Pennsylvania Animal Diagnostic Laboratory System
PADLS Conferences Spring 2001 2. Detection of Drugs
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Respiratory difficulties are one on the most commonly treated conditions of the racing equine. One mode of treatment and maintenance is the use of anticholinergic drugs. Examples of such drugs would include atropine, glycopyrrolate, and ipratropium. Many anticholinergic drugs (such as glycopyrrolate and ipratropium) are quaternary amine compounds. This type of compound is not easily isolated or analyzed by traditional methodologies geared towards more lipophilic substances.

Glycopyrrolate has traditionally been screened by enzyme-linked immunosorbent assay (ELISA). Hydrolysis of the isolated quaternary compound to a unique fragment (cyclopentyl mandelic acid) is then amenable to detection and confirmation by routinely used derivatization methods and gas-chromatography-mass spectrometry (GC-MS). Recently, ELISA presumptive identifications have failed to be confirmed using this approach. In addition, quantities of the benzyl analog of cyclopentyl mandelic acid were identified. This suggested the possibility that a drug other than glycopyrrolate was causing the initial ELISA indications. Unfortunately, this fragment is common to an entire group of drugs and is therefor not unique. It therefore became necessary to develop a method to isolate, screen and confirm a group of drugs, which included anticholinergics cross-reacting on ELISA, as well as other related anticholinergic quaternary compounds.

This method has directly led to the identification of several previously unreported anticholinergic compounds in the race horse.

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