Absorption of Drugs Through the Oral Mucosa. III. Fat-Water Solubility Coefficient of Alkaloids

Abstract

It has been shown that the absorption of drugs from the mouth is strictly a selective process.1,2 With even a closely related group of drugs, such as the common alkaloids, marked differences are exhibited by the individual members. Apomorphine, for instance, can be effectively administered by simple sublingual application, whereas morphine is very poorly absorbed. The diacetyl derivative of morphine is absorbed fairly well, whereas the monomethyl derivative is absorbed very poorly. Since all 4 of these drugs are closely related both chemically and pharmacologically, the explanation for this phenomenon of selectivity might reasonably be expected to depend on physical differences. The most prominent suggestion is that of a correlation with the oil-water distribution coefficient. This relationship has been extensively developed for other problems of cell permeability,3,4 and also has been described as being the decisive factor in absorption through the oral mucosa.5 However, for this latter aspect of the cor...