Drugs which are most consistently reported as potentially being a problem are in bold

Antibiotics
Aminoglycosides
Neomycin
Gentamicin
Streptomycin
Kanamycin
Tobramycin
Macrolides
Erythromycin
Clarithromycin
Azirthromycin etc.

Fluoroquinolones
Norfloxacin
Offaxocin
Cirporfloxacin etc
Others:
Amikacin
Polymixin B
Colistin
Tetracyclines
Oxytetracyclines
Lincomycin & Clindamycin
Ampicillin

Cardiovascular Drugs
Beta Blockers (including topical/ocular-probably safe)
Quindine
Procainamide
Calcium Channel Blockers
Verapamil, Nimodipine & perhaps other calcium channel blocers - also probably safe
Clonidine
Bretylium (high doses)
ACE inhibitors May potentiate bone marrow suppression if on azathioprine

CNS Active
Diphenylhydantoin/Phenytoin
Trimethadione
Lithium
Chlorpromazine, Promazine
Trihexyphenidyl
Morphine and other narcotics
benzodiazapines & barbiturates - probably safe unless significant bulbar or respiratorty compromise is present
Amantadine

Anti-Rheumatic
Chloroquine
D-Penicillamine - can cause MG in some individuals, usually reversable
Prednisone - high doses can temporarily worsen MG within the first 1-2 weeks. There is NO reaction between Mestinon & Prednisone

Anaesthetic Agents
non-depolerizing agents
Pancuronium, Vecuronium and Atacurium - increased sensitivity in MG
Succinylcholine - Decreased effect in MG, increased if on pyridostigmine