Duration of positive urine for cocaine metabolite after ophthalmic administration: implications for testing patients with suspected Horner syndrome using ophthalmic cocaine.
OBJECTIVE
To determine the duration of positive urine for benzoylecgonine, the major metabolite excreted in the urine, after topical ophthalmic administration of cocaine as one would perform for testing the presence of Horner syndrome.


METHODS
Two drops of cocaine 10% were applied to each eye of 50 normal subjects. Urine samples were collected 4 to 6, 24, 48, 72, and 96 hours later. Each sample was assayed for benzoylecgonine using a screening competitive enzyme donor immunoassay followed by a highly specific and sensitive confirmatory gas chromatography-mass spectrometry assay. We employed assays and cutoff levels that fulfilled guidelines required by the Substance Abuse and Mental Health Services of the United States Department of Health and Human Services to mimic measures that exist for federal workplace drug testing.


RESULTS
Of the 50 subjects, there were 25 women and 25 men, ranging in age from 19 to 59 years (median age, 40 years). Positive screening samples were obtained in 47 of 50 subjects (94%) 4 to 6 hours, 35 of 50 (70%) 24 hours, and 1 of 50 (2%) 48 hours after topical application of cocaine. None of the samples tested positive at 72 hours or beyond. Using the confirmatory assay's cutoff as the gold standard for a positive test, the sensitivity of the screening assay was 96% 4 to 6 hours, 90% 24 hours, and 14% 48 hours after topical application. Urine benzoylecgonine concentration was negatively correlated with body mass index and positively correlated with urine creatinine concentration.


CONCLUSIONS
Patients should be informed that their urine may test positive for cocaine, if assayed according to US federal guidelines and using the protocol employed in this study, up to 2 days after undergoing testing for Horner syndrome.
Jacobson
D M
DM
Department of Neurology and Ophthalmology, Marshfield Clinic, Marshfield, Wisconsin 54449, USA. jacobsod@mfldclin.edu
Berg
R
R
Grinstead
G F
GF
Kruse
J R
JR
D000328:Adult; D003042:Cocaine / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000652:urine*; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006732:Horner Syndrome / Q000175:diagnosis* / Q000652:urine*; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D009883:Ophthalmic Solutions; D009994:Osmolar Concentration; D013566:Sympathomimetics / Q000008:administration & dosage*; D013997:Time Factors
D009883:Ophthalmic Solutions; D013566:Sympathomimetics; C005618:benzoylecgonine; D003042:Cocaine