Pharmacological Effect and Absorption of Ethylphenylephrine in Two Different Dosage Forms

A correlation between the ear temperature-lowering effect and blood level was investigated in rabbits and dogs after oral administration of two different dosage forms of ethylphenylephrine ; an uncoated tablet which showed a rapid dissolution rate in vitro test and a sustained release capsule that showed a gradual dissolution rate. The urinary excretion was also examined in dogs and men after the oral administration of two dosage forms. Absorption of the drug from the uncoated tablet was more rapid than that from the sustained release capsule in rabbits, dogs, and men. Absportion from the sustained release capsule extended over a long period. The ear temperature-lowering effect was well correlated with the blood level after the oral administration of two dosage forms in rabbits. No correlation was observed between the effect and the blood level in dogs ; the effect was weak in spite of the fast rise of the blood level in early stage after the administration of both dosage froms. About 70% of the dose during 48 hr period in dogs and 80% of the dose during 24 hr period in men were recovered in the urine after the administration of either the uncoated tablet or the sustained release capsule. About 60% of the total amount excreted in the urine was recovered as free ethylphenylephrine in dogs, but no free ethylphenylephrine was detected in human urine.