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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.
How Does It Work?
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.
What About Side Effects?
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.
Who Should Use It?
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.
How To Use It?
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.
3TC and Children
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).
Where To Get It?
3TC is available with a prescription through hospitals and
pharmacies, in 150mg pills for adults and in a strawberry-banana
flavored liquid for children.
HIV and the Brain
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.
This information
was provided by the Community AIDS Treatment Information
Exchange (CATIE). For more information, contact CATIE at
1-800-263-1638.
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