A Closer Look at Mestinon
Last updated: June 2023
There are many forms of myasthenia gravis (MG) but the exact cause is still not clear for everyone. While there is currently no cure, there are two general approaches to treatment: Long-term suppression of the body’s autoimmune response and a shorter-term fix for the neurotransmitter process itself.
For short-term relief, one drug dominates the field - pyridostigmine (Mestinon). So it is helpful to understand the mechanism, how it is usually prescribed, and what sort of effects the user might expect.
How it works
When a voluntary nerve stimulates a muscle fiber, it releases acetylcholine. The result is a contraction (twitch). Immediately, another enzyme (cholinesterase) jumps to break it down so that a new twitch can occur.1 Mestinon slows down the breakdown of the acetylcholine and so supports the contraction.
This drug does not change the cause of the problem, just the symptom.2 That’s why most people with MG will also be prescribed an immunosuppressant drug like prednisone in addition to Mestinon.
The action of Mestinon is very short-term. The tablets begin acting about 1 half hour after ingestion, and their effect diminishes within 4 hours.2
Pharmacists call it a labile drug meaning the timing of the dosage is very important. A person may see some really distinct effects an hour after taking it and then 5 hours later see symptoms return.2
There are now time-release versions available. Consult your neurologist and pharmacist to see if those are right for you. But Mestinon is still a temporary fix. It is generally not used at night when it is less necessary.2
It is also a drug that is normally delivered in a tablet that is fragile. When you get your month's prescription, you probably get 4 separate bottles. When a bottle is opened, the tablets get softer. There are alternate forms (liquid and time-release) but they may be more expensive even with your insurance. Check it up.
Possible side effects
While many people with myasthenia gravis tolerate Mestinon well, it has some side effects that need to be monitored. The most common are diarrhea and runny nose.3,4
Those taking the drug often take supplements to calm their digestive system on the advice of the prescribing doctor. And many report that they just “live with” a constant sniffle, in exchange for relief from double vision, ptosis, or swallowing issues.3,4
Because it is a neurological drug and a very labile one, take Mestinon exactly as prescribed. The symptoms of underdosage and overdosage are similar. If the correct dosage causes an improvement, you cannot assume that more drug or a more frequent dosage would be better. It could make symptoms worse or even send a person into a myasthenic crisis.1
Staying on schedule
The fact that Mestinon helps so many persons with myasthenia gravis in the short term is a great thing. But it requires structuring a person's life around a drug. You cannot simply say: "I'll take that pill when I get around to it."
If a person is juggling a job (or even a Zoom meeting) that requires a lot of close attention, the timing of the day's schedule might be determined by the drug. For long trips away from home, the side effects often come into play. So negotiating with the drug is a skill people need.
The success of Mestinon in short-term symptom relief shouldn’t distract users from careful use of anti-inflammatory, IVIG, and other treatments that address the condition itself.
Mestinon only treats symptoms. And of course, we cannot be diverted from our continual effort as a community to find and remedy the causes of this chronic and debilitating problem.
How often do you experience MG exacerbations/flares?