Westel

Uses

Westel Maleate Tablet: Each tablet contains Westel maleate 5 mg.

Westel Mesilate Syrup: Each 5 ml syrup contains Westel maleate 5 mg

Westel Mesilate Injection: Each 1 ml ampoule contains Westel mesilate 12.5 mg.

• For control of severe nausea and vomiting caused by radiation therapy, cancer chemotherapy, surgery, and other conditions.
• Relieving nausea, vomiting and attacks of dizziness or spinning sensations (vertigo) associated with Meniere's disease and other inner ear disorders.
• For the treatment of psychotic illness such as schizophrenia (hallucinations and hostility).
• Acute mania.
• For the short-term treatment of generalized non-psychotic anxiety.

Westel is also used to associated treatment for these conditions: Acute Migraine, Schizophrenia, Tension Headache, Non-psychotic generalized anxiety, Severe Nausea and vomiting

How Westel works

The mechanism of action of prochlorperazine has not been fully determined, but may be primarily related to its anti-dopaminergic effects. Westel blocks the D2 dopamine receptors in the brain, which are somatodendritic autoreceptors. Inhibition of D2 receptor signaling results in the blockade of postsynaptic dopamine receptors in the mesolimbic system and an increased dopamine turnover. Nausea and vomiting are proposed to arise from peripheral or central stimulation of serotonin type 3 (5-HT3) and dopamine type 2 receptors, the predominant receptors expressed at the chemoreceptor trigger zone (CTZ). Westel exerts antiemetic effects and was shown to inhibit apomorphine-induced vomiting by blocking D2 dopamine receptors in the CTZ..

Dosage

Westel dosage

Antiemetic:

Children (not recommended in children <10 kg or <2 years):

• 10-14 kg: 2.5 mg every 12-24 hours as needed; maximum: 7.5 mg/day
• 15-18 kg: 2.5 mg every 8-12 hours as needed; maximum: 10 mg/day
• 19-39 kg: 2.5 mg every 8 hours or 5 mg every 12 hours as needed; maximum: 15 mg/day

Adults: 5-10 mg 3-4 times/day; usual maximum:40 mg/day

Antipsychotic:

• Children 2-12 years (not recommended in children <10 kg or <2 years): 2.5 mg 2-3 times/day; increase dosage as needed to maximum daily dose of 20 mg for 2-5 years and 25 mg for 6-12 years
• Adults: 5-10 mg 3-4 times/day; doses up to 150 mg/day may be required in some patients for treatment of severe disturbances

Nonpsychotic anxiety:

• Adults: Usual dose: 15-20 mg/day in divided doses; do not give doses >20 mg/day or for longer than 12 weeks
• Elderly: Initial: 2.5-5 mg 1 -2 times/day; increase dose at 4 to 7 day intervals by 2.5-5 mg/day; increase dosing intervals (twice daily, thrice daily, etc) as necessary to control response or side effects; maximum daily dose should probably not exceed 75 mg in elderly; gradual increases (titration) may prevent some side effects or decrease their severity. Westel may be administered without regards of meal.

Side Effects

Drowsiness, jaw, neck, and back muscle spasms, fine worm-like tongue movements, rhythmic face, mouth, or jaw movements, slow or difficult speech, difficulty swallowing, restlessness and pacing, tremors, shuffling walk, skin rash, yellowing of the skin or eyes.

Toxicity

LD₅₀ and Overdose

Oral LD₅₀ in rats is 750 mg/kg. Intraperitoneal and subcutaneous LD₅₀ in mice are 191 mg/kg and 320 mg/kg, respectively. In placebo-controlled trials, there were increased incidences of mortality in elderly patients with dementia-related psychosis receiving antipsychotic medications. The risk of death in drug-treated patients was about 1.6 to 1.7 times that of placebo-treated patients. Deaths were largely resulting from cardiovascular, such as heart failure and sudden death, or infectious, such as pneumonia, conditions. Due to its antagonist action on dopamine receptors, prochlorperazine is associated with a risk for developing extrapyramidal symptoms such as tardive dyskinesia, which is a syndrome consisting of potentially irreversible, involuntary, dyskinetic movements. This risk is also conferred on other antipsychotic agents that block dopamine receptors. It is proposed that increased duration of the drug treatment is likely thus increased total cumulative dose of antipsychotic drugs administered to the patient leads to increased risk for developing the syndrome and the likelihood that it will become irreversible. As with other antipsychotic agents, prochlorperazine is associated with a risk for causing neuroleptic malignant syndrome (NMS), which is a potentially fatal symptom complex, which is manifested as hyperpyrexia, muscle rigidity, altered mental status and evidence of autonomic instability.

