As nouns the difference between antipsychotic and levomepromazine
is that
antipsychotic is (pharmacology) any of a group of drugs used to treat psychosis while
levomepromazine is an aliphatic phenothiazine neuroleptic drug, a low-potency antipsychotic with strong analgesic and antiemetic properties and certain serious side effects.
As an adjective antipsychotic
is (pharmacology) preventing or counteracting psychosis.