Emtricitabine was developed as a combined effort between Dr. Dennis C. Liotta, Dr. Raymond F. Schinazi, and Dr. Woo-Baeg Choi at Emory university and was patented by Emory through Triangle Pharmaceuticals under the trade name of Emtriva® in 1996. Triangle Pharmaceuticals has been owned by Gilead Sciences since 2003.

Emtriva®™ targets the HIV protein reverse transcriptase. By inhibiting this protein, it prevents the virus from converting its viral RNA into DNA that can be read by the host cell, halting the virus replication process. This drug is now being used in both HIV treatment as well as prevention in HIV PEP therapies.

Side effects

Emtriva®™ has relatively few side effects compared to other anti-HIV drugs. Most common side effects are diarrhoea and other gastrointestinal upsets. Insomnia, fatigue and depression can be associated with Emtriva® in some patients as well as dizziness and headaches. Rashes can occur as the result of a mild allergic reaction and skin discolouration has been seen in some patients, most commonly in those with dark skin and in children.  Like Kaletra®, Emtriva® can cause redistribution of body fat from the limbs to the torso.

The serious side effect of Emtriva® is the rare development of lactic acidosis where toxic lactic acid builds up in the muscles resulting in short-term muscle aches similar to those seen after exercise. This condition, if left untreated, can be fatal and you should consult your doctor if you experience unusual muscle aches along with fatigue and difficulty breathing.

Emtriva® is metabolised by the liver and can cause liver disease. Jaundice (yellowing of skin and eyes) is a sign of liver damage and you should seek medical assistance immediately if you notice any yellowing of skin or eyes. Other signs to watch for are darkening urine, going off your food, nausea, light coloured stools and abdominal pain.

Contraindications

Emtriva should not be taken by those who have shown allergies to drugs of a similar class. This drug is metabolised by the liver and so can exacerbate hepatitis. It is not approved for use in patients with Hepatitis as it may escalate prior liver damage. The same advice is given for patients with kidney disease or elderly patients as Entriva is eliminated from the body by the kidneys and may put added stress on this organ.

Alcohol use should be limited while on Entriva as the breakdown of alcohol will also stress the liver. Patients with Hepatitis should be monitored while on Entriva. While there have been case studies that show Entriva is effective against the Hepatitis B virus, others have seen a severe escalation in liver dysfunction and it is not currently approved for treatment of Hepatitis B.

Lactic acidosis is a rare side effect of Emtriva but is more likely to occur in patients that are overweight, female or who have been taking Emtriva or similar drugs for an extended period of time.

Current studies suggest that Emtriva does not harm a developing foetus and should be safe for use in pregnancy but there is not sufficient data to say it is definitely safe. As such it is suggested that Entriva is used only when absolutely necessary should the patient be pregnant. Entriva is secreted in breast milk and live HIV virus can be transmitted via breast milk even when the patient is taking antivirals.  It is advised that patients taking Entriva do not breastfeed their infants.

Drug interactions

Emtriva should not be taken along with other reverse transcriptase inhibitors such as lamivudine so it is essential you inform your doctor if you are taking any other anti-HIV drugs so they can ensure the correct dose. Other drugs may interact with Emtriva, make sure you inform your doctor of any medication or supplements you are taking.

Additional information

Emtricitabine is listed as an essential medicine by the World Health Organisation (WHO). It is one of the pioneer drugs in the fight against the spread of AIDS and its relatively few side effects and high safety profile make it a drug of choice for nuclease inhibitors.

As it acts against a viral protein that is able to mutate there are strains resistant to Emtriva, notably the M184V mutation (this means that the 184th amino acid in the protein has mutated from a methionine to a valine). Resistant strains are commonly seen in those who have been taking Emtriva or the closely related lamivudine for long periods. Those with resistant strains may need to be put on a different class of nuclease inhibitor such as Retrovir or Viread.

Emtriva has shown some effectiveness in the treatment of Hepatitis B virus (HBV) and some doctors will prescribe Emtriva for patients withHBV. However, due to the exacerbations of liver illness, treatment of HBV with Emtriva can cause symptoms to worsen. It is a case of which is worse, the virus or the effects of hepatitis.  Because of liver toxicity Emtriva is not recommended or approved for treatment of HBV despite possible antiviral properties.

For more information see:

WebMD – Emtriva

http://www.webmd.com/drugs/2/drug-76365/Emtriva®+oral/details#precautions

Gilead Sciences product information sheet – Emtriva

http://www.gilead.com/~/media/files/pdfs/medicines/hiv/Emtriva®/Emtriva®_pi.pdf