Promethazine is a prescription antihistamine used for allergies, nausea, motion sickness, and as a short-term sleep aid or sedative before procedures. It comes as tablets, syrup, suppositories, and injections. The most useful part of this page is straight talk about when promethazine helps, typical dosing ranges, and the safety red flags you should not ignore.
For allergy symptoms (sneezing, runny nose, itching) people usually take it as needed. For nausea or motion sickness, many doctors suggest taking a dose before travel or when symptoms start. In hospitals it’s used by IV or IM injection for severe nausea or to calm patients before procedures. Some prescribers also use it short-term for insomnia, but stronger or safer sleep options may be better for long-term use.
Typical oral doses for adults often fall in the 12.5–25 mg range, repeated every 4–6 hours as needed, with many sources capping daily doses near 100 mg. For children the dose is smaller and must be set by a clinician. Never give promethazine to infants under 2 years; that age group faces a serious risk of breathing problems.
Promethazine commonly causes drowsiness, dry mouth, dizziness, and blurred vision. Because it depresses the central nervous system, avoid alcohol and be careful with other sedating drugs like opioids, benzodiazepines, or some sleep aids. Combining them can cause dangerous breathing problems or excessive sedation.
Avoid promethazine if you’re already taking MAO inhibitors or if you have severe lung disease, low blood pressure, or severe liver problems unless a doctor advises otherwise. Older adults may experience more confusion, balance problems, and a higher fall risk. Tell your provider about all medicines and supplements you use so they can check for interactions.
If you’re pregnant or breastfeeding, ask your clinician before taking promethazine. Some providers prescribe it for severe morning sickness, but the risks and benefits should be reviewed together. If you become unusually sleepy, have trouble breathing, or notice a severe allergic reaction (rash, swelling, trouble breathing), stop the drug and seek emergency care.
Want to buy promethazine online? Use a licensed, reputable pharmacy that requires a prescription. Avoid sites that sell prescription drugs without asking for a valid prescription—those products may be counterfeit or unsafe. If you’re unsure about dose or whether promethazine is right for you, contact a pharmacist or your healthcare provider. Clear questions lead to safer use.
Need quick help deciding? Ask your doctor: is promethazine the best option for my symptom, what dose should I take, and what signs mean I should stop? That short conversation can prevent problems and get you better results faster.
