didanosine (Videx, Videx EC)

Didanosine is an oral medication that is used for the treatment of infections with the human immunodeficiency virus (HIV). It is in a class of drugs called reverse transcriptase inhibitors which also includes zalcitabine (Hivid), zidovudine (Retrovir), stavudine (Zerit), and lamivudine (Epivir). During infection with HIV, the HIV virus multiplies within the body's cells. The newly-formed viruses then are released from the cells and spread throughout the body where they infect other cells. In this manner, the infection spreads to new, uninfected cells that the body is continually producing, and HIV infection is perpetuated. When producing new viruses, the HIV virus must manufacture new DNA for each virus. Reverse transcriptase is the enzyme that the virus uses to form this new DNA. Specifically, didanosine is converted within the body to its active form (dideoxyadenosine triphosphate). This active form is similar to a chemical, deoxyadenosine triphosphate, that is required by the HIV virus to make new DNA. The reverse transcriptase uses dideoxyadenosine triphosphate instead of deoxyadenosine triphosphate for making DNA, and the dideoxyadenosine triphosphate that interferes with the reverse transcriptase. Didanosine does not kill existing HIV virus and it is not a cure for HIV. The FDA approved didanosine in October 1991.

What brand names are available for didanosine?

Videx, Videx EC

Is didanosine available as a generic drug?

GENERIC AVAILABLE: Yes

Do I need a prescription for didanosine?

Yes

The most severe side effects of didanosine are:

• inflammation of the pancreas (pancreatitis),
• liver failure, and
• nerve damage in the arms and legs (peripheral neuropathy).

Symptoms of peripheral neuropathy are tingling, numbness and pain in the feet or hands.

Other important side effects include:

• diarrhea,
• chills,
• fever,
• rash, stomach pain,
• headache,
• nausea and vomiting.

Adults weighing 60 kg or more should receive 400 mg once daily of the capsules or 200 mg twice daily of the powder. Adults weighing less than 60 kg require 250 mg once daily of the capsules and 125 mg twice daily of the powder.

Didanosine should be administered on an empty stomach because food reduces the absorption of didanosine by as much as 46%.

Didanosine powder contains an antacid which reduces the absorption of tetracycline (for example, Vibramycin, Minocin), ketoconazole (Nizoral), fluoroquinolone antibiotics (for example, ciprofloxacin [Cipro], Floxin), and other drugs that need stomach acid for absorption. Therefore, these drugs should be administered at least two hours before or after administration of didanosine solution.

Allopurinol (Zyloprim), tenofovir (Viread), and ganciclovir (Cytovene) increase blood levels of didanosine by reducing its elimination.

Although it is not known whether didanosine is excreted in breast milk, HIV-infected mothers should not breast feed because of the potential risk of transmitting HIV to an infant that is not infected.

What preparations of didanosine are available?

Capsules (Extended Release): 125, 200, 250, and 400 mg. Solution: 10 mg/ml

How should I keep didanosine stored?

Capsules and unmixed powder should be stored at room temperature, 15 C to 30 C (59 F to 86 F). The powder may be stored in the refrigerator at 2 C to 8 C (36 F to 46 F for up to 30 days after it is mixed with water.