Promethazine

Additional information

Pharmacokinetics and dosing

The pharmacokinetics of promethazine was evaluated in an open-label study with crossover design. Healthy subjects (18 men, 18 women) were randomized to two 12.5 mg suppositories, one 25 mg suppository, one 50 mg suppository, or 50 mg oral syrup. Promethazine pharmacokinetics was reported to be similar in men and women [1].

Effects

Promethazine and morphine as surgical premedication was evaluated in a double-blind study (96 men, 174 women). Patients were randomized to receive injections with either morphine 5 or 10 mg alone or in combination with promethazine 6.25 mg, 12.5 mg, or 25 mg. Promethazine 25 mg alone was also studied. The sedation level was assessed by a nurse at 15 and 30 minutes after injection and by the patient at 24h after surgery.  The authors report that men in the study had lower mean sedation scores than women, however, this effect could be explained by weight as the men were heavier than the women [2].

The antiemetic efficacy of promethazine was evaluated based on medical records for 369 patients undergoing radiofrequency catheter ablation performed during 4 years. Women had increased risk of nausea. Patients who received larger doses of promethazine had a lower incidence of vomiting [3].

Adverse events

No studies with a clinically relevant sex analysis regarding adverse effects of promethazine have been found.

Reproductive health issues

Regarding teratogenic aspects, please consult Janusmed Drugs and Birth Defects (in Swedish, Janusmed fosterpåverkan).

Other information

A study of case series of promethazine overdose explored the relationship between possible predictors and delirium. Women and men had similar probability to have delirium (26% vs. 29%) [4].

Promethazine is a potentially inappropriate medication for use in elderly [5]. In a large American study of 19.5 million emergency department visits, promethazine was among the five most common potentially inappropriate medications used. Female sex was associated with more potentially inappropriate medications than men, odds ratio 1.39 [6].