All of the following drugs aggravates Myasthenia gravis, EXCEPT:

Azathioprine has been the most commonly used immunosuppressive agent for MG because of its relative safety in most patients and long track record. Drugs that may exacerbate MG: Antibiotics: Aminoglycosides: e.g., streptomycin, tobramycin, kanamycin Quinolones: e.g., ciprofloxacin, levofloxacin, ofloxacin, gatifloxacin Macrolides: e.g., erythromycin, azithromycin, Nondepolarizing muscle relaxants for surgery: D-Tubocurarine (curare), pancuronium, vecuronium, atracurium Beta-blocking agents: Propranolol, atenolol, metoprolol Local anesthetics and related agents: Procaine, Xylocaine in large amounts Procainamide (for arrhythmias) Quinine derivatives: Quinine, quinidine, chloroquine, mefloquine (Lariam) Magnesium: Decreases ACh release Penicillamine: May cause MG Ref: Drachman D.B. (2012). Chapter 386. Myasthenia Gravis and Other Diseases of the Neuromuscular Junction. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.