Adverse interaction between steroid hormones and anticholinesterase drugs

Hydrocortisone, despite its lack of effect when used alone in a rat nervemuscle preparation, abolished the increase in muscle single-twitch tension produced by the anticholinesterase drugs neostigmine and pyridostigmine. Once the steroid had abolished the effect of these drugs, equivalent doses of the cholinesterase inhibitors were less effective than they had been before steroid was given. The results of these experiments indicate that a corticosteroid hormone may have an adverse pharmacologic interaction with anticholinesterase drugs in a mammalian nerve-muscle preparation. This significant adverse interaction might be the reason some patients with myasthenia gravis do not respond as well with corticosteroid plus anticholinesterase as with corticosteroid alone.