“Treating LEMS itself may help constipation,” says Dib. Taking amifampridine (Firdapse) or pyridostigmine (Mestinon) as prescribed matters, because both medicines work in ways that increase acetylcholine, a chemical messenger that helps nerves communicate with muscles, including those in the gastrointestinal tract.
- Amifampridine helps nerves release more acetylcholine. Its digestive side effects may include nausea, diarrhea, or cramping, though constipation has rarely been reported, Dib says.
- Pyridostigmine helps acetylcholine stay active longer. Because cholinesterase inhibitors such as pyridostigmine can increase colon movement, it may help bowel motility in some people with autonomic constipation, Dib says.
Navigating Laxatives Safely
If diet, fluids, changes in daily routine, and LEMS treatment are not enough, Dib recommends a stepwise plan for trying laxatives:
Osmotic Laxatives Polyethylene glycol, such as Miralax, pulls water into the colon so stool is softer and easier to pass. Dib considers osmotic laxatives a first medication step when lifestyle changes are not enough.
However, she notes that you may need to pay extra attention to staying hydrated and possibly have your electrolyte levels monitored when taking polyethylene glycol, especially if you have LEMS-related dizziness, blood pressure changes, or other autonomic symptoms.
Stool Softeners Docusate sodium can help soften stool and reduce straining, but it may not be enough if the main problem is that the colon is moving too slowly. Ask your doctor whether it should be paired with another option, such as a mild stimulant.
Stimulant Laxatives Senna and bisacodyl make the colon contract and can be effective, but Dib recommends using them as short-term or rescue options under medical guidance.
Stimulant laxatives should not be used if stool may be stuck or the bowel may be blocked, Dib says. In that situation, forcing the colon to contract can be harmful.
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