Hi, Ginny,
Thankfully, BP has come a long way from the 50s when lithium was the only med to take. Your father's doc is right; lithium cannot be used long term, it can damage the kidneys, thyroid and cause changes in the heart.
Today there are tons of choices, mood stabilizers: Lamictal (good antidepressant effect, too), Topamax, Trileptal, depakote
Antipsychotics (almost always used with a stabilzer for optimum effectiveness): Risperdal, Seroquel, Abilify.
Abilify is the newest generation antipsychotic that is being used (with caution) as monotherapy (meaning without another mood stabilizer) that seems to be very good, I am taking it but with 2 other mood stabilizers.
Is he seeing a psychiatrist? I am wondering because if the doc is concerned about the damage from lithium, he should know of these alternatives. If your dad isn't seeing a pdoc, he should be. If he is and the guy isn't up to par, he may want to think about changing.
I hope this helps! Shannon