Videx/Videx EC (didanosine, ddI)

January 2008     View PDF     En español
Reprinted from www.aidsmeds.com, US

What is Videx?
Videx EC is an HIV medication. It is in a category of HIV medications called nucleoside reverse transcriptase inhibitors (NRTIs). NRTIs prevent HIV from altering the genetic material of healthy CD4 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 originally approved as a chewable or dissolvable tablet by the US Food and Drug Administration in 1991. Videx EC capsules were approved by the FDA in 2000 and have since replaced Videx tablets.

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.

Videx EC must be used in combination with at least two other HIV drugs.

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What is known about Videx EC?
Enteric coated (delayed release) didanosine is available as Videx EC, the brand-name version of the drug, and as a generic formulation. A pharmacy may automatically dispense the generic version of delayed release didanosine in order to reduce the cost of treatment.

The correct dose of Videx EC is one 400mg capsule once a day (for people who weigh 132 pounds or more) or one 250mg capsule (for people who weigh less than 132 pounds). It is also possible to take Videx EC capsules twice a day: one 200mg capsule twice a day (for people who weigh 132 pounds or more) or one 125mg capsule twice a day (for people who weigh less than 132 pounds).

Videx EC should not be used by babies or children. Didanosine powder, sold as Videx, is necessary for pediatric patients.

Videx EC must be taken on an empty stomach (not eating within two hours before or one hour after taking Videx EC). Food and many liquids can prevent Videx EC from being properly absorbed into the bloodstream. Videx EC should be taken with water. It should not be taken with acidic juices, soda, or milk.

Videx EC can be taken with other medications.

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How effective is Videx EC? And what about resistance?

Numerous studies have demonstrated that Videx EC is effective for the treatment of HIV when combined with other HIV drugs, usually at least one other nucleoside reverse transcriptase inhibitor (NRTI) and either a protease inhibitor or non-nucleoside reverse transcriptase inhibitor (NNRTI). Videx EC should not be taken alone (as monotherapy).

The generic version of didanosine has been shown to be pharmacologically equivalent to the brand-name version of the drug, meaning that it achieves the same drug levels in the body as Videx EC. The generic version is also regulated by the FDA, meaning that the manufacturer must adhere to strict quality control measures.

For HIV-positive adults beginning anti-HIV drug therapy for the first time, Videx EC is listed as an "alternative" NRTI option by the United States Department of Health and Human Services in its treatment guidelines. Truvada (tenofovir plus emtricitabine) is listed as the "preferred" NRTI option.

The DHHS recommends against using Videx EC and Zerit (d4T) in the same drug combination. The risk of side effects, which are similar for Zerit and Videx EC, are increased when these drugs are used at the same time.

Therapy with Videx EC can cause certain changes (mutations) in HIV's structure to occur. Some mutations will prevent Videx EC from working against HIV. Some studies suggest that HIV is much more likely to become resistant to Videx EC if it is already resistant to Retrovir (zidovudine), another NRTI. If HIV is not resistant to Retrovir, resistance to Videx EC may develop much more slowly. If your viral load does not go undetectable or becomes detectable (and increases) while you are taking an HIV drug regimen, your doctor can order a drug-resistance test to determine if your HIV has mutations that are causing resistance to Videx EC and to help you figure out which NRTIs your HIV is still sensitive to.

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What about drug interactions?
HIV-positive people must be very careful about using Videx EC 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 EC have been associated with premature drug failure. If you are receiving Videx EC with either Sustiva or Viramune, you may want to discuss alternative options with your doctor.

Viread increases the amount of Videx EC in the body. This can increase the risk of experiencing side effects that can be caused by Videx EC, such as pancreatitis, peripheral neuropathy, and lactic acidosis. In turn, if Viread and Videx EC 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 EC, many experts recommend avoiding this combination altogether.

