Formulation and characterization of a fixed-dose microemulsion containing efavirenz, emtricitabine, and tenofovir

Despite a marked decrease in HIV/AIDS-related mortality, HIV remains one of the leading causes of death in specific populations. Despite concerted efforts to find a cure for HIV, to date, none exists. Current antiretroviral therapy inhibits replication of the virus without completely eradicating it. The successful inhibition of viral replication is only achieved using a combination of antiretrovirals, which inhibit viral replication at different stages of the HIV lifecycle. Efavirenz (EFV), emtricitabine (FTC), and tenofovir disoproxil fumarate (TDF) is one combination used for HIV management. The development of a novel fixed-dose microemulsion formulation of EFV, FTC, and TDF was undertaken. Microemulsions (ME) were manufactured using phase titration and drug loading, particle size, transparency, Zeta potential, and pH were determined. Transmission Electron Microscopy was used to visualize the microemulsion. <i>In vitro</i> release testing was used to evaluate active pharmaceutical ingredient release behavior. The optimized ME had an average Zeta potential of 33.8 mV and droplet size of 117 nm, determined using Dynamic Light Scattering and confirmed using Transmission Electron Microscopy. Powder X-ray diffraction and Differential Scanning Calorimetry analysis revealed the presence of a molecular dispersion of drugs. These findings demonstrate the potential value of using ME as a fixed-dose combination technology for the delivery of EFV, FTC, and TDF.