Tenofovir Disoproxil Fumarate – Antiviral Therapy

Tenofovir Disoproxil Fumarate (TDF) is a potent nucleotide reverse transcriptase inhibitor (NRTI) and a prodrug of tenofovir. It is one of the most thoroughly studied and widely used medications for the treatment of HIV infection and chronic Hepatitis B worldwide.

The mechanism of action involves the conversion of disoproxil fumarate into tenofovir after oral administration, which is then phosphorylated within cells to its active diphosphate form. Tenofovir diphosphate inhibits HIV-1 reverse transcriptase and Hepatitis B virus polymerase by competing with natural substrates and causing DNA chain termination. This prevents the virus from replicating and infecting new cells. TDF is effective against a broad range of viral strains and possesses a high barrier to resistance.

The drug is available in tablet form and is frequently included in "once-daily" fixed-dose combination regimens due to its long half-life.

Wikipedia page

Indications

Tenofovir Disoproxil Fumarate is indicated for the treatment of adults and pediatric patients (weight-dependent):

HIV-1 Infection: treatment in combination with other antiretroviral agents.
Pre-Exposure Prophylaxis (PrEP): reducing the risk of HIV-1 acquisition in high-risk individuals.
Chronic Hepatitis B: treatment of compensated and decompensated liver disease in adults and adolescents.

Dosage and administration

TDF dosing requires caution, particularly in patients with renal impairment.

Standard Dose: 300 mg (equivalent to 245 mg of tenofovir disoproxil) once daily.
Administration: taken orally, preferably with food to enhance absorption, though it may be taken without regard to meals.
Renal Adjustment: for patients with creatinine clearance less than 50 mL/min, the dosing interval is increased (e.g., to every 48 hours) or the dose is reduced.
Pediatric Use: dosage is determined by a physician based on the patient's body weight.

The use of TDF is restricted in the following clinical situations:

Hypersensitivity: allergic reactions to tenofovir or any tablet components.
Severe Renal Impairment: creatinine clearance less than 30 mL/min (unless on hemodialysis).
Pediatric Age: under 2 years for Hepatitis B and varying age limits depending on the region for HIV.
Co-administration: must not be taken with other products containing tenofovir (e.g., TAF) or adefovir.

Long-term TDF therapy requires monitoring of renal and bone health:

Gastrointestinal: nausea, vomiting, diarrhea, and flatulence.
Renal: risk of renal impairment and Fanconi syndrome (monitoring of creatinine and phosphate is required).
Bone Health: decrease in bone mineral density (osteomalacia, fracture risk).
General Symptoms: asthenia, dizziness, and headache.
Metabolic: hypertriglyceridemia and, rarely, lactic acidosis.

Frequently Asked Questions

Tenofovir disoproxil fumarate (TDF) is an antiviral agent belonging to the class of nucleotide reverse transcriptase inhibitors (NRTIs). It mimics the natural DNA building blocks that the virus uses to replicate. When the virus attempts to incorporate TDF into its genetic chain, the replication process is terminated, effectively halting viral production.

TDF exhibits dual activity: it is highly effective against both the human immunodeficiency virus (HIV-1 and HIV-2) and the hepatitis B virus (HBV). This makes it a cornerstone of treatment for patients with co-infection (carrying both viruses simultaneously).

Long-term use of TDF can lead to a decrease in bone mineral density (osteoporosis) and renal impairment (including rare cases of Fanconi syndrome). Patients are advised to regularly monitor serum creatinine levels and urine phosphorus. In some cases, a physician may prescribe calcium and vitamin D supplements.

The standard dose is 300 mg once daily. The drug is best absorbed when taken with a meal, although this is not strictly required. It is important to swallow the tablet whole and take it at the same time every day to maintain consistent protective levels in the body.

Yes, tenofovir disoproxil fumarate is a primary component of pre-exposure prophylaxis (PrEP) programs. When taken by HIV-negative individuals at high risk, it prevents the virus from establishing an infection after exposure. It is also used for post-exposure prophylaxis (PEP) if started within 72 hours of a potential exposure.