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3TC (lamivudine, Epivir) is an antiretroviral drug, similar to AZT, ddI, ddC and d4T, that inhibits the human immunodeficiency virus (HIV) from replicating. Like these other approved antiretrovirals, 3TC is a nucleoside analogue, which works by inhibiting an important enzyme that HIV uses to reproduce, thus preventing the creation of new virus.

3TC is approved to be used in combination with AZT for people with AIDS and HIV infection. While 3TC impairs HIV's ability to replicate, it will never be a cure for AIDS as it does not totally eradicate the virus from the body.

3TC inhibits the production of reverse transcriptase, an enzyme the virus needs in order to incorporate itself into the genetic material of the CD4+ cell. If HIV cannot incorporate itself into a cell, it cannot replicate.

3TC appears to be very well tolerated and most people who take the drug experience few or no side effects. The major problems that have been noted in the clinical trials include headaches, nausea, malaise and fatigue, diarrhea, neuropathy, low white blood cells and anemia (decrease in red blood cells). Very few of these reported side effects required people to discontinue 3TC. An increased incidence of pancreatitis was observed in children in clinical trials, but this does not appear to be the case for adults. One additional side effect in some adults appears to be hair loss.

3TC is approved in combination with AZT for adults and children with AIDS and HIV infection. It is still unknown whether 3TC will delay disease progression or prolong survival, although other drugs which have demonstrated similar effects on viral levels and CD4+ cell counts have shown benefit in this regard. Deciding when to begin or add anti-HIV therapies is still a topic of much debate. Some researchers believe that all people with CD4+ cell counts less than 500 should start an anti-HIV regimen with combination therapies, while others believe that looking at other factors, such as the development of symptoms of HIV-disease or high virus measurements using HIV RNA tests should guide decisions as to when to start therapy. This issue will be addressed in more detail later.

3TC has not been tested in pregnant women. Studies have shown that using AZT alone during third trimester pregnancy and during delivery significantly reduces the risk of transmitting HIV from mother-to-child. Whether adding 3TC to this regimen will be helpful or not has yet to be studied.

Clinical trials of 3TC in adults suggest that the optimum dose of the drug is 150mg twice a day. Results from clinical trials suggest that the 150mg twice a day dose is as effective as the 300mg twice a day dose when used in combination with AZT. The drug is administered orally, in pill form, and taking 3TC with or without food does not appear to change the effectiveness of the drug. For adults with low body weight (less than 110 pounds or 50 kg), the recommended dose is 2mg/kg of body weight twice daily.

The recommended dose for children (3 months to 12 years of age) is four mg/kg of body weight twice daily, with a maximum dose of 150mg twice daily.

Because 3TC is partially processed through the kidneys, concurrent use of drugs which have kidney toxicities may increase the risk of side effects of 3TC. Examples of these include amantadine, cimetidine, ethambutol, ranitidine and TMP/SMX (Bactrim or Septra).

3TC is available with a prescription through hospitals and pharmacies, in 150mg pills for adults and in a strawberry-banana flavored liquid for children.

Because HIV can infect brain cells, it's important to consider a drug's ability to reach the brain when putting together an anti-HIV regimen. It's probably wise to include at least one drug that has been shown to cross the blood-brain barrier to some useful degree as part of your regimen. These include AZT (zidovudine, Retrovir), d4T (stavudine, Zerit), abacavir (Ziagen), nevirapine (Viramune), amprenavir (Agenerase) and to a lesser degree indinavir (Crixivan) and 3TC (lamivudine, Epivir). Efavirenz (Sustiva) has not been shown to cross the barrier to a significant degree, but some experts speculate that it might have some useful effect in impacting HIV in the spinal fluid.