Hello, The medicines you mentioned are usually given to before starting dental procedures to counter bacterial infections and pain. Tiredness and joint pain, these are commonly observed side effects of Cifran which will go away slowly. If this bothers you a lot, I suggest contact your dentist and follow his advice and see if he suggests change in that.Usually every medicine has some side effects but doctors prescribe these as per patient s overall condition and history for maximum benefit. So, do not worry and stop taking the medicine if this keeps getting worse and talk to your dentist. Stress can cause delay in menstruation. There are other factors as well but I suggest wait for few more days. Even then the same thing persists then visit a gynecologist for it. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Manisha Auradkar, General & Family Physician