A Randomized, Placebo-Controlled, Blinded, Crossover, Pilot Study of the Effects of Dextromethorphan/Quinidine for the Treatment of Neurobehavioral Symptoms in Adults with Autism.

Davidovitch et al. (2020) ran a small crossover trial with autistic adults. Each person took DM/Q pills for four weeks and placebo pills for four weeks. Neither the adults nor the raters knew which pill came first.

The team tracked irritability, aggression, and side effects every week. They wanted to see if the cough-syrup ingredient DM/Q could calm severe mood swings.

DM/Q beat placebo on irritability scores. Caregivers also saw less hitting and yelling while the adults were on the drug.

No serious side effects showed up. Sleep, appetite, and heart rhythm stayed normal.

Hansen et al. (1989) tested a different serotonergic drug, fenfluramine, in autistic kids and saw zero benefit. The studies seem to clash, but the kids were younger and the drug worked through a different pathway.

Petry et al. (2007) reviewed antidepressants for adults with intellectual disability. Only half of adults improved, and the gains were small. DM/Q appears to give faster, clearer relief from irritability.

Gwynette et al. (2020) used brain stimulation instead of pills on autistic adults and also saw mood gains. Both studies say adults with autism can respond to biological treatments, but DM/Q is easier to prescribe in most clinics.

If you serve autistic adults who punch walls or scream for hours, DM/Q is a new option you can bring to the psychiatrist. Start with the medical team, track irritability weekly, and keep behavior data so you can judge real-world change alongside the drug effect.