Tetracaine protects against cocaine lethality in mice

The effect of amiodarone pretreatment on survival of mice with cocaine toxicity

INTRODUCTION

Cocaine is a common drug of abuse and use has been associated with ventricular dysrhythmias. Published guidelines suggest that amiodarone is the first line antidysrhythmic for ventricular tachycardia and fibrillation. However, the effects amiodarone in the setting of cocaine toxicity are unknown and unstudied. The purpose of this study was to evaluate the safety and efficacy of amiodarone pretreatment in a murine model of acute cocaine toxicity.

METHODS

This was a randomized, blinded, placebo controlled investigation using male CF-1 mice weighing 29-37 g. First, the safety of an intraperitoneal dose of amiodarone (40 mg/kg) was confirmed in 5 mice. Second, based on preliminary investigations, an approximate intraperitoneal LD50 dose of cocaine (110 mg/kg) was identified and used as the cocaine dose in this study. Animals were then randomized to 2 groups. The control group received 0.5 mL of intraperitoneal 0.9% saline 30 minutes before cocaine. The study group received 40 mg/kg of intraperitoneal amiodarone (40 mg/kg) 30 minutes before cocaine. A blinded observer monitored mice for 2 hours after cocaine administration.

RESULTS

No mice in the amiodarone-only group developed any signs of toxicity or died. In the saline + cocaine group 31/32 (96.9%; 95% CI 83.8 to 99.9) mice seized with a median time to seizure of 2.5 minutes, and 23/32 (71.9%; 95% CI 52.3 to 86.3) died with a median time to death of 5.5 minutes. In the amiodarone + cocaine group 31/33 (93.9%; 95% CI 79.0 to 99.3) mice seized with a median time to seizure of 2.0 minutes, and 24/33 (72.7%; 95% CI 54.5 to 86.7) died with a median time to death of 6.0 minutes. All animals that died did so within 9 minutes. The difference in the proportion of animals dying in the amiodarone + cocaine group compared to the saline + cocaine group was 0.008 (-21 to 22%).

CONCLUSIONS

In this study, pretreatment with amiodarone in cocaine poisoned mice resulted in no change in seizure incidenceor mortality. However, definite conclusions about the reason for these findings cannot be drawn from this model.

The effects of lidocaine pretreatment on cocaine neurotoxicity and lethality in mice

OBJECTIVE

To evaluate the effects of an antiarrhythmic dose of lidocaine on cocaine-induced ataxia, seizures, and death in mice.

METHODS

A randomized, controlled, blinded investigation was conducted using 220 female Swiss albino mice. Groups of 20 animals received intraperitoneal (IP) administration of either 31.6 mg/kg of lidocaine hydrochloride in 0.9% NaCl (ten animals) or an equal volume of 0.9% NaCl solution (ten animals). After 5 minutes, all the animals received IP cocaine in incremental doses ranging from 40 to 110 mg/kg. The animals were observed for ataxia, seizures, and death. The animals pretreated with lidocaine were compared with the control animals for the number of adverse effects from cocaine at each dose tested.

RESULTS

Lidocaine significantly increased the overall incidences of cocaine-induced ataxia (p = 0.02) and seizures (p < 0.001). However, pretreatment with lidocaine offered protection against cocaine lethality (p < 0.0001).

CONCLUSION

In this preexposure model, lidocaine protects mice against cocaine-induced lethality. These effects seem to be independent of convulsive activity. Further study is required to determine the safety and efficacy of lidocaine for the management of cocaine-induced arrhythmias.