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# Tenofovir Disoproxil Fumarate (TDF)
## Overview
Tenofovir disoproxil fumarate (TDF) is a nucleotide analog reverse transcriptase inhibitor (NtRTI). It is a prodrug of tenofovir.
## Primary Indications
* Treatment of Human Immunodeficiency Virus (HIV) infection in combination with other antiretroviral agents.
* Treatment of chronic Hepatitis B virus (HBV) infection.
## Adult Dosing
* **HIV Infection:** 300 mg orally once daily.
* **Chronic HBV Infection:** 300 mg orally once daily.
## Pediatric Dosing
* **HIV Infection:**
* **Ages 2 to <12 years:** 10 mg/kg orally once daily, not to exceed 300 mg per dose.
* **Ages 12 years and older:** 300 mg orally once daily.
* **Chronic HBV Infection:** Dosing for pediatric patients is not established.
## Dose Adjustments
* **Renal Impairment:** Dose adjustment is required based on creatinine clearance (CrCl).
* CrCl 30-49 mL/min: 300 mg every 48 hours.
* CrCl <30 mL/min or end-stage renal disease requiring dialysis: 300 mg every 72 hours (or 300 mg once weekly after dialysis).
* *Note:* Closely monitor renal function.
## Contraindications
* Hypersensitivity to tenofovir disoproxil fumarate or any component of the formulation.
## Adverse Effects
* **Common:** Diarrhea, nausea, vomiting, rash, headache.
* **Serious:**
* **Nephrotoxicity:** Acute renal failure, Fanconi syndrome.
* **Hepatotoxicity:** Lactic acidosis, severe hepatomegaly with steatosis.
* **Bone Mineral Density:** Decreased bone mineral density (osteomalacia).
* Immune reconstitution inflammatory syndrome (IRIS).
## Key Drug Interactions
* **Nephrotoxic agents:** Concomitant use with drugs that are potentially nephrotoxic (e.g., aminoglycosides, NSAIDs, certain antivirals) may increase the risk of renal toxicity. Separate administration if possible.
* **Didanosine:** Increased risk of pancreatitis and elevated plasma concentrations of didanosine. Avoid concomitant use.
* **Lopinavir/Ritonavir:** Ritonavir may increase tenofovir concentrations. Monitor for adverse effects.
## Monitoring
* **Baseline and periodic renal function:** Serum creatinine, BUN, and urinalysis.
* **Baseline and periodic electrolytes.**
* **Baseline and periodic bone mineral density.**
* **Liver function tests:** Especially in patients with HBV or co-infected with HCV.
* **HIV viral load and CD4 count** in HIV-infected patients.
* **HBV viral load** in HBV-infected patients.
## Clinical Pearls
* TDF is associated with a higher incidence of renal and bone adverse events compared to tenofovir alafenamide (TAF). Consider TAF in patients with pre-existing renal or bone disease.
* TDF should be taken with a full glass of water, preferably with a meal.
* Discontinuation in patients with HBV may lead to severe exacerbation of hepatitis.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making therapeutic decisions. Local protocols may dictate specific dosing or monitoring requirements.
