Prochlorperazine (Compazine, Compro)
Prochlorperazine
Compazine® | Compro™
Classification:
Gastrointestinal Agents
Psychotropic Agents
Description: Prochlorperazine, a piperazine phenothiazine, is an oral and parenteral antiemetic and antipsychotic agent. It is most closely related to the high-potency neuroleptics such as perphenazine. Prochlorperazine is mainly used for the management of nausea and vomiting but it shares many of the actions and adverse effects of the antipsychotics. Prochlorperazine was approved by the FDA in 1956. The branded product Compazine® was discontinued from production in 2003, but many generics are available.
Mechanism of Action: Prochlorperazine blocks postsynaptic dopamine receptors in the mesolimbic system and increases dopamine turnover by blockade of the D2 somatodendritic autoreceptor. After ~12 weeks of chronic therapy, depolarization blockade of dopamine tracts occurs. The decrease in dopamine neurotransmission has been found to correlate with the antipsychotic effects. This D2-blockade is also responsible for the strong extrapyramidal effects observed with this drug. Dopamine blockade in the chemoreceptor trigger zone accounts for the antiemetic effects. Prochlorperazine possesses moderate anticholinergic and alpha-adrenergic receptor blocking effects. Blockade of alpha1-adrenergic receptors produces sedation; muscle relaxation; and cardiovascular effects such as hypotension, reflex tachycardia, and minor changes in ECG patterns.
Compro Suppositories (Supp 25 mg)
Pharmacokinetics: Prochlorperazine is rapidly absorbed following oral administration, but there is considerable individual variation in peak plasma concentrations because the drug undergoes metabolism in the gastric mucosa and on first pass through the liver. Following IM or PO administration (tablets or syrup), absorption is rapid. Onset of action occurs in about 30 - 60 minutes. Antipsychotic effects are gradual, with considerable individual variation, and peak effects may not occur for 6 weeks to 6 months.
Prochlorperazine is widely distributed into body tissues and fluids, and crosses the blood-brain barrier. The drug is highly plasma protein-bound (91 - 99%), predominantly to alpha1-acid glycoprotein. The drug crosses the placenta and is excreted into breast milk. Metabolism is extensive, but the metabolites have not been shown to have pharmacological activity. Some conjugation with glucuronides occurs, and these along with unconjugated metabolites account for most of the drug found in urine. Metabolites and unchanged drug can be detected for some months after discontinuation of the drug. Some excretion may occur via the biliary tract and feces. The duration of activity is 4 - 6 hours.
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[ Revised 12/13/2006 10:38:00 AM ]
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