Pharmacokinetics of lamivudine administered alone and with trimethoprim-sulfamethoxazole.

OBJECTIVE: To determine the effect of multiple dosing of combined sulfamethoxazole and trimethoprim on the single-dose pharmacokinetics of lamivudine. METHODS: Fourteen subjects with human immunodeficiency virus who had CD4+ cells > or = 200/mm3 received two single doses of 300 mg lamivudine, separated by 7 to 14 days, in a randomized two-day crossover study. Treatment consisted of lamivudine alone versus trimethoprim-sulfamethoxazole (160/180 mg) daily on days 1 through 4 followed by lamivudine plus trimethoprim-sulfamethoxazole on day 5. Blood and urine were collected over 24 to 32 hours to determine lamivudine, trimethoprim, sulfamethoxazole, and N-4-acetylsulfamethoxazole concentrations. RESULTS: Coadministration of a single dose of lamivudine and trimethoprim-sulfamethoxazole after daily dosing for 5 days altered the pharmacokinetics of lamivudine. A 43% increase in area under the concentration-time curve (AUC infinity) and a 35% decrease in renal clearance (CLR) were observed when lamivudine was coadministered with trimethoprim-sulfamethoxazole compared with lamivudine alone. The geometric least-squares trimethoprim-sulfamethoxazole were as follows: AUC infinity, 10,124 (9,432-10,866) and 14,448 (13,461-15,508) ng . hr/ml, respectively; CLR, 16.6 (14.1-19.4) and 10.8 (9.5-12.6) L/hr, respectively. Coadministration did not significantly alter the pharmacokinetics of trimethoprim or sulfamethoxazole. CONCLUSIONS: Coadministration of lamivudine with trimethoprim-sulfamethoxazole resulted in an increased AUC infinity and a decreased CLR of lamivudine. However, given the favorable safety profile of lamivudine, it is unlikely that this interaction will result in a significant increase in concentration-related toxicity at the doses studied.

Pharmacokinetics, absolute bioavailability, and absorption characteristics of lamivudine.

Lamivudine is a novel cytosine nucleoside analog, reverse transcriptase inhibitor that has shown activity against human immunodeficiency virus (HIV) types 1 and 2 and hepatitis B virus in vitro. This study was conducted to compare the absolute bioavailability, pharmacokinetics, and absorption characteristics of oral solution, 100-mg capsule, and 100-mg tablet formulations of lamivudine with those of intravenous lamivudine. Twelve patients with HIV were enrolled in a single-center, randomized, open-label, four-way cross-over study. Treatment arms consisted of 100 mg intravenous lamivudine (administered over 1 hour), 100 mg oral lamivudine (1 mg/mL), a 100-mg capsule, and a 100-mg tablet, each followed by a 3- to 14-day washout period. Serial blood samples over 24 hours were obtained after each dose administration. Serum concentration data were analyzed to determine pharmacokinetic parameter estimates including area under the curve (AUC), terminal half-life (t1/2), mean residence time (MRT) for each formulation, systemic clearance, oral clearance, and apparent volume of distribution (Vd). Absolute bioavailability and in vivo mean absorption time (MAT) and mean dissolution time (MDT) were calculated for the oral formulations. Deconvolution techniques were used to calculate the input rate for the oral solution, capsule, and tablet. The two one-sided t test was used to determine bioequivalency among oral formulations with respect to logarithmic transformed estimates of AUC and maximum peak concentration (Cmax). Mean (CV) systemic clearance and Vdss after intravenous administration of lamivudine were 22.6 L/h (15%) and 99 L (28%), respectively; mean t1/2 ranged from 8.41 to 9.11 hours for all formulations; and MRT ranged from 4.42 to 5.77 hours for all formulations. Mean absolute bioavailability ranged from 86% to 88% for the oral solution, capsule, and tablet. All oral formulations were considered bioequivalent for AUC and Cmax. The MAT was 1.32 hour for the oral solution, and MDT was 0.03 and -0.11 hours for the capsule and the oral solution, respectively. The oral formulations of lamivudine examined in this study demonstrated acceptable bioavailability for oral administration. The solid oral formulations (capsule and tablet) show rapid dissolution properties with an absorption rate similar to or exceeding those observed with the oral solution. This suggests that dissolution is not an important factor for the rate of absorption of lamivudine. The use of deconvolution techniques using PCDCON provides valuable insight into the absorption characteristics of lamivudine.

