Prochlorperazine and chlorpromazine are examples of this class of Phenothiazines. Phenothiazines antagonize the D2 receptor, most notably in the area postrema in the brain. IV, PO, and rectal (PR) formulations are available. Side effects include dizziness, headache, and extrapyramidal symptoms, including dystonia and tardive dyskinesia. Chlorpromazine is used for the management of schizophrenia; to control nausea and vomiting; for relief of restlessness and apprehension before surgery; for acute intermittent porphyria; as an adjunct in the treatment of tetanus; to control the manifestations of the manic type of manic-depressive illness; for relief of intractable hiccups; for the treatment of severe behavioral problems in children (1 to 12 years of age) marked by combativeness and/or explosive hyper-excitable behavior (out of proportion to immediate provocations), and in the short-term treatment of hyperactive children who show excessive motor activity with accompanying conduct disorders consisting of some or all of the following symptoms: impulsivity, difficulty sustaining attention, aggressivity, mood lability, and poor frustration tolerance. Chlorpromazine acts as an antagonist (blocking agent) on different postsysnaptic receptors -on dopaminergic-receptors (subtypes D1, D2, D3 and D4 - different antipsychotic properties on productive and unproductive symptoms), on serotonergic-receptors (5-HT1 and 5-HT2, with anxiolytic, antidepressive and antiaggressive properties as well as an attenuation of extrapyramidal side-effects, but also leading to weight gain, fall in blood pressure, sedation and ejaculation difficulties), on histaminergic-receptors (H1-receptors, sedation, antiemesis, vertigo, fall in blood pressure and weight gain), alpha1/alpha2-receptors (antisympathomimetic properties, lowering of blood pressure, reflex tachycardia, vertigo, sedation, hypersalivation and incontinence as well as sexual dysfunction, but may also attenuate pseudoparkinsonism - controversial) and finally on muscarinic (cholinergic) M1/M2-receptors (causing anticholinergic symptoms like dry mouth, blurred vision, obstipation, difficulty/inability to urinate, sinus tachycardia, ECG-changes and loss of memory, but the anticholinergic action may attenuate extrapyramidal side-effects). Additionally, Chlorpromazine is a weak presynaptic inhibitor of Dopamine reuptake, which may lead to (mild) antidepressive and antiparkinsonian effects.

Chlorpromazine - Dopamine Antagonist Pathway References