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Background and objectives Activated clotting factor FXI ( FXIa) has been postulated to play a significant role in thromboembolic events potentially associated with the administration of intravenous immunoglobulin. The purpose of this study was to demonstrate that thrombogenic agents, in particular FXIa and FXI, are depleted or inactivated in Privigen®. Materials and methods The ability of the purification process to deplete FXIa from plasma was studied. All steps of the Privigen® production were investigated for potential activation of FXI to FXIa with spiking experiments. Results Privigen® contains no procoagulant activity as determined by FXIa chromogenic assay, non-activated partial thromboplastin time (NaPTT) and thrombin generation assays (TGA, FXIa-like activity). The coagulation times were >200 s in the NaPTT test. FXIa was below the detection limit of 0·14 ng/ ml (chromogenic assay) and below the quantification limit of 0·2 ng/ ml (TGA). FXIa spiking experiments showed that the analytical methods used can detect traces of procoagulant activity in immunoglobulin samples. FXIa spiking and kinetic experiments during the octanoic acid fractionation step showed that a substantial reduction in FXIa specific activity (by ≥99·9% within 40 min of octanoic acid incubation) was reached already at an early stage of the manufacturing process. These results were confirmed in vivo: in a modified Wessler test, no thrombus was reported. Conclusion The Privigen® manufacturing process has the capability to remove thrombogenic factors: octanoic acid precipitation, designed to remove a variety of contaminants during immunoglobulin purification, also removes almost all FXIa from plasma and further purification steps do not activate FXI. [ABSTRACT FROM AUTHOR]

Human vascular endothelial cells may serve as targets and a reservoir for human immunodeficiency virus type 1 (HIV-1). The antiviral activity of HIV protease inhibitors is reported to be related directly to the intracellular amount of the drug. To assess intracellular concentrations of two HIV protease inhibitors, human umbilical venous endothelial cells (HUVECs) were exposed for 3 h and 24 h to 100, 10 and 1 mg/L indinavir and saquinavir. Intracellular drug concentrations and the total drug amount in the supernatant were measured by means of high-performance liquid chromatography (HPLC). Exposure of HUVECs to 10 and 1 mg/L indinavir and saquinavir resulted in undetectable intracellular drug levels in 6 × 105 cells/well. Incubation of cells with solutions of 100 mg/L indinavir and saquinavir led to mean intracellular concentrations of indinavir (132 ± 56 mg/L after 3 h and 150 ± 29 mg/L after 24 h, respectively) and of saquinavir (96 ± 10 mg/L after 3 h and 100 ± 5 mg/L after 24 h) that were comparable to the levels determined for the substances in the supernatant over time (P > 0.001). These data indicate that intracellular concentrations of indinavir and saquinavir correlate well with the extracellular levels. Consequently, measurements of drug concentrations in patient's plasma by HPLC are assumed to be a good means of monitoring the intracellular drug concentration. [ABSTRACT FROM PUBLISHER]

The aim of this study was to determine the effect of varying the application time of Mitomycin-C (MMC) on the scleral concentration of MMC. The sclerae of 14 human donor eyes were used for this study. The episcleral sides of the 4 scleral quadrants of each donor eye were exposed for 0.5, 1, 3 and 5 min to round, 8 mm-diameter sponges soaked with 50 μl of 0.2 mg/ml MMC. After 40-ml irrigation with saline, a central 8-mm diameter scleral disk was punched out, homogenized and analyzed with high performance liquid chromatography (HPLC). The scleral MMC concentrations (μg/g) after 0.5, 1, 3 and 5 min application times were 6.40 (±3.38), 9.02 (±2.40), 12.31 (±3.37), and 13.97 (±3.83). The differences of scleral MMC concentration in paired t-tests were statistically significant comparing 0.5 with 1 and 1 with 5 min application. However the effect was relatively small within the range of usual application times (1 to 5 min), and 64% of the MMC was delivered to the sclera within the first min. [ABSTRACT FROM AUTHOR]

