Side effects like diarrhoea, vomiting and nausea may potentially be porphyrinogenic through reduction in carbohydrate intake.

Very common side effects of tenofovir disoproxil are diarrhoea, vomiting and nausea. These side effects can be confused with an acute porphyric attack and may potentially be porphyrinogenic if leading to a decrease in carbohydrate intake.

Tenofovir is not a substrate, inhibitor or inducer of CYP450 enzymes. No pharmacokinetic porphyrinogenic effects are suspected.

Tenofovir belongs to the class 6-aminopurines

Tenofovir is a nucleotide reverse transcriptase inhibitor indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection in adults and pediatric. It is also indicated for the treatment of chronic hepatitis B. It is administered orally.

Tenofovir disoproxil is first converted to tenofovir monophosphate and then converted to the active metabolite tenofovir diphosphate by cellular enzymes (SPC). Tenofovir is excreted by the kidney by both glomerular filtration and active tubular secretion. Tenofovir is not a substrate, inhibitor or inducer of CYP450 enzymes (Kearney 2004). Although, tenofovir has been reported to be a weak inhibitor of CYP1A2 (Lexi-interact, SPC) it is unlikely that this is clinically relevant.

Uneventful use of the emtricitabine and tenofovir disoproxil combination (ATC-code: J05AR03) is reported in 1 patient with acute intermittent porphyria.