From the Guidelines
Promethazine should be used with caution and at the lowest effective dose, typically ranging from 12.5 to 25 mg, due to its potential for significant sedative and anticholinergic effects, as well as risks of respiratory depression, particularly in vulnerable populations such as the elderly and young children 1.
Key Considerations
- Promethazine is a phenothiazine with antihistamine, sedative, antiemetic, and anticholinergic properties, making it useful for treating allergic reactions, motion sickness, nausea, vomiting, and as a sedative 1.
- The medication's effects are evident within 5 minutes of intravenous administration, with a duration of action of 4 to 6 hours and a plasma half-life of 9 to 16 hours 1.
- Common side effects include drowsiness, dry mouth, blurred vision, and constipation, necessitating cautious use in patients with certain medical conditions like glaucoma, urinary retention, or respiratory disorders 1.
Clinical Use
- Promethazine can be used as an adjunct for sedation during minor surgical and endoscopic procedures, with the usual dose being 12.5 to 25 mg intravenously, infused slowly to minimize the risk of hypotension 1.
- In the management of cannabinoid hyperemesis syndrome, promethazine may be considered for acute and short-term care, although opioids should be avoided due to the risk of worsening nausea and addiction 1.
- For patients with medically refractory gastroparesis, promethazine is not a first-line treatment option, but it may be considered in certain cases where other antiemetic agents have failed 1.
Safety and Precautions
- Promethazine should not be used in children under 2 years due to the risk of respiratory depression, and its use in elderly patients requires careful consideration of the potential for increased sensitivity to its sedative and anticholinergic effects 1.
- Patients taking promethazine should avoid alcohol and other central nervous system depressants, as these can intensify the sedative effects of the medication 1.
From the FDA Drug Label
Promethazine hydrochloride tablets are useful for: Perennial and seasonal allergic rhinitis. Vasomotor rhinitis. Allergic conjunctivitis due to inhalant allergens and foods. Mild, uncomplicated allergic skin manifestations of urticaria and angioedema. Amelioration of allergic reactions to blood or plasma. Dermographism Anaphylactic reactions, as adjunctive therapy to epinephrine and other standard measures, after the acute manifestations have been controlled. Preoperative, postoperative, or obstetric sedation. Prevention and control of nausea and vomiting associated with certain types of anesthesia and surgery. Therapy adjunctive to meperidine or other analgesics for control of post-operative pain Sedation in both children and adults, as well as relief of apprehension and production of light sleep from which the patient can be easily aroused. Active and prophylactic treatment of motion sickness. Antiemetic therapy in postoperative patients.
The main uses of promethazine are for:
- Allergic reactions
- Sedation
- Nausea and vomiting
- Pain relief
- Motion sickness as stated in the drug label 2
From the Research
Promethazine Overview
- Promethazine is a histamine H1 receptor competitive antagonist with antihistaminic, sedative, anti-kinetotic, antiemetic, and antimuscarinic effects 3
- It has been used as a treatment option for a variety of indications, including nausea and vomiting, since its approval in 1951 3
Efficacy and Safety
- Low-dose intravenous promethazine (6.25 or 12.5 mg) has been shown to relieve nausea and vomiting as effectively as intravenous ondansetron 4 mg 4
- However, promethazine has significant sedative effects, especially when used in conjunction with narcotic analgesics, and has been associated with rare but serious limb-threatening adverse effects after extravasation or inadvertent intra-arterial injection 3, 5
- Ondansetron has been found to have a favorable safety profile and demonstrated efficacy in undifferentiated nausea and vomiting, with none of the central and autonomic nervous system side effects noted with promethazine 5, 6
Comparison with Ondansetron
- Studies have compared the efficacy of promethazine and ondansetron in treating nausea and vomiting, with mixed results:
- One study found that ondansetron and promethazine reduced nausea similarly, but promethazine was associated with significantly more sedation 6
- Another study found that promethazine was significantly more effective than ondansetron for treating postoperative nausea and vomiting after failed ondansetron prophylaxis 7
- A review of promethazine recommended its use as an alternative antiemetic in the emergency department due to its distinct mechanism of action, but cautioned against its use due to the risk of serious patient harm 3
Dosage and Administration
- The standard dosage of promethazine is 25 mg, but low-dose intravenous promethazine (6.25 or 12.5 mg) has been shown to be effective in relieving nausea and vomiting 4
- Promethazine 6.25 mg was found to be as effective as higher doses in treating postoperative nausea and vomiting after failed ondansetron prophylaxis 7
- The U.S. Food and Drug Administration has recommended dilution and administration guidelines for intravenous promethazine and stated a preference for intramuscular administration 3