STUDIES ON THE DURATION OF ACTION OF DRUGS II. MYDRIATIC ACTIONS OF EPINEPHRINE AND ATROPINE

¹ From the Department of Pharmacology of Cornell University Medical College, New York City

1. The duration of action of graded doses of epinephrine and atropine as indicated by the persistence of mydriasis, was studied after intravenous, intraarterial and intraocular injections.

a. The persistence of epinephrine mydriasis varies from about one second with 0.0005 to 0.0025 mgm. to more than three hours with 2 mgm. following intravenous injections; from about ten to forty-five seconds with 0.0005 to 0.002 mgm. to about eighty seconds with 0.004 mgm. following injections into the common carotid artery; and from about three minutes with 0.001 mgm. to two and one-half hours with 0.05 mgm. following intraocular injections.

b. The persistence of atropine mydriasis varies from four hours with 0.05 mgm. to about twenty-four hours with 0.5 mgm. following intravenous injections; and from about four hours with 0.00005 mgm. to about fifty hours with 0.001 mgm. following intraocular injections.

The figures obtained afford the basis for a rough calculation not only of the duration of mydriasis to be expected after an injection of a given amount of these drugs, but also conversely, the amount of epinephrine or atropine responsible for a given duration of mydriasis.

2. A given dose of epinephrine injected into the carotid artery produces less lasting mydriasis in the opposite eye than a similar dose given intravenously.

3. A method for approximate determination of circulation time is presented.

4. Paraldehyde sensitizes the eye to epinephrine mydriasis.

5. Intraocular injection into the cat's eye is proposed as a sensitive method for detecting minute quantities of atropine. We wish to express our indebtedness to Dr. Robert A. Hatcher for the many valuable suggestions throughout the course of this work.