When to Start Tenofovir
Tenofovir should be initiated immediately upon diagnosis in all HIV-infected individuals with detectable viremia, regardless of CD4 count, and in chronic hepatitis B patients meeting specific treatment criteria based on viral load, ALT levels, and fibrosis status.
HIV Treatment Initiation
All HIV-Positive Patients
Tenofovir-based antiretroviral therapy (ART) should be started as soon as HIV infection is confirmed with detectable viremia 1. The evidence strongly supports immediate treatment initiation for both individual health benefits and reduction of HIV transmission through viral suppression 2.
Recommended regimens include:
- Tenofovir alafenamide (TAF) or tenofovir disoproxil fumarate (TDF) combined with emtricitabine or lamivudine, plus a third agent (typically an integrase inhibitor like dolutegravir or bictegravir) 1, 2
- TAF is preferred over TDF in patients with or at risk for kidney dysfunction, osteopenia, or osteoporosis 1
HIV/HBV Coinfection
For patients coinfected with HIV and hepatitis B, tenofovir-based therapy is mandatory and should be initiated immediately 1, 3, 2. The regimen must include tenofovir (TAF or TDF) plus either lamivudine or emtricitabine to suppress both viruses simultaneously 3, 4. This is critical because these agents have dual activity against HIV and HBV.
Key consideration: When switching ART regimens in HIV/HBV coinfected patients, tenofovir must be continued unless contraindicated. If switching to a tenofovir-free regimen, alternative HBV suppressive therapy is required 1.
Chronic Hepatitis B Treatment Initiation
Adults and Adolescents ≥12 Years
Tenofovir should be started in chronic hepatitis B patients when they meet treatment criteria 5, 6:
Immediate treatment indications:
- Compensated or decompensated cirrhosis with any detectable HBV DNA
- HBV DNA ≥2000 IU/mL with elevated ALT (>2× upper limit of normal for males, >1.5× for females)
- Significant liver fibrosis (≥F2) on biopsy or non-invasive assessment
- Family history of HCC or cirrhosis with HBV DNA >2000 IU/mL
Emerging evidence: Recent data suggests earlier treatment may be beneficial even in patients with moderate-to-high viral loads (HBV DNA 4-8 log₁₀ IU/mL) and normal or mildly elevated ALT, as this reduces risk of hepatocellular carcinoma and hepatic decompensation 7. While current guidelines haven't fully incorporated this, the ATTENTION trial showed a significant reduction in serious liver-related events with early tenofovir alafenamide treatment.
Pediatric Patients
- HIV treatment: Tenofovir can be initiated in children ≥2 years old weighing ≥17 kg at 8 mg/kg once daily (maximum 300 mg) 6
- Chronic hepatitis B: Approved for children ≥12 years old weighing ≥35 kg at 300 mg once daily 6
HIV Pre-Exposure Prophylaxis (PrEP)
When to Start PrEP
Tenofovir-based PrEP should be initiated as soon as feasible for individuals at substantial risk of HIV acquisition 1:
High-risk populations include:
- Men who have sex with men with HIV incidence ≥2% per year
- HIV-seronegative partners of HIV-infected persons without viral suppression
- Persons with diagnosed sexually transmitted infections
- Persons who engage in transactional sex
- Persons who inject drugs and share needles
Regimen options:
- Daily oral PrEP: TDF/emtricitabine 300/200 mg once daily (for all populations) 1
- For MSM with kidney/bone concerns: TAF/emtricitabine daily 1
- On-demand PrEP (2-1-1 dosing): Only for MSM - double dose 2-24 hours before sex, then single doses at 24 and 48 hours after the first dose 1
Pre-PrEP Requirements
Before initiating tenofovir-based PrEP 1, 2:
- Mandatory: Negative laboratory-based HIV antigen/antibody test within 7 days (plus HIV RNA if acute infection suspected)
- Mandatory: Serum creatinine and estimated creatinine clearance
- Mandatory: Hepatitis B surface antigen testing
- Screen for sexually transmitted infections
- Vaccinate against hepatitis A and B if not immune
Critical contraindications for TDF-based PrEP:
- Creatinine clearance <60 mL/min 2
- Osteopenia or osteoporosis 2
- Use caution in chronic hepatitis B (ensure alternative HBV treatment if PrEP discontinued) 2
Immunosuppression and HBV Reactivation Prophylaxis
HBsAg-Positive Patients
All HBsAg-positive patients starting immunosuppressive therapy should begin prophylactic tenofovir (TAF or TDF preferred over entecavir) at the time of transplantation or immunosuppression initiation 5. Continue for at least 6-12 months after completing immunosuppressive therapy, or 18 months for B-cell depleting therapies 5.
HBsAg-Negative, Anti-HBc-Positive Patients
- High-risk immunosuppression: Start prophylactic tenofovir 5
- Moderate/low-risk immunosuppression: Monitor HBsAg and/or HBV DNA every 3 months; if monitoring not feasible, initiate prophylaxis 5
Renal Dosing Adjustments
For patients with renal impairment, tenofovir dosing must be adjusted 6:
- CrCl 30-49 mL/min: 300 mg every 48 hours
- CrCl 10-29 mL/min: 300 mg every 72-96 hours
- Hemodialysis: 300 mg every 7 days or after ~12 hours of dialysis
Important: TAF is not recommended when CrCl <30 mL/min; TDF requires dose adjustment but can be used 2.
Critical Monitoring After Initiation
- HIV treatment: Check viral load at 1 month, then every 3-6 months 1
- HBV treatment: Monitor ALT, HBV DNA, and HBsAg every 3-6 months 8
- PrEP: HIV testing every 3 months, creatinine at 1 month then quarterly for first year, then every 6 months 1
- All patients: Monitor renal function (creatinine, phosphorus, urinalysis) before starting and periodically during treatment 2, 6
Common Pitfalls to Avoid
- Never start tenofovir-based PrEP without confirming HIV-negative status - this could lead to single-drug HIV treatment and resistance 1
- Don't discontinue tenofovir in HIV/HBV coinfected patients without ensuring alternative HBV suppression - severe hepatitis flares can occur 1, 6
- Don't use TDF in patients with significant renal impairment or bone disease - switch to TAF or adjust dosing 1, 2
- Don't forget HBV screening before switching to tenofovir-sparing HIV regimens - risk of HBV reactivation exists 9, 10