Products
Didanosine was commercially available in the form of capsules (Videx EC). It was first approved in 1991 as the second HIV drug after AZT (EC = enteric coated, capsules filled with enteric granules).
Structure and properties
Didanosine (C10H12N4O3, Mr = 236.2 g/mol) corresponds to 2′,3′-dideoxyinosine, a synthetic nucleoside analog of deoxyadenosine. The 3′-hydroxy group is replaced by a hydrogen atom. Didanosine exists as a white crystalline powder that is soluble in water. It is a prodrug that is biotransformed intracellularly to the active metabolite dideoxyadenosine triphosphate (ddATP).
Effects
Didanosine (ATC J05AF02) is antiviral against HI viruses. The effects are due to inhibition of the enzyme reverse transcriptase, which transcribes viral RNA into DNA and is important for viral replication. Dideoxyadenosine triphosphate is incorporated into viral DNA as the wrong substrate, leading to chain termination.
Indications
For treatment of infection with HIV as part of combination antiretroviral therapy.
Dosage
According to the SmPC. Capsules are taken fasting once or twice daily, 2 hours before or after meals. Food taken at the same time reduces absorption to a significant extent.
Contraindications
Didanosine is contraindicated in cases of hypersensitivity. For complete precautions, see the drug label.
Interactions
Drug-drug interactions are possible with drugs that may cause peripheral neuropathy or pancreatitis. Interactions have been reported with hydroxyurea, tenofovir, ribavirin, allopurinol, ganciclovir, ketoconazole, methadone, and alcohol.
Adverse effects
The most common potential adverse effects include diarrhea, peripheral neurologic symptoms, neuropathy, nausea, headache, rash, and vomiting. Didanosine may rarely cause inflammation of the pancreas (pancreatitis) and other serious adverse reactions.