This prospective crossover study compared the pharmocokinetics of meropenem by continuous infusion and by intermittent administration in critically ill patients. Fifteen patients were randomized to receive meropenem either as a 2 g iv loading dose, followed by a 3 g continuous infusion (CI) over 24 h, or by intermittent administration (IA) of 2 g iv every 8 h (q8h). Each regimen was followed for a period of 2 days, succeeded by crossover to the alternative regimen for the same period. Pharmacokinetic parameters (mean ± SD) of CI included the following: concentration at steady state (Css) was 11.9 ± 5.0 mg/L; area under the curve (AUC) was 117.5 ± 12.9 mg/L.h. The maximum and minimum serum concentrations of meropenem (Cmax, Cmin) and total meropenem clearance (CItot) for IA were 110.1 ± 6.9 mg/L, 8.5 ± 1.0 mg/L and 9.4 ± 1.2 L/h, respectively. The AUC during the IA regimen was larger than the AUC during CI (P < 0.001). In both treatment groups, meropenem serum concentrations remained above the MICs for the most common bacterial pathogens. We conclude that CI of meropenem is equivalent to the IA regimen and is therefore suitable for treating critically ill patients. Further studies are necessary to compare the clinical effects of CI and IA in this patient group. [ABSTRACT FROM PUBLISHER]

Phlebitis is a severe local adverse event related to the use of parenteral macrolides. In order to evaluate the effect of azithromycin and erythromycin on human venous endothelial cells, we set up an in vitro model. The intracellular levels of purine nucleotides, as adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP) and guanosine 5'-triphosphate (GTP), were measured by means of high-performance liquid chromatography. Incubation of cells with 2 mg/mL azithromycin and erythromycin resulted in a rapid decline of intracellular ATP from 12.5 +/- 0.9 nmol/million cells to 4.1 +/- 0.3 and 2.6 +/- 0.4 nmol/million cells, respectively, after 60 min. In addition, ADP was extensively depleted from 2.1 +/- 0.17 nmol/million cells to 0.8 +/- 0.09 and 0.8 +/- 0.13 nmol/million cells after 60 min. After exposure of 0.5 mg/mL azithromycin and erythromycin, no significant decline of intracellular high-energy phosphate levels occurred after 20 and 60 min. Based on these results, solutions of azithromycin and erythromycin may not be well tolerated and may cause local adverse reactions even if diluted according to the manufacturer's recommendation. [ABSTRACT FROM AUTHOR]

Background: Severe hemolysis rarely occurs in patients receiving intravenous immunoglobulin (IVIG) therapy. A systematic review was performed to assess the incidence of IVIG-related hemolysis and the impact of patient and product risk factors., Study Design and Methods: A systematic literature search for terms related to "IVIG products", "hemolysis," and "adverse events" was conducted in Embase for articles published between January 1, 2015, and May 31, 2021. Studies with no clinical datasets, no IVIG treatment, or where IVIG was used to treat hemolytic conditions were excluded. Of the 430 articles retrieved, 383 were excluded based on titles/abstracts and 14 were excluded after in-depth review., Results: In total, 33 articles were analyzed and separated into observational studies (n = 16), clinical trials (n = 8), and case reports (n = 9). The incidence proportion for IVIG-related hemolysis ranged from 0% to 19% in observational studies and 0%-21% in clinical trials. A higher incidence of IVIG-related hemolysis was consistently reported in patients with blood groups A and AB. Hemolysis occurred more frequently in patients treated with IVIG for some conditions such as Kawasaki disease; however, this may be confounded by the high dose of IVIG therapy. IVIG-related hemolysis incidence was lower in studies using IVIG products citing manufacturing processes to reduce isoagglutinin levels than products that did not., Conclusion: This analysis identified patient and product risk factors including blood group, IVIG dose, and IVIG manufacturing processes associated with elevated IVIG-related hemolysis incidence., (© 2022 CSL Behring L.L.C. Transfusion published by Wiley Periodicals LLC on behalf of AABB.)

