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Didanosine
See also Nucleoside analogue reverse transcriptase inhibitors (NRTIs)
General information
Didanosine (2′,3′-dideoxyinosine, ddI) is a purine analogue reverse transcriptase inhibitor. The major clinical adverse effects reported during the first years of use of didanosine were acute pancreatitis and a painful neuropathic syndrome (due to a peripheral neuropathy), which appeared to be related to both dosage and cumulative dose [ ]. However, the incidence of acute pancreatitis and peripheral neuropathy in these studies was lower than in earlier studies with didanosine [ , ]. This may be related to the fact that treatment was started earlier or to the use of lower dosages (200–400 mg/day) in these studies compared with earlier studies. In the latter studies, gastrointestinal symptoms, most notably nausea and vomiting, were the most commonly reported adverse effects in patients taking didanosine. Minor adverse effects include insomnia, headaches, anxiety, irritability, rash, increased plasma uric acid concentration, and increased hepatic transaminase activities combined with a rash [ ]. There were no toxic effects of didanosine on hematological laboratory indices [ ].
Drug studies
Observational studies
The use of didanosine 125–200 mg bd plus interferon alfa-2b in AIDS-associated Kaposi’s sarcoma has been studied in 68 patients [ ]. Withdrawal of didanosine was required in cases of peripheral neuropathy, rises in serum amylase activity, and hypertriglyceridemia.
Comparative studies
In 44 patient with HIV infection, didanosine added to tenofovir was associated with progressive loss of mtDNA content and reduced cyclo-oxygenase activity over 12-months compared with tenofovir alone [ ]. In another study in 61 individuals didanosine + stavudine exposure was associated with mtDNA depletion in peripheral blood mononuclear cells and subcutaneous fat [ ].
Placebo-controlled studies
In a study of 168 patients with virological failure didanosine was compared with placebo in addition to optimized background treatment [ ]. The incidence of adverse events was similar in the two groups (38% with didanosine and 36% with placebo). Most of the adverse events were gastrointestinal (20%) or affected the nervous system (14%). Only five patients (4.5%) in the didanosine group and two (3.6%) in the placebo group complained of grade 1–2 diarrhea; no grade 3 diarrhea was reported. One patient in the didanosine group had a grade 2 rise in serum lipase activity, and one in the placebo group had a grade 3 rise.
Organs and systems
Sensory systems
Eyes
Didanosine has been associated with retinopathy attributed to irreversible loss of retinal pigment epithelium accompanied by partial loss of the choriocapillaris and neurosensory retina in the mid-periphery. In a single case of retinopathy the electrophysiological abnormalities improved after didanosine withdrawal [ ]. Retinal depigmentation has also been described in children taking didanosine [ ].
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