Effects of AIDS and gender on steady-state plasma and intrapulmonary ethambutol concentrations.

Our objective was to study the steady-state plasma and intrapulmonary orally administered ethambutol concentrations in healthy volunteers and subjects with AIDS. Ethambutol (15 mg/kg of body weight) was administered orally once daily to 10 men with AIDS, 10 healthy men, 10 women with AIDS, and 10 healthy women. The mean (+/-standard deviation [SD]) CD4 cell count for the 20 subjects with AIDS was (350 +/- 169) x 10(6) cells per liter. Blood was obtained for drug assay 2 h after the last dose and at the completion of bronchoalveolar lavage, performed 4 h after the last dose. Standardized bronchoscopy was performed without systemic sedation. The volume of epithelial lining fluid (ELF) was calculated by the urea dilution method. The total number of alveolar cells (AC) was counted in a hemocytometer, and differential cell counting was performed after cytocentrifugation. Ethambutol was measured by a new, sensitive and specific liquid chromotography-mass spectrometry method. The presence of AIDS, as defined in this study, or gender was without significant effect on the concentrations of ethambutol in plasma at 2 or 4 h or in ELF at 4 h following the last dose. Plasma drug concentrations (mean +/- SD) at 2 and 4 h were 2.1 +/- 1.2 and 2.1 +/- 0.8 microg/ml, respectively, and both values were not significantly different from the concentration of ethambutol in ELF at 4 h (2.2 +/- 1.1 microg/ml). The concentration of ethambutol was significantly greater in AC in all four groups (range, 44.5 +/- 15.6 to 82.0 +/- 39.4 microg/ml) than in ELF or plasma and was approximately 30 to 240 times the reported MIC for ethambutol-susceptible strains of Mycobacterium tuberculosis. The AC ethambutol concentration (mean +/- SD) in the smoking women (97.2 +/- 32.1 microg/ml) was more than twice the concentration in all other nonsmoking subjects (45.2 +/- 16.8 microg/ml) combined (P < 0.05). Two- and 4-h concentrations of ethambutol in plasma were not affected by AIDS status or gender. The high AC/plasma and AC/ELF concentration ratios suggest that substantial antimycobacterial activity resides in these cells. The data confirm earlier observations of active transport ex vivo of ethambutol into pulmonary macrophages.

Effects of AIDS and gender on steady-state plasma and intrapulmonary ethionamide concentrations.

Ethionamide, 250 mg every 12 h for a total of nine doses, was administered to 40 adult volunteers (10 men with AIDS, 10 healthy men, 10 women with AIDS, and 10 healthy women). Blood was obtained for drug assay prior to administration of the first dose, 2 h after the last dose, and at the completion of standardized bronchoscopy and bronchoalveolar lavage, which were performed 4 h after the last dose. Ethionamide was measured in epithelial lining fluid (ELF) and alveolar cells (AC) using a new mass spectrometric method. The presence of AIDS or gender was without significant effect on the concentrations of ethionamide in plasma, AC, or ELF. Plasma concentrations (mean +/- standard deviation [SD]) were 0.97 +/- 0.65 and 0.65 +/- 0.35 microg/ml at 2 and 4 h after the last dose, respectively, and both values were significantly greater than the concentration of ethionamide in AC (0.38 +/- 0.47 microg/ml) (P < 0. 05). The concentration of ethionamide was significantly greater in ELF (5.63 +/- 3.8 microg/ml) than in AC or plasma at 2 and 4 h and was approximately 10 to 20 times the reported MIC for ethionamide-susceptible strains of Mycobacterium tuberculosis. For all 40 subjects, the ELF/plasma concentration ratios (mean +/- SD) at 2 and 4 h were 8.7 +/- 11.7 and 9.7 +/- 5.6, respectively. We conclude that the absorption of orally administered ethionamide, as measured in this study, was not affected by gender or the presence of AIDS. Ethionamide concentrations were significantly greater in ELF than in plasma or AC, suggesting that substantial antimycobacterial activity resides in this compartment.

