What is the recommended dosage for promethazine (Phenergan)?

From the Guidelines

The recommended dosage of promethazine for adults is 12.5 to 25 mg intravenously, infused slowly, with a total dose of 25-100 mg as an adjuvant to narcotics and benzodiazepines, as evident from the study published in Gastroenterology in 2012 1. When considering the dosage of promethazine, it's essential to take into account the patient's age, weight, and the condition being treated.

• For adults, the typical dose is 12.5 to 25 mg taken every 4 to 6 hours as needed, with a maximum daily dose of 100 mg.
• For children over 2 years, the dose is usually calculated at 0.25 to 0.5 mg per kg of body weight every 4 to 6 hours as needed.
• Promethazine should not be given to children under 2 years due to the risk of respiratory depression, as stated in the study published in the Journal of Allergy and Clinical Immunology in 2008 1. The clinical effects of promethazine are evident within 5 minutes of intravenous administration, and its duration of action is 4 to 6 hours, with a plasma half-life of 9 to 16 hours, as reported in the study published in Gastroenterology in 2007 1. It's crucial to follow the healthcare provider's specific instructions, as they will tailor the dosage to the individual patient's needs, taking into account factors such as liver impairment and the potential for drug interactions, as highlighted in the study published in Gastroenterology in 2012 1.

From the FDA Drug Label

DOSAGE AND ADMINISTRATION Promethazine Hydrochloride Tablets USP are contraindicated for children under 2 years of age The average oral dose is 25 mg taken before retiring; however, 12.5 mg may be taken before meals and on retiring, if necessary. Single 25-mg doses at bedtime or 6.25 to 12. 5 mg taken three times daily will usually suffice. For children, promethazine hydrochloride tablets, syrup, or rectal suppositories, 12. 5 to 25 mg twice daily, may be administered. The average effective dose of promethazine hydrochloride for the active therapy of nausea and vomiting in children or adults is 25 mg 12.5- to 25-mg doses may be repeated, as necessary, at 4- to 6-hour intervals. For nausea and vomiting in children, the usual dose is 0. 5 mg per pound of body weight, and the dose should be adjusted to the age and weight of the patient and the severity of the condition being treated. Adults usually require 25 to 50 mg for nighttime, presurgical, or obstetrical sedation. Promethazine hydrochloride in 12. 5- to 25-mg doses for children and 50-mg doses for adults the night before surgery relieves apprehension and produces a quiet sleep.

The dosage for promethazine varies based on the condition being treated.

• For allergy, the average oral dose is 25 mg taken before retiring.
• For motion sickness, the average adult dose is 25 mg taken twice daily.
• For nausea and vomiting, the average effective dose is 25 mg.
• For sedation, adults usually require 25 to 50 mg for nighttime, presurgical, or obstetrical sedation.
• For pre- and postoperative use, the usual adult dosage is 50 mg promethazine HCl. 2

From the Research

Dosage for Promethazine

The dosage for promethazine can vary depending on the specific use case and population.

• For the treatment of postoperative nausea and vomiting, studies have shown that low-dose promethazine (6.25 mg) can be as effective as higher doses (12.5 mg or 25 mg) with less sedation 3, 4, 5.
• A study comparing granisetron, promethazine, or a combination of both for the prevention of postoperative nausea and vomiting found that a combination of low-dose granisetron and promethazine (6.25 mg) was more effective than promethazine monotherapy 6.
• The pharmacokinetics of promethazine after administration of rectal suppositories and oral syrup have been studied, with results showing highly variable absorption and a mean relative bioavailability ranging from 70% to 97% for the suppository treatments 7.

Specific Dosage Recommendations

• For adult ambulatory surgery patients, 6.25 mg of promethazine IV has been shown to be as effective as 12.5 mg IV in controlling postoperative nausea and vomiting, with less sedation 4.
• For hospitalized elderly patients, a starting dose of 6.25 mg IV promethazine has been suggested, as it is as effective as higher doses and has fewer adverse drug reactions 5.
• For the prevention of postoperative nausea and vomiting in females undergoing outpatient laparoscopies, a combination of low-dose granisetron and promethazine (6.25 mg) has been shown to be more effective than promethazine monotherapy 6.