Didanosine remains a cornerstone
nucleoside analogue for the treatment of
HIV infection. A potential problem with the buffered formulations of
didanosine is the likelihood of interactions with other drugs that require an acidic pH for absorption or can be chelated by
cations in the
buffer. An encapsulated enteric-coated (EC) bead formulation of
didanosine has been approved and is routinely used as an alternative to the chewable/dispersible buffered
tablet formulation. The objective of this study was to evaluate the single-dose pharmacokinetics of
didanosine EC at 240 mg/m2 in 10 HIV-infected children.
Didanosine EC was administered at time 0 on an empty stomach with no other concomitant medications. Blood samples were collected at pre-dose, 0.5, 1, 2, 4, 8 and 12 h post-dose.
Didanosine was measured in plasma using radioimmunoassay. Ten subjects completed the intensive pharmacokinetic evaluation; data are available for eight participants. Plasma concentrations of
didanosine following EC administration were analysed using non-compartmental methods. Median (range) AUCinfinity, Cmax, Tmax and CL/F for
didanosine following EC administration were 2385 (1291, 3966) ng x h/ml, 854 (300, 1799) ng/ml, 3.0 (1.0, 8.1) h and 3.3 (2.7-6.4) l/h/kg, respectively. Results from this study indicate that the
didanosine Cmax is decreased and Tmax is prolonged, but total exposure of
didanosine in plasma following
didanosine EC administration appears similar to previous data collected in HIV-infected children following buffered
didanosine administration.