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.