Promethazine is an antihistamine used to help prevent nausea and vomiting during travel or after surgery. It can also be used to treat allergic reactions and anaphylaxis.
This medicine works by blocking the action of histamine in the brain and spinal cord. This helps produce anti-nausea, anti-allergy and sedative effects.
Promethazine is available in the US as a prescription medicine in forms such as tablets, oral solution, suppositories and injection. It should only be used as prescribed by a doctor.
What it is used for
Promethazine may be indicated to prevent or treat:
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Nausea and vomiting during travel or after surgery;
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Allergic reactions, such as hives;
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Insect bites;
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Itchy skin;
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Anaphylactic reaction.
In addition, injectable promethazine may be used as a pre-anesthetic medication before surgery, as it can increase the effect of pain relievers and cause mild sedation.
This medicine works by blocking the action of histamine in the brain and spinal cord. This can help reduce allergy symptoms and control the body’s nausea and vomiting response.
Because promethazine also acts on the brain, it can cause mild sedation. For this reason, it may be used before surgery.
Promethazine brand names
Promethazine has been sold under the brand name Phenergan and is also available in generic form as “promethazine hydrochloride.”
In the US, promethazine may be available as tablets, oral solution, suppositories or injectable solution, depending on the prescription and product availability.
How to use
How promethazine is used depends on the form prescribed, which may include:
1. Promethazine 25 mg tablet
Promethazine 25 mg tablets should be taken by mouth with a glass of water. The doses normally recommended for adults are 2 to 6 tablets per day, divided into 2, 3 or 4 doses, with the largest dose taken at night.
To help prevent nausea and vomiting before travel, the usual recommendation is 1 tablet of 25 mg about 30 minutes to 1 hour before the trip. This dose may be repeated every 6 to 8 hours if needed, or as directed by a doctor.
Promethazine usually starts working about 20 minutes after the tablet is taken. Its effects generally last 4 to 6 hours, but may last up to 12 hours.
2. Injectable promethazine 50 mg/2 mL
Injectable promethazine is used in hospitals. It is given as an injection directly into the muscle by a nurse under medical supervision.
The dose of injectable promethazine should be determined by a doctor. It may range from 25 to 50 mg, and the dose should not exceed 100 mg per day.
Possible side effects
The most common side effects of promethazine include drowsiness, dry mouth, constipation, vertigo, dizziness, ringing in the ears, double vision, confusion, nausea, vomiting, stomach pain, heart palpitations, slow heartbeat, urinary retention and orthostatic hypotension.
Promethazine can also cause sensitivity to light. For this reason, exposure to sunlight or ultraviolet light should be avoided during or soon after treatment.
In addition, promethazine may cause extrapyramidal reactions. These can include symptoms such as body, leg or arm tremors, lip biting, frowning, uncontrolled eye rolling, slow body movements, muscle pain or stiffness, or mental confusion.
In these cases, promethazine should be stopped and the nearest emergency room should be sought.
Immediate medical attention or the nearest emergency room should be sought if symptoms of a severe allergic reaction to promethazine occur. These may include difficulty breathing, a feeling that the throat is closing, or swelling of the mouth, tongue or face.
Does Phenergan make you sleepy?
Yes. Phenergan generally causes sleepiness, which is one of the most common side effects of this medicine.
This happens because promethazine acts on the brain by blocking the action of histamine. It can cause significant drowsiness, sedation, fatigue, and changes in cognitive function and memory.
For this reason, caution is needed with activities such as driving, operating heavy machinery or performing dangerous tasks. Alcohol can increase drowsiness and dizziness when used during treatment with promethazine, so alcoholic beverages should be avoided.
Who should not use it
Promethazine should not be used by children under 2 years old. It should also not be used by people with blood disorders caused by other phenothiazines, urinary retention related to uterine or prostate conditions, glaucoma, or allergy to promethazine, other phenothiazine derivatives or any ingredient in the formula.
Promethazine should also not be used during pregnancy or breastfeeding unless recommended by a doctor after weighing the benefits for the woman and the risks to the baby.