The pharmacokinetics of oral CdA (0.24 mg/kg) was studied in 4 patients (1 with hairy cell leukaemia and 3 with B-cell chronic lymphocytic leukaemia) to determine any effect of food and fasting with and without omeprazole. Food intake did not significantly influence the bioavailability of CdA (42% after food intake vs 46% while fasting) but it did reduce the maximum plasma concentration (C(max)) by 40%; 83 compared to 116 nM while fasting. The time to reach maximum concentration (t(max)) was delayed about 0.8 h after food intake. Pretreatment with omeprazole did not significantly influence the bioavailability of CdA (51% vs 46% without), or the interindividual variability in bioavailability in the fasting state (C. V 0.26 with and C. V 0.27 without). In conclusion, there was a small, though not statistically significant reduction in the bioavailability of CdA after food intake. Omeprazole did not significantly improve the bioavailability of CdA.