understanding of the physiology of normal ageing and the impact of disease processes and drugs on this physiological functioning. For the regulatory agency, evaluation of both efficacy and toxicity data in elderly patients for a drug-in-development is required; however, at present these data will be obtained in a 'young' elderly group, whereas much of the clinical use of the drug will be in the 'old' elderly. Extrapolation from one group to the other is required, although the relevance of this extrapolation is unknown. It is reassuring that, so far, few if any drug effects or toxicities have been identified which are truly unique to the elderly, though the magnitude of pharmacological or toxicological effects may differ.

Fourteen obese subjects (mean body weight, 124 kg; percent of ideal body weight [IBW], 178%) and ten control subjects of normal body habitus (mean body weight, 67 kg; 92% IBW) received 300 mg of phenytoin sodium by ten-minute intravenous infusion. Obese subjects compared with controls had prolonged phenytoin elimination half-life (19.9 v 12.0 hours). Total metabolic clearance of phenytoin was greater in obese than in control groups, although the difference was not significant (59 v 39 mL/min). Phenytoin half-life, inversely proportional to clearance and directly proportional to volume of distribution (Vd), was prolonged in obesity mainly as a result of the increase in Vd in obese subjects (84 v 40 L). Phenytoin loading dose should be calculated on the basis of IBW plus the product of 1.33 times the excess weight over IBW. Very obese individuals will require large absolute loading doses of phenytoin to rapidly achieve therapeutic drug concentrations.

Technical grade dinitrotoluene (DNT), a mixture composed predominantly of 2,4- and 2,6-DNT but containing lesser amounts of 2,3-, 2,5-, 3,4- and 3,5-DNT, has been shown to be a hepatocarcinogen in rats, The mutagenicity of these compounds has been evaluated using the CHO/HGPRT system, a quantitative mammalian somatic cell mutational assay. Dinitrotoluenes were tested for their ability to induce mutation to 6-thioguanine (TG) resistance in the presence and absence of microsomal preparations (PMS) from rats pretreated with the mixed function oxidase inducer Aroclor 1254. A marked difference in cytotoxicity of the isomers was observed. However, neither technical grade DNT nor any of the purified isomers resulted in a significant increase in the TG-resistant fraction of surviving cells, with or without added PMS.

The benzodiazepine derivative flurazepam (FLZ) is widely used as a hypnotic, but the relative contributions of FLZ and its metabolites desalkylflurazepam (DA-FLZ), hydroxyethylflurazepam (ETOH-FLZ), and flurazepam aldehyde (CHO-FLZ) to overall clinical activity remain uncertain. A single 20 mg/kg dose of FLZ.HCl was administered to mice, with plasma and brain concentrations of FLZ and metabolites determined during 5 h after dosage. Brain and plasma concentrations of FLZ were maximal at 0.5 h after dosage, then declined rapidly in parallel, whereas those of DAFLZ were maximal at 2 h, then declined slowly. Concentrations of ETOH-FLZ, the most polar metabolite, were maximal at 0.5 h, and were undetectable after 3 h. Little CHO-FLZ was detected in either brain or plasma. A single 30-mg oral dose of FLZ.HCl was given to 18 human volunteers, with plasma levels determined over 9 days. FLZ was detected in plasma at low concentrations for no more than 3 h after dosage. ETOH-FLZ concentrations were higher and persisted for 8 h after dosage. CHO-FLZ reached intermediate peak levels and was present longer than FLZ or ETOH-FLZ. In contrast, DA-FLZ achieved the greatest peak concentrations, occurring at 10 h after dosage. Levels declined very slowly, with a mean half-life of 71.4 h, and were still detectable 9 days after FLZ dosage. Plasma free fractions (percent unbound) in mice were 40.3, 51.4, and 25.0% for FLZ, ETOH-FLZ and DA-FLZ, respectively; in humans, values were 17.2, 35.2, and 3.5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Six elderly male (65-75 years), seven elderly female (64-88 years), 15 young male (22-38 years), and nine young female (25-37 years) volunteers, all of normal body weight and clinically without cardiac or renal dysfunction, received a single 25-mg intravenous dose of lidocaine. Plasma concentrations of lidocaine were determined from blood samples drawn during 8 h following the lidocaine dose. Elimination half-life (t1/2) was markedly prolonged in elderly male subjects as compared with that in young male subjects (mean +/- SE: 2.70 +/- 0.21 versus 1.66 +/- 0.09 h; p less than 0.001). No difference in t1/2 was noted among female subjects (2.27 +/- 0.21 versus 2.07 +/- 0.07 h). Volume of distribution was greater in women than in men but was not influenced by age. Instead, prolongation in t1/2 in elderly men was the result of a highly significant decrease in total metabolic clearance (12.9 +/- 2.0 versus 19.8 +/- 1.5 ml/min/kg; p less than 0.05). No significant change in total metabolic clearance of lidocaine was noted between elderly and young women (18.3 +/- 2.0 versus 21.1 +/- 1.6 ml/min/kg). The findings suggest that in the elderly male patient without evidence of congestive heart failure or other coexisting chronic disease, the initial loading dose of lidocaine should be the same as for a young patient. However, to achieve comparable plasma concentrations and therapeutic effect during continuous infusion therapy, the elderly male patient should have the continuous infusion rate decreased by an average of at least 35%.

