Serious. These medicines may interact and cause very harmful effects. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.
How the interaction occurs:
Hormonal contraceptives may slow down how quickly your liver processes tizanidine.
What might happen:
The amount of tizanidine in your blood may increase and cause more side effects than normal, including severe low blood pressure and drowsiness.
What you should do about this interaction:
Let your healthcare professional (e.g. doctor or pharmacist) know right away that you are using these medicines together. Let your doctor know if you have any fainting or dizziness episodes. Your doctor may want to change the dose of your tizanidine. Use caution when performing tasks that require alertness.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.Zanaflex (tizanidine hydrochloride) US prescribing information. Acordia Therapeutics, Inc. July, 2006.
2.Granfors MT, Backman JT, Laitila J, Neuvonen PJ. Oral contraceptives containing ethinyl estradiol and gestodene markedly increase plasma concentrations and effects of tizanidine by inhibiting cytochrome P450 1A2. Clin Pharmacol Ther 2005 Oct;78(4):400-11.