I would speak to him AND his parents. I've never heard of someone being diagnosed with ANY disorder by a Nurse Practitioner.
And to be honest, I'd be more leery of the Zoloft (which is an SSRI and can cause or increase mania in some bipolar patients).
Seroquel is usually tried when the person with bipolar is a very strong manic phase when diagnosed.
Neither Zoloft OR Seroquel is a mood stabilizer and it always concerns me when someone is diagnosed with a mood disorder and they are not given one of the stabilizers that is available.
Lithium (I've been on it for 20 years with great results)
Valproic acid (Depakene),
Gabapentin (Neurontin) Not FDA approved for bipolar disorder
Oxcarbazepine (Trileptal) Not FDA approved for bipolar disorder
Topiramate (Topamax) Not FDA approved for bipolar disorder
May I ask how old your boyfriend is? You are to be commended for wanting to stand behind him. Bipolar Disorder can be very difficult to keep under control, and it does take skin of Teflon for loved ones of us bipolars to survive...
Your desire to educate yourself, and finding us here(!) is wonderful!!