Myoclonus after dextromethorphan administration in peritoneal dialysis

Area of Science:

• Pharmacogenomics
• Clinical Pharmacology
• Nephrology

Background:

• A 64-year-old male with chronic renal failure undergoing peritoneal dialysis developed acute neurological symptoms.
• The patient was prescribed dextromethorphan for a cough and sputum, leading to adverse effects.

Observation:

• Following a 30 mg dose of dextromethorphan, the patient experienced myoclonus, tremor, agitation, slurred speech, and diaphoresis.
• These symptoms persisted even after discontinuing the medication, necessitating hospitalization for evaluation.

Findings:

• The patient was found to have CYP2D6 (*)1/(*)10 genotype, indicating impaired metabolism of dextromethorphan.
• Elevated blood concentrations of dextromethorphan and lower than expected levels of its metabolite, dextrorphan, were observed.
• The co-administration of metoprolol was considered, with potential interactions at the CYP2D6 enzyme level.

Implications:

• This case highlights the potential for dextromethorphan-induced myoclonus in patients with specific CYP2D6 polymorphisms, particularly those with impaired renal function.
• Genetic testing and careful consideration of drug-drug interactions are crucial for optimizing medication safety and preventing adverse drug reactions.
• Understanding pharmacogenetic profiles can guide therapeutic decisions and improve patient outcomes in managing common conditions.