In an anaesthetized dog model, serum kinetics and CSF entry were determined after i.v. administration of the following 8 drugs: salicylic acid (as acetylsalicylic acid), antipyrine, acetaminophen (paracetamol), lidocaine (lignocaine), trimipramine, amitriptyline, haloperidol, and imipramine. Kinetic variables were evaluated in relation to in-vitro lipophilicity, measured by the reverse-phase high-pressure liquid chromatographic (HPLC) retention index. After correction for individual values of serum binding (determined as the CSF: serum ratio at equilibrium), in-vivo volume of distribution was highly correlated with HPLC retention (r = 0.92). Conversely, the time of peak CSF concentration and the CSF entry half-life were negatively correlated with HPLC retention (r = -0.83 and -0.63, respectively). Thus lipophilicity is a physiochemical property which has an influence on the peripheral distribution of drugs as well as their rate of entry into CSF.

Digoxin pharmacokinetics were studied in 16 obese (mean +/- SD weight, 100.2 +/- 36.8 kg) and 13 control (64.6 +/- 10.5 kg) subjects. All subjects had normal renal function and no other coexisting disease. After administration of 0.75 mg digoxin by intravenous infusion, multiple plasma samples obtained over the 96 hours following infusion were analyzed for digoxin concentration by radioimmunoassay. Pharmacokinetic parameters were determined by weighted iterative nonlinear least squares regression analysis. Elimination half-life (t 1/2) was not different between obese and control groups (35.6 +/- 10.5 vs 41.2 +/- 16.7 hours). Absolute volume of distribution (Vd) also was not different (981 +/- 301 vs 937 +/- 397 liters), nor was total clearance of digoxin (328 +/- 82 vs 278 +/- 87 ml/min). Elimination t 1/2 was significantly negatively correlated with clearance among all subjects (r = -0.46; p less than 0.01). Using percent ideal body weight (IBW) as a measure of obesity, no correlation was found between percent IBW and Vd (r = 0.03). Thus digoxin is similarly distributed into IBW in obese and normal weight subjects, and there is no significant distribution of digoxin into excess body weight over IBV. In addition, there is no difference in total metabolic clearance or elimination half-life between obese and control subjects. Digoxin loading and maintenance dosage should be calculated on the basis of IBW, which reflects lean body mass, rather than TBW, which reflects adipose tissue weight in addition to lean body mass.

Plasma protein binding in seven severely burned (35% to 85% of body) patients 1 to 25 days after burn injury was examined for two drugs: diazepam (DZ), which binds mainly to serum albumin (ALB), and imipramine (IMI), which binds primarily to alpha 1-acid glycoprotein (AAG). Protein binding was determined by equilibrium dialysis, and AAG concentrations were measured by radial immunodiffusion. AAG concentrations increased from 36 to 99 mg/dl (day 1) to 221 to 268 mg/dl (days 5 to 20). The IMI free fraction values decreased from 11.2%-19.7% to 5.5%-7.8% and correlated well with AAG concentrations. IMI free fraction values were lower in burned patients (10.8% +/- 0.8%) than in healthy controls (15.3% +/- 0.7%). In contrast, DZ free fraction did not correlate with AAG or ALB concentrations. The DZ free fraction ranged from 1.5% to 8.04%, and changes in a given individual did not relate to time after injury. Free fraction of DZ was higher in the burned population (3.5% +/- 0.37%) than in healthy controls (1.25% +/- 0.05%). Basic drugs that are highly bound to AAG may show progressive, increased binding after burn injury, whereas drugs binding to ALB may decrease after burn injury. Such binding changes can alter the interpretation of total serum or plasma drug concentrations.