Myoclonic Jerks Secondary to Piperacillin and Nafcillin

A 66-year-old male receiving intravenous piperacillin and nafcillin for a post-surgical wound infection developed intermittent myoclonic jerks of all four extremities that disappeared after discontinuation of these two medications. In addition there was a mild yet definite intermittent encephalopathic effect; head computed tomography examination as negative and there was no prior history for seizure or myoclonus. These two beta lactam ring antibiotics are structurally similar to penicillin, which is well known to induce not only myoclonus but also seizure activity by reducing the gamma-aminobutyric acid (GABA) induced inhibitory currents by inducing an open chloride channel block of the GABA type A receptors within the brain. Clinicians need to be fully aware of the potential epileptogenic effects of piperacillin, nafcillin, and related antibiotics.