Hiccup and apparent myoclonus after hydrocodone: Review of the opiate-related hiccup and myoclonus literature

The author recently encountered a patient with hiccups, intermittently acco mpanied by apparent focal rhythmic diaphragmatic myoclonus after hydrocodon e administration. Review of the literature disclosed a paucity of previous reports of hiccup, but many reports of myoclonus after opiate administratio n. A wide variety of opiates and routes of administration have been implica ted, but high doses and the presence of other agents (antipsychotics, antie metics, nonsteroidal antiinflammatory agents, antidepressants) may pose spe cial risks. Review of the literature suggests three types of opiate-related myoclonus. Opiate-induced myoclonus (OIM) is often generalized and is eith er periodic or associated with rigidity. Opiate-induced myoclonus frequentl y occurs in the context of underlying medical conditions, D2 antagonist coa dministration, or other drugs (nonsteroidal anti-inflammatory agents, antid epressants), and usually responds to either naloxone or benzodiazepines. In trathecal OIM has not been linked to D2 antagonist coadministration or benz odiazepine responsiveness but may be associated with nonsteroidal antiinfla mmatory agents. Opiate withdrawal myoclonus may be stimulus-sensitive, asso ciated with D2 antagonist coadministration, and responsive to benzodiazepin es and unresponsive to naloxone. There are several problems in interpreting the literature, and more study is needed. Opiatergic, serotonergic, dopami nergic, and other mechanisms are considered.