ddI, trade name Videx (also known as didanosine), is a an anti-HIV treatment in the same class of drugs as AZT, ddC, d4T and 3TC. These drugs are called nucleoside analogs. The body breaks down these drugs into chemicals that stop HIV from infecting uninfected cells in the body, but they do not help cells that have already been infected with the virus. As people with AIDS lose T4 cells - one of the immune systems main defenses - they become more likely to get infections and illnesses.

New Public Health Service HIV treatment guidelines say that the best way to use ddI is in combination with other anti-HIV drugs. The guidelines recommend combinations of three or four anti-HIV drugs as first treatment for HIV:

• Two nucleoside analogs (AZT+3TC, d4T+3TC, d4T+ddI, AZT+ddI, or AZT+ddC) with one of the following: Crixivan, Fortovase, Norvir, Sustiva, Viracept or Norvir and Fortovase combined.
• If one of the above combinations cannot be used, an alternative is two nucleoside analogs (same combinations as listed above) with Viramune or Rescriptor.

There have also been encouraging results from studies of ddI in combination an old anti-cancer drug called hydroxyurea. The Network has a separate Simple Fact Sheet on hydroxyurea, call for a free copy.

Dosage: ddI usually comes in the form of a large, flavored tablet that can be chewed or dissolved in water, or in a powder that gets dissolved in water. A new, smaller, mandarin-flavored tablet has recently been approved. This new tablet is softer and dissolves in water faster than the old tablet. Because food can slow down the body's absorption of ddI, people should take the drug at least half an hour before, or two hours after eating. The recommended adult dose of ddI is based on body weight. People weighing over 60kg should take 200mg twice daily while those weighing less than 60kg should take 125mg twice daily. Tablets are available in 25, 50, 100, 150 and 200 mg dosages. At least two of the appropriate strength tablets should be taken at each dose, normally in the morning and evening.

Once-Daily ddI: In a recent study, once-daily ddI dosing didn't seem to work as well as twice-daily dosing. Although ddI can be given once-daily under certain circumstances, the US Food and Drug Administration (FDA) recommends that ddI be taken twice-daily if possible. The FDA says, "Although once-daily dosing frequency is available, it should only be considered for people whose management requires once-daily dosing." This will likely mean people having to take complicated drug combinations. Because ddI has to be taken on an empty stomach, it can be difficult to take the drug twice-daily if you're also taking other drugs that have food restrictions. [See Bristol-Myers issues letter about change in Videx dosing, also Letter to Doctors]

Side effects: The most common side effects reported are stomach pain, diarrhea, peripheral neuropathy and pancreatitis. Peripheral neuropathy is a kind of nerve damage that shows up as a burning or tingling pain in the hands and feet. Pancreatitis can appear as a pain in the stomach area that goes through to your back. If pancreatitis isn't caught soon enough, it can be very serious. Careful monitoring of blood enzymes called amylase and lipase can provide an early warning of pancreatitis. If you're taking ddI avoid alcohol, which can increase risk of pancreatitis. Recent studies have also suggested that taking ddI in combination with d4T (Zerit) and/or hydroxyurea may increase the risk of pancreatitis.

Liver damage (also called chemical hepatitis), seizures, headaches, abnormal bone marrow function, and allergic reactions are less commonly reported side effects.

Drug interactions: ddI should not be taken in combination with dapsone as as ddI significantly lowers the levels of dapsone in the body. If you're taking ddI and the protease inhibitor Crixivan or the NNRTI drug Rescriptor, you should take these drugs at least an hour before ddI. If you are taking intravenous pentamidine for PCP at the same time as ddI, there is an increased risk of pancreatitis. You should avoid taking ddI with the drug allopurinol as this drug significantly increases ddI levels in the body. Because ddI pills contain antacid, you should not take additional antacids when using ddI.

Using children's ddI: There is a version of ddI for children. Children's ddI comes in cherry or mint flavor and must be mixed with an antacid (Mylanta DS Liquid or extra strength Maalox Plus suspension or Maalox TC suspension). Some adults find the children's version of ddI easier to take than the tablets. For adults, children's ddI can be mixed by a pharmacist to give a strength of 20mg of ddI per milliliter of liquid. This way, 20 milliliters (mL) of children's ddI will provide the usual daily adult ddI dose of 400mg. If you're having trouble taking ddI tablets, ask your doctor about trying the children's version.

Bristol-Myers Squibb, who make Videx, has Reimbursement Assistance and Temporary Assistance Programs for people having trouble affording the drug. Call (800) 272-4878 for more information.

Note: The FDA has issued a revised warning letter to doctors regarding pancreatitis and ddI. Letter to Doctors regarding better results with twice daily dosing.

The Simple Facts Project is a program of the AIDS Treatment Data Network (The Network). This information does not intend to promote or endorse any specific treatment for any health related condition.