What medications do you find helpful to reduce drooling associated with antipsychotics?  

Atropine Ophthalmic Solution 1%: 1 GTT SL QHS. The two leading theories explaining the mechanism of sialorrhea are: Potent agonism at muscarinic M4 receptors. Blockade of alpha-2 adrenergic receptors. Both mechanisms increase salivary flow. Atropine Ophthalmic Solution is absorbed locally. I...

Atropine drops have been my first-line treatment. I've also used glycopyrrolate in the 1-3 mg range. Caution for constipation for that one. Other options, citing from "The Clozapine Handbook" by Meyer and Stahl: Clonidine Botox to the salivary glands  Ipratropium bromide 0.06% spray, 1-3 ...

This is not an uncommon problem with some of my patients who are on clozapine. I had the best results with benztropine. However, side effects can be problematic, especially constipation or tachycardia which I have to carefully monitor.

I am posting a review article here. I would be hesitant about using benztropine (constipation, urinary retention, cognitive effects). Clozapine patients are prone to constipation to begin with. Here is the article by Syed et al., PMID 18646130.