Neurology/Myasthenia gravis drugslow yield

Myasthenia gravis drugs

also: pyridostigmine · anticholinesterase · myasthenic crisis · drugs to avoid

Overview

Symptomatic and immunosuppressive treatment of myasthenia gravis — plus the crucial list of drugs that WORSEN it.

Mechanism

Pyridostigmine inhibits acetylcholinesterase → more ACh at the neuromuscular junction → improved transmission (symptomatic). Immunosuppression (steroids, azathioprine) treats the underlying antibody-mediated disease. Crisis is treated by removing antibody (IVIG / plasma exchange).

Indications

Myasthenia gravis (symptomatic + immunosuppression)
Myasthenic crisis

The agents

Pyridostigmineanticholinesterase

oral

Symptomatic; cholinergic AEs (cramps, diarrhoea, salivation); excess → cholinergic crisis.

Prednisolone / azathioprineimmunosuppression

Disease-modifying; steroids can transiently worsen at initiation.

IVIG / plasma exchangecrisis

Myasthenic crisis (respiratory failure) — plus ventilatory support.

Adverse effects

Cholinergic crisis (excess pyridostigmine)serious

Salivation, miosis, weakness — distinguish from myasthenic crisis.

Immunosuppression effectsserious

Cautions & contraindications

Drugs that worsen MG: aminoglycosides, macrolides, fluoroquinolones, β-blockersall

Impair neuromuscular transmission → can precipitate crisis.

Magnesium sulfate (caution)all

Worsens neuromuscular blockade.

Interactions

As above — many antibiotics + β-blockers worsen MG

Monitoring & kinetics

Respiratory function (FVC) in crisis; symptom control

Oral pyridostigmine; IVIG/PLEX for crisis.

Source: BNF — Myasthenia gravis