I was on mag after my water broke at 31 weeks. I was on for 7 days. Immediately you feel like you are on fire from inside your body. Generally the nurses turn your AC on to the lowest possible setting. After awhile you will still run hot but not feel like you are on fire. I lost all of my reflexes and struggled to pull my head off the bed. It also blurred my vision so much that reading was out, and TV was barely enjoyable. The good news is you do feel drowsy so you can sleep a lot. Also I remember my nasal passages swelling a lot. My husband had to run to walmart to gets humidifier because my nose was bleeding from the swelling and dryness. Anyway, it worked to get me to the crucial 32 week mark. Just remember how important it is whether it is fun or not.
The Dr put me on it to lower my blood pressure and admitted me to the hospital. I wasn't allowed to walk until 24 hours after they took me off of it.