Harvard developed a scale (from 1 to 3) that ranks drugs according to their anticholinergic burden. A good proxy for anticholinergic burden is to look at the binding affinity of a drug for muscarinic receptors (e.g., M1, M2). Tighter binding to muscarinic (and nicotinic) receptors is reflected by a smaller Kd (dissociation constant).Some common examples of OTC and prescription drugs include:
- diphenhydramine (Benedryl)
- trihexyphenidyl (Artane)
- benztropine mesylate (Cogentin)
- biperiden (Akineton)
- clomipramine (Anafranil)
- chlorpromazine (Thorazine)
Further reading: Drugs That Impair Memory.