Dextromethorphan/quinidine: in pseudobulbar affect

Pseudobulbar affect is characterized by uncontrollable, inappropriate laughing and/or crying that is either unrelated or out of proportion to the emotions felt by the patient and occurs in patients with neurological disorders, such as amyotrophic lateral sclerosis (ALS), multiple sclerosis or traumatic brain injury. Dextromethorphan/quinidine is indicated in the US for the treatment of pseudobulbar affect. Dextromethorphan, when its metabolism is inhibited by the coadministration of quinidine, has been shown to have a positive effect on the symptoms of pseudobulbar affect. Dextromethorphan/quinidine 20 mg/10 mg twice daily was associated with a significantly greater decrease in the rate of pseudobulbar affect episodes per day (primary endpoint) than placebo in the 12-week, randomized, double-blind, placebo-controlled, multicentre STAR trial (Safety, Tolerability, And efficacy Results trial of AVP-923 in PBA [pseudobulbar affect]) involving patients with pseudobulbar affect and ALS or multiple sclerosis. Moreover, the mean change from baseline in Center for Neurologic Study-Lability Scale score at 12 weeks was significantly greater among recipients of dextromethorphan/quinidine 20 mg/10 mg twice daily than those receiving placebo. Dextromethorphan/quinidine 20 mg/10 mg twice daily was generally well tolerated. The drug has been shown to cause dosage-dependent corrected QT interval (QTc) prolongation; however, in the STAR trial, dextromethorphan/quinidine 20 mg/10 mg twice daily appeared to be well tolerated with regard to QTc prolongation.