Medicines to avoid or use with caution in myasthenia gravis

In myasthenia gravis the immune system produces antibodies that block or damage the receptors where nerves signal to muscles. Healthy people have a large safety margin at that junction, so a drug that slightly reduces transmission is unnoticed. Myaware explains that people with MG have depleted reserves, so even minor interference can cause significant weakness, and that more than 30 commonly used drugs can interfere.

That does not mean avoiding all medicines. Most people with MG take many drugs safely. It means the prescriber needs to know the diagnosis, weigh benefit against risk, and watch for changes in strength after starting something new.

The Myaware drugs page identifies telithromycin, a ketolide antibiotic, as the one exceptional drug that must be avoided because it has caused deaths. It says penicillamine, used in rheumatoid arthritis, can trigger myasthenia and so should be avoided. For medicines used in neurology and psychiatry, it says evidence of problems is limited, none is absolutely banned, but caution is advised with new prescriptions.

The page points readers to a downloadable list for the full picture and to a contraindicated medicines list published by NHS Scotland. It adds that its information applies to myasthenia gravis, not to congenital myasthenic syndromes or Lambert-Eaton syndrome, which have different drug considerations.

Several groups of medicines are commonly flagged in MG safety lists because they can affect neuromuscular transmission. The NHS information page for ciprofloxacin carries a myasthenia gravis caution in its heading, showing that one of the most widely used antibiotic families needs care. Other groups that clinicians typically weigh up include certain other antibiotics, some heart and blood pressure medicines, magnesium given intravenously, some muscle relaxants used in anaesthesia and certain injections for cosmetic or neurological use.

The NHS azathioprine pages add a practical point: people due to have an operation that needs muscle relaxants should tell the doctor beforehand. Azathioprine is itself used in MG, and the NHS names myasthenia gravis among the linked conditions. Always check the current local list before relying on a general summary like this one.

• Antibiotics: infection is itself a trigger, so the choice needs thought rather than avoidance of treatment.

• Anaesthesia and surgery: tell the anaesthetist, who can choose drugs and doses accordingly.

• Dental and eye procedures that involve injections or sedation.

• Over-the-counter products and supplements, including magnesium.

Carry a card or phone note that says you have myasthenia gravis, the names of your regular medicines and the contact for your neurology team. Show it at every pharmacy, A&E visit, dental appointment and hospital stay. Ask the pharmacist to flag MG on your record.

When a new medicine is prescribed, ask whether it is known to affect myasthenia and whether there is an alternative. If you start a new drug and notice more fatigue, double vision, drooping eyelids, slurred speech, trouble chewing or swallowing, or a weaker voice, contact the prescriber or neurology team promptly rather than waiting to see.

The NHS describes three approaches: avoiding triggers, medicines to improve muscle weakness, and sometimes surgery to remove the thymus gland. MedlinePlus adds anticholinesterase medicines, immunosuppressive medicines, monoclonal antibodies, and plasmapheresis or intravenous immunoglobulin for severe episodes. Regular gentle exercise, rest and a healthy diet are encouraged.

Because some of these treatments themselves lower immunity, infection risk and drug interactions are part of normal monitoring. The wider guide to myasthenia gravis covers diagnosis and outlook.

The NHS says that if symptoms suddenly worsen, for example severe breathing or swallowing difficulty, urgent hospital treatment may be needed. MedlinePlus calls severe weakness affecting the breathing muscles a myasthenic crisis, a life-threatening emergency.

Call 999 for breathlessness, inability to swallow saliva, a weak cough or sudden collapse. Tell the ambulance crew and the emergency team that you have myasthenia gravis, because some routine emergency drugs need adjusting.