Availability of mesalazine (5-aminosalicylic acid) from enemas and suppositories during steady-state conditions.

The local and systemic bioavailability of a mesalazine enema (Pentasa, Ferring A/S, Denmark) and a mesalazine suppository (Pentasa, Ferring) was assessed during steady-state conditions. Eleven healthy subjects took 1 g of the enema or the suppository twice daily for 1 week, with a drug-free period of at least 1 week in between. At the end of each treatment period the urine and faeces were collected for 48 h, and the concentrations of mesalazine and the metabolite acetyl-mesalazine were measured. Plasma concentrations of drug and metabolite were measured hourly during a 12-h dose interval. The faecal water concentration of mesalazine was significantly higher after suppository treatment (55.7 mmol/l) compared with enema treatment (31.7 mmol/l) (p less than 0.01). The systemic absorption was low; 15% of daily mesalazine dose was recovered in urine after enema treatment and 10% after suppositores (p less than 0.01). Plasma concentrations were low, and no accumulation of either mesalazine or acetyl-mesalazine occurred. In conclusion, the enema and the suppository can be continuously administered as 1 g of mesalazine twice daily, respectively, giving high faecal water concentrations of mesalazine and a low systemic absorption.