Pyridostigmine in myasthenia gravis

Komfeld, P, Samuels, A.J., Wolf, R.L., and Osserman, K.E., Metabolism of C-labeUed pyridostigmine in myasthenia gravis. Evidence for multiple metabolites. Neurology, 26, 634, 1970. 

Pyridostigmine is similar to neostigmine but has a less powerful action that is slower in onset and slightly longer in duration, and perhaps fewer visceral effects. It is used in myasthenia gravis. 

Pyridostigmine, a cholinesterase inhibitor, is used as an antagonist for curariform paralysis and in myasthenia gravis. 

The answer is a. (Hardman, pp 161-169.) Although all of the listed compounds inhibit the activity of the cholinesterases, only edrophonium chloride is used in the diagnosis of myasthenia gravis. The drug has a more rapid onset of action (1 to 3 min following intravenous administration) and a shorter duration of action (approximately 5 to 10 min) than pyridostigmine... 

Apart from neostigmine, pyridostigmine and ambenonium are the other standard drugs used in the treatment of myasthenia gravis. 

The therapeutic uses of neostigmine include the treatment of atony of the urinary bladder and postoperative abdominal distention. In addition, it antagonizes the action of rf-tubocurarine and curariform drugs. Edrophonium, neostigmine, or pyridostigmine may be used to diagnose myasthenia gravis. Because edrophonium has the shortest duration of action, it is most often used for this purpose. 

Pyridostigmine [peer id doe STIG meen] is another cholinesterase inhibitor that is used in the chronic management of myasthenia gravis. Its duration of action (3-6 hours) is longer than that of neostigmine (2-4 hours). 

The pharmacologic treatment of myasthenia gravis is based on increasing the amount of available acetylcholine by use of oral cholinesterase inhibitors such as neostigmine or pyridostigmine. Pyridostigmine bromide (Mestinon) is used most often and effectively relieves myasthenic symptoms in small muscles innervated by cranial nerves, particularly those involved in ptosis. 

Severe urticaria and anaphylaxis associated with pyridostigmine (an unspecified dose) occurred in a 54-year-old woman with myasthenia gravis (9). Urticaria started almost immediately after introduction of the drug but was partially controlled by the antihistamine cetirizine. However, pyridostigmine was stopped after 2 months and the urticaria resolved completely. Rechallenge with oral pyridostigmine led to an anaphylactic reaction that was treated with subcutaneous adrenaline. There were no sequelae. 

Myasthenia gravis is a progressive disorder characterized by muscle weakness eye muscles are often the first affected. Research has shown it to be an autoimmune disease in which the victim forms antibodies to his or her nicotinic acetylcholine receptors at motor endplates. It is characterized by fatigability and weakness of the skeletal muscles, especially those of the eyes. Approximately 90% of the patients have droopy eyelids and double vision. Treatments include corticosteroids and thymectomy to reduce the actions of the immune system and anti-ChE agents such as pyridostigmine to improve the effectiveness of the receptors that remain. 

Pyridostigmine is a carbamate that is used in the treatment of myasthenia gravis, a neuromuscular disease. It can also be used as a method of protection against nerve agent poisoning. Carbamates can occupy the catalytic site of acetylcholinesterase (AchE), which temporarily prevents phosphorylation. 

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