Emtricitabine is not metabolised by CYP enzymes. Data indicates that it does not induce CYP3A4 or inhibit CYP3A4 and other CYP enzymes. Side effects such as nausea and diarrhoea may be potentially porphyrinogenic through reduction in carbohydrate intake.

Emtricitabine is indicated in combination with other antiretroviral medicinal products for the treatment of HIV-1 infected adults and children aged 4 months and over. Very common side effects that can be confused with an acute porphyria attack are diarrhoea and nausea. Other common side effects are insomnia and headache.

The metabolism of emtricitabine is limited. It is metabolised via oxidation and conjugation, but not via CYP isoenzymes (Up to date). Less than 4% of emtricitabine is bound to proteins and 86% is excreted in urine with 13% as metabolites, while 14% is excreted in faces as unchanged drug. The elimination half-life is 10 hours. In vitro studies have shown that emtricitabine does not inhibit CYP1A2, CYP2A6, CYP2B6, CYPC9, CYP2C19, CYP2D6 or CYP3A4 (SPC). In an in vivo study subjects received emtricitabone/tenofovir disproxil in combination with tacrolimus, a CYP3A4 substrate. It was concluded that there was no clinically relevant pharmacokinetic interaction between emtricitabone/tenofovir disproxil and tacrolimus when administered together (Chittick 2008). This indicates that emtricitabone does not inhibit or induce CYP3A4.