– Sofpironium bromide (BBI 4000) is an anticholinergic agent used in the study of primary axillary hyperhidrosis (PAH). Sofpironium bromide reduces sweating by inhibiting M3 muscarinic receptors in eccrine glands at the application site. Sofpironium bromide also has a high afnity for the M1, M2, M4 and M5 subtypes.