Which acetylcholinesterase inhibitor is commonly prescribed for myasthenia gravis due to its longer duration than neostigmine?

• A. Pyridostigmine
• B. Physostigmine
• C. Carbamylcholine
• D. Demecarium

Answer: (A)

In myasthenia gravis, the aim is to boost acetylcholine at the neuromuscular junction by inhibiting acetylcholinesterase, providing longer-lasting improvement of muscle strength. Pyridostigmine is preferred because it has a longer duration of action than neostigmine, allowing for effective daily management with regular dosing. It is a quaternary ammonium compound, so it doesn’t cross into the brain easily, which reduces central side effects and makes it better tolerated for chronic use. Physostigmine, while an acetylcholinesterase inhibitor, crosses the blood-brain barrier and often has a less predictable duration, leading to more central effects. Carbamylcholine (carbachol) is a direct cholinergic agonist, not an acetylcholinesterase inhibitor, so it doesn’t fit the treatment approach. Demecarium is a very long-acting AChE inhibitor used mainly for ocular conditions, and its systemic effects make it unsuitable for MG management.