Emtricitabine

Emtricitabine (em-tri-SIT-uh-bean) is a prescription drug used for the treatment of HIV infection.

Emtricitabine belongs to a family of antiretroviral drugs called nucleoside analog reverse transcriptase inhibitors (NRTIs). Other members of this family include zidovudine (AZT, Retrovir) and didanosine (ddI, Videx).

Emtricitabine is marketed as Emtriva by Gilead Sciences in the United States.

Chemical Structure of Emtricitabine, Source:Wikimedia Commons

Uses

Emtricitabine was approved by the Food and Drug Administration (FDA) in 2003 for use with other antiretroviral agents in the treatment of HIV infection in adults. It was approved for use in children over the age of three months in 2005. Like other antiretroviral agents, Emtricitabine does not cure or prevent HIV infection or AIDS and does not reduce the risk of passing the virus to other people.

How Emtricitabine is Taken

Emtricitabine is taken by mouth and is available in the following dosage forms: capsules containing 200 mg of active drug, or oral solution containing 10 mg of active drug per one mL. It can be taken with or without food. Emtricitabine is also marketed in combination form with tenofovir as Truvada, and with efavirenz and tenofovir as Atripla.

The recommended daily dose is determined by age as follows:

Adults (18 years of age and older)

• One 200 mg capsule taken once a day.
• 240 mg (24 mL) oral solution taken once a day.

Infants (0-3 months of age)

• 3 mg/kg of the oral solution administered once a day .

Children (3 months through 17 years of age)

• 6 mg/kg of the oral solution up to a maximum of 240 mg (24 mL) taken once a day.
• One 200 mg capsule taken once a day for children who weigh more than 33 kg and who can swallow an intact capsule.

It is currently not known if emtricitabine is excreted in human milk. Mothers should avoid nursing while taking emtricitabine.

How Emtricitabine Works

Emtricitabine is structurally similar to the DNA building blocks that HIV uses to make copies of itself. An HIV enzyme called reverse transcriptase attaches emtricitabine to the growing viral DNA chain. This stops the DNA chain from growing, and HIV is unable to continue making copies of itself.

Emtricitabine is only active against HIV-1. It has no activity against a related virus that causes AIDS, HIV-2.

How the Body Affects Emtricitabine

Emtricitabine is rapidly absorbed from the stomach with peak circulating levels in the blood occurring at 1–2 hours after a dose.

The drug is eliminated from the body in the urine (86%) and feces (14%) in the form of several metabolites.

Side Effects

The most common side effects (occurring in more than 3% of treated patients) include the following:

• Abdominal pain
• Asthenia (feelings of weakness or lack of energy)
• Headache
• Diarrhea
• Fatigue (tiredness)
• Dyspepsia (indigestion)
• Nausea
• Vomiting
• Arthralgia (joint aches)
• Myalgia (muscle aches)
• Abnormal dreaming
• Depression
• Dizziness
• Insomnia
• Neuropathy/peripheral neuritis (nerve disorders in the arms or legs)
• Paresthesia (tingling)
• Increased coughing
• Rhinitis (runny nose)
• Rash

Skin discoloration on the palms of the hands and soles of the feet was reported with higher frequency in emtricitabine-treated patients than in control groups, but the mechanism of skin discoloration is unknown.

Risks and Precautions

Some patients treated with emtricitabine and other antiretroviral medications have developed lactic acidosis (a buildup of an acid in the blood).

Some patients have also developed serious liver problems while taking emtricitabine, such as liver enlargement (hepatomegaly) and fat in the liver (steatosis).

Redistribution of body fat including central obesity, dorsocervical fat enlargement ("buffalo hump"), peripheral or facial wasting, breast enlargement, and "cushingoid appearance" have been observed in patients receiving antiretroviral therapy, including emtricitabine.

There have been reports of severe worsening of hepatitis B infections after stopping emtricitabine in people who are infected with both HIV and hepatitis B.

Drug Interactions

Emtricitabine should not be taken along with Atripla or Truvada which already contain emtricitabine. Emtricitabine should not be used in people who are taking lamivudine, a similar antiretroviral drug which can be found in Combivir, Epivir, Epzicom, and Trizivir.

Effectiveness

In study 301A, 571 adult patients infected with HIV who had never received anti-HIV medications (treatment-naive) were given either emtricitabine plus didanosine and efavirenz, or stavudine plus didanosine and efavirenz. In the emtricitabine group, 78% had a drop in the HIV viral load to undetectable levels compared with 59% in the stavudine group.^[1]

In a study of HIV-infected people who were stable on an anti-HIV regimen (Study 303), 404 study subjects were randomized (assigned by chance) to either continue their current anti-HIV regimen or change lamivudine to emtricitabine. The number of people in the study who maintained an HIV viral load that was undetectable was statistically the same in both groups, indicating that emtricitabine was as effective as lamivudine when used with other anti-HIV medications.^[2]

Clinical Trials

Clinical research trials are ongoing with emtricitabine. For a list of trials please visit ClinicalTrials.gov.

References

1. ↑ Saag MS, Cahn P, Raffi F, et al. Efficacy and safety of emtricitabine vs stavudine in combination therapy in antiretroviral-naive patients: a randomized trial. JAMA. 2004 Jul 14;292(2):180-9. Abstract | Full Text | PDF
2. ↑ Benson CA, van der Horst C, Lamarca A,et al. A randomized study of emtricitabine and lamivudine in stably suppressed patients with HIV. AIDS. 2004 Nov 19;18(17):2269-76. Abstract

External Links

Gilead: Emtriva Official Site

AIDSinfo (NIH): Emtricitabine

MedLine Plus: Emtricitabine

Food and Drug Administration (FDA): Emtricitabine Patient Information Sheet