Background: The passive transfer of antibodies specific to blood groups A and B (also called isoagglutinins) contained in immunoglobulin (Ig)G products for intravenous administration (IVIG) is believed to be largely responsible for rare but sometimes serious IVIG-related hemolytic events. We present in this work a modification of the manufacturing process of Privigen-a 10% l-proline-stabilized IVIG product-that allows extensive reduction of isoagglutinin concentrations in the final product., Study Design and Methods: An additional immunoaffinity chromatography (IAC) step was introduced toward the end of the manufacturing process of Privigen. Isoagglutinin titers were measured using the indirect agglutination method and a published flow cytometry-based binding assay. Quality attributes, such as microorganism counts and concentration of endotoxins, IgG, IgA, IgM, aggregates, and so forth were measured using standardized procedures., Results: The introduction of an IAC step in the manufacturing process of Privigen resulted in an 88% to 90% reduction in isoagglutinins between the feed of the chromatography column and the flow-through fraction. All other product quality attributes measured were nearly identical before and after IAC. This process modification resulted in a three-titer-step reduction in isoagglutinin levels in the final IgG product compared to Privigen lots produced by the unmodified process., Conclusion: Introducing an isoagglutinin-specific IAC step in the manufacturing process of Privigen is an efficient strategy for reduction of anti-A and anti-B titers. Such reductions might help minimize the risk of hemolytic events in patients receiving IVIG therapy., (© 2015 AABB.)

Background: The first intravenous immunoglobulin G (IVIG) preparations for clinical use were produced from human plasma by Cohn-like fractionation processes. To achieve higher purity and yield, chromatography-based processes were developed. Using two products as examples, we compare the capacity of these two manufacturing processes to reduce the levels of anti-A and anti-B isoagglutinins in IVIG, which are believed to be responsible for rare hemolytic adverse events., Study Design and Methods: The isoagglutinin levels of Sandoglobulin (lyophilized, sucrose-stabilized IVIG produced by Cohn-like fractionation) and Privigen (10% l-proline-stabilized IVIG produced by a chromatography-based process) were measured by the indirect agglutination test (IAT). The intrinsic isoagglutinin reduction capacity of each fractionation step was assessed in laboratory- and industry-scale experiments using the IAT and a flow cytometry-based immunoglobulin-binding assay, respectively., Results: The median anti-A isoagglutinin titer recorded in 248 Sandoglobulin lots was three titer steps lower than the one measured in 651 Privigen lots (1:2 vs. 1:16). Over the entire process, we measured a five-titer-step isoagglutinin reduction in laboratory-scale Cohn-like fractionation; the largest reduction was observed between Fraction (F)II+III and FII. An overall four-titer-step reduction was recorded in the industry-scale process. In contrast, none of the steps of the chromatography-based manufacturing process caused any decrease in anti-A isoagglutinin content. Similar results were obtained for anti-B isoagglutinin reduction., Conclusion: Unlike Cohn-like fractionation, chromatography-based IVIG manufacturing processes do not have an intrinsic capacity for isoagglutinin reduction. The addition of dedicated isoagglutinin reduction steps may help minimize the potential risk of hemolysis in IVIG-treated patients., (© 2015 AABB.)

