Phenergan (Promethazine): Uses, Dosage & Safety

If you've heard of Phenergan, you likely know it helps with nausea or allergies. Phenergan is the brand name for promethazine, an older but widely used antihistamine that also works as an anti-nausea drug and sedative. This page gives you clear, practical info on what it does, how people usually take it, and the safety points to watch for.

How Phenergan is commonly used

People use Phenergan for several things: allergy symptoms (itching, runny nose), motion sickness, nausea and vomiting, and to help with sleep or anxiety before procedures. It comes in tablets, syrup, suppositories and injections. For travel sickness, many take a dose about an hour before travel; for allergy relief, people often take it when symptoms flare. If a doctor gives an injection, that’s usually in a clinic setting for stronger nausea control.

Because it causes drowsiness, some doctors prescribe it before minor procedures or to help with severe itching. It’s also used in hospitals for nausea when other drugs aren’t working. If you’re thinking about using Phenergan for children, talk to a pediatrician first — there are important age and dose limits.

Dosage, side effects and safety tips

Dosage varies by reason for use and age. Adults typically take lower single doses several times a day as needed. Don’t mix it with alcohol or other sedatives; the combination can slow breathing and make you dangerously drowsy. Common side effects include sleepiness, dry mouth, blurred vision, and constipation. Some people feel restless or dizzy instead of sleepy.

Important warnings: do not give Phenergan to infants or toddlers unless a doctor specifically approves — it can cause severe breathing problems in very young children. Older adults may be more sensitive to confusion and dizziness. Promethazine can also interact with opioids, muscle relaxants, sleep meds, and MAO inhibitors — always tell your provider about other medicines you take.

If you’re pregnant or breastfeeding, check with your healthcare provider. Promethazine is sometimes used in pregnancy for severe nausea, but a provider will weigh benefits and risks. Store the medicine at room temperature away from light and moisture, and keep it out of reach of children.

Quick tips: avoid driving or operating heavy machinery until you know how Phenergan affects you; use caution in hot weather (it can affect your body’s temperature control); and if you notice trouble breathing, severe dizziness, high fever, or unusual muscle stiffness, seek medical help right away.

Want to know if Phenergan fits your situation? Talk to your pharmacist or doctor. They can confirm proper dosing, check for interactions, and suggest safer alternatives if needed.