indication

For the treatment of schizophrenia, control nausea and vomiting, For relief of restlessness and apprehension before surgery, adjunct in the treatment of tetanus, control the manifestations of the manic type of manic-depressive illness.

pharmacology

Chlorpromazine is a psychotropic agent indicated for the treatment of schizophrenia. It also exerts sedative and antiemetic activity. Chlorpromazine has actions at all levels of the central nervous system-primarily at subcortical levels-as well as on multiple organ systems. Chlorpromazine has strong antiadrenergic and weaker peripheral anticholinergic activity; ganglionic blocking action is relatively slight. It also possesses slight antihistaminic and antiserotonin activity.

mechanism of action

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 extrapypramidal 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. This action could also account for psychomotor agitation and amplification of psychosis (very rarely noted in clinical use).

toxicity

Agitation, coma, convulsions, difficulty breathing, difficulty swallowing, dry mouth, extreme sleepiness, fever, intestinal blockage, irregular heart rate, low blood pressure, restlessness

biotransformation

Extensively metabolized in the liver and kidneys. It is extensively metabolized by cytochrome P450 isozymes CYP2D6 (major pathway), CYP1A2 and CYP3A4. Approximately 10 to 12 major metabolite have been identified. Hydroxylation at positions 3 and 7 of the phenothiazine nucleus and the N-dimethylaminopropyl side chain undergoes demethylation and is also metabolized to an N-oxide. In urine, 20% of chlopromazine and its metabolites are excreted unconjugated in the urine as unchanged drug, demonomethylchlorpromazine, dedimethylchlorpromazine, their sulfoxide metabolites, and chlorpromazine-N-oxide. The remaining 80% consists of conjugated metabolites, principally O-glucuronides and small amounts of ethereal sulfates of the mono- and dihydroxy-derivatives of chlorpromazine and their sulfoxide metabolites. The major metabolites are the monoglucuronide of N-dedimethylchlorpromazine and 7-hydroxychlorpromazine. Approximately 37% of the administered dose of chlorpromazine is excreted in urine.

absorption

Readily absorbed from the GI tract. Bioavailability varies due to first-pass metabolism by the liver.

half life

~ 30 hours

route of elimination

Kidneys, ~ 37% excreted in urine

drug interactions

Amphetamine: Decreased anorexic effect, may increase psychotic symptoms

Artemether: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Benzphetamine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Bromocriptine: The phenothiazine decreases the effect of bromocriptine

Cisapride: Increased risk of cardiotoxicity and arrhythmias

Dexfenfluramine: Decreased anorexic effect, may increase psychotic symptoms.

Dextroamphetamine: Decreased anorexic effect, may increases psychotic symptoms

Diethylpropion: Decreased anorexic effect, may increase psychotic symptoms

Donepezil: Possible antagonism of action

Fenfluramine: Decreased anorexic effect, may increase psychotic symptoms

Galantamine: Possible antagonism of action

Gatifloxacin: Increased risk of cardiotoxicity and arrhythmias

Grepafloxacin: Increased risk of cardiotoxicity and arrhythmias

Guanethidine: Chlorpromazine may decrease the effect of guanethidine.

Levofloxacin: Increased risk of cardiotoxicity and arrhythmias

Lumefantrine: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Mazindol: Decreased anorexic effect, may increase psychotic symptoms

