Muscarinic agonists toxicity

Bethanechol Muscarinic agonist t negligible effect at nicotinic receptors Activates Mi through M3 receptors in all peripheral tissues causes increased secretion, smooth muscle contraction (except vascular smooth muscle relaxes), and changes in heart rate Postoperative and neurogenic ileus and urinary retention Oral and parenteral, duration 30 min does not enter central nervous system (CNS) Toxicity Excessive parasympathomimetic effects, especially bronchospasm in asthmatics Interactions Additive with other parasympathomimetics... 

Muscarinic agonists are administered subcutaneously to achieve an acute response and orally to treat more chronic conditions. Should serious toxic reactions to these drugs arise, atropine sulfate (0.5—1 mg in adults) should be given subcutaneously or intravenously. Epinephrine (0.3—1 mg, subcutaneously or intramuscularly) also is of value in overcoming severe cardiovascular or bron-choconstrictor responses. 

Succinylcholine Agonist at nicotinic acetylcholine (ACh) receptors, especially at neuromuscular junctions depolarizes may stimulate ganglionic nicotinic ACh and cardiac muscarinic ACh receptors Initial depolarization causes transient contractions, followed by prolonged flaccid paralysis depolarization is then followed by repolarization that is also accompanied by paralysis Placement of tracheal tube at start of anesthetic procedure t rarely, control of muscle contractions in status epilepticus Rapid metabolism by plasma cholinesterase normal duration, 5 min Toxicities Arrhythmias hyperkalemia transient increased intraabdominal, intraocular pressure postoperative muscle pain... 

NEUROTOXIN constituent of the fly agaric fungus Amanita muscaria and various /nocyfte spp. It is a very potent MUSCARINIC CHOLINOCEPTOR AGONIST with pronounced PARASYMPATHOMIMETIC actions. It is a HYPOTENSIVE, causes bronchoconstriction and stimulates gut, bladder and exocrine glands. Stereoisomers show only a fraction of the activity, and it is valuable as a pharmacological tool in studies on muscarinic receptors. It is very toxic orally, with stimulatory actions on the CNS (atropine sulphate may be used as an antidote). 

D. Clinical Use Asthma. Muscarinic blockers are useful in one-third to two-thirds of asthmatic patients agonists are effective in almost all. For acute bronchospasm, therefore, the beta agonists are usually preferred. However, in chronic obstructive pulmonary disease (which is often associated with acute episodes of bronchospasm), the antimuscarinic agents may be more effective and less toxic than beta agonists. 

OP binding to a subset of muscarinic receptors can be either beneficial or toxic depending on the location of the target tissue (central or peripheral), the agonist or antagonist action of the OP, and the location and function... 

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