I Have Just Started Using HydraAlazine . I've Taken Four

I have just started using hydraAlazine . I've taken four doses in two days,one a 10am and one a 4pm. At 12 am. in the following morning my body stars to ache, back, arms legs, neck, head. Is this a normal side effect and how long do I excpect to have these symptoms? It's not really bad, about a
5 on a 1 to 10 scale, I get an opxy 5-325 at 1.30 am. and that relieves the pain. Don't get the pain during the day, I take the oxy's every 6 hrs.