Phenergan

Phenergan Medication Overview

Phenergan (promethazine) is a prescription medication classified as a phenothiazine, which is used to treat allergy symptoms, nausea and vomiting, motion sickness, and as a sedative or sleep aid. It may also be used for sedation and premedication before surgical procedures.

Pharmacological Properties

Phenergan’s primary mechanism of action is as a histamine H1 receptor antagonist, providing effective relief from allergy symptoms. It also exhibits strong anticholinergic and sedative effects. Additionally, it possesses significant antiemetic properties and can be used as a local anesthetic due to its sodium channel-blocking effects.

Indications for Use

Indications for Phenergan include relief of allergy symptoms such as rash, itching, sneezing, runny nose, and watery eyes. It’s also indicated for prevention and control of nausea and vomiting, motion sickness, and as a preoperative sedative. It may be used for sedation in certain medical procedures and in cases of anxiety.

Dosage and Administration

Dosage of Phenergan is tailored to the patient’s specific needs and medical condition. It can be administered orally, rectally, or by injection, and the route of administration will vary by indication. For allergies, the typical oral dose for adults is 25 mg before bed or 12.5 mg before meals and at bedtime. For nausea and vomiting, the usual dose is 25 mg with doses spaced out as necessary.

Preparation and Storage

Phenergan is available in various forms including tablets, rectal suppositories, syrup, and injectable solutions. Storage requirements may vary by product form but generally, Phenergan should be stored between 20°C to 25°C (68°F to 77°F) in a tightly closed container away from light and moisture.

Contraindications and Cautions

Phenergan is contraindicated in children under 2 years of age, those who have demonstrated a hypersensitivity to promethazine or other phenothiazines, and in cases of comatose states or in individuals with severe central nervous system depression. Use with caution in patients with underlying medical conditions like asthma, seizure disorders, and cardiovascular disease.

Drug Interactions

Phenergan may interact with other medications, potentiating the effects of CNS depressants including alcohol; anticholinergic agents; MAO inhibitors, which can prolong and intensify anticholinergic effects; and epinephrine, which can reduce the efficacy of epinephrine in treating hypersensitivity reactions.

Adverse Effects

Common adverse effects of Phenergan include drowsiness, dizziness, blurred vision, dry mouth, and fatigue. Less commonly, it can cause disorientation, mood changes, seizures, and neuroleptic malignant syndrome. Because of its sedative properties, it may impair physical and mental capabilities, and it can cause respiratory depression in young children.

Pregnancy and Lactation

In pregnancy, Phenergan should only be used if the benefits justify the potential risks to the fetus. It is classified as FDA pregnancy category C. It’s unknown if promethazine passes into breast milk; therefore, caution should be exercised when administered to a nursing woman.

Overdose and Management

In case of overdose, symptoms may include severe drowsiness, dizziness, fainting, and respiratory depression. Immediate medical attention is required, and management of overdose includes symptomatic and supportive therapy. Activated charcoal may be administered within two hours of ingestion to reduce absorption.

Phenergan Withdrawal

While not generally considered to have a high potential for dependence, abrupt discontinuation after long-term use may cause withdrawal symptoms. Tapering the dose gradually under medical supervision is recommended when the decision to discontinue therapy is made.