Study Objective: To measure plasma nitrate concentrations after inhalation of nitric oxide for treatment of adult respiratory distress syndrome (ARDS) and sepsis., Design: Prospective pilot study., Setting: Intensive care unit at a university-affiliated hospital., Patients: Nine consecutive medical intensive care unit patients with ARDS and sepsis., Interventions: After diagnosis of ARDS, all patients received a balloon-tipped triple-lumen thermodilution pulmonary artery catheter (Baxter Healthcare Corp, Irvine, CA). Inhaled nitric oxide was initiated starting at a dose of one part per million and titrated according to the maximal achievable increase in arterial oxygenation. Hemodynamic measurements including intrapulmonary shunt fraction and blood as analyses were performed before nitric oxide application, as well as 1 and 24 hours after starting nitric oxide, respectively. Plasma samples for determination of nitrate were taken from the arterial line and from the pulmonary thermodilution catheter and analyzed using high-performance liquid chromatography., Measurements and Main Results: Eight of 9 patients were nitric oxide responders (intrapulmonary shunt decrease >5%). There was no statistically significant increase in nitrate plasma concentration measured both in peripheral arterial and in mixed venous blood with inhaled nitric oxide up to a concentration of 40 parts per million., Conclusion: Inhalation of nitric oxide in patients with ARDS and sepsis does not result in increased plasma nitrate concentrations.

Background: Ofloxacin is a quinolone administered to patients with severe infections. Pharmacokinetic data on ofloxacin in critically ill patients on renal replacement therapy are sparse and conflicting., Methods: Eight patients with anuric acute renal failure were administered 400 mg of ofloxacin intravenously. The pharmacokinetics of ofloxacin was analyzed during continuous venovenous hemofiltration (CVVH) with a high-flux polysulfone membrane. Serum and ultrafiltrate levels of ofloxacin were measured by means of high-performance liquid chromatography., Results: Mean serum ofloxacin concentration peak was 5.5 +/- 0.7 mg/L. Elimination half-life, hemofiltration clearance, and total removal were 2.8 +/- 0.5 hours, 89.9 +/- 4.5 mL/min, and 76.9% +/- 7.1%, respectively., Conclusion: Ofloxacin is significantly and rapidly eliminated by CVVH with a high-flux polysulfone membrane.

An improved rapid method for the identification of yeasts and yeast-like fungi from clinical sources which is based on fatty acid profiles obtained by gas-liquid chromatography (GLC) is described. The fatty acid profile database is based upon internal standardisation and using the relative retention times and the retention index of the analysed fatty acids. Differentiation between yeast species was achieved by the quantitative and qualitative comparison of measured fatty acid profiles with those in the database. A total of 1024 clinical isolates were analysed by GLC to test the validity of the database. 96.2% of all tested samples were identified correctly to the species level by the improved GLC method.

Objective: Cefpirome is a new semisynthetic cephalosporin, primarily eliminated by the kidneys, that requires dosage adjustment in patients with kidney failure. The optimal dosing regimen of cefpirome in patients with continuous veno-venous hemofiltration (CVVH) is unknown., Methods: Pharmacokinetic properties of cefpirome were investigated in eight anuric patients with acute kidney failure treated by CVVH. All patients received a dosage of 2 g cefpirome every 8 hours after starting the hemofiltration with high-flux polysulfone membranes. Concentrations of cefpirome in plasma and ultrafiltrate were measured by HPLC., Results: Total clearance and hemofiltration clearance of cefpirome were 589.1 +/- 164.5 mL/min and 43.3 +/- 7.8 mL/min, respectively. Serum elimination half-life was 2.36 +/- 0.59 hours. The highest plasma drug concentration was 14.8 +/- 3.2 microg/mL, and it declined to trough levels of 3.1 +/- 0.8 microg/mL at the end of the dosing interval., Conclusion: On the basis of previously published pharmacodynamic characteristics of cefpirome and the pharmacokinetic parameters obtained in this study, we calculated a required total daily dose of 2 g every 8 hours to achieve sufficient plasma antibiotic levels to cover the majority of target pathogens. However, this dosage may be insufficient during CVVH for intermediate resistant strains of Pseudomonas aeruginosa.

