Drowsiness is patient-specific, and you're probably best off talking to your psychiatrist. I have similar issues. It took my body several months to stop being drowsy after a dose of mood stabilizer. My psychiatrist titrates my doses up very slowly, and even then, each increase is followed by a period of increased drowsiness. Good luck.

Sometimes psychiatrists put patients on a range of mood stabilizers as a "layering" technique. The aim is to give you the cumulative impact that a high dose of one mood stabilizer would have, while trying to minimize side effects (assuming that smaller doses of different medications will have a smaller individual side effect, and thus a smaller cumulative side effect). Ask your doctor if this is what he is doing (re: Supanova's question about why you're on three medications that are supposed to have the same effect).