There is no known antidote for prochlorperazine thus overdose treatment should be supportive and symptomatic. Overdose of prochlorperazine may produce dystonic reactions that involve extrapyramidal mechanism. To reduce these symptoms, antiparkinsonism drugs, barbiturates, or diphenhydramine may be used. Symptoms of central nervous system depression, such as somnolence or coma, may also be observed. Amphetamine, destroamphetamine, or caffeine and sodium benzoate may be used to induce stimulatory effects. In contrast, agitation and restlessness may also be seen in case of overdose. Other possible manifestations include convulsions, EKG changes and cardiac arrhythmias, fever, and autonomic reactions such as hypotension, dry mouth and ileus. Hypotension can be responded with the standard measures for managing circulatory shock.

Nonclinical Toxicology

In a rat developmental or reproductive toxicity study, abnormalities in both the reproductive measures and neurobehavioral testing were observed following administration of 25 mg/kg of prochlorperazine.

Use in specific populations

As the use of antipsychotic agents during the third trimester of pregnancy is associated with a risk for extrapyramidal and/or withdrawal symptoms following delivery, the use of prochlorperazine in pregnant patients is generally not recommended and it should be limited after careful consideration of the potential benefit of drug therapy justifying the potential risk to the fetus. Caution should be exercised when prochlorperazine is administered to a nursing mother. While lower doses of prochlorperazine is reported to be safe for elderly patients, caution is still advised, especially those with higher susceptibility to hypotension and neuromuscular reactions.

Precaution

Caution should be taken while performing tasks that require alertness, such as driving or using machinery. Use of alcohol can cause extreme drowsiness. This medication may increase sensitivity to sunlight. Prolonged sun exposure should be avoided and a sunscreen and protective clothing should be taken when anybody is exposed to the sun. This medication can reduce sweating making more susceptible to heat stroke.

Interaction

Alcohol, barbiturate & other sedatives may increase the CNS depressant action. Some drugs like Antacids, antiparkinson's drug, lithium may interfere the absorption of Westel. This drug may interfere the plasma concentration of Propanolol, Phenobarbital.

Food Interaction

• Avoid alcohol. The drug may intensify or prolong the action of central nervous system depressants.

Westel Alcohol interaction

[Moderate] GENERALLY AVOID:

Concurrent use of ethanol and phenothiazines may result in additive CNS depression and psychomotor impairment.

Also, ethanol may precipitate dystonic reactions in patients who are taking phenothiazines.

The two drugs probably act on different sites in the brain, although the exact mechanism of the interaction is not known.

Patients should be advised to avoid alcohol during phenothiazine therapy.

Westel Drug Interaction

Moderate: lorazepam, diphenhydramine, duloxetine, fentanyl, pregabalin, metoprolol, metoprolol, polyethylene glycol 3350, acetaminophen / hydrocodone, albuterol, alprazolam, ondansetronUnknown: docusate, omega-3 polyunsaturated fatty acids, esomeprazole, acetaminophen, acetaminophen, cyanocobalamin, ascorbic acid, cholecalciferol

Westel Disease Interaction

Major: dementia, acute alcohol intoxication, cardiovascular disease, CNS depression, head injuryModerate: anticholinergic effects, breast cancer, dystonic reactions, hematologic toxicity, liver disease, NMS, parkinsonism, renal dysfunction, respiratory disorders, seizure disorders, tardive dyskinesia

Volume of Distribution

In a preliminary pharmacokinetic study involving healthy volunteers, the mean apparent volume of distribution following intravenous administration of 6.25 mg and 12.5 mg prochlorperazine were approximately 1401 L and 1548 L, respectively. Westel is reported to be distributed to most body tissues with high concentrations being distributed into liver and spleen. There is evidence that phenothiazines are excreted in the breast milk of nursing mothers.

Elimination Route

Following oral administration, prochlorperazine is reported to be well absorbed from the gastrointestinal tract. The onset of pharmacological action is about 30 to 40 minutes following oral administration and 10 to 20 minutes following intramuscular administration. The duration of action for all routes is about 3 to 4 hours. Following oral administration in healthy volunteers, the mean oral bioavailability was about 12.5%. In these patients, the time to reach the peak plasma concentrations was about 5 hours. Repeated oral dosing resulted in an accumulation of prochlorperazine and its metabolite. Following multiple twice daily dosing, the steady state of prochlorperazine was reached by 7 days.

Half Life

Following intravenous and single oral dose administration, the terminal elimination half live were 9 and 8 hours, respectively.

Clearance

The mean plasma clearance (CL) of prochlorperazine following intravenous administration in healthy volunteers was approximately 0.98L/h x kg. The mean renal clearance was about 23.6 mL/h.

Elimination Route

Westel is reported to be mainly excreted via the feces and bile. Low quantities of unchanged prochlorperazine and its metabolite were detectable in the urine.

Pregnancy & Breastfeeding use

No evidence of adverse effects of this drug has been reported during pregnancy & lactation.

Contraindication

Hypersensitivity to prochlorperazine or any component of the formulation, severe CNS depression; coma; should not be used in children <2 years of age or <10 kg.

Acute Overdose

Symptoms of overdose include deep sleep, coma, extrapyramidal symptoms, abnormal involuntary muscle movements, and hypotension.

Storage Condition

Store in a cool and dry place, protected from light and moisture.

Innovators Monograph

You find simplified version here Westel