Effect of food coadministration on 5-aminosalicylic acid oral suspension bioavailability

Single doses of 1 gm 5-aminosalicylic acid (5-ASA) suspension was administered to 24 healthy volunteers during both fasting and fed conditions. For subjects in a fasting state, plasma 5-ASA and acetyl 5-ASA concentrations peaked rapidly 1 hour after dosing to 14.72 micrograms/ml and 11.4 micrograms/ml, respectively. The elimination half-life of 5-ASA was 51.9 minutes, whereas the acetyl 5-ASA half-life could not be determined. A mean of 78.3% of the dose was excreted in the urine, with 5-ASA accounting for 21.2% of the dose and acetyl 5-ASA accounting for the balance. Only 11.3% of the dose was eliminated in the feces, consisting mostly of acetyl 5-ASA. Food coadministration reduced 5-ASA and acetyl 5-ASA systemic relative bioavailability to 44% and 76%, respectively, compared with the fasting treatment. Urinary excretion of the salicylates was reduced to 46.8%, and fecal salicylate elimination increased almost 100%--to 24.2% of the total dose.