Abstract
1) The intestinal absorption of aminopyrine as a representative of the basic drugs was investigated to prove the validity of equation (1) described previously. 2) From the three evidences, that is, a good fit of the data at pH 7.01 to equation (3), the statistical treatment of all the data, and the experiment at equilibrium state, it is concluded that aminopyrine penetrates the intestinal barrier with each specific coefficient, Pu and Pi, according to equation (1). 3) Respective values of the coefficients were statistically determined and the estimated value of Pu was 0.00266 (cc./cm./min.) and that of Pi 0.000242 (cc./cm./min.). From the ratio of Pu/Pi, it may be expected that aminopyrine is absorbed in its undissociated form according to Overton's hypothesis. 4) A fact that aminopyrine slowly penetrates the intestine is consistent with the result reported by Hogben, et al.
