A Myoclonic Reaction with Low-Dose Hydromorphone

Abstract

To report a case of myoclonus associated with the use of a low dose of the opioid analgesic hydromorphone. A 55-year-old white man with a history of nonobstructive hypertrophic cardiomyopathy was hospitalized for treatment of severe chest pain. On hospital day 1, intravenous hydromorphone (6 doses, total dose of 4 mg) was administered. The pain continued and, on day 2, the dose was increased, with a total of 6 mg administered on day 2. The patient developed uncontrollable jerking movements of the head, neck, arms, and legs after he received the hydromorphone. The myoclonic movements stopped within a few hours following discontinuation of hydromorphone and did not recur. Myoclonus is a neuroexcitatory symptom that has been reported with chronic, high-dose administration of hydromorphone in patients with impaired renal function. The hydromorphone-3-glucuronide metabolite is devoid of analgesic activity and has been shown to cause neuroexcitatory effects. This patient's symptoms appeared soon after hydromorphone was initiated and resolved in a timely manner after the medication was discontinued. Based on the patient's presentation and course of therapy, it is probable, as indicated by the Naranjo probability scale, that the myoclonic symptoms were induced by hydromorphone. This case was unique, however, in that the patient received hydromorphone for only a short duration and did not have impaired renal function. Neuroexcitatory effects of hydromorphone may occur at relatively low doses in patients without renal dysfunction. Early recognition and intervention are required to achieve resolution of these symptoms and prevent further sequelae to the patient.