Nucleotide reverse transcriptase inhibitor Pregnancy: A large amount of data on pregnant women (more than 1,000 pregnancy outcomes) indicate no malformations or foetal/neonatal toxicity, and animal studies do not indicate reproductive toxicity — use during pregnancy may be considered if necessary. Third-trimester exposure has been shown to reduce mother-to-infant HBV transmission when given in addition to hepatitis B immune globulin and vaccine for the infant. Breast-feeding: tenofovir is excreted in human milk at very low levels and infant exposure is considered negligible — mothers with HBV infection may breast-feed if the newborn is adequately managed for hepatitis B prevention at birth, but women living with HIV are recommended not to breast-feed in order to avoid transmission. (The US label lists Pregnancy Category B.)

Tenofovir disoproxil

Brand names: Viread

Tenofovir disoproxil is a nucleotide reverse transcriptase inhibitor prodrug used within combination antiretroviral regimens for HIV and for chronic hepatitis B, and as a component of HIV pre-exposure prophylaxis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 245 mg (one tablet) once daily for the treatment of HIV-1 or of chronic hepatitis B

Route: Oral — taken with food

Frequency: Once daily

Source: UK SPC (eMC) for Tenofovir disoproxil 245 mg Film-Coated Tablets, §4.2 (https://www.medicines.org.uk/emc/product/8138/smpc). Therapy should be initiated by a physician experienced in the management of HIV infection and/or treatment of chronic hepatitis B. The same 245 mg once daily dose applies to adults AND adolescents aged 12 to <18 years weighing ≥35 kg. DURATION IN CHRONIC HEPATITIS B: the optimal duration is unknown — in HBeAg positive patients without cirrhosis, treat for at least 12 months after confirmed HBe seroconversion or until HBs seroconversion or loss of efficacy; in HBeAg negative patients without cirrhosis, treat at least until HBs seroconversion or evidence of loss of efficacy (discontinuation may also be considered after at least 3 years of stable virological suppression with regular ALT/HBV DNA monitoring afterwards to detect late virological relapse); in adults with decompensated liver disease or cirrhosis, treatment cessation is not recommended. Reassess regularly beyond 2 years of treatment. MISSED DOSE: if missed within 12 hours of the usual time, take with food as soon as possible and resume the normal schedule; if missed by more than 12 hours and it is almost time for the next dose, skip it. VOMITING: if the patient vomits within 1 hour of taking the dose, another tablet should be taken; if more than 1 hour after, no further dose is needed. ELDERLY: no data on which to make a dose recommendation over 65 years. HEPATIC: no dose adjustment required; monitor closely for exacerbation of hepatitis if discontinued in chronic hepatitis B (with or without HIV co-infection). PAEDIATRIC: safety and efficacy in HIV-1 infected children or children with chronic hepatitis B under 2 years of age have not been established (no data); use is not recommended in paediatric patients with renal impairment. The US label in the bundle is tenofovir disoproxil FUMARATE 300 mg (stated to be equivalent to 245 mg tenofovir disoproxil — a salt difference, do not treat the two numbers as different doses) and additionally sets out a weight-band paediatric regimen for HIV-1 in children aged 2 to <12 years; verify any under-18 dosing against a children's formulary and against the UK SPC. §4.5 was not retrieved in this bundle.

Dose adjustments

Renal

Tenofovir is eliminated renally and exposure increases in renal dysfunction — in adults with renal impairment use only if the potential benefits outweigh the risks. Mild impairment (creatinine clearance 50–80 ml/min): limited data support 245 mg once daily. Moderate impairment (30–49 ml/min): if a different formulation is not possible, 245 mg every 48 hours may be used. Severe impairment (<30 ml/min): 245 mg every 72–96 hours (twice a week). Haemodialysis: 245 mg every 7 days following completion of a haemodialysis session (generally once weekly assuming three approximately 4-hour sessions per week, or after 12 hours cumulative haemodialysis). These interval adjustments have not been confirmed in clinical studies and may be sub-optimal — monitor clinical response and renal function closely. No dosing recommendation for non-haemodialysis patients with creatinine clearance <10 ml/min. Calculate creatinine clearance before starting, then monitor creatinine clearance and serum phosphate at 2–4 weeks, at 3 months and every 3–6 months thereafter (more often if at risk). Use is not recommended in paediatric patients with renal impairment.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients (UK SPC §4.3; the US label states 'None')

Side effects

Renal impairment, renal failure (rare) and proximal renal tubulopathy including Fanconi syndrome (uncommon), sometimes leading to bone abnormalities and infrequently contributing to fractures — renal monitoring is required
Gastrointestinal events — usually mild to moderate; approximately one third of HIV-1 patients experience adverse reactions on tenofovir disoproxil with other antiretrovirals, and about 1% of adults discontinued because of GI events
Nausea — the most frequent adverse reaction in HBV clinical trials (5.4%); approximately one quarter of hepatitis B patients experience adverse reactions, most of which are mild
Acute exacerbation of hepatitis — reported both on treatment and in patients who have discontinued hepatitis B therapy
Decline in renal function (initial fall of approximately 4.9 ml/min by Cockcroft-Gault in the first 4 weeks, then approximately 1.41 ml/min per year); decreases in bone mineral density and lactic acidosis/severe hepatomegaly with steatosis are labelled warnings (US label)

Interactions

Other medicinal products containing tenofovir disoproxil or tenofovir alafenamide — must not be co-administered
Adefovir dipivoxil — must not be co-administered
Didanosine — co-administration is not recommended (tenofovir disoproxil increases didanosine concentrations; the US label warns dose reduction and close monitoring for didanosine toxicity are warranted)
Nephrotoxic medicinal products (e.g. aminoglycosides, amphotericin B, foscarnet, ganciclovir, pentamidine, vancomycin, cidofovir, interleukin-2) — avoid with concurrent or recent use; the US label adds drugs eliminated by active tubular secretion (aciclovir, valaciclovir, ganciclovir, valganciclovir, gentamicin, high-dose or multiple NSAIDs) may increase tenofovir and/or co-administered drug concentrations
Triple nucleoside/nucleotide therapy — high rates of early virological failure and resistance were reported when tenofovir disoproxil was combined with lamivudine plus abacavir, or lamivudine plus didanosine, as a once-daily regimen. US label: co-administration decreases atazanavir concentrations (use atazanavir with ritonavir), and certain HIV-1 protease inhibitors or HCV drugs increase tenofovir concentrations — monitor for tenofovir toxicity. Note: UK §4.5 was not retrieved; verify the full list

Clinical monograph

How it works

It is converted to tenofovir and then to the active diphosphate, which inhibits viral reverse transcriptase and terminates viral DNA chain elongation.

Prescribing in practice

It can cause renal toxicity, including proximal tubulopathy and Fanconi syndrome, so renal function must be assessed before and during treatment.
Discontinuation in patients co-infected with hepatitis B may precipitate severe acute hepatic flares, requiring careful monitoring.
It is associated with reductions in bone mineral density and should be used with caution where osteoporosis or fracture risk is a concern.

Monitoring

Monitor renal function and serum phosphate before and periodically during treatment, with hepatic monitoring after withdrawal in hepatitis B co-infection.

Counselling the patient

Report new bone pain, muscle weakness or reduced urine output.
Do not stop treatment abruptly without specialist advice if you have hepatitis B.
Take it regularly with your other antiretrovirals.

Evidence & guidelines

Its antiviral efficacy is well established, and use for HIV pre-exposure prophylaxis with emtricitabine is supported by trials such as iPrEx and is recommended by NICE.

Reference: BHIVA; NICE TA481; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways