How is Bethanechol as direct acting cholinergic agonist?

Structure like Ach, acetate replaced by carbamate, choline methylated. Not hydrolyzed by acetylcholinesterase, inactivated by hydrolysis by other esterases. Lack nicotinic action! due to methylation, but has strong muscarinic activity. Major actions on bladder and GI, duration of action 1 hour. Actions: increase intestinal motility and secretions, stimulates detursor muscle of bladder whereas sphincter is relaxed, causing expulsion of urine. Therapeutic uses: uro treatment in case of atonic bladder (postpartum/ post op/ non obstructive urinary retention). treat megacolon (abnormal colon dilation). Adverse effects (generalized cholinergic effects sweating, salivation, decreased BP, nausea, abdo pain, diarrhea, bronchospasm