Appropriate Use of Promethazine

Promethazine is a phenothiazine derivative with potent antihistaminic and sedative-hypnotic effects. The injectable form is currently registered for the treatment of uncomplicated allergic conditions of the immediate type; treatment and prevention of motion sickness, drug-induced nausea, post-operative nausea and vomiting; and as a sedative for pre-operative, post-operative, and obstetric use.

However, the Institute for Safe Medication Practices (ISMP) recommend that injectable promethazine no longer be used in hospitals. Promethazine is a known vesicant that can cause severe tissue injury if perivascular extravasation or unintentional intra-arterial injection occurs. Potential sequelae include thrombophlebitis, venous thrombosis, paralysis, abscess, tissue necrosis, and gangrene. Surgical intervention, including fasciotomy, skin grafts, and amputation, have been required in some cases.

To limit the risk of these events, deep intramuscular injection is the preferred parenteral route of administration for promethazine; intra-arterial and subcutaneous use is contraindicated. However, there are many safer therapeutic alternatives that should be considered. For example, a 5HT₃ antagonist such as granisetron, ondansetron, palonosetron, or tropisetron may be an appropriate alternative for nausea and vomiting.

If intravenous promethazine is considered appropriate, the following points should be considered:

• Dilute the contents of the ampoule to reduce the vesicant effects;
• Limit the dose;
• Administer slowly;
• Use only large patent veins (preferably via a central venous access site, avoid hand or wrist veins); and
• Discontinue injection immediately if the patient complains of burning or pain.