Drug Absorption from the Rectum II: Rates of Absorption and Elimination from the Blood for Various Suppository Bases

Abstract

To facilitate the calculations involved in Teorell's equation No. 25, a program in Fortran with Format was used in the IBM 1410 digital computer system. Using plasma salicylate levels, the rates of drug absorption and elimination from the blood and the specific apparent body volumes were determined for salicylic acid and sodium salicylate administered in 4 different suppository bases. The rate of absorption for sodium salicylate was found to be greater than that for salicylic acid except for polyoxyethylene sorbitan monostearate base. The rates of elimination from the blood for the 2 drug forms do not vary significantly. The specific apparent volumes for salicylic acid were less than that for the sodium salt, suggesting a lesser degree of storage for the acid form. Since Teorell's equation assumes apparent first-order rates of absorption and elimination from the blood, and this equation describes the data presented, this suggests that salicylic acid and its sodium salt are absorbed into the blood from the 4 bases tested and eliminated from the blood by apparent first-order kinetics. Two sets of data from the literature were also analyzed, and constants for 2 other sets could not be computed because of limitations on the computer.