Levothyroxine Ciprofloxacin

THYROID HORMONES QUINOLONES -CIPROFLOXACIN i levels of levothyroxine and possible therapeutic failure The mechanism has not been elucidated the concurrent administration of ciprofloxacin with levothyroxine may interfere with the absorption of levothyroxine and result in lower than expected levels The interaction may be minimized by separating dosing of the two agents ciprofloxacin should be taken several hours before or after taking levothyroxine... 

Noninterfering acetaminophen, N-acetylprocainamide, amikacin, amitriptyline, amlodi-pine, carbamazepine, cefotaxime, ceftazidime, chloramphenicol, ciprofloxacin, cisapride, clindamycin, clonidine, codeine, cyclosporine, digoxin, diphenhydramine, disopyramide, ethosuximide, fluconazole, gentamicin, gentamicin, heparin, labetalol, levothyroxine, li-docaine, lithium, methotrexate, metronidazole, minoxidil, nafcillin, nifedipine, phenobar-bital, phenobarbital, phenytoin, phenytoin, primidone, procainamide, propranolol, quini-dine, ranitidine, salicylic acid, theophylline, tobramycin, tobramycin, valproic acid, warfarin... 

There is a report of unexplained hypothyroidism in two patients taking levothyroxine who had also been taking oral ciprofloxacin for 3 to 4 weeks. 

An 80-year-old patient with advanced thyroid cancer taking levothyroxine 125 micrograms daily required treatment with oral ciprofloxacin 750 mg twice daily and intravenous dicloxacillin for osteomyelitis complicating a fracture. After 4 weeks of treatment she complained of increasing tiredness, and was found to have a markedly raised TSH level (10 times of the upper limit of normal). Increasing the levothyroxine dose to 200 micrograms daily did not have any effect on TSH, so the dose was returned to 125 micrograms. The ciprofloxacin was then stopped, and the thyroid function tests rapidly normalised. ... 

Another women stable taking levothyroxine 150 micrograms daily had a more than 10-fold increase in TSH levels after taking ciprofloxacin 500 mg twice daily for 3 weeks. When administration of levothyroxine and ciprofloxacin was separated by 6 hours, thyroid function tests normalised, which suggests that concurrent administration somehow reduces the absorption of levothyroxine. 

This interaction is not established, but the two cases suggest that longterm ciprofloxacin should be considered as a possible cause of hypothyroidism in patients taking levothyroxine. Further study is needed. 

Cholongitas E, Georgousaki C, Spyrou S, Katsogridakis K, Dasenaki M. Stevens-Johnson syndrome related to ciprofloxacin, possibly enhanced by overadministration of levothyroxine. Dermatol Online J 2009 15(11) 16. 

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