- WHAT IS ddI?
- WHO SHOULD TAKE ddI?
- WHAT ABOUT DRUG RESISTANCE?
- HOW IS ddI TAKEN?
- WHAT ARE THE SIDE EFFECTS?
- HOW DOES ddI REACT WITH OTHER DRUGS?
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PrintddI (Videx®), is a drug used for antiviral therapy. It
is manufactured by Bristol-Myers Squibb. ddI is also known as
didanosine or dideoxyinosine.
ddI is a nucleoside analog reverse transcriptase inhibitor,
or nuke. These drugs block the reverse transcriptase enzyme. This
enzyme changes HIV’s genetic material (RNA) into the form of DNA.
This has to occur before HIV’s genetic code gets inserted into
an infected cell’s own genetic codes.
ddI?
ddI was approved as an antiviral drug for people with HIV infection.
There are no absolute rules about when to start antiviral drugs.
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. Fact Sheet 411
has more information about guidelines
for the use of antiviral medications.
If you take ddI with other antiviral drugs, you can reduce
your viral load to extremely low levels, and increase your T-cell
counts. This should mean staying healthier longer.
RESISTANCE?
Many new copies of HIV are mutations. They are slightly different
from the original virus. Some mutations can keep multiplying even
when you are taking an antiviral drug. When this happens, the
drug will stop working. This is called “developing resistance”
to the drug. See Fact Sheet 414
for more information on resistance.
Sometimes, if your virus develops resistance to one drug, it
will also have resistance to other antiviral drugs. This is called
“cross-resistance”.
Resistance can develop quickly. It is very important to
take antiviral medications according to instructions, on schedule,
and not to skip or reduce doses.
HOW
IS ddI TAKEN?
ddI is available as a chewable tablet (which can also be dissolved
in water) and as a powder that is dissolved in water. The recommended
dose of ddI for adults is based on weight. For people weighing
more than 132 pounds, the dose is 200mg (milligrams) in tablet
form, or 250mg of powder, twice a day. For those weighing less
than 132 pounds, the dose is 125mg in tablet form, or 167mg of
powder, twice a day.
In November 1999, the FDA approved a new formulation of ddI
that can be taken just once a day. The dosage is two 200 mg tablets
taken at the same time. The new tablets cannot be used for twice
a day dosing. However, in July 2000, the FDA said that twice-daily
dosing of ddI is preferred. Once-daily dosing should only be used
by adults with a special need to take their medications just once
a day. If you want to change how often you take ddI, talk to
your doctor.
If you have had liver or kidney problems, the dose of ddI may
need to be reduced.
ddI cannot be absorbed in an acid environment. ddI contains
a buffer to reduce the effects of stomach acid. ddI is taken
on an empty stomach, 30 minutes before eating or two hours after
a meal. Taking ddI with food may reduce blood levels by as much
as 50%.
Bristol-Myers Squibb developed a new “enteric coated”
version of ddI called Videx EC. It can be taken as a single capsule
once a day. Videx EC does not contain a buffer, so side effects
and drug interactions could be reduced. The FDA approved Videx
EC in October 2000. Videx EC should be taken with an empty stomach.
Do not chew it; swallow it whole.
WHAT
ARE THE SIDE EFFECTS?
When you start any antiviral treatment you may have temporary
side effects such as headaches, hypertension, or a general sense
of feeling ill. These side effects usually get better or disappear
over time.
The most common side effects of ddI are diarrhea, headaches,
vomiting and rash. Diarrhea, caused by the buffer in the tablets,
is sometimes severe.
The most serious side effects of ddI are peripheral neuropathy,
pancreatitis, and lactic acidosis:
is a form of nerve damage. It usually shows up as tingling, numbness,
or a sharp burning sensation in the feet, legs, or hands. The
nerve damage is usually temporary and will go away if you stop
taking ddI, or reduce the dose. If you continue to take ddI after
nerve damage shows up, it may become permanent. See Fact
Sheet 553 for more information.
Pancreatitis is an inflammation of the pancreas, a large
gland located behind the stomach. Pancreatitis can be fatal. If
you are taking ddI and have sharp pain near your stomach, back,
or sides, with nausea and vomiting, stop taking ddI immediately
and call your doctor.
Lactic acidosis is a buildup of lactic acid in the blood.
This is a by-product of abnormal energy production by the cells.
It may be caused by damage to the mitochondria. See Fact
Sheet 554 for more information on mitochondrial
toxicity. Lactic acidosis can cause severe damage to the pancreas
and liver. Symptoms of lactic acidoss can include weight loss,
abdominal pain, and severe fatigue.
REACT WITH OTHER DRUGS?
ddI may be more effective if taken with hydroxyurea.
However, this increases the risk of developing pancreatitis.
Methadone decreases blood levels of ddI
ddI should not be combined with ddC
(zalcitabine, Hivid®).
Pregnant women should not take ddI and d4T at the same
time due to an increased risk of lactic acidosis.
Do not take ddI at the same time as a protease inhibitor.
Separation times are different for different protease inhibitors.
Check the instructions for your medications.
Levels of ddI are increased if it is taken with tenofovir
(Viread) or ribavirin (used to treat hepatitis C). Patients taking
ddI with either of these drugs should watch carefully for signs
of ddI side effects.
Revised November
16, 2002
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