The anxiolytic buspirone causes insomnia in a small minority of patients. What existent medication would theoretically (or in practice) best treat this insomnia? Buspirone from my understanding is an agonist of the 5-HT1A autoreceptors, has very weak antagonism of the D2 receptors. There is also evidence that one of buspirone's metabolites increases plasma norepinephrine and epinephrine levels. I'm trying to think of a medication that would best block the effects of whatever it is that causes the insomnia. Buspirone is a tad "dirty" in that it and its metabolites affect many things so it's hard to say what causes the insomnia.