Active Ingredient

Promethazine

Promethazine is a type of medication known as an antihistamine. It is often used to treat allergy symptoms and is also effective in preventing nausea and vomiting.

This medication can also be used to help with sleep issues and may be prescribed for other conditions as advised by a healthcare provider.

Written By Douglas C. Goldberg, MD

Reviewed By Philip Schein, MD

Last Updated 28 Nov 2025

Available Promethazine Brands

Promethazine

Strengths 25mg

Phenergan

Strengths 25mg

Promethazine Uses

Promethazine is commonly used for a variety of conditions related to allergies and nausea.

Relief of allergy symptoms such as runny nose and itching
Prevention and treatment of nausea and vomiting
Inducing sedation or sleep
Relief of motion sickness
Pre-operative sedation

How Promethazine Works

Promethazine works by blocking histamine receptors in the body. Histamine is a substance produced during allergic reactions that can cause symptoms like itching and sneezing.

By blocking these receptors, Promethazine helps reduce allergy symptoms. It also affects other receptors in the brain, which can help control nausea and induce sedation.

Common side effects of Promethazine

While not everyone experiences side effects, some individuals may encounter mild and temporary reactions.

Drowsiness
Dizziness
Dry mouth
Blurred vision
Constipation
Confusion
Restlessness

If you experience any severe or persistent symptoms, it’s important to contact your doctor.

Avoid driving or operating heavy machinery until you know how Promethazine affects you.
Limit alcohol consumption as it can increase drowsiness.
Inform your doctor of any other medications you are taking to avoid interactions.
Do not use Promethazine if you have certain medical conditions without consulting a doctor.
Monitor for any unusual side effects and report them to your healthcare provider.

Always consult your doctor for personalized medical advice and before starting or stopping any medication.

Frequently Asked Questions

What is Promethazine used for?

Promethazine is used to treat allergy symptoms, prevent nausea and vomiting, and can also be used as a sedative.

How quickly does Promethazine work?

Promethazine typically starts working within 20 minutes to an hour after taking it, depending on the form used.

Can I take Promethazine with other medications?

It’s important to consult your doctor before combining Promethazine with other medications to avoid potential interactions.

Is Promethazine safe for long-term use?

The safety of long-term use should be evaluated by your healthcare provider, as it depends on individual health conditions and needs.

Can Promethazine cause drowsiness?

Yes, drowsiness is a common side effect of Promethazine. It’s advised not to drive or operate machinery until you know how it affects you.