Phenergan

Phenergan contains promethazine hydrochloride, a first-generation antihistamine with sedative, antiemetic, and antipruritic properties.

It is prescribed for a range of conditions including allergic rhinitis, urticaria, insomnia, motion sickness, nausea, and as a pre-operative sedative.

Promethazine blocks histamine H1 receptors, reducing the symptoms of allergic reactions such as sneezing, itching, and hives.

It also antagonises muscarinic acetylcholine receptors and dopamine receptors, accounting for its antiemetic and sedative effects.

The pronounced central nervous system depression makes it useful for short-term management of sleep disturbance but also means it impairs alertness and reaction times.

Phenergan is available in tablet, liquid, and injectable formulations.

The oral preparations are commonly used in general practice, while injectable promethazine is used in hospital settings for severe allergic reactions and post-operative nausea.

Due to its long duration of action (typically 6 to 12 hours), a single evening dose of Phenergan can provide overnight relief of allergic symptoms and aid sleep.

However, residual drowsiness the following morning is a recognised concern and should be considered before driving or operating machinery.

For allergic conditions: take 25 mg at night, or 10 to 25 mg two to three times daily as needed. For short-term sleep disturbance: take 25 to 50 mg at bedtime.

For motion sickness: take 25 mg the night before travel and repeat the following morning if needed.

Swallow tablets whole with water. The oral liquid should be measured with the supplied dosing device. Take the medication at the same times each day where practical.

Phenergan is not recommended for use in children under two years of age due to the risk of respiratory depression.

In children aged 2 to 5, dosing must be determined by the prescriber based on body weight.

Adults: 25 mg at bedtime for allergies and sleep disturbance, increased to 25 mg two to three times daily if required. Maximum 100 mg daily.

For motion sickness: 25 mg the night before travel, repeated the next morning.

Children 5 to 10 years: 10 to 25 mg at bedtime. Children 2 to 5 years: 5 to 15 mg at bedtime, as directed by the prescriber. Not suitable for children under 2 years.

Elderly patients should start at lower doses due to increased sensitivity to sedative and anticholinergic effects.

Drowsiness is the most prominent side effect and may persist into the following day. Dry mouth, blurred vision, dizziness, and constipation result from the drug's anticholinergic activity.

Urinary retention is possible, particularly in older men with prostatic enlargement.

Restlessness, agitation, and involuntary movements (dystonias) may occur, especially in children and younger adults. These extrapyramidal reactions are typically dose-related and reversible.

Photosensitivity, increased appetite, and weight gain have been reported with regular use. Rarely, blood dyscrasias, jaundice, and severe skin reactions have occurred.

In children under two years, promethazine carries a risk of fatal respiratory depression, which is why it is contraindicated in this age group.

Phenergan causes significant sedation. Do not drive, operate heavy machinery, or drink alcohol while taking this medication.

The sedative effect may be amplified by other central nervous system depressants including benzodiazepines, opioids, and other antihistamines.

Use with caution in elderly patients, who are more susceptible to anticholinergic effects such as confusion, constipation, and urinary retention.

Phenergan should be avoided in patients with narrow-angle glaucoma, prostatic hypertrophy causing urinary retention, or epilepsy.

Inform your prescriber if you are pregnant or breastfeeding. Promethazine is generally avoided in late pregnancy due to the risk of neonatal sedation.

Phenergan is contraindicated in children under two years of age, in individuals with known hypersensitivity to promethazine or other phenothiazines, and in patients in a comatose state or with significant central nervous system depression.

It must not be administered intra-arterially.

Avoid use in patients who have taken monoamine oxidase inhibitors (MAOIs) within the preceding 14 days, as the interaction may cause severe hypotension and CNS depression.