I agree that safety is most important. I do wonder if carbamazepine (carbamazepine ER) might be a medication your psychiatrist may consider. Carbamazepine ER is completely weight neutral for me. It does have some drug interactions, though, but I don't believe it interacts with Lithium. I've lost 40 lbs in six months (dieting) on the combo of carbamazepine ER and Lithium (and Geodon). It apparently does have an interaction with Seroquel, but not one that prevents my psychiatrist from prescribing them together. Dosage issue. I'm not sure how it is with Saphris.

Carbamazepine ER is also called name brand Tegretol in the US, and Equetro, Carbatrol or Epitol in some other places. Generic is available and works fine for me. I have virtually no side effects from it, especially after the initial adjustment. It does require some blood work, but no more than divalproex sodium or definitely no more than Lithium.