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Promethazine Hydrochloride

Anti-emetic drugs Prescription
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Indications

Allergic Rhinitis Urticaria Insomnia Allergy

Histaphen is indicated as a potent, long-acting antihistamine that also has anti-emetic and sedative (calming) effects. It is used for the symptomatic treatment of allergic conditions affecting the respiratory tract and the skin, as well as for sensitisation reactions to drugs or foreign proteins and for anaphylactic reactions. It is also indicated for sedation, allergic rhinitis, urticaria and insomnia, as an adjunct to pre-operative sedation in surgery and obstetrics, and as a sedative for children.

⚠️ Always consult a registered physician before taking any medicine.

Pharmacology

Promethazine, a phenothiazine derivative, blocks postsynaptic mesolimbic dopamine receptors in the brain. It has a strong α-adrenergic blocking effect and suppresses the release of hypothalamic and hypophyseal hormones. By competing with histamine for the H1-receptor, and through a muscarinic blocking effect that may account for its antiemetic action, it also reduces stimuli reaching the brainstem reticular system.

Taken orally, promethazine is well absorbed from the gastrointestinal tract. Its clinical effects appear within 20 minutes and generally last four to six hours, though they may persist for up to 12 hours. The liver metabolizes promethazine into a variety of compounds, with promethazine sulfoxide and N-demethylpromethazine sulfoxide as the main metabolites found in the urine.

Pregnancy & Breastfeeding

Pregnancy & Breastfeeding: Studies in humans and animals have not shown promethazine to be harmful during pregnancy, but it should still be avoided unless your physician feels it is clearly needed. Phenergan is not recommended in the two weeks before delivery, as it may cause irritability and excitability in the newborn. When taken in high doses late in pregnancy, promethazine has been linked to prolonged neurological disturbances in infants. It should therefore be used during pregnancy only after weighing the potential benefits to the mother against the possible risks to the baby. Promethazine passes into breastmilk and may cause irritability and excitability in a nursing infant.

⚠️ Talk to your doctor before taking any medicine during pregnancy or while breastfeeding.

Dosage Reference

⚠️ Reference ranges from official sources only. Consult your doctor for personalized dosing.

Adults: Oral dose for adults: Start with one 25 mg tablet at night. This may be increased to two or three 25 mg tablets at night if necessary. In allergic conditions, more frequent administration, twice or three times daily, may be necessary, starting with one or two 10 mg tablets and increasing as required. Elderly: No specific dosage recommendations. Children: They may be treated more conveniently with the elixir containing 5 mg per 5 ml. As an antihistamine in allergy, children aged 2 to 5 years may be given 5 to 15 mg, and children aged 5 to 10 years 10 to 25 mg. Where two doses are required in 24 hours, the lower dose stated should be given. As a sedative, children aged 2 to 5 years may be given 15 to 20 mg, and children aged 5 to 10 years 20 to 25 mg, given as a single night-time dose. Parenteral dose for adults: 25 to 50 mg by deep intramuscular injection or, in an emergency, by slow intravenous injection after diluting the 2.5% solution to 10 times its volume with water for injection. The maximum parenteral dose is 100 mg. Children aged 5 to 10 years: 6.25 to 12.5 mg by deep intramuscular injection.