Involvement of neutrophils in the control of blood parasites in malaria has been reported. Both, mononuclear phagocytes and neutrophils are known to be stimulated by cytokines such as TNF-alpha in order to augment the defence potency against the parasites. Previously, it has been shown that serum-G-CSF concentrations are increased in patients with bacterial sepsis. In vitro studies have shown that P. falciparum - infected erythrocytes induce the release of G-CSF by several cells such as endothelial cells and monocytes, however, nothing is known about G-CSF serum concentrations during the clinical course of severe P. falciparum malaria. Thus, it was the aim of the present study to investigate the time course for G-CSF serum concentrations in patients with complicated P. falciparum malaria, and to correlate these values with other mediators of inflammation and hematopoesis. Twenty-six patients suffering from complicated P. falciparum malaria were included in the study, and 20, age and sex matched, healthy volunteers were used as the negative control group. Serum samples for determination of G-CSF were taken on day 0, 7 and 14, and measured by ELISA. We found significantly increased serum concentrations of G-CSF in patients with complicated P. falciparum malaria on day 0, values decreasing to within the normal range by day 7. A significant correlation was found between G-CSF (d0) and procalcitonin, the parasite count, erythropoietin and macrophage inflammatory protein, however no correlation could be shown for the neutrophil count. In conclusion, on the day of hospital admission, elevated serum concentrations of G-CSF were detected in patients with complicated P. falciparum malaria, which might indicate a role of G-CSF in the acute defence mechanism against the parasites.

The aim of this study was to measure plasma homocysteine and laminin concentrations in patients with nonbacteremic systemic inflammatory response syndrome (SIRS) and to compare them with those of a healthy control group. Concerning laminin, significant increased concentrations could be observed in the SIRS group compared to the control group, but for homocysteine, no significance could be observed. In summary, homocysteine and laminin levels are not useful in the prediction of a patient's outcome.

The aim of this study was to determine the penetration of intravenously administered meropenem into the human aqueous humor and vitreous. Thirty patients about to undergo cataract surgery and fourteen patients about to undergo vitrectomy received a 2 g dose of meropenem before surgery. Specimens of aqueous humor or vitreous and blood were obtained intraoperatively and analyzed by high performance liquid chromatography (HPLC). The study was designed as a non-randomized prospective trial. Thirty min to 12 hr after administration, mean aqueous humor levels of 13.4 and 1.1 mg/l and vitreous levels between 8.94 and 1.08 mg/l were found, respectively. The peak concentrations are distinctly above the in vitro measured minimum inhibitory concentration of meropenem for 90% (MIC90) of almost all relevant gram-positive and gram-negative organisms, including Pseudomonas aeruginosa and Enterobacteriaceae. With regard to its broad spectrum, high antibacterial activity, and good penetration into ocular fluids, meropenem seems to be an alternative to currently used systemic drugs. Its usefulness in perioperative prophylaxis, as initial therapy after perforating or penetrating injuries, or in the therapy of bacterial endophthalmitis has yet to be proved.

Cytokines, such as tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and tumor necrosis factor-soluble receptor (TNF-sR), and adhesion molecules, e.g. vascular adhesion molecule-1 (VCAM-1) and E-selectin, play an important role in the pathogenesis of bacterial sepsis. Experimental data on cytokine expression during candidaemia are controversial. In this study, plasma concentrations of cytokines and adhesion molecules were compared between patients with sepsis due to Candida albicans and bacterial sepsis. Plasma levels of TNF-alpha, TNF-sR, IL-6, VCAM-1 and E-selectin, were determined in 20 patients with sepsis due to C. albicans, in 20 patients with bacterial sepsis, and in 20 controls on days 1, 7 and 14. On day 1, elevated plasma levels of TNF-alpha, TNF-sR and IL-6 were detected in both sepsis groups compared to controls. On day 1, VCAM-1 levels were higher, and E-selectin levels were lower in patients with Candida sepsis than in patients with bacterial sepsis (p < 0.05). At any time, VCAM-1 levels were significantly greater in patients with Candida sepsis than in patients with bacterial sepsis (p < 0.05). Non-survivors, regardless of the etiology of sepsis, had higher blood levels of IL-6, TNF-sR and E-selectin than survivors. The cytokines, TNF-alpha, IL-6 and TNF-sR, and the adhesion molecules, VCAM-1 and E-selectin, are involved in sepsis due to C. albicans as in bacterial sepsis.

