A Comparison of Tenofovir Predose Concentrations in Generic Pre-exposure Prophylaxis Formulations: A Short Communication.

BACKGROUND: There is extensive evidence to show that pre-exposure prophylaxis (PrEP) using tenofovir disoproxil fumarate (TDF)-based formulations dramatically reduces the risk of HIV acquisition among individuals without HIV infection. Here, the authors aim to compare tenofovir plasma predose concentrations in subjects taking PrEP daily versus on demand and using different TDF-based generic formulations. METHODS: Subjects providing informed signed consent for the measurement of tenofovir plasma levels were included in the study. Predose drug concentrations were stratified according to PrEP administration and the type of TDF-based formulation. The control group consisted of patients with HIV infection who were matched for renal function and were administered branded TDF that was not combined with boosted-antiretroviral drugs. RESULTS: The study consisted of 100 subjects (mean age, 39 ± 10 years; body weight, 77 ± 11 kg). A wide distribution in tenofovir predose concentrations was observed, with values ranging from 17 to 297 ng/mL (coefficient of variation 77%). No significant differences were noted in tenofovir predose concentrations between subjects who were administered PrEP daily (n = 75) or on demand (n = 25) [94 (35-255) versus 104 (37-287) ng/mL; P = 0.476]. Comparable tenofovir predose concentrations were found between patients with HIV infection (n = 220) who were administered branded TDF and those without HIV infection who were treated with 5 different generic TDF-based formulations with generics-to-branded ratios. These were always within the range of 80%-125% and were used to define bioequivalence. CONCLUSIONS: The marketed generic formulations of TDF delivered tenofovir plasma predose concentrations comparable with those delivered by branded formulations.

Assessment of Antiepileptic Drug Concentrations in HIV-Infected versus HIV-Negative Patients: A Retrospective Analysis.

INTRODUCTION: A higher rate of subtherapeutic psychotropic drug concentrations was recently found in HIV-infected versus HIV-negative patients. In this study, we sought to investigate if this trend could also apply to antiepileptic drugs. METHODS: Overall, 700 HIV-infected patients were screened during the first 2 years after the introduction of our outpatient polytherapy management service (Gestione Ambulatoriale Politerapie [GAP]) in the search for subjects with antiepileptic drug trough concentration assessments. The distribution of such concentrations was compared with that in HIV-negative patients monitored over the same period. RESULTS: The search identified 97 HIV-infected patients concomitantly receiving antiretroviral and antiepileptic drugs, for a total of 310 drug measurements. Overall, 30%, 64% and 6%, versus 28%, 65% and 7%, of the antiepileptic concentrations measured in HIV-infected versus HIV-negative patients (1090 patients, for a total of 3488 antiepileptic concentrations measured) were below, within, or above the therapeutic targets, respectively. The antiepileptic drug valproate was associated with the highest risk of subtherapeutic drug concentrations, with 57% and 46% of determinations below the therapeutic range in HIV-positive and HIV-negative patients, respectively. Remarkably, the concentrations of valproate were significantly lower in HIV-infected versus HIV-negative patients (47.9 ± 21.2 versus 53.9 ± 21.6 mg/L; p < 0.05). CONCLUSION: In our retrospective study, most HIV-infected patients had antiepileptic drug concentrations falling within the therapeutic targets, with the exception of valproate, which was associated with a higher rate of subtherapeutic concentrations compared with other antiepileptic drugs.