Tetracaine protects against cocaine lethality in mice.

STUDY HYPOTHESIS

Tetracaine will enhance cocaine toxicity.

STUDY POPULATION

Two hundred forty female Swiss albino mice weighing 27 to 45 g.

METHODS

Intraperitoneal injections of tetracaine and cocaine were given to groups of ten mice each in a controlled, blinded fashion. Either tetracaine or an equal volume of normal saline was given five minutes 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 studies), or one-twentieth of the dose of cocaine (which approximates the ratio used in tetracaine, epinephrine, and cocaine). Lethality was recorded at 24 hours. Lethality between groups was compared with a Wilcoxon 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, pretreatment with tetracaine significantly decreases cocaine lethality.