Some drugs can have clear effects on Myasthenia Gravis, including Neuromuscular junction blockers, antibiotics, prednisone, chloroquine, D-penicillamine, interferons, and others. In rapid-onset drug-induced Myasthenia Gravis, myasthenic signs develop within days which rapidly disappear after drug withdrawal. Anti-Acetylcholinesterase antibodies are absent. This disorder may unmask a pre-existing neuromuscular transmission disorder or may exacerbate pre-existing Myasthenia Gravis, i.e. subclinical Myasthenia Gravis becomes manifest after drug treatment, or known MG becomes more severe. Certain drugs are linked with aggravation of Myasthenia Gravis, including pain management medications, tricyclic antidepressants and some antiepileptic medications, and should be used with caution.