SCIENCE / MEDICINE : False Readings on Cocaine Use

People who receive a common local anesthetic may test positive for illegal cocaine use up to two days after treatment, doctors at Fairfax Hospital in Falls Church, Va., warned last week. They said that applying half a teaspoon of tetracaine, Adrenalin and cocaine solution, called TAC, to the skin for local anesthesia before stitching up a cut or wound will produce a positive urine test for cocaine for up to 48 hours.

Similar effects can occur when the topical cocaine solution is used before surgery on the eye or nose, as well as for certain dental procedures, the doctors reported in Annals of Emergency Medicine.

One day after receiving TAC, more than three-quarters of the 18 patients in the study “clearly failed” a standard test used to screen people for illegal drug use, said Dr. Michael Altieri, who directed the study.