What is the incidence of akathisia from intravenous (IV) Compazine (prochlorperazine) in the emergency department?

Incidence of Akathisia from IV Prochlorperazine in the Emergency Department

Intravenous prochlorperazine causes akathisia in approximately 36-44% of emergency department patients within one hour of administration, making it an extremely common adverse effect that emergency physicians must anticipate and manage.

Documented Incidence Rates

The incidence of akathisia from IV prochlorperazine (10 mg dose) has been well-established through prospective emergency department studies:

• 44% incidence in the landmark prospective controlled study by Vinson et al., where 44 of 100 patients receiving IV prochlorperazine developed akathisia within 1 hour 1
• 36.9% incidence in the 2-minute infusion group of a randomized controlled trial examining infusion rates 2
• 36% incidence in the control group of a trial evaluating diphenhydramine prophylaxis 3
• 16% incidence in a broader descriptive study that included both IV and IM routes and assessed patients within 2 weeks of discharge 4

The severity distribution among those who developed akathisia was: mild (32%), moderate (50%), and severe (18%) 1.

Clinical Context from Guidelines

Guidelines acknowledge akathisia as a recognized adverse effect of prochlorperazine across multiple clinical settings:

• The American Family Physician guidelines list akathisia, pseudo-parkinsonism, tardive dyskinesia, and dystonia as known adverse reactions to prochlorperazine 5
• ASCO antiemetic guidelines include prochlorperazine as a dopamine receptor antagonist option but do not specifically quantify akathisia risk 5

Risk Mitigation Strategies

Prophylactic Diphenhydramine

Adjuvant diphenhydramine 50 mg IV significantly reduces akathisia incidence from 36% to 14%, representing a 61% relative risk reduction 3. This prophylactic approach results in:

• Absolute risk reduction of 22% (95% CI 6-38%) 3
• Odds ratio of 0.39 (95% CI 0.18-0.85) for developing akathisia 3
• Trade-off: increased sedation (33 mm vs 12 mm increase on visual analog scale, p<0.001) 3

Infusion Rate Modification

Slowing the infusion rate from 2 minutes to 15 minutes showed a trend toward reduced akathisia (36.9% vs 23.7%, representing a 36% relative reduction) but did not reach statistical significance (p=0.07) 2. This strategy is not reliably effective for prevention.

Treatment of Established Akathisia

For patients who develop akathisia after prochlorperazine administration, IV diphenhydramine rapidly and effectively treats symptoms, reducing mean akathisia scores from 9.8 to 1.2 points (mean reduction 8.5 points, 95% CI 7.8-9.4, p<0.0001) within 30 minutes 6.

Delayed Symptoms

Delayed akathisia symptoms developing within 48 hours after a single IV dose are uncommon, occurring in approximately 3% of patients 1. The vast majority of akathisia manifests within the first hour of administration.

Clinical Pitfalls

• Do not assume akathisia is rare: With incidence rates of 36-44%, akathisia should be expected in roughly one-third to nearly half of patients receiving IV prochlorperazine 2, 1, 3
• Recognize the distressing nature: Akathisia significantly disrupts patient care and causes substantial patient distress 3
• Consider prophylaxis routinely: Given the high incidence, prophylactic diphenhydramine should be strongly considered, particularly when sedation is not contraindicated 3
• Dystonia also occurs: While less common than akathisia (4% incidence), dystonic reactions are another important adverse effect to monitor 4