Single-dose intrapulmonary pharmacokinetics of rifapentine in normal subjects.

The intrapulmonary pharmacokinetics of rifapentine were studied in 30 volunteers who received a single, oral dose of rifapentine (600 mg). Subgroups of five subjects each underwent bronchoscopy and bronchoalveolar lavage (BAL) at timed intervals following drug administration. Drug concentrations, including the concentration of the primary metabolite 25-desacetyl rifapentine, were determined in plasma, BAL fluid, and alveolar cells (AC) by high-pressure liquid chromatography. The concentrations in epithelial lining fluid (ELF) were calculated by the urea diffusion method. The concentration-time data were fit to two-compartment (plasma) or one-compartment (AC and ELF) models. The peak concentrations in plasma, ELF, and AC, 26.2, 3. 7, and 5.3 microg/ml, respectively, occurred at 5, 5, and 7 h after drug administration, respectively. The half-lives and areas under the curve for plasma, ELF, and AC were 18.3 h and 520 microg. h/ml, 20.8 h and 111 microg. h/ml, and 13.0 h and 133 microg. h/ml, respectively. Although the intrapulmonary rifapentine concentrations were less than the plasma rifapentine concentrations at all time periods, they remained above the proposed breakpoint for M. tuberculosis (0.5 microg/ml) for the 48-h observation period. These data provide a pharmacokinetic rationale for extended-interval dosing. The optimum dosing regimen for rifapentine will have to be determined by controlled clinical trials.

Cibenzoline for symptomatic ventricular arrhythmias: a prospective, randomized, double-blind, placebo controlled trial and a long term open label study.

To assess the efficacy and safety of cibenzoline, 18 patients with symptomatic premature ventricular complexes (30/h or more) on baseline 48 h Holter monitors were randomized to oral cibenzoline versus placebo. The cibenzoline and placebo doses were increased from 130 to 160 mg bid after one week if premature ventricular complex (PVC) suppression was less than 75%. The double-blind placebo controlled phase (phase 1) lasted for two weeks prior to the open label long term study (phase 2). Efficacy was defined as suppression of at least 75% PVCs, 85% couplets and 90% ventricular tachycardia on follow-up 48 h Holter monitoring. At the six month mark of phase 2, patients were placed on placebo for seven days to evaluate for spontaneous resolution of PVCs. Of the seven patients on cibenzoline in phase 1, four had a positive response, one had partial control (73% suppression of PVCs) and two noted dizziness and withdrew. Of the 11 patients randomized to placebo, nine noted no change, two had a significant decrease in PVCs and one noted dizziness and withdrew. Fifteen patients were enrolled in phase 2 on open label cibenzoline at 130 to 160 mg bid. At a mean follow-up of 17 +/- 4 months (range 12 to 25), eight patients had control of symptomatic ventricular arrhythmias without adverse effects, three patients did not respond to cibenzoline, one had PVC recurrence after initial control on cibenzoline, one died of myocardial infarction without arrhythmias, one had spontaneous resolution of PVCs and one was withdrawn because of poor compliance. In conclusion, cibenzoline is effective in controlling symptomatic PVCs and is moderately well tolerated.

Antiarrhythmic efficacy of desipramine.

The effect of desipramine on chronic ventricular ectopic depolarizations (VEDs) was studied in 10 patients with at least 30 VEDs per hour. A single-blind, placebo-controlled, dose-ranging protocol was followed. Efficacy was defined as a decrease in VED frequency of at least 75%, base on three 24 hour ambulatory ECGs obtained on each dose. Among seven patients with analyzable data, one responded to 75 mg daily, and three others responded to 150 mg daily. Six of the seven patients demonstrated decreases in VED frequency with increases in desipramine serum concentration. Among five patients with episodes of nonsustained ventricular tachycardia, desipramine completely abolished the episodes in two, and reduced the frequency of episodes by at least 90% in two others. Adverse reactions were common, and necessitated drug discontinuation or dose reduction in five patients. Desipramine has an antiarrhythmic effect in patients with chronic ventricular ectopy, but its clinical utility is limited by adverse effects.