Hi, Cycloreg contains norethisterone which is used in the treatment of various menstrual problems such as irregular, heavy or painful periods, premenstrual symdrome or PMS and endometriosis. Cycloreg contains only norethisterone, a natural female sex hormone, progesterone. Take this medication as directed by your gynaecologist. Cycloreg may cause back pain, muscle pain, joint pain etc as its side effects. Other side effects of Cycloreg are nausea, vomiting, abdominal pain, indigestion, headache, sweating, fatigue, unusual tiredness and weakness, dryness of mouth, changes in body weight, impaired wound healing, mood swings, depression, breast tenderness and enlargement, changes in sleep pattern, vaginal discharge, vaginal bleeding, changes in sex drive, easily bruising or bleeding, allergic reactions, changes in appetite etc. If these side effects persist for long or bother you, then you should consult your doctor first for medical attention. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards,, Dr. Zubayer Alam, General And Family Physician,