Fact Sheet Number 426
(Preveon)
- WHAT IS ADEFOVIR DIPIVOXIL?
- WHO SHOULD TAKE ADEFOVIR?
- WHAT ABOUT DRUG RESISTANCE?
- HOW IS ADEFOVIR TAKEN?
- WHAT ARE THE SIDE EFFECTS?
- HOW DOES ADEFOVIR REACT WITH OTHER
DRUGS?
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PrintDIPIVOXIL?
Adefovir dipivoxil, also called Preveon® or bis-POM PMEA,
is a drug used for antiviral
therapy. It is manufactured by Gilead Sciences. Adefovir
has not been approved by the FDA for use against HIV. In November
1999, an expert panel advised the FDA not to approve the drug.
The panel was mainly concerned about possible kidney damage.
In December 1999, Gilead announced it would stop development
of adefovir dipivoxil for use against HIV in the United States.
Development will continue in the US against Hepatitis B, and
in Europe against HIV.
Adefovir is a nucleotide analog reverse transcriptase inhibitor,
or nuke. These drugs stop HIV from multiplying by preventing the
reverse transcriptase enzyme from working. This enzyme changes
HIV’s genetic material (RNA) into the form of DNA. This step has
to occur before HIV’s genetic code gets inserted into an infected
cell’s genetic codes.
In addition to fighting HIV, adefovir helps control Hepatitis
B and cytomegalovirus (CMV).
ADEFOVIR DIPIVOXIL?
Most doctors start antiviral
therapy when a person has some symptoms of HIV disease, has
a T-cell count (CD4+ cells)
below 500, or has a viral load
(a measure of the amount of virus in the blood) over 30,000.
There are no absolute rules about when to start antiviral drugs.
Some people want to “hit HIV hard and early”, starting
with the strongest drugs to preserve the immune system. Others
want to save the strongest drugs until they are needed, later
in the course of HIV disease. You and your doctor should consider
your T-cell count, your viral load, any symptoms you are having,
and your attitude about taking HIV medications.
RESISTANCE?
The HIV virus is sloppy when it makes copies of its genetic code
(RNA). Many new copies of HIV are mutations: they are slightly
different from the original virus. Some mutations can continue
to multiply even when you are taking an antiviral drug. When this
happens, the drug will stop working. This is called “developing
resistance” to the drug.
Resistance to adefovir takes a long time to develop. With combination
therapy (taking more than one antiviral drug at the same time),
HIV mutates much more slowly and it takes much longer for resistance
to develop.
A benefit of adefovir is that it works against several strains
of HIV that are already resistant to AZT,
Sometimes, if you develop resistance to one drug, you will
also have resistance to other antiviral drugs. This is called
“cross-resistance”. However, adefovir seems to have
very little cross resistance with other antiviral drugs. In fact,
the mutation that makes HIV resistant to the drug 3TC
actually makes adefovir work better.
TAKEN?
The normal adult dose of adefovir has not yet been decided. At
first, people were taking 120 mg, once daily. However, because
of kidney abnormalities, the manufacturer is now focusing on a
dosage of 60 mg, once daily.
Adefovir reduces the amount of the amino acid carnitine in
your body. People taking adefovir need to take a daily supplement
of 500 mg of carnitine.
Adefovir can be taken with or without food.
EFFECTS?
With the start of any anti?viral treatment there may be temporary
side effects such as headaches, high blood pressure, or a general
sense of feeling ill. These side effects are likely to get better
or even disappear over time.
The most common side effects of Adefovir are nausea, vomiting
and loss of appetite. The carnitine supplements that are taken
with adefovir can also cause some stomach upset.
Almost 40% of people taking adefovir for more than 6 months
have abnormal laboratory values for kidney tests. You might not
know when these problems start, so your doctor should do lab work
every month while you are taking adefovir.
REACT WITH OTHER DRUGS?
Adefovir causes a 50% drop in the blood level of delavirdine.
Other drug interaction studies are still going on.
Adefovir is intended to be used as part of combination antiviral
therapy against HIV. It should normally be used along with a nucleoside
analog reverse transcriptase inhibitor (nuke) plus a non-nucleoside
reverse transcriptase inhibitor (NNRTI) or a protease inhibitor.
Revised December 5, 1999
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