Moderate. These medicines may cause some risk when taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
Rifampin may increase the amount of levothyroxine your body absorbs, but it may also speed up how quickly your body processes levothyroxine.
What might happen:
The effects of your levothyroxine may be changed. Some patients may experience increased effects (hyperthyroidism), such as weight loss, rapid heartbeat, nervousness, sweating, tremor, fatigue, and difficulty sleeping. Other may experience decreased effects (hypothyroidism) such as fatigue, sluggishness, constipation, stiffness, muscle cramps, loss of appetite, excessive weight gain, or dry skin.
What you should do about this interaction:
Let your healthcare professionals (e.g. doctor or pharmacist) know that you are taking these medicines together. Let your doctor know if you have any signs or symptoms of hyperthyroidism or hypothyroidism.Your healthcare professionals may already be aware of this interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.
1.Goldberg AS, Tirona RG, Asher LJ, Kim RB, Van Uum SH. Ciprofloxacin and rifampin have opposite effects on levothyroxine absorption. Thyroid 2013 Nov;23(11):1374-8.
2.Isley WL. Effect of rifampin therapy on thyroid function tests in a hypothyroid patient on replacement L-thyroxine. Ann Intern Med 1987 Oct; 107(4):517-8.
3.Nolan SR, Self TH, Norwood JM. Interaction between rifampin and levothyroxine. South Med J 1999 May;92(5):529-31.