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 μg/ml and 11.4 μg/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. Clinical Pharmacology and Therapeutics (1990) 48, 26–33; doi: 10.1038/clpt.1990.113