Abstract
Life-threatening toxicity due to calcium channel blocker ingestion is commonly encountered by emergency medicine physicians and toxicologists. Despite a vast array of research on its treatment, results have proven inconsistent. The goal of this study is to evaluate potential vasopressor effects of triiodothyronine (T3) in rats poisoned with verapamil. Following anesthesia and intubation, ten Sprague–Dawley rats were given intravenous verapamil infusion of 10 mg/kg/h. This dose was titrated until a mean arterial pressure (MAP) of 50–55 mmHg was achieved and maintained for a period of at least 5 min. The verapamil infusion was then maintained at that rate. Five rats were randomized to receive a T3 bolus of 0.4 mcg/kg preceding an infusion of 1.5 mcg/kg/day which was doubled every 2 min until any of the following endpoints: systolic blood pressure of 100 mmHg, an elapsed time of 60 min, or death. The other five received an equal volume of normal saline solution. The primary outcome measure was survival with secondary outcomes of MAP and heart rate. The T3 group did have a slightly longer, yet not statistically significant, average time to cessation of electrical activity—30.0 ± 14.4 min versus 23.8 ± 9.5 min in the placebo group. Average MAP decreased nearly identically in the two groups. Heart rates were not reliable indicators of toxicity in this rat model as there was little decrease until immediately prior to death in most animals. Despite significant variability in toxicity among individual animals, no statistically significant difference in survival time, heart rate, or MAP was found between groups treated with T3 and those receiving saline.
Keywords: Calcium channel blocker, Toxicity, Verapamil, Triiodothyronine, Thyroid hormone
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Acknowledgments
Funding for this experiment was provided by the following research grants: the Pittsburgh Emergency Medicine Foundation and American College of Medical Toxicology Jazz Pharmaceuticals Research Award. The results of this study were presented at the 2008 North Amercian Congress of Clinical Toxicology as a poster presentation and abstract.
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