Prochlorperazine is an antipsychotic drug that belongs to phenothiazine group. It acts by inhibiting the effects of a chemical in the brain called dopamine by blocking the D2 dopamine receptors. Though it is antipsychotic drug, it is also used in nonpsychotic disorders such as vertigo (spinning sensation), vomiting and anxiety.
The chemical name of prochlorperazine is 2-chloro-10-[3-(4-methyl-1-piperazinyl)-prophyl] phenothiazine and molecular formula is C20H24CIN3S. It is well absorbed from the gastrointestinal tract after oral administration and distribute widely. Onset of action is 30 to 40 minutes after oral administration, 60 minutes for suppository and 10 to 20 minutes after intramuscular injection. Duration of action is 3 to 4 hours. Prochlorperazine is metabolized mainly in the liver and is excreted through the feces. Learn more.
Mechanism of action:
► Prochlorperazine acts on chemoreceptor trigger zone. It is an area located on the lateral walls of the fourth ventricle in the brain. Chemoreceptor trigger zone initiates vomiting in abnormal situations. Prochlorperazine blocks the dopamine receptors in the chemoreceptor trigger zone and stops vomiting.
► Another action of prochlorperazine on vestibular apparatus. It is a part of the inner ear that maintains equilibrium of our body by sending signals to the brain via vestibular nerve. It is excessively stimulated in vestibular disorders and producing a spinning sensation called vertigo. Prochlorperazine suppress this vestibular apparatus and stops vertigo.
► Prochlorperazine also act on mesolimbic system in the brain. This system contains a group of neuron that release dopamine. Schizophrenia develops from excessive functioning of this group of neuron. Prochlorperazine blocks the dopamine receptors in the mesolimbic system and exerts its antipsychotic effect.
► Prochlorperazine is highly effective in vertigo due to vestibular disorders such as labyrinthitis and Meniere’s disease.
► It is used for the control of nausea and vomiting caused by migraine, cancer chemotherapy, radiotherapy, surgery and other conditions.
► It is used for the treatment of psychotic disorders such as schizophrenia and acute mania.
► Prochlorperazine may be helpful for short term relief of anxiety.
Prochlorperazine should be avoided in the following conditions:
► In patients with reduced consciousness level particularly when these conditions are due to intoxication of alcohol, hypnotics, narcotics or others central depressant drugs.
► In severely depressed patients.
► In patients with blood dyscrasias, kidney dysfunction, liver dysfunction, Parkinson’s disease, pheochromocytoma, severe cardiovascular diseases or a history of hypersensitivity to prochlorperazine.
Use of prochlorperazine in pregnancy and lactation:
Safety of use of prochlorperazine during pregnancy has not been established. So, it should be avoided during pregnancy. Prochlorperazine may be excreted into the breast milk. Therefore, breast feeding should be suspended during therapy or drug should be avoided during lactation.
Prochlorperazine is available as tablet, capsule, syrup, suppository and injectable (intramuscular and intravenous) form.
► Tablet forms: Each tablet contains 5 or 10 mg prochlorperazine maleate.
► Sustain release capsule form: Each capsule contains 10 or 15 mg prochlorperazine maleate.
► Liquid form: Each 5 ml syrup contains 5 mg prochlorperazine mesylate or edisylate.
► Injectable form: Each ml injection contains 5 mg prochlorperazine mesylate or edisylate.
► Suppository form: Each suppository contains 2.5, 5, 10 or 25 mg prochlorperazine base.
Prochlorperazine should be started with lower dosage, then increase the dose gradually until an optimal response is achieved. It may be given in both children and adult but children below two years of age are not recommended.
► To control vertigo and vomiting, the usual dose of prochlorperazine is 5 to 10 mg three or four times a day in adult and 2.5 to 5 mg two or three times a day in children.
► In psychotic disorders, the usual starting dose is 10 mg three or four times a day in adult and 5 mg two or three times a day in children. In severe cases, the doses may reach up to 100 to 150 mg per day in adult and 20 to 25 mg in children. For maintenance therapy, the doses should be reduced to the minimum effective level.
► In anxiety, the usual dosage is 5 mg three or four times a day in adult. Do not intake in doses more than 20 mg per day and for longer than 12 weeks.
Click here to learn more about dosage guideline of prochlorperazine.
The most important side effects of prochlorperazine are Parkinsonism, acute muscular dystonia, tardive dyskinesia and akathisia. These usually occur with high doses, particularly in children and elderly persons.
- Parkinsonism – Its manifestations are muscle rigidity, tremor, slowness of body movement, mask like faces and festinating gait.
- Acute muscular dystonia – It is the bizarre spasms of the face, tongue and neck muscles that producing grimacing, torticollis and locked jaw.
- Tardive dyskinesia – Tardive dyskinesia is the rhythmical involuntary movements of the face, mouth, tongue, jaw or limb.
- Akathisia – Features of akathisia are restlessness, feeling of discomfort and apparent agitation.
Other side effects of prochlorperazine are lethargy, drowsiness, mental confusion, aggravation of seizures in epilepsy, postural hypotension, cardiac arrhythmia, dry mouth, constipation, urinary hesitancy in elderly males, blurring of vision, photosensitivity, skin rash, blood dyscrasias and cholestatic jaundice. Learn more.
Patients should be warned about drowsiness effect of prochlorperazine and advised not to drive or operate machinery during therapy. This drug may increase sensitivity to sunlight. Prolonged exposure to sunlight should be avoided, and a sunscreen and protective clothing should be used when body is exposed to sun. Prochlorperazine may interfere the thermoregulatory mechanisms and making more susceptible to heat stroke. Therefore, patients should be advised to avoid heat exposure. Learn more.
Prochlorperazine overdose may cause different toxic manifestations including cardiac arrhythmias, hypotension, hypothermia, severe extra pyramidal muscular dystonic reactions, drowsiness, loss of consciousness. If the patient is seen within 6 hours after ingestion of drug, gastric lavage may be attempted. Treatment is supportive. Activated charcoal may be given. There is no specific antidote of prochlorperazine. Learn more.