Cocaine Recovery from Rabbit and Cat Aqueous Humor

Abstract

In 1930 the statement was made “At present there is no method sufficiently delicate to determine quantitatively the amount of cocaine present in the anterior chamber as it arrives from the conjunctival sac after clinical instillation.” 1

Recently, a method 2 was developed whereby cocaine can be quantitatively recovered from body fluids. The essential features of this method follow:

To the deproteinized fluid supposedly containing cocaine, is added 1 cc. of a 1% solution of phosphomolybdic acid in normal sulphuric acid. After mixing and centrifuging, the precipitate is washed with water which, after another centrifuging, is decanted and discarded. One cc. of N/5 sulphuric acid, 1 cc. of 2% aqueous solution of hydroquinone, and after shaking, 1 cc. of carbonate-sulphite solution are successively added to the precipitate. This develops a color which is read in the Duboscq microcolorimeter against a standard prepared by adding the above reagents to 1 cc. of a solution of approximately equal alkaloid content.

With solutions of cocaine in aqueous humor the probable analytical error is 20% or less with the concentrations employed, which concentrations are approximately at the limit of colorimetric reading.

By this method we have succeeded in recovering cocaine from rabbits' aqueous humor in so small a concentration as 1-18,000, and 1-25,000 in aqueous humor of the cat.

Normal rabbits and cats of both sexes and various breeds received, after pupillary measurements, several instillations of 4% cocaine until the cornea became desensitized and a pupillary dilatation of 2 mm. or more occurred under uniform lighting. This usually required from ½ to 1 ½ hours. The animals were then lightly anesthetized with ether; the eyes were washed with normal saline in most cases, and the aqueous humor was extracted with the hypodermic needle and tuberculin syringe by means of the sclero-corneal approach used by Koppanyi. 3