TAF is not recommended if eGFR is <15mL/min. • In regions with high HIV prevalence, especially sub-Saharan Africa, testing for HIV should be undertaken before commencing hepatitis B treatment to ensure an optimal ARV drug regimen for HIV and HBV coinfection for people testing positive. People coinfected with HIV and HBV would typically be treated with dual NRTI inhibitors, including TDF with 3TC or FTC together with an anchor drug (most commonly DTG). For those switching ARV drug regimens, the HBV component of the regimen (TDF) should always be maintained. TDF or TAF + 3TC (or FTC) is the preferred NRTI backbone for people with both HIV and hepatitis B and can also be used for people with TB and pregnant women. ETV is not an appropriate option for people with both HIV and hepatitis B. If access to TDF alone is challenging, dual treatment with TDF or TAF plus 3TC or FTC can be given to monoinfected people.

• Assessment of baseline risk for renal dysfunction and measurement of baseline renal function should be considered before initiating antiviral therapy to inform the choice of regimen (see section 16.2). Significant loss of renal function is uncommon with TDF although caution is required for older people or those with comorbidities.
• In countries where TDF monotherapy or ETV are not yet widely available for hepatitis B, access to treatment may be enhanced if TDF + FTC combination treatment available through ART programmes or existing procurement can be used for HBV monoinfection.
• Co-administration of rifampicin, phenytoin and carbamazepine with TAF are currently contraindicated.
• Discontinuation of agents with activity against HBV may cause serious hepatocellular damage resulting from reactivation of HBV replication; patients should be advised against stopping these medications before achieving specified criteria and only under supervision and careful monitoring (see Chapter 18).
• Use of IFN may be considered in very specific circumstances (such as an add-on strategy). Trials examining the effect of newer potentially curative strategies with RNA interference have incorporated IFN to improve efficacy.