Hypertensive crisis and myocardial infarction following massive clonidine overdose

OBJECTIVE: TO describe a patient who experienced a hypertensive crisis and myocardial infarction following a massive dose of parenteral clonidine. CASE SUMMARY: A 62-year-old white woman with stage 3 breast cancer metastat ic to the spine and a history of hypertension received a combined injection of hydromorphone 48.3 mg and clonidine 12.24 mg subcutaneously in an attem pt to refill an epidural infusion pump. She promptly developed mental deter ioration, blurred vision, worsening respiration, tachycardia, She was immed iately treated with naloxone, but subsequently experienced hypertensive urg ency, a short-duration tonic-clonic seizure, and an anteroseptal myocardial infarction. Cardiac catheterization showed no arteriolar narrowing or bloc kage, but an anterior infarct was confirmed. DISCUSSION: Clonidine is a commonly used alpha-adrenergic agonist. At usual oral doses of 0.2-2 mg/d, it acts centrally to produce hypotensive effects ; at doses >7 mg/d, it acts peripherally to stimulate alpha(1)- and alpha(2 )-adrenergic receptors, leading to vasoconstriction and increased blood pre ssure. These effects are not easy to control by standard medical therapies and can cause significant CONCLUSIONS Clonidine, although a safe medication with usual dosages, must be used with caution when given in injectable form. An overdose of this alp ha-adrenoreceptor agonist can produce Significant vasospasm and hypertensiv e emergency. Drugs used to treat overdose, such as naloxone, can potentiate clonidine's adverse effects, leading to further morbidity.