Calcium polycarbophil a water-absorbing polymer is the calcium salt of polyacrylic acid cross-linked with divinylgly col. It has been developed as a treatrnent for constipation ordiarrhoea associated with conditions such as irritable bowel S ldrome. It releases calcium ions under acidic conditions and its pharmacological actions are due to the polycarbophil thus produced (Da lOf 1982). The pharmacological efficacy of calcium polycarbophil has been proven in clinical trials (Winkelstein 1964; LaCorte et al 1982) although the mechanisms of the anti-constipation or anti-diarrhoeal action of calcium polycarbophil have not been clarified. Calcium polycarbophil and polycarbophil are chemically (Child et al 1955) and physiologically inert (Grossman et al 1957; Roth 1960) and are not absorbed om the gastrointestinal tract into the systemic circulation (Child et al 1955). Therefore the physicochemical properties of these compounds must be important in generating the pharmacological effects in the gastrointestinal lumen. However little investigation of the physicochemical properties of calcium polycarbophil have been reported except for studies of the swelling ratios of polycarbophil at various pHs and at various ionic strengths (Ch'ng et al 1985; Park & Robinson 1985).
The purpose of this study was to investigate the physico chemical properties of calcium polycarbophil in order to throw light on the mechanisms of the anti-constipation and antì diarrhoeal action of this pol ηer. In this study we evaluated the decalcification of calcium polycarbophil and the effects of various factors such as pH ionic strength osmolarity and metal ions in the gastrointestinal fluid on the equilibrium swelling and viscosity (as an indicator of fluidity) of polycarbophi 1 ......