TETRACAINE PROTECTS AGAINST COCAINE LETHALITY IN MICE

Study hypothesis: Tetracaine will enhance cocaine toxicity. Study popu lation: Two hundred forty female Swiss albino mice weighing 27 to 45 g . Methods: Intraperitoneal injections of tetracaine and cocaine were g iven to groups of ten mice each in a controlled, blinded fashion. Eith er tetracaine or an equal volume of normal saline was given five minut es before one of six incremental doses of cocaine, ranging from 60 to 110 mg/kg. The experiment was repeated twice using two different doses of tetracaine: either an LD10 (40 mg/kg determined from preliminary s tudies), or one-twentieth of the dose of cocaine (which approximates t he ratio used in tetracaine, epinephrine, and cocaine). Lethality was recorded at 24 hours. Lethality between groups was compared with a Wil coxon sign-rank test. Results: Tetracaine reduced cocaine lethality at all doses. This reduction in lethality was statistically significant at both tetracaine doses (P<.05). Conclusion: In the mouse, pretreatme nt with tetracaine significantly decreases cocaine lethality.