Meperidine: Increased sedation and hypotension

Mesoridazine: Increased risk of cardiotoxicity and arrhythmias

Methamphetamine: Decreased anorexic effect, may increases psychotic symptoms

Metrizamide: Increased risk of convulsions

Phendimetrazine: Decreased anorexic effect, may increases psychotic symptoms

Phenmetrazine: Decreased anorexic effect, may increase psychotic symptoms

Phentermine: Decreased anorexic effect, may increase psychotic symptoms

Phenylpropanolamine: Decreased anorexic effect, may increase psychotic symptoms

Pindolol: Increased effect of both drugs

Propranolol: Increased effect of both drugs

Rivastigmine: Possible antagonism of action

Sparfloxacin: Increased risk of cardiotoxicity and arrhythmias

Tacrine: The therapeutic effects of the central acetylcholinesterase inhibitor (AChEI), Tacrine, and/or the anticholinergic/antipsychotic, Chlorpromazine, may be reduced due to antagonism. This interaction may be beneficial when the anticholinergic action is a side effect. AChEIs may also augment the central neurotoxic effect of antipsychotics. Monitor for extrapyramidal symptoms and decreased efficacy of both agents.

Tacrolimus: Additive QTc-prolongation may occur increasing the risk of serious ventricular arrhythmias. Concomitant therapy should be used with caution.

Tamoxifen: Chlorpromazine may decrease the therapeutic effect of Tamoxifen by decreasing the production of active metabolites. Concomitant therapy should be avoided.

Tamsulosin: Chlorpromazine, a CYP2D6 inhibitor, may decrease the metabolism and clearance of Tamsulosin, a CYP2D6 substrate. Monitor for changes in therapeutic/adverse effects of Tamsulosin if Chlorpromazine is initiated, discontinued, or dose changed.

Terbinafine: Terbinafine may reduce the metabolism and clearance of Chlorpromazine. Consider alternate therapy or monitor for therapeutic/adverse effects of Chlorpromazine if Terbinafine is initiated, discontinued or dose changed.

Terfenadine: Increased risk of cardiotoxicity and arrhythmias

Tetrabenazine: May cause dopamine deficiency. Monitor for Tetrabenazine adverse effects.

Thioridazine: Increased risk of cardiotoxicity and arrhythmias

Thiothixene: May cause additive QTc-prolonging effects. Increased risk of ventricular arrhythmias. Consider alternate therapy. Thorough risk:benefit assessment is required prior to co-administration.

Tolterodine: Chlorpromazine may decrease the metabolism and clearance of Tolterodine. Monitor for adverse/toxic effects of Tolterodine.

Toremifene: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Consider alternate therapy. A thorough risk:benefit assessment is required prior to co-administration.

Tramadol: Chlorpromazine may decrease the effect of Tramadol by decreasing active metabolite production.

Trimethobenzamide: Trimethobenzamide and Chlorpromazine, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Monitor for enhanced anticholinergic effects.

Trimipramine: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Chlorpromazine, a strong CYP2D6 inhibitor, may also decrease the metabolism and clearance of Trimipramine, a CYP2D6 substrate. Caution should be used during concomitant therapy.

Triprolidine: The antihistamine, Triprolidine, may increase the arrhythmogenic effect of the phenothiazine, Chlorpromazine. Monitor for symptoms of ventricular arrhythmias. Additive anticholinergic and CNS depressant effects may also occur. Monitor for enhanced anticholinergic and CNS depressant effects.

Trospium: Trospium and Chlorpromazine, two anticholinergics, may cause additive anticholinergic effects and enhanced adverse/toxic effects. Monitor for enhanced anticholinergic effects.

Venlafaxine: Chlorpromazine, a CYP2D6 inhibitor, may decrease the metabolism and clearance of Venlafaxine, a CYP2D6 substrate. Monitor for changes in therapeutic/adverse effects of Venlafaxine if Chlorpromazine is initiated, discontinued, or dose changed.

Vorinostat: Additive QTc prolongation may occur. Consider alternate therapy or monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).

Ziprasidone: Additive QTc-prolonging effects may increase the risk of severe arrhythmias. Concomitant therapy should be avoided.

Zuclopenthixol: Additive QTc prolongation may occur. Consider alternate therapy or use caution and monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP). Chlorpromazine, a strong CYP2D6 inhibitor, may increase the serum concentration of zuclopenthixol by decreasing its metabolism. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of zuclopenthixol if chlorpromazine is initiated, discontinued or dose changed.