ORLANDO, Fla. — In his session, Paul Zarkowski, MD, clinical assistant professor, University of Washington, highlighted the top 10 most prevalent medication interactions that limit efficacy in psychiatric regimens.
“The guts of this [session] is using practical pharmacology to avoid mistakes that are limiting efficacy in your patients,” Zarkowski said. “We’ve got a lot of receptors, but we’ve only got a few neurotransmitters to manipulate in, and if you start adding more and more medications you start getting blocking action of the other medications.”
Most people with major depression are typically on two antidepressants and are also on two antipsychotics during that same period, he said. For anxiety disorders, patients are often on multiple anxiety medications. Research is lacking on what happens when you combine medications, according to Zarkowski. However, oftentimes these drugs have conflicting mechanisms of action.
“When deciding which of the three indications or which combinations of medications to put on this list, I decided there would be three types of evidence,” he said. “Number one, the fact that they do the opposite thing; number two, that they antagonize each other at a very specific receptor; and the last, which is the most-rare evidence of all, is clinical study.
Each of these categories separated into 10 classifications representing the most common psychiatric drug interactions limiting efficacy. These included:
- prazosin and venlafaxine
- clozapine and sertraline;
- clonidine and mirtazapine;
- ropinirole and olanzapine;
- propranolol and atomoxetine;
- amphetamine-dextroamphetamine and alprazolam;
- donepezil and oxybutynin;
- amphetamine-dextroamphetamine and haloperidol;
- amitriptyline and naltrexone; and
- fluoxetine and cyproheptadine.
“More and more medicines are combined in which there are no tests for the combination and they’re working on the receptors,” Zarkowski concluded. “There’s a possibility that you can have results that you don’t think you’re going to have based on the testing alone.” – by Savannah Demko
Zarkowski P. Doing more by prescribing less: Top 10 drug interactions that limit efficacy. Presented at: Psych Congress; Oct. 25-28, 2018; Orlando, Fla.
Disclosure: Zarkowski reports no relevant financial disclosures.