Background: Nitric oxide (NO), an endogenous product of L-arginine oxidation, seems to account for the vasodilatatory effect of the endothelium-derived relaxing factor. It was the aim of the present study to measure serum nitrate concentrations, the degradation product of nitric oxide in patients with peripheral arterial occlusive disease (PAOD)., Patients and Methods: 20 patients with PAOD in Fontaine stage IIb, 10 patients in stage III and IV respectively were included in the study. Serum samples for determination of nitrate were taken at admission after fasting overnight. Nitrate concentrations were determined using a recently developed high performance liquid chromatography which allows direct measurement of nitrate. The control group comprised 14 age and risk factor matched volunteers., Results: We found significantly increased nitrate concentrations in patients with PAOD compared to the control group [stage IIb: 6.65 +/- 1.58 mumol/l; stage III: 6.94 +/- 1.85 mumol/l, stage IV: 7.05 +/- 1.16 mumol/l; control: 4.41 +/- 1.24 mumol/l], however no significance was calculated within the different PAOD groups. There was no association of either diabetes mellitus, hypertension and smoking behaviour with increased nitrate levels., Conclusion: These data might indicate that NO might be involved in adaptive vasodilatation already in the early phase of the disease. The source of nitrate in PAOD patients, however, remains unclear.

Mycophenolic acid (MPA) is nowadays in broad clinical use as a substitute for azathioprine. An immunoassay for MPA recently received approval for clinical applications. The high performance liquid chromatography (HPLC) assay for measuring MPA and its glucuronide conjugate (MPAG) we describe here is not only rapid and simple but also extremely sensitive at plasma levels obtained during standard immunosuppressive regimens. The determination of MPAG is possible without any change of the chromatographic conditions (detection wavelength of 214 nm, mobile phase: acetonitrile and 50 mmol/l o-phosphoric acid (50:50, V/V), run time: 15 min). The required equipment is a standard HPLC system including a simple UV-detector. Sample volume of 400 microl is required for both determinations. Detection limit is 0.25 micromol/l for MPA and 5 micromol/l for MPAG. Linearity is excellent for serial dilutions (0.5-25 micromol/l for MPA, 25-500 micromol/l for MPAG) and high accuracies favour the method described. More than 2000 plasma samples tested for MPA in patients after heart transplantation within one year and more than 500 samples for MPAG underline the clinical applicability of this assay.

Levels of procalcitonin (ProCT) have been found to be elevated in individuals with severe bacterial infections such as sepsis and peritonitis, and this correlates well with the severity of the disease. Recently, increased levels have been described in melioidosis and Plasmodium falciparum malaria. In this study ProCT levels were measured in 27 Thai patients with complicated malaria before and during/after treatment with artesunate and mefloquine. Initial parasite counts averaged 290,680/microl (range = 533-1,147,040). On admission, ProCT levels were elevated in all but one patient (median = 40 ng/ml, range = 0.04-662, normal values < 0.5 ng/ml). With treatment, levels decreased to 1.3 ng/ml (range = 0.01-6.5). Nitrite/nitrate levels in patients were higher than in controls throughout the study. The ProCT levels correlated with initial parasite density (P < 0.05), which is a marker of disease severity, and with nitrite/nitrate levels (P < 0.05). Based on the changes of ProCT levels over the course of the disease a possible role in the acute-phase reaction seems likely.

