New Onset Generalized Tonic Clonic Seizures after Intravenous Tramadol with Ondansetron

Aims: Tramadol hydrochloride is a centrally acting opioid analgesic. Ondansetron is a selective serotonin receptor (5-HT3) antagonist, primarily used for prevention and treatment of drug-induced and postoperative nausea and vomiting. Tramadol and ondansetron have reported good safety profile in the recommended doses. These two drugs are commonly co-administered. This study aims to highlight a rare but severe adverse effect of co-administration of intravenous tramadol with ondansetron.

Presentation of the Case: A 42-year-old female without prior history of seizure disorder or chronic drug use or acute metabolic or electrolyte disturbances, received tramadol 100 mg with ondansetron 8 mg intravenously before general anesthesia. Within six minutes of the injections, she developed generalized tonic clonic seizures. Seizures were immediately terminated with propofol 50 mg, followed by mask ventilation, tracheal intubation and controlled ventilation. She had an uneventful recovery from surgery under general anesthesia and was later discharged home in a favorable condition. Postoperative MRI brain and EEG were normal.

Discussion: Tramadol is known to precipitate seizures at higher than recommended doses. Patients with prior seizure disorders and patients receiving selective serotonin re-uptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants, antipsychotics can also have seizures precipitated by tramadol. Our patient received a normal dose of tramadol; neither had she any known risk factors for seizures, nor any prior seizure disorder. She did not receive any drug that adversely interacts with tramadol or ondansetron to precipitate seizure, except the co-administration of normal doses of intravenous tramadol with ondansetron.

Conclusion: We conclude that intravenous tramadol with ondansetron at recommended doses can precipitate seizures even in a patient without underlying seizure disorder.