Emtricitabine/tenofovir disoproxil fumarate

Tenofovir disoproxil fumarate (TDF) and emtricitabine are available in a fixed-dose combination tablet combining 245mg TDF and 200mg emtricitabine. Emtricitabine is a nucleoside reverse transcriptase inhibitor (NRTI) and TDF is a nucleotide reverse transcriptase inhibitor (NtRTI). These drugs reduce the amount of HIV in the body.

The combination is marketed as Truvada by Gilead Sciences and in equivalent generic versions. Truvada was approved for HIV treatment in combination with at least one other drug in the United States in 2004 and the European Union in 2005.

The combination of TDF and emtricitabine is also approved for use as pre-exposure prophylaxis against HIV infection.

Effectiveness

Truvada was approved based on the findings of study GS-01-934, which compared TDF, emtricitabine and efavirenz to zidovudine, lamivudine and efavirenz. In this study, participants received TDF and emtricitabine co-formulated as Truvada from weeks 96 to 144. The study showed that the TDF-containing combination resulted in superior virological suppression to the zidovudine-containing combination at weeks 48 and 144. (Gallant) (Arribas)

The 48-week results of the HEAT study showed that Kivexa (abacavir/lamivudine) and Truvada (emtricitabine/TDF) resulted in similar rates of viral suppression when combined with efavirenz and were equally well tolerated. (Smith)

Tenofovir and emtricitabine are active against hepatitis B and are recommended components of antiretroviral therapy for people co-infected with hepatitis B and HIV.

Taking it

The standard dose of Truvada is one tablet once a day, with or without food, in combination with at least one other anti-HIV drug.

Side effects

The most common side effects of TDF/emtricitabine are diarrhoea, vomiting, nausea, dizziness, headache, rash, feeling weak, pain, stomach pain, difficulty sleeping, abnormal dreams, feeling bloated, flatulence, or allergic reactions, such as wheezing, swelling or feeling light-headed.

See Tenofovir disoproxil fumarate (Viread) – detailed information for further information about the potential effects of TDF on kidney function and bone mineral density.

Drug interactions

TDF/emtricitabine should not be used with the following drugs:

• tenofovir alafenamide
• lamivudine
• adefovir dipivoxil
• didanosine

Taking emtricitabine/TDF with some other drugs can increase the risk of kidney damage. These include:

• Antibacterials: aminoglycosides, vancomycin
• Antivirals: cidofovir, foscarnet, ganciclovir,
• amphotericin B
• interleukin-2
• non-steroidal anti-inflammatory drugs (NSAIDs, to relieve bone or muscle pains)
• pentamidine

Regular monitoring of kidney function should take place when TDF/emtricitabine is used in combination with a boosted protease inhibitor or with direct-acting antiviral treatment for hepatitis C, owing to the potential for these agents to boost levels of TDF.

Resistance

Failure of a regime containing emtricitabine is likely to lead to the emergence of the M184V mutation, causing high-level resistance to lamivudine and low-level resistance to abacavir.

See Tenofovir disoproxil fumarate (Viread) – detailed information for further information on tenofovir resistance.

Pregnancy

The British HIV Association recommends the use of TDF as a preferred option for antiretroviral treatment during pregnancy in combination with other HIV drugs. See Tenofovir disoproxil fumarate (Viread) – detailed information for further details.

Children

TDF/emtricitabine is approved for use in children and adolescents aged 12 years and over, weighing 35kg and over.

Further information

For more information on emtricitabine and TDF, including side effects, resistance and drug interactions, see Emtricitabine (Emtriva) – detailed information  and Tenofovir disoproxil fumarate (Viread) – detailed information.