Effects of some calcium modulators on monensin toxicity

Area of Science:

• Veterinary Toxicology
• Pharmacology

Background:

• Monensin is a toxic ionophore for domestic animals, particularly equines, when ingested via contaminated feed.
• No specific antidotes or treatments are currently known for monensin toxicosis.
• Cardiovascular drugs affecting calcium influx were explored for potential interactions with monensin toxicity.

Purpose of the Study:

• To evaluate the effects of various cardiovascular drugs on monensin toxicity in mice.
• To determine if antagonizing calcium influx could mitigate or exacerbate monensin poisoning.

Main Methods:

• Mice were pretreated with cardiovascular drugs (calcium channel blockers, calmodulin antagonist, adrenergic blockers, cardiac glycoside) 30 minutes before administration of lethal doses of monensin.
• Lethal doses ranged from 80 to 140 mg/kg, with the calculated LD50 of monensin being 108 mg/kg.
• Effects on monensin toxicity were assessed by observing mortality rates and calculating changes in LD50.

Main Results:

• Calcium channel blockers (verapamil, diltiazem, lidocaine) significantly potentiated monensin toxicity, decreasing the LD50.
• Chlorpromazine, propranolol, and digoxin did not significantly affect monensin toxicity.
• The potentiation of toxicity by certain calcium modulators suggests complex mechanisms beyond simple calcium ion influx.

Conclusions:

• Excess calcium ion influx may not be the sole mechanism underlying monensin toxicosis.
• Certain cardiovascular drugs can significantly alter the toxicity profile of monensin.
• Further research is needed to elucidate the precise mechanisms of monensin toxicity and potential therapeutic interventions.