THE RELATIONSHIP BETWEEN CHOLINESTERASE INHIBITION AND THE PHARMACOLOGICAL ACTION OF DI-ISOPROPYL FLUOROPHOSPHATE (DFP)

¹ Pharmacology Section, Medical Division, Edgewood Arsenal, Maryland

1. Rats, dogs and monkeys appeared to show no physiological abnormality when the cholinesterase of the blood and tissues was reduced to a low percentage of its normal activity by di-isopropyl fluorophosphate. The signs associated with further reduction are described.

2. It was found that determinations of serum and red cell cholinesterase inhibition following the administration of di-isopropyl fluorophosphate do not provide accurate estimates of the activity of the enzyme in the tissues, excepting possibly during the period immediately following a single dose. Such measurements can be used advantageously to follow rates of absorption.

3. No deterioration was detected in solutions of di-isopropyl fluorophosphate in peanut oil following autoclaving for one hour or storage at room temperature for one year.

4. The concentration of a peanut oil solution of di-isopropyl fluorophosphate had little effect on its rate of absorption from an intramuscular site in dogs.

5. The effective intramuscular:oral dosage ratio for di-isopropyl fluorophosphate in peanut oil was found to be approximately 1:4 in monkeys and humans.

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