Phenergan (Promethazine) – Uses, Dosage, Side Effects & FAQs

When you see Phenergan, a prescription antihistamine (promethazine) used for allergy relief, nausea control, and sedation. Also known as promethazine, it belongs to the Antihistamines, drugs that block histamine receptors to reduce allergic reactions family. First‑generation antihistamines like Phenergan often cause Sedation, a drowsy effect that can be useful for short‑term sleep aid but may limit daytime activities. The medicine is also common for Motion sickness, a condition causing nausea and vomiting during travel, because it calms the inner‑ear signals that trigger the feeling. In short, Phenergan treats allergy symptoms, also helps control nausea, and belongs to the antihistamine class – three clear connections you’ll see throughout our guide.

How Phenergan works and what to expect

Phenergan blocks H1 histamine receptors, which stops the cascade that leads to itching, watery eyes and runny nose. By cutting that signal, the drug reduces the body’s allergic response and also quiets the vestibular system, which is why it eases motion‑related nausea. Because it crosses the blood‑brain barrier, it produces a calming effect that many users describe as gentle drowsiness. This sedation is a double‑edged sword: it can help patients who need to rest after surgery, but it also means you shouldn’t drive or operate heavy machinery until you know how you react. Common side effects include dry mouth, blurry vision, and low blood pressure, especially when taken with other sedatives. If you’re pregnant, diabetic, or on monoamine‑oxidase inhibitors, talk to your doctor first – the interaction risk is higher with other central nervous system depressants.

Phenergan comes in tablets, syrup, and injectable forms, each suited for different situations. The oral tablet is handy for chronic allergy management, while the syrup works well for children who can’t swallow pills. The injectable is reserved for hospital use, such as pre‑operative sedation or severe allergic reactions. Typical adult dosing ranges from 12.5 mg to 25 mg every 4‑6 hours, never exceeding 200 mg per day. Children’s doses are weight‑based, usually 0.5 mg per kilogram. Always follow the prescription label and never double up to chase a quicker effect – the drug’s half‑life is long enough that buildup can lead to excessive sedation. When you need an alternative, newer second‑generation antihistamines like loratadine have less drowsiness but may not be as strong for nausea.

Below you’ll find a curated collection of articles that dive deeper into Phenergan’s role in allergy treatment, compare it with other antihistamines, and explain how to manage its side effects safely. Whether you’re looking for dosage charts, interaction warnings, or real‑world tips on staying alert while on the medication, the posts ahead cover the full spectrum of practical information you’ll need.