Haloperidol is a typical butyrophenone type antipsychotic that exhibits high affinity dopamine D 2 receptor antagonism and slow receptor dissociation kinetics.  It has effects similar to the phenothiazines .  The drug binds preferentially to D 2 and α 1 receptors at low dose (ED 50 = and mg/kg, respectively), and 5-HT 2 receptors at a higher dose (ED 50 = mg/kg). Given that antagonism of D 2 receptors is more beneficial on the positive symptoms of schizophrenia and antagonism of 5-HT 2 receptors on the negative symptoms, this characteristic underlies haloperidol's greater effect on delusions, hallucinations and other manifestations of psychosis.  Haloperidol's negligible affinity for histamine H 1 receptors and muscarinic M 1 acetylcholine receptors yields an antipsychotic with a lower incidence of sedation, weight gain, and orthostatic hypotension though having higher rates of treatment emergent extrapyramidal symptoms .
Generally speaking, the two most generally accepted methods to prove the safety of a generic version of a drug are to either repeat most of the chemistry, animal and human studies originally done, or to show that the drug performs comparably with the original brand name drug. This second option is called a "comparative bioavailability" study. During this type of study, volunteers are given the original drug, and then separately later the generic drug. The rates at which the drug is delivered to the patient (into their blood stream or otherwise absorbed) are measured to ensure they are the same. Because the same active ingredient is used the major concern is just that it delivers the common chemical(s) at the same rate so that they have the same effect. Please note that the methods that the manufacturers use may vary from country to country.