What is the recommended dosing, safety considerations, contraindications, and alternatives for Stemetil (prochlorperazine) in an adult without dementia, cardiac conduction disease, or electrolyte abnormalities?

Stemetil (Prochlorperazine) Clinical Guide

Recommended Dosing for Adults

For acute nausea/vomiting or dizziness, start prochlorperazine 5 mg three times daily orally, with a mean effective dose of approximately 15 mg/day for up to 7 days. 1

• Standard oral dosing: 5 mg three times daily (15 mg/day total) 1
• Alternative routes: Can be given as slow IV infusion (diluted), deep IM injection, or buccal formulation 2
• Buccal preparation: Achieves faster onset of action (significantly faster relief at p=0.04) and higher plasma concentrations compared to oral, particularly beneficial when nausea may limit oral absorption 3
• Duration: Limit treatment to approximately 7 days for acute symptoms 1
• Dose adjustments: Reduce dose in older or frail patients due to increased fall risk 4

Absolute Contraindications

Do not use prochlorperazine in patients with Parkinson's disease or dementia with Lewy bodies due to severe risk of extrapyramidal symptoms. 4

• Parkinson's disease: Absolutely contraindicated due to high risk of worsening motor symptoms 4
• Dementia with Lewy bodies: Absolutely contraindicated due to severe EPS risk 4

Strong Cautions (Use Only With Careful Monitoring)

Exercise extreme caution in patients with seizure disorders, dementia, glaucoma, or history of leukopenia/neutropenia. 4

• Seizure disorders: Prochlorperazine lowers seizure threshold 4
• Dementia (non-Lewy body): Increased risk of adverse neurologic effects and falls 4
• Glaucoma: Anticholinergic effects may worsen intraocular pressure 4
• Leukopenia/neutropenia history: Can cause drug-induced blood dyscrasias requiring monitoring 4
• QTc prolongation risk: Avoid concurrent use with other QT-prolonging medications when possible 4
• Cardiac conduction disease: Although your patient lacks this, prochlorperazine is contraindicated with concurrent dofetilide, trimethoprim/sulfamethoxazole, or verapamil due to drug interactions 2

Extrapyramidal Symptom Risk and Management

Akathisia is the most common extrapyramidal symptom with prochlorperazine, occurring in approximately 14% of patients, typically within the first week of treatment. 5

Risk Profile

• Incidence: 14% develop extrapyramidal symptoms, predominantly akathisia 5
• Timing: Symptoms typically emerge within the first week 5
• High-risk populations: Young males, elderly patients, those with prior EPS history 6

Recognition of EPS

• Akathisia: Subjective restlessness, pacing, inability to sit still—often misinterpreted as anxiety 6
• Acute dystonia: Sudden muscle spasms affecting neck, eyes (oculogyric crisis), or torso 6
• Drug-induced parkinsonism: Bradykinesia, tremors, rigidity 6

Immediate Management of Acute EPS

• For acute dystonia: Administer benztropine 1-2 mg IM/IV or diphenhydramine 12.5-25 mg IM/IV for rapid relief (improvement within minutes) 6
• For akathisia or parkinsonism: Consider benztropine 1-2 mg daily, though less consistently effective for akathisia than dystonia 6
• Primary strategy: Reduce prochlorperazine dose or discontinue the drug entirely 6

Prevention Strategy

• Do not use prophylactic anticholinergics routinely—reserve for treatment of actual symptoms 6
• Monitor closely during the first week for early signs of restlessness or muscle rigidity 6

Superior Alternatives

Consider switching to perospirone (atypical antipsychotic) if antiemetic therapy beyond 7 days is needed, as it shows 0% incidence of extrapyramidal symptoms compared to 14% with prochlorperazine. 5

Atypical Antipsychotic Alternatives

• Perospirone: 4-8 mg/day orally, demonstrated equivalent antiemetic efficacy (4% nausea/vomiting vs 8% with prochlorperazine, p=NS) but 0% EPS incidence 5
• Olanzapine: 2.5-5 mg orally or subcutaneously, lower EPS risk than prochlorperazine 2
• Quetiapine: 25 mg orally, minimal EPS risk, though more sedating 2

Non-Antipsychotic Alternatives

• Promethazine: 25 mg IV, though significantly less effective than prochlorperazine (31% treatment failure vs 9.5%, p=0.03) and causes more sedation (71% vs 38%, p=0.002) 7

Efficacy Data

Prochlorperazine provides significantly faster and more complete relief than promethazine, with time to complete relief significantly shorter (p=0.021) and fewer treatment failures (9.5% vs 31%, p=0.03). 7

• Onset: Buccal formulation achieves significantly faster onset than oral (p=0.04) 3
• Symptom relief: Significant reduction in dizziness episodes, nausea, vomiting, and lightheadedness at 7 days (p<0.0001) 1
• Treatment failures: Only 9.5% with prochlorperazine vs 31% with promethazine 7

Critical Monitoring Parameters

• Week 1: Monitor daily for akathisia (restlessness, pacing), acute dystonia (muscle spasms), or parkinsonism (tremor, rigidity) 5
• Ongoing: Assess for drowsiness (38% incidence), though less than promethazine 7
• Elderly patients: Monitor for falls, confusion, and orthostatic hypotension 4
• Duration: Reassess need for continued therapy after 7 days; do not use chronically without clear indication 1

Common Pitfalls to Avoid

• Misinterpreting akathisia as anxiety: Akathisia presents as motor restlessness, not purely psychological anxiety—requires dose reduction or discontinuation, not anxiolytics 6
• Routine prophylactic anticholinergics: Do not prescribe benztropine or diphenhydramine prophylactically; use only for actual EPS 6
• Prolonged use: Limit to 7-10 days for acute symptoms; chronic use increases EPS risk without added benefit 1
• Ignoring contraindications: Never use in Parkinson's disease or Lewy body dementia regardless of symptom severity 4
• Combining with other QT-prolonging drugs: Check medication list for concurrent QT-prolonging agents 4