What is the proper administration method for Tenofovir (Antiretroviral medication)?

How to Administer Tenofovir

Tenofovir is administered orally as a once-daily tablet, with the specific formulation, dosing schedule, and monitoring requirements determined by the clinical indication (HIV treatment vs. PrEP) and patient characteristics (renal function, bone health, and population group).

For HIV Treatment

Standard Dosing

• Tenofovir disoproxil fumarate (TDF) 300 mg once daily orally is the standard dose for HIV treatment, typically combined with other antiretrovirals as part of a complete regimen 1, 2.
• Administer with or without food, though oral bioavailability is enhanced with a high-fat meal 2.
• Tenofovir alafenamide (TAF) 25 mg once daily is an alternative formulation with lower systemic tenofovir exposure, preferred for patients with renal or bone concerns 3.

Renal Dosing Adjustments (TDF only)

• No adjustment needed if creatinine clearance ≥50 mL/min 4, 2.
• Creatinine clearance 30-49 mL/min (moderate impairment): Give TDF 300 mg every 48 hours 4.
• Creatinine clearance 10-29 mL/min (severe impairment): Give TDF 300 mg every 72-96 hours (twice weekly) 4.
• End-stage renal disease on hemodialysis: Give TDF 300 mg once weekly after dialysis session (hemodialysis efficiently removes tenofovir with 54% extraction) 4.
• TAF requires no dose adjustment for any degree of renal impairment, including ESRD on hemodialysis 3.

Hepatic Impairment

• No dose adjustment needed for any degree of hepatic impairment with either TDF or TAF 3, 4, 2.

For HIV Pre-Exposure Prophylaxis (PrEP)

Standard Daily PrEP Regimen

• TDF 300 mg/emtricitabine 200 mg (Truvada) once daily is the recommended first-line oral PrEP for all at-risk populations 5.
• For MSM: Start with a double dose (2 tablets) on day 1, then continue once daily to achieve maximal protection within 24 hours 5.
• For all other populations: Standard once-daily dosing achieves maximal protection in approximately 7 days 5.

Event-Driven "2-1-1" PrEP (MSM Only)

• This regimen is recommended ONLY for men who have sex with men 5.
• Dosing schedule: Take 2 tablets of TDF/emtricitabine 2-24 hours before sexual activity, then 1 tablet 24 hours later, then 1 tablet 24 hours after that 5.
• Continue daily dosing until 48 hours after the last sexual contact 5.

TAF-Based PrEP (Limited Indication)

• TAF 25 mg/emtricitabine 200 mg (Descovy) once daily is recommended specifically for MSM with creatinine clearance 30-60 mL/min OR those with osteopenia/osteoporosis 5, 6.
• No loading dose for Descovy (unlike TDF/emtricitabine) 6.
• NOT recommended for cisgender women or event-driven dosing 7, 6.

Discontinuation Timing

• MSM on daily TDF/emtricitabine: Continue for 2 days after last at-risk exposure 5.
• All other populations on daily TDF/emtricitabine: Continue for 7 days after last at-risk exposure 5.

Critical Pre-Administration Requirements for PrEP

Mandatory Testing Before Starting

• Combined HIV antibody/antigen test (add HIV RNA if acute infection suspected) to exclude HIV infection 5, 7.
• Serum creatinine and estimated creatinine clearance (do not start TDF-based PrEP if <60 mL/min) 5, 7.
• Hepatitis B surface antigen 5, 7.
• Hepatitis C antibody 5, 7.
• STI screening (gonorrhea, chlamydia by NAAT at all exposed sites) 5, 7.

Ongoing Monitoring During PrEP

• Every 3 months: HIV testing with combined antibody/antigen assay 5, 7.
• Every 3 months: Three-site STI screening (rectal, pharyngeal, urogenital) 7.
• At 1 month, then quarterly for first year, then annually: Creatinine clearance 5.
• Every 3-6 months for high-risk patients: Those >50 years, on hypertension/diabetes medications, or baseline eGFR <90 mL/min 7.

Important Clinical Caveats

Hepatitis B Co-infection

• Patients with chronic HBV switching HIV regimens must continue tenofovir (TAF or TDF) to maintain HBV suppression 5.
• Risk of severe hepatitis flare or hepatic decompensation if tenofovir is discontinued in HBV-infected patients, especially those with cirrhosis 7.

Drug Interactions Requiring Dose Modification

• Didanosine: Tenofovir increases didanosine exposure by 44-60%; monitor for didanosine toxicity 2, 8.
• Atazanavir: Requires dosage modification when co-administered with tenofovir 2.
• TAF dosing may need adjustment when co-administered with certain medications; review drug interactions 5.

Contraindications

• Do not start TDF-based PrEP if creatinine clearance <60 mL/min 7.
• Do not prescribe TDF-based PrEP for patients with osteopenia/osteoporosis (use TAF-based Descovy for MSM instead) 7, 6.
• Never initiate PrEP in patients with undiagnosed HIV infection 5, 7, 6.

If HIV Infection Occurs During PrEP

• Immediately add a boosted protease inhibitor (darunavir/ritonavir or darunavir/cobicistat) and/or dolutegravir to the TDF/emtricitabine while awaiting resistance testing 7.
• Switch to a recommended initial antiretroviral regimen once HIV is confirmed 7.