What Causes Cramps In The Thighs Followed By Nausea And Dizziness?

I have been having leg cramps for several years and nothing seems to alleviate them completely. It was recently suggested that perhaps my blood pressure medication might be the cause. I have been taking losartan POT since June 2012 (50 mg in am and 50 mg in pm). Would another BP drug be preferable - or could something else be causing the severe cramping? I have tried (and still taking) magnesium, am now on thyroid med, both of which seemed to help some. Yesterday I was awakened at 3 am with a severe upper thigh cramp - followed by nausea and dizziness and high blood pressure reading. Went to the ER and they did several tests, all of which were normal. No heart malfunction or blood clots. I m at a loss as to what is causing this problem as otherwise I m in great shape - blood work is amazing for someone my age (72) according to the hospital doctor. Any help you could give me would be greatly appreciated as these leg/toe cramps are such a nuisance, as well as painful. Thank you.