Absorption of Atropine From Muscle

¹ From the Physiology Division, Directorate of Medical Research, Chemical Warfare Laboratories, Army Chemical Center, Maryland

Rates of absorption of atropine after intramuscular injection have been studied by measuring colorimetrically the residual drug in guinea pig muscle. Effects of volume and concentration of the injected solution and the presence of hyaluronidase and polyvinylpyrrolidone on the absorption rates were investigated. Results indicate that, within the range of volumes and concentrations used, for a constant amount of atropine the smaller the volume of injected solution the faster the drug cleared the muscle; solutions of similar volume showed initially faster absorption when a lower concentration of drug was present. Addition of hyaluronidase produced an immediate increase in the clearance rate: four times as much atropine cleared the muscle in the first 35 seconds compared to an untreated solution. Addition of polyvinylpyrrolidone had no appreciable effect.