Unstoppable menstruation induced by the concomitant use of tizanidine and warfarin

Women, be careful out there.
http://www.cadrj.com/qikan/epaper/zhaiyao.asp?bsid=17703

Abstract   

A 51-year-old woman with rheumatic heart disease and cerebral embolism received warfarin for about one year and the dosage was reduced gradually from 2.25 mg/d to 1.5 mg/d. At the same time, she was given tizanidine 2 mg thrice daily (2 mg twice daily at the first week)because of her right upper limb spasticity. About 20 days later, her menstruation started and lasted more than 20 days. Tizanidine was withdrawn and, 5-6 days later, her menstruation stopped. Laboratory examination showed the following results: prothrombin time 19.5 s, prothrombin activity 64.9%, prothrombin time ratio 1.56, international normalized ratio 1.61, partial thromboplastin time 37.2 s, thromboplastin time 13.5 s, fibrinogen 3.8 g/L. Warfarin was continued at the same dose as before. The situation of prolonged menstrual period and increased menstrual flow did not reccur at a one-year follow-up.