TAC topical anesthesia produces positive urine tests for cocaine

The combination of tetracaine, adrenalin, and cocaine (TAC) has become increasingly popular as a topical anesthetic for the suturing of simple skin lacerations. The purpose of this study was to determine the effects of TAC on a urine drug test for cocaine. On the morning after the use of TAC, 14 of 18 patients (78%) studied had positive screening tests for benzoylecgonine (cocaine metabolite) by the enzyme multiplied immunoassay test (EMIT) method. All specimens also were analyzed by gas chromatography and mass spectrometry, the reference standard for analysis of drugs of abuse in urine, and 15 of the specimens (83%) were positive. Four of 18 positive specimens (22%) still had positive EMIT drug screens on the morning of the next day, an average of 36 hours after use of TAC. We recommend that physicians who use TAC solution as a local anesthetic caution their patients that they may fail a urine drug screen for cocaine if they are tested within 36 to 48 hours of the administration of the use of TAC.