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# Tenofovir Disoproxil Fumarate (TDF)
## Overview
Tenofovir disoproxil fumarate (TDF) is a nucleotide analog reverse transcriptase inhibitor (NtRTI) used in the treatment of HIV-1 infection and chronic Hepatitis B virus (HBV) infection.
## Primary Indications
* Treatment of HIV-1 infection in combination with other antiretroviral agents.
* Treatment of chronic Hepatitis B virus (HBV) infection.
## Adult Dosing
* **HIV-1:** 300 mg orally once daily.
* **HBV:** 300 mg orally once daily.
## Pediatric Dosing
* **HIV-1 (age 2 to <12 years or weighing 17 kg to <30 kg):** 10 mg/kg orally once daily.
* **HIV-1 (age 2 to <12 years or weighing 30 kg to <40 kg):** 15 mg/kg orally once daily.
* **HIV-1 (age 2 to <12 years or weighing ≥40 kg):** 300 mg orally once daily.
* **HIV-1 (age 6 months to <2 years):** Dosing is weight-based and may vary. Refer to specific pediatric HIV treatment guidelines.
* **HBV:** Not established in pediatric patients.
## 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: 300 mg every 72 hours.
* Hemodialysis: 300 mg every 7 days after a full dose on the day of dialysis.
* Dosing for pediatric patients with renal impairment should follow specific guidelines.
## Contraindications
* Hypersensitivity to tenofovir disoproxil fumarate or any of its components.
## Adverse Effects
* **Renal:** Acute kidney injury, Fanconi syndrome, elevated serum creatinine.
* **Metabolic:** Lactic acidosis, lipodystrophy, hypophosphatemia.
* **Gastrointestinal:** Nausea, diarrhea, vomiting, abdominal pain.
* **Other:** Headache, rash,asthenia.
## Key Drug Interactions
* **Nephrotoxic Agents:** Concomitant use with other nephrotoxic drugs (e.g., aminoglycosides, NSAIDs, certain antivirals like cidofovir or adefovir) may increase the risk of renal toxicity.
* **Tenofovir Alafenamide (TAF):** TDF and TAF are prodrugs of tenofovir; do not coadminister.
* **Lopinavir/Ritonavir:** Increased tenofovir exposure. Consider monitoring renal function.
## Monitoring
* **Renal Function:** Serum creatinine and urinalysis (including urine protein and glucose) at baseline and periodically throughout treatment.
* **Serum Phosphorus:** Monitor in patients with pre-existing renal impairment or at risk for renal toxicity.
* **Liver Function Tests:** For patients with HBV.
* **CD4+ cell count and HIV viral load:** For patients with HIV.
## Clinical Pearls
* TDF is renally cleared; dose adjustments are critical in patients with impaired renal function.
* Bone mineral density should be monitored, especially in patients with risk factors for osteoporosis.
* Patients should be advised to report any new or worsening kidney problems, such as changes in the amount of urine.
* TDF may be associated with a higher risk of renal and bone toxicity compared to tenofovir alafenamide (TAF).
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always verify current prescribing information, clinical guidelines, and individual patient factors before making treatment decisions.
