Ciprofloxacin how long to take effect. He is worried about long term effects. . . . . Long-term carcinogenicity studies in rats and mice . . . . If you have any CNS infections, cipro must be used with caution. . to them and stay that way for as long as a . Methadone usually takes about an hour to fully feel the effects. . . Take ciprofloxacin with a full glass of water (8 ounces). or a personal or family history of "Long QT . I would like to know more about this topic, since I take Cipro when ... more