Nitric oxide (NO) has recently been shown to be cytotoxic to both microfilariae and adult Brugia malayi in vitro and in a murine model, as well against Onchocerca lienalis microfilariae in vitro. We studied the kinetics of nitrite/nitrate, both stable end products of NO, by high-pressure liquid chromatography during microfilaricidal chemotherapy in four filariasis (three Loa loa, and one Onchocerca volvulus) patients. High serum levels of nitrite/nitrate were released during microfilarial clearance and sustained elevated levels were observed six months after chemotherapy, suggesting a role of NO in the elimination of microfilariae in human filariasis.

The pharmacokinetic properties of meropenem were investigated in nine critically ill patients treated by continuous venovenous hemofiltration (CVVH). All patients received one dose of 1 g of meropenem intravenously. High-flux polysulfone membranes were used as dialyzers. Meropenem levels were measured in plasma and ultrafiltrate by high-performance liquid chromatography. The total body clearance and elimination half-life were 143.7 +/- 18.6 ml/min and 2.46 +/- 0.41 h, respectively. The post- to prehemofiltration ratio of meropenem was 0.24 +/- 0.06. Peak plasma drug concentrations measured 60 min postinfusion were 28.1 +/- 2.7 microgram/ml, and trough levels after 6 h of CVVH were 6.6 +/- 1.5 microgram/ml. The calculated total daily meropenem requirement in these patients with acute renal failure and undergoing CVVH was 2,482 +/- 321 mg. Based on these data, we conclude that patients with severe infections who are undergoing CVVH can be treated effectively with 1 g of meropenem every 8 h.

Previous studies have reported increased serum concentrations of nitrite/nitrate - the degradation products of nitric oxide - in Plasmodium vivax malaria and uncomplicated Plasmodium falciparum malaria. In all these studies, however, nitrite/nitrate has been measured spectrometrically using Griess reagent which carries major disadvantages in the determination of serum nitrite/nitrate. The method does not allow an exact differentiation of nitrite and biogenic amines that are physiologically present in plasma. In the present study we introduce high-performance liquid chromatography as a new, accurate and cost effective method for determination of serum nitrite/nitrate levels. Significantly increased nitrate concentrations were found in malaria patients and serum values remained above normal levels for at least 21 days. It could be shown that our HPLC method is a sensitive and cost-effective method for direct determination of nitrite/nitrate in serum samples, which is not influenced by the presence of biogenic amines.

Azithromycin was given as a single oral dose (20 mg/kg of body weight) to 12 volunteers in a crossover study with roxithromycin (8 to 12 mg/kg) and clarithromycin (8 to 12 mg/kg). Flow cytometry was used to study the phagocytic functions and the release of reactive oxygen products following phagocytosis by neutrophil granulocytes prior to administration of the three drugs, 16 h after azithromycin administration, and 3 h after clarithromycin and roxithromycin administration. Phagocytic capacity was assessed by measuring the uptake of fluorescein isothiocyanate-labeled bacteria. Reactive oxygen generation after phagocytosis of unlabeled bacteria was estimated by the amount of dihydrorhodamine 123 converted to rhodamine 123 intracellularly. Azithromycin resulted in decreased capacities of the cells to phagocytize Escherichia coli (median [range], 62% [27 to 91%] of the control values; P < 0.01) and generate reactive oxygen products (75% [34 to 26%] of the control values; P < 0.01). Clarithromycin resulted in reduced phagocytosis (82% [75 to 98%] of control values; P < 0.01) but did not alter reactive oxygen production (84% [63 to 113%] of the control values; P > 0.05). Roxithromycin treatment did not affect granulocyte phagocytosis (92% [62 to 118%] of the control values; P > 0.05) or reactive oxygen production (94% [66 to 128%] of the control value; P > 0.05). No relation between intra- and/or extracellular concentrations of azithromycin and/or roxithromycin and the polymorphonuclear phagocyte function and/or reactive oxygen production existed (P > 0.05 for all comparisons). These results demonstrate that the accumulation of macrolides in neutrophils can suppress the response of phagocytic cells to bacterial pathogens after a therapeutic dose.