Kloorifenamiini

Kloorifenamiini, also known as chlorphenamine or chlorpheniramine, is a first-generation antihistamine used to relieve symptoms of allergic rhinitis, urticaria, conjunctivitis, and other hypersensitivity reactions. It is also found in many over-the-counter cold and flu remedies to reduce rhinorrhea and sneezing.

Mechanism: It acts as an antagonist at histamine H1 receptors, reducing the effects of endogenous histamine. Because it is a small, lipophilic molecule, it crosses the blood–brain barrier, contributing to sedation. It also has anticholinergic activity, which can cause dry mouth, blurred vision, and urinary retention.

Pharmacokinetics: After oral administration it is readily absorbed from the gastrointestinal tract, reaching peak levels in a few hours. It is extensively metabolized by the liver, with several metabolites excreted in urine. The elimination half-life varies among individuals and can be extended in the elderly.

Uses: Indicated for relief of symptoms associated with allergic rhinitis, hay fever, conjunctival irritation, and itching due to urticaria. It is sometimes used as an add‑on therapy for cough suppression in combination products.

Adverse effects and safety: Common adverse effects include drowsiness, sedation, dizziness, dry mouth, blurred vision, and urinary retention. Because of sedation and anticholinergic effects, caution is advised when driving or operating machinery and in the elderly. It may interact with alcohol, sedatives, and other CNS depressants. Use in pregnancy and lactation requires medical advice.

Regulation: In many countries chlorphenamine is available OTC but in others may require a prescription or be restricted to combination products. Always follow local guidance.