Luther Gwaza1,2, John Gordon3, Jan Welink4, Henrike Potthast5, Hubert Leufkens1,4, Matthias Stahl6, Alfredo García-Arieta7. 1. Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht, the Netherlands. 2. Medicines Control Authority of Zimbabwe, Harare, Zimbabwe. 3. Division of Biopharmaceutics Evaluation, Bureau of Pharmaceutical Sciences, Therapeutic Products Directorate, Health Canada, Ottawa, Canada. 4. Medicines Evaluation Board, Utrecht, the Netherlands. 5. Sub department of Biostatistics and Pharmacokinetics, Federal Institute for Drugs and Medical Devices, Bonn, Germany. 6. The Prequalification of Medicines Programme Quality Assurance and Safety: Medicines, Essential Medicines and Health Products, World Health Organization, Geneva, Switzerland. 7. División de Farmacología y Evaluación Clínica, Departamento de Medicamentos de Uso Humano, Agencia Española de Medicamentos y Productos Sanitarios, Madrid, Spain.
Abstract
BACKGROUND: The scaling-up of access to antiretroviral therapy, particularly in low- to middle-income countries, was facilitated by the introduction and widespread use of generic antiretroviral medicines and fixed-dose combinations. Generic medicines are approved by regulatory authorities based on the demonstration of bioequivalence with the innovator or reference product, as well as meeting quality standards. In clinical practice, however, it is not unusual for generics to be interchanged between each other. This study investigated the differences in bioavailability between WHO-prequalified first-line antiretroviral generics by means of adjusted indirect comparisons to ensure interchangeability between these generics. METHODS: Data on 34 products containing emtricitabine, tenofovir disoproxil fumarate, lamivudine and efavirenz in single formulations or fixed-dose combinations were included in the analysis. The 90% CI for the adjusted indirect comparisons was calculated using the homoscedastic method that uses the conventional t-test, and assumes homogeneity of variances between the studies and small sample sizes. The combined standard deviation of both bioequivalence studies was calculated from the variability of each individual study. RESULTS: The adjusted indirect comparisons between generics showed that the differences, expressed as 90% CIs, are less than 30%. Confidence in the interchangeability of two generic products was reduced if the mean difference between the test and reference in the original studies is more than 10%. CONCLUSIONS: From a bioequivalence perspective, the generic antiretroviral medicines prequalified by WHO are interchangeable with the reference, as well as between each other without safety or efficacy concerns.
BACKGROUND: The scaling-up of access to antiretroviral therapy, particularly in low- to middle-income countries, was facilitated by the introduction and widespread use of generic antiretroviral medicines and fixed-dose combinations. Generic medicines are approved by regulatory authorities based on the demonstration of bioequivalence with the innovator or reference product, as well as meeting quality standards. In clinical practice, however, it is not unusual for generics to be interchanged between each other. This study investigated the differences in bioavailability between WHO-prequalified first-line antiretroviral generics by means of adjusted indirect comparisons to ensure interchangeability between these generics. METHODS: Data on 34 products containing emtricitabine, tenofovir disoproxil fumarate, lamivudine and efavirenz in single formulations or fixed-dose combinations were included in the analysis. The 90% CI for the adjusted indirect comparisons was calculated using the homoscedastic method that uses the conventional t-test, and assumes homogeneity of variances between the studies and small sample sizes. The combined standard deviation of both bioequivalence studies was calculated from the variability of each individual study. RESULTS: The adjusted indirect comparisons between generics showed that the differences, expressed as 90% CIs, are less than 30%. Confidence in the interchangeability of two generic products was reduced if the mean difference between the test and reference in the original studies is more than 10%. CONCLUSIONS: From a bioequivalence perspective, the generic antiretroviral medicines prequalified by WHO are interchangeable with the reference, as well as between each other without safety or efficacy concerns.