(Searching for a listing of drugs that affect the acetylcholine system, was unable to find the info on the myasthenia.org site which a few of the postings on this forum have cited. thought I would share the following

http://www.myastheniawa.info/drugs.html

This article is a practical guide to those drugs which may affect Myasthenia Gravis, with advice as to how to minimise the impact when a decision is made to use one of these drugs. It is intended for use by the treating doctor or dentist, and whilst it will hopefully inform those who have MG, it is not intended to replace professional advice. Each case is different, and only the treating professional can advise in individual situations.

The information is set out under the headings of diseases or conditions that the various drugs are used for so that the patient with Myasthenia Gravis can take it to their GP, Specialist, Hospital Doctor or Dentist and they can easily see which drugs can be used.

[top]

How Drugs may worsen MG

Drugs may worsen MG by

interfering with neuromuscular transmission. As MG also affects neuromuscular transmission, it may lead to worsening symptoms. The better controlled the MG, the less the risk of these drugs being a problem.
increasing muscle weakness in a more general manner, thus making the MG weakness more noticeable.
There are a few clear cut examples of drugs that can actually cause a temporary form of autoimmune MG which usually settles once the drug is ceased. It is less clear whether these drugs will worsen pre-existing MG.

Many reports of drugs affecting MG have caused problems in only one person, or a perhaps a few. Some drugs can theoretically cause problems but have not actually done so in the clinical setting. This means that the majority of MG patients can take the drugs without problems, and the benefits of the treatment should not be denied to them. The important point is for patients and doctors alike to be alert to the early signs of an exacerbation of the MG when a new drug is started, even if it is not on the list.

It is also important to remember that many acute illnesses themselves can worsen MG, and in many of these case reports it has been impossible to tell if it was the drug or the illness that was the problem e.g. was the pneumonia caused by an unrecognised flare up of MG, with aspiration into the lung, or was the worsening MG due to the pneumonia or the antibiotic used to treat it?