Phenergan

What is Phenergan?

Phenergan is an anti-nausea medication that works to combat the symptoms of nausea and motion sickness. It’s often used for the effects of day-to-day issues such as travel sickness, but in rarer cases it can also be used to treat the after-effects of surgery ― like vomiting and pain ― that can be felt after you’ve had an operation.

Phenergan’s active ingredient, promethazine hydrochloride, is a type of drug called a phenothiazine. It works by blocking a natural chemical called histamine that your body produces during an allergic reaction. This means that as well as being an effective treatment against nausea, Phenergan is also used for reducing allergy symptoms.

How does Phenergan work?

Phenergan works by lowering the effects of histamine in the brain, changing the way the chemicals in your brain take action. Its active ingredient, promethazine, works by dulling the sensitivity of histamine receptors in the part of your brain associated with vomiting.

Promethazine blocks histamine receptors without actually stopping the release of histamine. This stops the vomiting centre from becoming activated by inflammatory stimulus, and so helps to stop nausea and motion sickness.

What doses of Phenergan are there?

Phenergan comes in doses of 10mg, 20mg and 25mg doses for adults, to be taken two to three times per day. The dosage will depend on the type and strength of your nausea. You should always refer to the patient information leaflet for details.

How to take Phenergan

You should take Phenergan as instructed by your clinician, and in line with your patient information leaflet. If you’re unsure, you can always talk to our clinician for help.

The dose you’ll take will depend on the reason that you’re taking Phenergan (whether it’s for nausea and vomiting, allergies, or as a sedative). To take Phenergan, you must:

• Take the medicine orally.
• Not take it for more than seven days. If your symptoms aren’t better after this period of time you should let your clinician know.
• Only follow your clinician for dosage guidance. If you feel that the dose you’re taking isn’t right, don’t alter it yourself.

How long does it take Phenergan to work?

Phenergan is a quick and effective treatment for nausea, and the symptoms of nausea should reduce within 20 minutes of taking it. Don’t take more than the prescribed amount if your symptoms don’t feel like they’re getting better. Always remember to speak to your doctor or clinician for advice if you’re not sure about anything.

How long can I take Phenergan for?

Phenergan shouldn’t be taken for more than a period of seven days. If your symptoms haven’t gone down within the week you should talk to our clinician, who can advise you of what your next course of action could be.

What should I do if I make a mistake when taking Phenergan?

If you accidentally take more Phenergan than you’ve been advised to by your clinician, then you should seek medical help as soon as possible. Don’t take an extra dose to make up for a forgotten dose, just take it when you remember or skip that dose if it’s too close to your next one.

Medically reviewed by

Dr Daniel Atkinson

GP Clinical Lead

on August 02, 2022.

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