Written and medically reviewed by Dorcas Morak, Pharm.D
Have you ever heard of promethazine (brand name Phenergan)? If you’ve experienced allergies, motion sickness, or nausea, there’s a good chance this medication came up as a treatment option. But what exactly does it do—and how does it work? Whether you’ve been prescribed it or are simply curious, here’s what you need to know
What Conditions Is Promethazine Used For?
Promethazine is a versatile medication with multiple uses. It may be recommended for the following:
Allergy Symptoms Promethazine helps relieve symptoms like runny nose, itchy eyes, sneezing, and skin rashes. It’s often used to manage allergic rhinitis, conjunctivitis, and skin reactions like dermographism.
Nausea and Vomiting This medication is commonly used in hospitals to prevent or treat nausea and vomiting, especially after surgery or as part of chemotherapy regimens.
Motion Sickness Planning a trip? Promethazine may help prevent motion sickness. Taken about 30 to 60 minutes before traveling, it works by calming the inner ear and brain centers responsible for balance and nausea.
Sedation Promethazine has sedative effects and may be used to help patients relax before surgery or procedures. It can also help manage anxiety or occasional sleep disturbances.
How Does Promethazine Work?
Promethazine works by blocking three key chemicals in the body:
- Histamine (H1 receptor blocker): Reduces allergy symptoms
- Dopamine: Helps control nausea and vomiting
- Acetylcholine (anticholinergic effects): Contributes to its sedative and anti-nausea properties
This combination of effects makes it useful across a variety of conditions, particularly those involving nausea, allergies, and anxiety.
What Are the Side Effects of Promethazine?
As with most medications, side effects are possible. Common ones include:
- Drowsiness or sedation
- Dizziness or lightheadedness
- Dry mouth
- Blurred vision or constipation (less common) Serious side effects—though rare—can include breathing problems, confusion, seizures, or abnormal heart rhythms. Always seek medical attention if you experience severe or unusual symptoms.
Important: Promethazine may also interact with other medications, increasing the risk of side effects or complications. Learn more in our full guide: 7 Promethazine Interactions You Should Know About
Can You Save on Promethazine?
Yes! The RxLess™ Assurance Plan can help you save significantly on promethazine—no insurance required. Just use the free RxLess™ app or visit the website to:
- Search for your medication and confirm the strength, form, and quantity
- Compare prices at local pharmacies and select the best price for your prescription
- Save your discount and show it to the pharmacist when you pick up your medication! This way, you can get the medication you need without overpaying.
Final Tip:
Always take promethazine exactly as prescribed. It can interact with other medications and cause drowsiness, so avoid alcohol and be cautious when driving or operating machinery.