Ribavirin (Rebetol; Copegus), one of the two drugs that are often prescribed to treat hepatitis C, can increase Videx EC levels inside cells. Researchers have not yet determined the correct dose of Videx EC for HIV-positive people who are also taking ribavirin to treat their hepatitis C infection. In turn, it is probably best to avoid combining these drugs.

Because Videx EC 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 EC 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 EC levels in the bloodstream. Videx EC can increase Cytovene levels in the bloodstream. No dosing recommendations have been made.

Methadone, a drug frequently used to help people recovering from heroin addiction, can decrease the amount of Videx EC in the bloodstream. This can result in an HIV drug regimen being less effective against HIV, which can cause drug resistance.

Combining Videx EC with Zerit, 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 US Food and Drug Administration (FDA) has recommended that HIV-positive women not take these two drugs together while they are pregnant.

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What about side effects?
Lactic acidosis, which can be fatal, and severe liver problems (fatty liver) have been reported in people taking nucleoside reverse transcriptase inhibitors (NRTIs). These problems are more likely to occur in HIV-positive people taking Zerit or Zerit in combination with Videx EC. Contact your doctor immediately if you experience nausea, vomiting, or unusual or unexpected stomach discomfort; weakness and tiredness; shortness of breath; weakness in the arms and legs; yellowing of the skin or eyes; or pain in the upper stomach area.

Videx EC can cause inflammation of the pancreas (pancreatitis). Pancreatitis is a rare but serious side effect that can be life-threatening in some cases. Notify your doctor immediately if you develop symptoms of pancreatitis, including nausea, vomiting, diarrhea, and abdominal pain. You should avoid alcohol while you are taking Videx EC, as alcohol can increase the risk of damage to your pancreas.

A common side effect of Videx EC is peripheral neuropathy, which can result in pain, tingling, numbness, or burning in the hands and/or feet. Stopping Videx EC and starting another NRTI that does not usually cause peripheral neuropathy — for example, Retrovir (zidovudine) or Ziagen (abacavir) — is often the best way to stop peripheral neuropathy.

Other common side effects include stomach aches, nausea, diarrhea, dry mouth, and central nervous system effects (e.g., anxiety, headaches, trouble sleeping, irritability, and restlessness). Very often, these side effects improve within a few months/weeks of starting Videx EC.

Damage to the eyes is another serious side effect that can be caused by Videx EC. This is more likely to occur in HIV-positive children taking Videx powder or Videx EC.

HIV drug regimens containing NRTIs, including Videx EC, can cause increased fat levels (cholesterol and triglycerides) in the blood, abnormal body-shape changes (lipodystrophy; including increased fat around the abdomen, breasts, and back of the neck, as well as decreased fat in the face, arms, and legs), and diabetes.

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Can pregnant women take Videx EC?
Videx EC is classified by the FDA as a pregnancy category B drug. Pregnancy category B means that animal studies have failed to demonstrate a risk to the fetus, but there are no adequate and well-controlled studies in pregnant women. HIV-positive women who become pregnant should discuss the benefits and possible side effects of anti-HIV treatment to help protect their babies from HIV.

It is not known whether Videx EC passes into breast milk and what effects it may have on a nursing baby. However, to prevent HIV transmission of the virus to uninfected babies, it is recommended that HIV-positive mothers not breast-feed.

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Who should not take Videx?
Before taking this medication, tell your doctor if you have: kidney disease; liver disease; a history of pancreatitis; a history of lactic acidosis or elevated lactate levels; a history of peripheral neuropathy. You may not be able to take Videx EC, or you may require lower doses or special monitoring during treatment, if you have any of these conditions.

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Where can I learn more about clinical trials that are using Videx EC?
If you would like to find out if you are eligible for any clinical trials that include Videx EC, there is an interactive web site run by ACRIA, the AIDS Community Research Initiative of America.

Another useful service for finding clinical trials is AIDSinfo.nih.gov, a site run by the US National Institutes of Health. They have "health information specialists" you can talk to at their toll-free number at 1-800-HIV-0440 (1-800-448-0440).

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