How should I write a medication order for promethazine (Phenergan)?

How to Write a Promethazine (Phenergan) Order

Write promethazine orders with specific route, dose (12.5-25 mg), frequency (every 4-6 hours as needed), and administration instructions, prioritizing oral or IM routes over IV due to serious tissue injury risks, and never use in children under 2 years of age. 1

Essential Order Components

Route Selection (Critical Safety Consideration)

• Avoid IV administration whenever possible due to FDA black box warning for risk of serious tissue injury including thrombophlebitis, tissue necrosis, and gangrene with extravasation or inadvertent intra-arterial injection 2, 3
• Prefer IM injection if parenteral route is necessary, as FDA labeling now states preference for intramuscular administration 3
• Oral route is equally effective if GI absorption is intact and should be first-line when tolerated 2
• If IV administration is unavoidable, order must specify: dilution required, slow infusion rate (≤25 mg/min), and ensure proper IV placement 2

Dosing Specifications

For Nausea/Vomiting (most common indication):

• Adults: 12.5-25 mg every 4-6 hours as needed 4, 1
• Use lower doses (6.25-12.5 mg) for antiemetic purposes - equally effective as 25 mg but causes significantly less sedation 2, 5
• Children ≥2 years: 0.5 mg/kg (12.5-25 mg) every 4-6 hours as needed 1
• Maximum frequency: every 4 hours 4, 1

For Allergies:

• Adults: 25 mg at bedtime, or 12.5 mg before meals and at bedtime, or 6.25-12.5 mg three times daily 1
• Adjust to smallest effective dose after initiation 1

For Sedation:

• Adults: 25-50 mg at bedtime 1
• Children ≥2 years: 12.5-25 mg at bedtime 1

For Motion Sickness:

• Adults: 25 mg twice daily, first dose 30-60 minutes before travel 1
• Children ≥2 years: 12.5-25 mg twice daily 1

Sample Order Format

Example order for nausea/vomiting:

• "Promethazine 12.5 mg PO every 4-6 hours as needed for nausea/vomiting"
• "Promethazine 25 mg IM every 4-6 hours as needed for nausea/vomiting (if oral route not tolerated)"

If IV route absolutely necessary (not recommended):

• "Promethazine 12.5 mg IV every 4-6 hours as needed for nausea/vomiting - MUST dilute and infuse slowly over at least 10-15 minutes, verify IV placement before administration"

Critical Contraindications and Warnings

Age Restrictions

• Absolutely contraindicated in children under 2 years of age due to risk of fatal respiratory depression 1, 6
• Black box warning specifically addresses pediatric respiratory depression risk 1

Duration Limitations

• Inappropriate for chronic use due to risks of extrapyramidal effects and neuroleptic malignant syndrome 2
• Limit to short-term, intermittent use only 2
• Consider alternative agents if symptoms persist beyond several days 2

High-Risk Populations

• Elderly patients: increased risk of cognitive impairment, anticholinergic effects, and falls 4
• Patients on opioids: additive sedation and respiratory depression risk 2, 5
• Patients with prostatic hypertrophy, elevated intraocular pressure, or cognitive impairment 4

Pharmacokinetic Considerations for Timing

• Onset of action: 5 minutes IV, 20 minutes PO 2
• Duration of action: 4-6 hours (effects may persist up to 12 hours) 2
• Half-life: 9-16 hours 2
• Order frequency should account for 4-6 hour duration when writing "as needed" parameters 2

Common Pitfalls to Avoid

• Never order "promethazine IV push" - must specify slow infusion if IV route used 2
• Never order without specifying maximum frequency - risk of cumulative respiratory depression with repeated dosing 2
• Never order for children without verifying age ≥2 years 1
• Avoid ordering in combination with other CNS depressants without dose adjustment 5
• Do not order for chronic/daily use - only for intermittent symptom management 2

Monitoring Parameters to Include

• Monitor for excessive sedation, especially when combined with opioids or other CNS depressants 5
• Watch for extrapyramidal symptoms (dystonia, akathisia) - have diphenhydramine 25-50 mg available for treatment 4
• Monitor for anticholinergic effects: confusion, urinary retention, dry mouth 5
• Assess respiratory rate before each dose, especially in elderly or when combined with opioids 2