While effective, lithium causes weight gain, can be cardiotoxic, cause hypothyroidism, tremor, polydipsia, polyuria, nausea, vomiting and diarrhea. It also requires periodic blood draws to check levels and monitor renal function.
If this is acceptable to you, or your friend, great. But given the high rate of non-compliance due to side effects, you may want to consider alternatives.
Depakote is fine but comes with multiple side effects as well. It also requires periodic blood draws to check levels and hepatic function.

Lamictal is relatively weight-neutral, does not require constant monitoring and helps with both maintenance and bipolar depression. It can cause headaches and a rash which, if it progresses, can lead to Stevens-Johnson syndrome. But otherwise, the side effect profile is much more benign.