Getting High by Going Down

Can oral sex make you fail a drug test?

A Manhattan cop who tested positive for cocaine claims he got the drugs in his system by performing oral sex on his girlfriend, whom he later discovered was a regular user. The New York Daily News reported yesterday that since the officer voluntarily submitted to the arm-hair drug test, he won’t be allowed to return to the force, regardless. Can you really “passively ingest” drugs via cunnilingus?

Yes, but not enough to fail a drug test. You’d have to ingest at least 200 milligrams of cocaine over three months before it could be reliably detected in your body hair. (That’s the equivalent of about two lines.) It’s unclear exactly how much cocaine comes out in the vaginal secretions of a regular user, but it’s likely to be a very small amount.

We do have some equivalent information for men. A 1996 paper suggests that chronic users might excrete a peak level of 0.01 milligrams of cocaine per gram of semen  after the consumption of a particularly heavy dose. Since a typical ejaculation contains around two grams of semen, it would take 10,000 precisely timed sexual encounters over that three-month stretch before a nonuser faced any risk of failing a drug test. (According to court records, the cop and his girlfriend had sex “three or four times per week.”) The study did point out that “absorption of cocaine from the vagina or rectum is generally efficient,” but such a process would be unlikely to generate positive test results (or euphoria) in the partners of cocaine-using males.

Bonus Explainer: Court records in the New York case also said that the couple “would often sweat” during sex. Could skin-to-skin contact have caused a false positive on the exam? It’s possible. Cocaine does get secreted in sweat at levels as high as 100 nanograms per milliliter. In theory, that’s more than enough for some sweat-tainted arm hair to return a false positive. Yet a good lab would have subjected the test hair to a thorough washing procedure, which would have removed any surface contamination and leached out any traces of cocaine or its metabolites that managed to penetrate the outer layers of the hair. In the most stringent testing procedures, the levels of cocaine found in the wash residue are then subtracted from the levels found in the cleansed hair sample, which further reduces the chances of external contamination causing a false positive.

Explainer thanks Ed Cone of ConeChem Research and Bill Thistle of Psychemedics Corp.

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