Feeling sick like that is more likely the drug itself than the divided dose, I'd think. What is it you're taking? It could be that your dose was raised too high for you, or that it was raised too fast. Or, it could actually be unrelated -- sometimes I've come down with a bug just at the right time to make me think it was a drug reaction.

A lot of drugs are given in divided doses. Some are short acting, and need multiple doses; others are given in divided doses to help maintain a more stable blood level. It depends on teh drug.

Good luck.