Alcohol and Alcoholism Vol. 35, No. 4, pp. 324-330, 2000
© 2000 Medical Council on Alcoholism
KINETIC STUDY OF ACAMPROSATE ABSORPTION IN RAT SMALL INTESTINE
Departamento de Farmacia y Tecnología Farmacéutica, Facultad de Farmacia, Universidad de Valencia, Avda Vte Andrés Estellés s/n. 46100 Burjassot, Valencia and Instituto de Investigación Citológicas (FVIB) Amadeo de Saboya 4, 46010, Valencia, Spain
Received 25 October 1999; first review notified 3 February 2000; accepted 10 February 2000
Acamprosate (calcium bis acetyl-homotaurine), a homotaurine derivative, a structural analogue of 
-aminobutyric acid (GABA) and an upper homologue of taurine, is a relatively new drug used to prevent relapse in weaned alcoholics. When administered orally as enteric-coated tablets at relatively high doses, this drug has a bioavailability of about 11%; however, the intestinal absorption mechanism has not been studied in depth. The present study was therefore planned to characterize the intestinal transport of acamprosate in the rat and the effect of chronic alcohol treatment on this process, quantifying its kinetic parameters and investigating possible inhibitors. Using an in vitro technique, acamprosate absorption was measured in the rat intestine from three different groups: alcohol group [fed a liquid diet containing 5% (w/v) ethanol for 4 weeks], isocaloric pair-fed control, and a solid diet group. Intestinal acamprosate absorption was found to occur mainly by passive diffusion with a diffusive permeability of 0.213 ± 0.004 cm/h in control pair-fed animals, 0.206 ± 0.001 cm/h in animals receiving chronic alcohol treatment, and 0.193 ± 0.001 cm/h in the solid diet group. Inhibition studies showed that at a 10–3 M acamprosate concentration, some compounds such as GABA, taurine, proline, and glycine at 40 mM each did not affect acamprosate transport. Nevertheless, when a lower concentration of the drug (10–4 M was assayed, a significant reduction of acamprosate transport in the presence of taurine or GABA 40 mM was found. These results suggest that acamprosate in the rat jejunum, could be transported, in part, by a carrier system. Further experiments using different concentrations of taurine (10, 20, and 80 mM) showed that the maximum inhibition (32%) is achieved at 20 mM of taurine. These latter results suggest that acamprosate and taurine share, at least, an intestinal carrier system in rat jejunum. From the above results, it can be concluded that there are probably two pathways involved in the intestinal absorption of acamprosate: passive diffusion and mediated transport, with the former being predominant. Moreover, neither chronic ethanol intake nor the type of diet seems to alter the intestinal absorption of the drug.