Promethazine

Promethazine is a first-generation antihistamine used to treat a variety of conditions, including allergies, nausea, motion sickness, and short-term sleep disturbances. It belongs to the phenothiazine class of medications and works by blocking histamine (H1) receptors in the brain and body.

While not an opioid or controlled drug, promethazine is known for its sedative effects, which have contributed to both legitimate medical use and misuse when combined with other substances.

Medical Uses of Promethazine

Promethazine has multiple approved applications in both the USA and UK, including:

• Allergy relief: Effective for hay fever, hives, and skin rashes.

• Nausea and vomiting: Commonly prescribed for motion sickness, post-surgery sickness, and drug-induced nausea.

• Sleep aid: Due to its sedative properties, sometimes used short-term for insomnia.

• Cold and flu symptoms: Found in some cough syrups (often combined with decongestants or codeine in prescription formulations).

• Pre-surgery sedation: Occasionally used in hospitals to calm patients before procedures.

How Promethazine Works

Promethazine blocks histamine H1 receptors, reducing the body’s allergic response. It also has anticholinergic and sedative effects, which explain its wide range of uses.

Effects include:

• Reduced allergic reactions (itching, sneezing, watery eyes)

• Relief from nausea and vomiting

• Sedation and drowsiness

• Drying of respiratory secretions (helpful in colds and flu)

Side Effects of Promethazine

Common side effects:

• Drowsiness

• Dizziness

• Dry mouth

• Blurred vision

• Constipation

Serious risks (less common):

• Respiratory depression (especially in children under 2 years, which is why it’s not recommended for them)

• Severe allergic reaction (rare)

• Confusion or agitation in older adults

• Heart rhythm disturbances in sensitive patients

 Because of its sedative power, promethazine should not be combined with alcohol, opioids, or other sedatives.

Forms and Dosage

Promethazine is available in different forms, depending on the condition being treated:

• Tablets (10mg, 25mg, 50mg)

• Oral solution/syrup

• Injectable form (used in hospitals for nausea or sedation)

• Suppositories (for severe nausea when oral medication isn’t possible)

 Dosage depends on age, medical condition, and use case (allergies vs nausea vs sleep aid). It should always be taken under medical supervision.