THE ABSORPTION, DISTRIBUTION, EXCRETION AND FATE OF PARA-AMINOSALICYLIC ACID

¹ Department of Pharmacology, The George Washington University School of Medicine, Washington, D. C.

(1) Methods are presented for the rapid determination of p-aminosalicylic acid (PASA) in urine, plasma or tissues as free amine, conjugated amines, or free phenol.

(2) In various studies on rats, dogs and humans the sodium salt of PASA was found to be rapidly and totally absorbed and rapidly excreted. About eighty-five percent of the administered dose can be accounted for in the urine within ten hours.

(3) After administration of PASA, recovery of one or more conjugated amines is highest in man (sixty per cent of total dose), next in the rat (ten per cent) and least in the dog (zero per cent).

(4) Three compounds containing a free amino group and two compounds containing a conjugated amino group were separated in the urine of one individual taking PASA. Two of the free amino compounds are believed to be unchanged PASA and p-aminosalicyluric acid and one of the conjugated amino compounds to be acetylated PASA.

(5) No demonstrable storage of PASA occurs after single or repeated doses in rats. By far the highest concentrations are temporarily attained in the kidney, the lung and liver, and appreciable amounts are bound by plasma proteins.

(6) After a single oral four gram dose or following repeated two and one-half gram doses every six hour in humans, a maximum level of approximately 100 mgm. per liter is rapidly attained which falls to less than 10 mgm. per liter within six hours.

(7) It is recommended that PASA be administered clinically as the sodium salt and/or with adequate amounts of sodium bicarbonate to guard against crystalluria, acidosis and to decrease nausea.

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