Is there a risk that analgesics exacerbate myasthenia gravis?/nA 30-year-old woman with well-contro

Fråga: Is there a risk that analgesics exacerbate myasthenia gravis?

A 30-year-old woman with well-controlled myasthenia gravis (MG) has a disc hernia and uses paracetamol (Alvedon) and tramadol (Tradolan) on demand. However, she gets drowsy by tramadol and wants another analgesic to complement paracetamol. The questioner wants to be sure that this change of medication does not interfere with her MG.

Other medications are: pyridostigmine (Mestinon) every four hours, potassium chloride (Kalium Retard) 750 mg three times daily, citalopram 20 mg once daily, zopiclone (Imovane) 7.5 mg at night.

Sammanfattning: Gabapentin should probably be avoided, but antidepressives and analgesics seem to be safe in myasthenia gravis.

Svar: The question of analgesics in myasthenia gravis (MG) has previously been answered in Drugline (1). Nothing was then found on contraindicated analgesics or antidepressants in MG.

However, high doses of a cough syrup containing codeine and squill oxymel (expectorant) have been described to cause myopathy with myasthenic features. The authors claimed the expectorant rather than codeine was responsible for the myopathy (2).

An updated search has not revealed any new information in this area other than that gabapentin, commonly used for neuropathic pain, may unmask or worsen MG as described in two case reports (3,4). In the first report, the authors also could show that gabapentin unmasked myasthenic features in rats with experimental autoimmune MG (3). Drugline no 13305 (year 1998) Davies DM, Ferner RE, de Glanville H, editors. Davie´s textbook of adverse drug reactions. 5th ed. Philadelphia: Lippincott-Raven Publishers; 1998 Boneva N, Brenner T, Argov Z. Gabapentin may be hazardous in myasthenia gravis. Muscle Nerve 2000;23(8):1204-1208 Scheschonka A, Beuche W. Treatment of post-herpetic pain in myasthenia gravis: exacerbation of weakness due to gabapentin. Pain 2003;104(1-2):423-424