Didanosine (ddI), sold under the brand name Videx among others, is a medication used to treat HIV/AIDS. It is used in combination with other medications as part of highly active antiretroviral therapy (HAART). It is of the reverse-transcriptase inhibitor class.
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Didanosine was first described in 1975 and approved for use in the United States in 1991.
Adverse effects
The most common adverse events with didanosine are diarrhea, nausea, vomiting, abdominal pain, fever, headache, and rash. Peripheral neuropathy occurred in 21-26% of participants in key didanosine trials. Other reported serious adverse events are retinal changes, optic neuritis and alterations of liver functions. The risk of some of these serious adverse events is increased by drinking alcohol.
In February 2010, the United States Food and Drug Administration issued a statement that patients using didanosine (Videx) are at risk for a rare but potentially fatal liver disorder, non-cirrhotic portal hypertension.
Drug interactions
- A significant interaction has also been recorded with allopurinol, and administration of these drugs together should be avoided.
- Alcohol can exacerbate didanosine's toxicity, and avoiding drinking alcohol while taking didanosine is recommended.
Mechanism of action
Didanosine (ddI) is a nucleoside analogue of adenosine. It differs from other nucleoside analogues, because it does not have any of the regular bases, instead it has hypoxanthine attached to the sugar ring. Within the cell, ddI is phosphorylated to the active metabolite of dideoxyadenosine triphosphate, ddATP, by cellular enzymes. Like other anti-HIV nucleoside analogs, it acts as a chain terminator by incorporation and inhibits viral reverse transcriptase by competing with natural dATP.
Pharmacokinetics
Oral absorption of didanosine is fairly low (42%) but rapid. Food substantially reduces didanosine bioavailability, and the drug should be administered on an empty stomach.