Factors Contributing to the Antiviral Effectiveness of Tenofovir.

Over 1 million people in the United States are living with human immunodeficiency virus (HIV), which may progress to AIDS. The use of antiviral therapy has successfully controlled the rate of viral growth in patients. Antiviral agents improve the quality of life and reduce the potential for spreading HIV; HIV is currently considered a chronic disease provided patients are compliant with their antiviral medications. Tenofovir is a nucleoside transcriptase inhibitor that prevents viral replication and is approved for treatment of HIV and chronic hepatitis B infection. Tenofovir is an antiretroviral drug used alone and in combination with other nucleoside reverse-transcriptase inhibitor agents to lower viral load in HIV patients. Tenofovir is administered as a prodrug to increase bioavailability. The prodrug forms of tenofovir are tenofovir disoproxil fumarate, approved in 2001, and tenofovir alafenamide, approved in 2016. Tenofovir is extensively used in controlling HIV, as it is administered once daily, allowing for good compliance. This minireview discusses the impact of food, age, and drug transporters on tenofovir absorption and clearance. The changes in dosing that are needed in the presence of renal impairment, which is a common occurrence with HIV chronic disease progression, will also be discussed. The potential special conditions occurring with fixed-combination doses containing tenofovir will also be reviewed, including the use of cobicistat, a cytochrome P450 3A4 inhibitor. The short review also addresses some newer preparations using niosomes to improve tenofovir absorption and delivery to the target cells.