What is Videx and Videx
Videx and Videx EC are anti-HIV medications.
They are in a category of HIV medications called
nucleoside reverse transcriptase inhibitors
(NRTIs). NRTIs prevent HIV from altering the
genetic material of healthy T-cells. This prevents
the cells from producing new virus and decreases
the amount of virus in the body.
Videx, manufactured by Bristol-Myers Squibb,
was the second drug approved for the treatment
of HIV, and was approved by the U.S. Food and
Drug Administration in 1989.
Generic versions of delayed-release didanosine
(similar to Videx EC), manufactured by Barr
Laboratories, are now available. It was approved
by the FDA in December 2004.
This lesson reviews both Videx buffered tablets,
which can be taken once or twice a day, and
Videx EC, a capsule that only needs to be taken
once a day. They are the same drug, but come
in different forms and are taken differently.
Because Videx EC is considered to be easier
to take and does not contain an antacid buffer
(which can cause stomach upsets and prevents
many other medications from being taken at the
same time as Videx tablets and powder), most
HIV-positive adults are now taking Videx EC.
Videx or Videx EC must be used in combination
with at least two other anti-HIV drugs.
What Are the Drug Interactions
with Videx EC?
HIV-positive people must be very careful about
using Videx in combination with Viread (tenofovir).
There are two important warnings to know about:
Drug regimens consisting of Sustiva (efavirenz)
or Viramune (nevirapine) plus Viread and Videx
have been associated with premature drug failure.
If you are receiving Viread and Videx EC with
either Sustiva or Viramune, you may want to
discuss alternative options with your doctor.
Viread increases the amount of Videx/Videx EC
in the body. This can increase the risk of experiencing
side effects that can be caused by Videx, such
as pancreatitis, peripheral neuropathy, and
lactic acidosis. In turn, if Viread and Videx
are used together, Videx EC should be taken
at a dose of 250mg once a day (reduced from
the usual daily dose of 400mg a day).
Because there are now a number of concerns regarding
the use of Viread in combination with Videx/Videx
EC, many experts recommend avoiding this combination
Ribavirin (Rebetol; Copegus), one of the two
drugs that are often prescribed to treat hepatitis
C, can increase Videx levels inside cells. Researchers
have not yet determined the correct dose of
Videx for HIV-positive people who are also taking
ribavirin to treat their hepatitis C infection.
In turn, it is probably best to avoid combining
Because Videx can cause pancreatitis, it should
be used carefully in combination with other
drugs that can also cause pancreatitis. These
include intravenous pentamidine and TMP/SMX
(Bactrim; Septra). It is also possible that
combining Videx with hydroxyurea, a cancer drug
that has been studied as a treatment for HIV,
increases the risk of pancreatitis.
The oral form of Cytovene (ganciclovir), a treatment
used to prevent CMV from recurring in people
who have had this disease, can decrease Videx
and Videx EC levels in the bloodstream. Videx
and Videx EC can increase Cytovene levels in
the bloodstream. No dosing recommendations have
Methadone, a drug frequently used to help people
recovering from heroin addiction, can decrease
the amount of Videx in the bloodstream. This
can result in an anti-HIV drug regimen being
less effective against HIV, which can cause
Combining Videx with Zerit (d4T), another nucleoside
reverse transcriptase inhibitor (NRTI), may
increase the risk of developing lactic acidosis.
This is especially true in HIV-positive pregnant
women who take both of these drugs together.
In turn, the U.S. Food and Drug Administration
(FDA) has recommended that HIV-positive women
not take these two drugs together while they
What Are the Drug Interactions
with Videx Buffered Tablets?
Because Videx buffered tablets contain an antacid
buffer to neutralize acid in the stomach (this
is necessary for Videx to be absorbed properly
into the bloodstream), it should not be taken
at the same time as medications that require
acid in the stomach. Examples of medications
that require acid in the stomach include Atrisone
(dapsone), Sporanox (itraconazole), Nizoral
(ketoconazole), Cipro (ciprofloxacin), and quinolones.
These medications should be taken at least two
hours before or two hours after taking Videx.
Videx buffered tablets should not be taken at
the same time as any of the available protease
inhibitors, especially Reyataz (atazanavir).
The protease inhibitors should be taken at last
two hours before or two hours after taking Videx.
Videx buffered tablets can be taken at the same
time as Viramune (nevirapine) and Sustiva, two
non-nucleoside reverse transcriptase inhibitors
(NNRTIs). Rescriptor (delavirdine), another
NNRTI, should be taken two hour before or two
hours after taking Videx.
Methadone, a drug used to treat heroin addiction,
can decrease the amount of Videx (from the buffered
tablets only) in the bloodstream. As a result,
it's probably best to switch from Videx buffered
tablets to Videx EC capsules if methadone is
also being used.
Adverse Events / Toxicity
/ Side Effects
Pancreatitis, which has been fatal in some cases,
is one of the most serious adverse effects reported
in patients receiving didanosine. The frequency
of pancreatitis is dose-related, with an incidence
in adult patients between 1% and 7% and in pediatric
patients between 3% and 13%. Pancreatitis has
occurred during didanosine therapy in both treatment-experienced
and treatment-naive patients, regardless of
the degree of immunosuppression. Didanosine
treatment should be suspended in patients with
suspected pancreatitis and discontinued in patients
with confirmed pancreatitis.
Lactic Acidosis and Hepatomegaly
The use of didanosine and other nucleoside analogues,
either alone or in combination with other antiretrovirals,
has been associated with lactic acidosis and
severe hepatomegaly with steatosis, including
some fatal cases. Risk factors include female
gender, obesity, and prolonged exposure to antiretroviral
lactic acidosis has been reported in pregnant
women who received an antiretroviral regimen
that included didanosine and stavudine. Cases
have occurred in patients with and without known
risk factors for liver disease.
use should be suspended in any patient who develops
clinical or laboratory findings suggestive of
lactic acidosis or pronounced hepatotoxicity,
which may include hepatomegaly and steatosis
even in the absence of marked transaminase elevations.
Peripheral neuropathy, manifested by numbness,
tingling, or pain in the hands or feet, has
been reported in patients taking didanosine.
In recent studies, peripheral neuropathy was
reported in 21% to 26% of patients taking didanosine
in conjunction with stavudine (d4T, Zerit) and
either nelfinavir (Viracept, and HIV protease
inhibitor) or indinavir (Crixivan, and HIV protease
Common, less serious adverse effects include
central nervous system effects (anxiety, headache,
insomnia, irritability, and restlessness); dry
mouth; gastrointestinal disturbances (diarrhea,
dyspepsia, flatulence, nausea, vomiting); and
Other, less frequently reported, effects involve
the following organ systems: body as a whole
(alopecia, anaphylactoid reaction, asthenia,
chills/fever, pain, redistribution/accumulation
of body fat); cardiovascular (cardiomyopathy);
exocrine (sialoadenitis, parotid gland enlargement,
dry mouth); hematologic (anemia, leukopenia,
thrombocytopenia); metabolic (hyperglycemia,
hypoglycemia, diabetes mellitus); musculoskeletal
(myalgia, rhabdomyolysis with acute renal failure,
arthralgia, myopathy); and ocular (retinal changes,
optic neuritis, diplopia, dry eyes, optic atrophy,