Phenergan (promethazine): uses, side effects, and safety tips

Phenergan is the brand name for promethazine, a powerful antihistamine used for allergies, nausea, motion sickness, and as a short-term sleep aid. It works fast and can be very helpful, but it also causes strong drowsiness and has safety issues many people don’t expect. Read this to know when it helps, when to avoid it, and what to watch for.

How people use Phenergan

Doctors commonly prescribe Phenergan for: allergic reactions (itching, hives), nausea and vomiting after surgery or from motion sickness, and sometimes to help with sleep before procedures. Typical adult doses are small — often 12.5–25 mg every 4–6 hours for nausea. For sedation, higher short-term doses may be used, but total daily dosing should follow a prescriber’s advice. Don’t guess the dose; ask your pharmacist or doctor if you’re unsure.

Parents: don’t give Phenergan to children under 2 years old. In young kids it can cause dangerous breathing problems. For older children, only use under a doctor’s direction and with clear dosing instructions.

Safety, side effects, and common interactions

Most common side effects are drowsiness, dry mouth, blurred vision, and constipation. Because it causes heavy sedation, avoid driving, operating machines, or drinking alcohol while taking Phenergan. Mixing it with opioids, benzodiazepines, or alcohol increases the risk of severe breathing problems and extreme drowsiness.

Watch for serious warning signs and get medical help if you notice: trouble breathing, fainting, very slow heartbeat, severe dizziness, or signs of an allergic reaction like swelling of the face or throat. Promethazine can also worsen symptoms in people with certain medical problems — for example, it may cause confusion or falls in older adults and can affect breathing in people with respiratory issues.

If you’re pregnant or breastfeeding, talk with your provider. Some providers use promethazine in pregnancy for severe nausea, but you should only take it when a clinician recommends it.

Looking for alternatives? Over-the-counter options include diphenhydramine (Benadryl) which also sedates, and non-sedating options like loratadine (Claritin) for allergies. For nausea, prescription options like ondansetron may be more suitable and cause less drowsiness. Your choice depends on the symptom and your overall health.

Before using Phenergan, tell your prescriber about: other medicines you take (especially sedatives or strong painkillers), medical conditions (lung disease, heart problems, glaucoma), and if you are pregnant or breastfeeding. Keep doses exact, store medicines safely away from children, and follow up if side effects worry you.

Want more practical guides? Check our site for related posts on antihistamines, safe online pharmacies, and alternatives for nausea and sleep. If you’re unsure whether Phenergan is right for you, a quick call with your pharmacist or a visit to your clinician can save you headaches and keep you safe.