Venlafaxine Ingestion is Associated with Rhabdomyolysis in Adults: a Case Series

Rhabdomyolysis has been reported after venlafaxine ingestion. We wished to characterize the prevalence of this adverse effect in a realistic clinical setting. Therefore, a retrospective casenote review was performed, including 235 patients admitted to the Royal Infirmary of Edinburgh due to venlafaxine overdose between January 2000 and June 2006. Seizures occurred in 8.9% of the study population. Patients who suffered seizures had ingested larger quantities of venlafaxine than those who did not develop seizures; median (interquartile range) 2800 mg (2006-4350 mg) versus 1500 mg (900-2700 mg, p = 0.001). Raised CK values were more prevalent in those with seizures than those without seizures (61.1% versus 25.7% respectively, p = 0.004). Nonetheless, a positive correlation was found between the quantity of venlafaxine ingested and CK across the whole group (rho = 0.201, 95% confidence interval 0.045-0.347), and in patients who had not developed seizures (rho = 0.174, 95% confidence interval 0.009-0.331). Venlafaxine overdose is associated with a high prevalence of acute muscle injury, both in patients who develop seizures and in those who do not. The clinical significance of this association merits further consideration.