Two-day therapy with cefuroxime axetil is effective for urinary tract infections in children.

Short-course therapy for pediatric urinary tract infection (UTI) remains controversial. The present study was undertaken to compare the effectiveness of cefuroxime axetil (Ceftin) as short-course (2-day) versus conventional (10-day) therapy for uncomplicated pediatric UTIs. In a randomized, controlled, prospective study, we enrolled 50 children, 2-11 years of age, to receive oral cefuroxime axetil, 125 mg twice a day, for either 2 or 10 days. UTI was defined as at least 10(5) colonies/ml of a single pathogen isolated on clean catch, or at least 10(4) colonies/ml on a catheterized specimen. A 10-fold or greater reduction in colony count of the initially isolated organism (3-5) days after stopping therapy was considered a bacteriologic success, as long as the absolute colony count was below the threshold for UTI described above. Patients were followed for 15 months with multiple repeat urine cultures and radiologic studies. Twenty-five of the 50 patients enrolled were withdrawn, including 12 for initially inadequate colony counts. Eight of 12 patients in the short-course group (67%), versus 12 of 14 in the conventional-therapy group (86%), were initial bacteriological successes, a nonsignificant difference. All 37 initially isolated uropathogens were sensitive to cefuroxime axetil in vitro. Cefuroxime axetil is an effective antimicrobial for uncomplicated pediatric UTIs. Two-day therapy with cefuroxime axetil appears to be as effective as 10-day therapy, although sample size was limited in this study.

Clinical comparison of cefuroxime axetil and amoxicillin/clavulanate in the treatment of patients with acute bacterial maxillary sinusitis.

PURPOSE: This multicenter study compared the clinical and bacteriologic efficacy of two oral antibiotics, cefuroxime axetil and amoxicillin/clavulanate, in the treatment of acute bacterial maxillary sinusitis. PATIENTS AND METHODS: Three hundred seventeen patients with clinical and radiographic evidence of acute maxillary sinusitis were enrolled at nine centers and were randomly assigned to receive 10 days of treatment with cefuroxime axetil 250 mg twice daily (n = 157) or amoxicillin/clavulanate 500 mg three times daily (n = 160). Patients were assessed for both clinical and bacteriologic responses once during treatment (5 to 7 days) and twice after treatment (1 to 3 days and 4 weeks). Bacteriologic assessments were based on needle aspirates of the maxillary sinus obtained pretreatment and, when possible, at the first posttreatment visit. RESULTS: Organisms were isolated from the pretreatment sinus aspirates of 198 of 317 (62%) patients, with the primary isolates being Streptococcus pneumoniae (22%), Haemophilus spp. (17%), Staphylococcus aureus (13%), and Haemophilus influenzae (10%). A satisfactory clinical outcome (cure or improvement) was achieved in 85% (98 of 115) and 82% (102 of 124) of the clinically evaluable patients treated with cefuroxime axetil or amoxicillin/clavulanate, respectively (P = 0.446). With respect to the eradication of the bacterial pathogens, a satisfactory outcome (cure or presumed cure) was obtained in 84% (31 of 37) and 87% (34 of 39) of bacteriologically evaluable patients treated with cefuroxime axetil or amoxicillin/clavulanate, respectively (p = 0.567). Treatment with amoxicillin/clavulanate was associated with a significantly higher incidence of drug-related adverse events (13% versus 3%, p = 0.001), particularly diarrhea (8% versus 1%, p = 0.001). Two patients in the cefuroxime axetil group and three patients in the amoxicillin/clavulanate group withdrew from the study due to adverse events. CONCLUSIONS: Our results indicate that cefuroxime axetil twice a day is as effective as amoxicillin/clavulanate three times a day in the treatment of acute bacterial maxillary sinusitis but produces fewer adverse effects.