When should Tenofovir be started, what are the recommended dosing regimens for HIV‑1 and chronic hepatitis B, and what baseline assessments and monitoring are needed?

Tenofovir Initiation, Dosing, and Monitoring

When to Start Tenofovir

For HIV-1 infection, tenofovir (as tenofovir disoproxil fumarate [TDF] or tenofovir alafenamide [TAF]) should be initiated immediately upon diagnosis as part of a combination antiretroviral regimen, regardless of CD4 count or viral load. 1

For chronic hepatitis B, tenofovir should be started in adults and pediatric patients ≥12 years (≥35 kg) with compensated liver disease who meet treatment criteria. 2 The FDA-approved indications include:

• Nucleoside-treatment-naïve patients with active viral replication and either elevated ALT or significant liver fibrosis 2
• Treatment-experienced patients with documented lamivudine resistance 2
• Patients with decompensated liver disease (though evaluated in limited numbers) 2

Emerging evidence suggests early treatment with TAF may benefit HBeAg-negative patients with moderate-to-high viremia (HBV DNA 4-8 log₁₀ IU/mL) even when ALT is normal or mildly elevated (males <70 U/L, females <50 U/L), as this significantly reduces hepatocellular carcinoma and hepatic decompensation risk. 3 At median 17.7 months follow-up, early TAF treatment reduced serious liver-related events by 79% (hazard ratio 0.21, p=0.027) compared to observation. 3

Special Consideration: HIV/HBV Coinfection

All HIV-infected patients must be screened for HBV, and if coinfected, tenofovir plus emtricitabine (or lamivudine) should be used as the NRTI backbone of the antiretroviral regimen. 1, 4 This dual-active regimen is mandatory because:

• Single-agent therapy risks HIV resistance development 4
• Tenofovir-containing regimens must be continued even when switching HIV therapy to prevent HBV reactivation 1

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Dosing Regimens

HIV-1 Treatment

Adults and pediatric patients ≥12 years (≥35 kg): 300 mg TDF once daily, taken orally without regard to food 2

Pediatric patients 2 to <12 years (≥17 kg): Weight-based dosing at 8 mg/kg once daily (maximum 300 mg), administered as follows: 2

• 17 to <22 kg: 150 mg once daily
• 22 to <28 kg: 200 mg once daily
• 28 to <35 kg: 250 mg once daily
• ≥35 kg: 300 mg once daily

Weight should be monitored periodically and dose adjusted accordingly. 2

Chronic Hepatitis B Treatment

Adults and pediatric patients ≥12 years (≥35 kg): 300 mg TDF once daily or 25 mg TAF once daily, taken orally without regard to food 2, 5

The optimal duration of treatment is unknown. 2

Safety and efficacy in pediatric patients with chronic hepatitis B weighing <35 kg have not been established. 2

Renal Dose Adjustments (TDF Only)

Creatinine clearance (CrCl) ≥50 mL/min: No dose adjustment needed; routine monitoring required 2

CrCl 30-49 mL/min (moderate impairment): 300 mg every 48 hours 2, 6

CrCl 10-29 mL/min (severe impairment): 300 mg every 72-96 hours 2, 6

Hemodialysis patients: 300 mg every 7 days (or after approximately 12 hours of cumulative dialysis), administered after dialysis session 2, 6

These dosing intervals are based on pharmacokinetic modeling and have not been clinically validated; therefore, close monitoring of clinical response and renal function is essential. 2 High-flux hemodialysis efficiently removes tenofovir with an extraction coefficient of 54%. 6

TAF is not currently recommended when estimated CrCl is <15 mL/min, though it appears safe above this threshold. 5

Hepatic Impairment

No dose adjustment is warranted for hepatic impairment (Child-Pugh class A). 6 TDF pharmacokinetics are unaffected by hepatic dysfunction because tenofovir is renally eliminated. 6

TAF is not currently recommended in moderate or severe hepatic impairment (Child-Pugh class B or C). 5

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Baseline Assessments

Before Initiating Tenofovir

All patients require: 2

• Estimated creatinine clearance (using Cockcroft-Gault method) 2, 6
• Serum creatinine 7
• Serum phosphorus 7
• Urine glucose 7
• Urine protein 7

For HIV patients: 2

• HIV-1 genotypic resistance testing (if available)
• HBV screening (hepatitis B surface antigen, anti-HBs, anti-HBc) 4
• CD4 count and HIV viral load

For HBV patients: 2

• HBeAg status
• HBV DNA level
• ALT level
• Assessment for cirrhosis/decompensation
• Prior treatment history and resistance testing (if treatment-experienced)

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Ongoing Monitoring

Renal Safety Monitoring

All patients on tenofovir require routine monitoring of: 7, 2

• Serum creatinine and estimated CrCl
• Serum phosphorus
• Urine glucose
• Urine protein

Monitoring frequency: 7, 2

• Patients with normal renal function: Periodic monitoring per standard clinical practice
• Patients with mild renal impairment (CrCl 50-80 mL/min): More frequent routine monitoring 2
• Patients with moderate-to-severe renal impairment or risk factors: Close monitoring of clinical response and renal function 2

Risk factors requiring heightened surveillance include: 7

• eGFR <60 mL/min/1.73 m²
• Proteinuria
• Low serum phosphate
• Diabetes
• Hypertension
• Concurrent nephrotoxic medications

Formulation Selection for Renal Risk

For treatment-naïve HBV patients with renal dysfunction or at risk for renal impairment, the Korean Association for the Study of Liver Diseases recommends using entecavir, TAF, or besifovir instead of TDF. 7 TAF demonstrates less nephrotoxicity and less decline in bone mineral density compared to TDF at 48,96, and 144 weeks of therapy. 5

For lamivudine-resistant HBV with acute kidney injury, TAF is preferred over entecavir because TAF retains activity against lamivudine-resistant strains without TDF-associated nephrotoxicity. 7

HBV-Specific Monitoring

For chronic hepatitis B patients: 2

• HBV DNA levels to assess virologic response
• ALT levels to monitor hepatic inflammation
• HBeAg/anti-HBe in HBeAg-positive patients
• Hepatic function (clinical and laboratory) for at least several months after discontinuation 2

Critical Warning: Post-Treatment Hepatitis Exacerbation

Severe acute exacerbations of hepatitis have been reported in HBV-infected patients who discontinue anti-hepatitis B therapy, including tenofovir. 2 Hepatic function must be monitored closely with both clinical and laboratory follow-up for at least several months after stopping treatment. 2 If appropriate, resumption of anti-hepatitis B therapy may be warranted. 2

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Key Clinical Pitfalls

Do not combine TDF with other tenofovir-containing products (ATRIPLA, COMPLERA, DESCOVY, GENVOYA, ODEFSEY, STRIBILD, TRUVADA, VEMLIDY). 2

Do not use tenofovir monotherapy for HIV/HBV coinfection—this risks HIV resistance. 4 Always use tenofovir with emtricitabine or lamivudine as part of a fully suppressive antiretroviral regimen. 1, 4

Do not discontinue tenofovir-containing regimens in HIV/HBV-coinfected patients when switching HIV therapy—continue a tenofovir-containing regimen to prevent HBV reactivation. 1

Breastfeeding while on TDF appears safe: Mean infant exposure is only 0.56 μg/kg/day (0.01% of weight-based infant dose), with undetectable infant plasma levels in most studies. 8