Steady-state pharmacokinetics of lamivudine once-daily versus twice-daily dosing in Chinese HIV-infected patients.

Objective: The present study aimed to compare the pharnnacokinetics of lamivudine in 300 mg once-daily and 150 mg twice-daily dosing regimens in HIV-infected Chinese patients. Methods: HIV-infected patients received lamivudine 300 mg once daily or 150 mg twice daily as part of a highly active antiretroviral therapy regimen. After the patients received lamivudine for at least 3 months, serial blood samples were collected for 24 hours. The samples were measured by a validated high-performance liquid chromatography (HPLC) assay. The pharmacokinetics of once-daily versus twice-daily dosing was evaluated by noncompartment models. Results: Ten patients received lamivudine 300 mg once daily and 5 patients received 150 mg twice daily. The C-max was significantly higher in the once-daily arm than the twice-daily arm (2.23 vs 1.61 mu g/mL, P < .05), whereas the C-min was markedly lower (0.05 vs 0.12 mu g/mL, P < .05). The half-lives were 3.32 hours and 2.62 hours, and AUC(24) values were 11.8 mu g/mL.h and 13.0 mu g/mL.h in the 300 mg once-daily and 150 mg twice-daily regimens, respectively (P > .05). Conclusion: The shorter half-life was observed first in Chinese HIV patients with once- and twice-daily regimens. The 300 mg once-daily regimen was associated with lower trough concentrations and remarkable interpatient variability. Further studies in large groups of HIV patients are needed to confirm the influence of shorter half-lives in Chinese patients on efficacy and toxicity.