Fluoroquinolone antibiotics block neuromuscular transmission.

Fluorinated 4-quinolones are widely used antibiotics. Several case reports describe the exacerbation of muscle weakness in myasthenia gravis patients treated with fluoroquinolones. We studied the effects of norfloxacin, ofloxacin, and pefloxacin on miniature endplate potentials (MEPPs) and currents. These antibiotics progressively decreased the amplitude of the MEPPs as drug concentrations were increased from 12.5 to 100 mg/L. Fluoroquinolones should be used only with great caution in disorders that compromise the safety margin of neuromuscular transmission.