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The pharmacokinetics of mezlocillin were examined after single 2- and 4-g intravenous injections to three groups of male patients with creatinine clearances of I >/= 60, II = 21 to 59, and III

The pharmacokinetics of the new aminoglycoside antibiotic netilmicin were examined after single intravenous injections at two different dose levels to elderly male patients. The durg obeyed two-compartment model kinetics in serum, and elimination was monoexponential from 1 to 2 h after dosing. Netilmicin levels in serum were above minimum inhibitory concentration values for most susceptible organisms for up to 8 h after dosing in normal individuals and for at least 12 h in uremic patients. Urine levels of netilmicin were uniformly above minimum inhibitory concentration values throughout 24 h after dosing. Netilmicin distribution characteristics were largely independent of both dose level and renal function. Netilmicin elimination kinetics were independent of dose level but were markedly influenced by renal function. Relationships are described between netilmicin elimination and renal function indicators, which provide a basis for dosage adjustment in individuals with renal function impairment.

The pharmacokinetics of cefamandole, a new cephalosporin, were investigated in 23 patients with urinary tract infections and normal or varying degrees of impairment of renal function. A daily dose of 1.5 to 3.0 g administered intramuscularly was tolerated well and resulted in very high urine concentrations. The pharmacokinetics of the antibiotic were compared with isotopically labeled [(131)I]hippurate and [(125)I]iothalamate, which were used for determination of effective renal plasma flow and glomerular filtration rate, respectively. It was shown that cefamandole was excreted by glomerular filtration as well as by active tubular secretion. Probenecid inhibited the tubular secretion of cefamandole. The serum half-life of cefamandole in patients with normal renal function was approximately 1.5 h and increased in patients along with increasing impairment of renal function. Our studies indicate that a dosage regimen of 1 g of cefamandole every 8 h in patients with normal renal function results in urine concentrations sufficiently high for treatment of most common urinary tract infections. In patients with impaired renal function, the dosage interval should be increased or the dosage lowered according to the serum creatinine values.

Rosamicin, a new macrolide substance, was investigated in dogs and humans with regard to its usefulness for the treatment of bacterial prostatitis and compared with the well-known macrolide erythromycin. In dogs with normal and experimentally infected prostates, concentration ratios for rosamicin in prostatic secretion, interstitial fluid (obtained from implanted tissue chambers), and tissue were significantly higher than for erythromycin. The difference was even more pronounced in human prostatic tissue, obtained by transurethral resection. With its broad spectrum against many common urinary pathogens, rosamicin seems to be a promising drug for the treatment of acute and chronic bacterial prostatitis.

Netilmicin and amikacin, two recently developed aminoglycosides, were compared in a prospective, randomized study of 57 male patients with complicated urinary tract infections. Both drugs were administered intramuscularly every 12 h for 7 to 10 days, netilmicin at 2 mg/kg and amikacin at 7.5 mg/kg. The two groups were comparable as to infecting bacteria and underlying pathology of the urinary tract. No patients had indwelling catheters. All microorganisms isolated were sensitive to both antibiotics. A total of 69% of the patients treated with netilmicin and 57% of the patients treated with amikacin were cured of the infection, as defined by a negative culture at 7 days after discontinuation of treatment. No major side effects were recorded, and no significant changes were noted in parameters of renal function. Of the patients treated with amikacin, 21% experienced temporary local pain at the injection site; no such effect was noted in the netilmicin-treated group. Therefore, netilmicin appeared to be as effective and better tolerated than did amikacin in the treatment of complicated urinary tract infection.

Serum levels and urinary excretion of cinoxacin were examined in healthy individuals after a two-step intravenous infusion in the presence and absence of probenecid. After dosing cinoxacin alone, steady-state serum levels were approached in 1 h and were maintained for an additional 2 h with a reduced infusion rate. After probenecid pretreatment, serum levels of cinoxacin continued to increase during 3 h of infusion, reaching levels approximately double those obtained with cinoxacin alone. The mean elimination half-life of cinoxacin from serum was increased from 1.3 to 3.5 h in the presence of probenecid, and renal clearance was significantly reduced, with 46% of dosed drug appearing in 7-h urines of probenecid-treated subjects compared with 68% in subjects receiving cinoxacin alone. Probenecid had no apparent influence on cinoxacin distribution in the body but caused a significant decrease in the rate of cinoxacin extrarenal elimination, possibly due to competition for a common metabolic pathway.

The clinical efficacy, patient tolerance, and pharmacokinetics of gentamicin and the single component gentamicin C(1) were studied after single and multiple doses in elderly male patients. Patient tolerance was extremely good at the dose levels used. There was some evidence of renal function impairment due to repeated intramuscular doses of gentamicin, but not gentamicin C(1). The antibiotics were equally effective against the organisms present in the urine of these patients. The pharmacokinetics of the two antibiotic forms were similar, although gentamicin C(1) appeared to have a larger distribution space.

Cephacetrile (CIBA 36' 278-Ba) and cephaloridine (both cephalosporin derivatives) were compared in dogs with regard to their possible nephrotoxicity, renal handling, and concentration in the renal lymph. No adverse acute effect of either drug on the glomerular filtration rate and effective renal plasma flow was found at very high concentrations in the plasma, with or without concomitant administration of a potent diuretic (furosemide). Cephaloridine was filtered only by the kidney, whereas there was evidence that cephacetrile was also excreted by tubular secretion at low concentrations. The renal lymph concentration of the two antibiotics (in the hilar as well as the capsular lymph vessels) was found to be significantly lower than the simultaneous arterial plasma concentrations. When concentrations in the plasma were high, the relative lymph concentrations of cephaloridine and cephacetrile were in the same range as those of iothalamate (70 to 90% of the arterial plasma level), whereas at low plasma concentrations the lymph concentration of cephacetrile was markedly lower, a finding possibly explained by the active tubular secretion of cephacetrile.

The pharmacokinetics, distribution, and plasma and renal clearance of a new aminoglycoside antibiotic, tobramycin, was studied in the treatment of 18 elderly male patients (average age, 69 years) with urinary tract infections. Ten of these patients had normal renal function and eight had impaired renal function of various degrees. After administration of 1 mg of tobramycin/kg of body weight every 6 to 8 h (two to three times the half-life), urine concentrations were found to be sufficient in the treatment of urinary tract infections caused by susceptible organisms. The renal clearance of tobramycin during constant intravenous infusion was also studied in eight patients. Good correlation was found between the patients serum creatinine and the half-life of tobramycin. The half-life of tobramycin in patients with normal renal function (serum creatine [Formula: see text] to 1.5 mg/100) was on the average 3 h. For practical purposes, therefore, the dosage of tobramycin in the treatment of urinary tract infections should be 1 mg/kg of body weight every 6 to 8 h in patients with normal renal function. For patients with impaired renal function, the dosage interval is calculated by multiplying the patients' serum creatinine by six. If the dosage intervals are kept unchanged, the dosage must be divided by the patients' serum creatinine. The initial loading dose should always be 1 mg/kg. The total renal clearance of tobramycin (92% of the glomerular filtration rate) was not influenced by the administration of probenecid, which indicates that tobramycin is excreted only by glomerular filtration.