Been on surmontil (trimipramine) 50 mg. for 12 yrs. now generic doesn't seem as effective. is generic the same formulation?

Yes and no: Generics must contain the same active ingredient as the branded product, but other ingredients (fillers) or delivery system (capsule vs pill vs gelcap vs specialized release system) may be different. Generics from other countries may not be tested as thoroughly to make certain dose of active ingredient is consistent. Discuss concerns with fp/doc &/or pharmacist.