Alerest

Approved Indications:

• Allergic rhinitis (seasonal or perennial)
• Urticaria (hives)
• Allergic conjunctivitis
• Angioedema
• Anaphylaxis (adjunct treatment) – usually following epinephrine
• Dermatographic urticaria
• Pruritus associated with allergic skin disorders (e.g., atopic dermatitis)
• Allergic reactions due to blood or plasma
• Vasomotor rhinitis
• Insect bite/sting allergic response
• Drug-induced allergic reactions

Off-label / Clinically Accepted Uses:

• Cold symptoms (rhinorrhea, sneezing) in combination with decongestants or analgesics
• Motion sickness prophylaxis
• Cough due to upper airway allergy
• Adjunct in hay fever and sinusitis

Route of Administration: Oral, intramuscular (IM), intravenous (IV), subcutaneous (SC)

Adults and Adolescents (≥12 years):

• Oral: 4 mg every 4–6 hours as needed; Maximum: 24 mg/day

Children (6–12 years):

• Oral: 2 mg every 4–6 hours as needed; Maximum: 12 mg/day

Children (2–5 years):

• Oral: 1 mg every 4–6 hours; Maximum: 6 mg/day

Geriatric Patients:

• Start with lower doses due to increased sensitivity; monitor for anticholinergic side effects

Renal/Hepatic Impairment:

• Use with caution; dose adjustment may be needed due to prolonged half-life

Parenteral (for emergency allergy/anaphylaxis support):

• IM/IV/SC: 10–20 mg every 4–6 hours, based on severity; adjust per response

Note:
Extended-release formulations (e.g., 8–12 mg twice daily) may be used for maintenance therapy.

Chlorpheniramine maleate is a first-generation antihistamine that acts as a competitive H1-receptor antagonist. It blocks histamine from binding to H1 receptors on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract. This reduces histamine-mediated symptoms like vasodilation, capillary permeability, and sensory nerve stimulation, leading to relief from sneezing, rhinorrhea, itching, and hives. Its central sedative and anticholinergic effects result from its ability to cross the blood-brain barrier.

• Absorption: Rapid and well absorbed orally
• Onset of Action: 30–60 minutes
• Peak Plasma Concentration: ~2.5 to 6 hours
• Bioavailability: 25–50% (subject to first-pass metabolism)
• Distribution: Widely distributed, crosses blood-brain barrier and placenta
• Protein Binding: ~70%
• Metabolism: Primarily hepatic via cytochrome P450 enzymes (mainly CYP2D6)
• Half-life: 12–15 hours (may be prolonged in elderly or renal impairment)
• Excretion: Renal (~35–65% as metabolites)

• Pregnancy:
  Chlorpheniramine is generally considered safe in pregnancy (FDA Category B), especially during the second and third trimesters. However, caution is advised in the first trimester due to potential risk of congenital abnormalities (limited data).
• Lactation:
  The drug is excreted in breast milk in small amounts. Although adverse effects in breastfed infants are rare, drowsiness or irritability may occur. Use with caution, especially in neonates or premature infants.

• Primary Class: Antihistamine (H1 receptor antagonist)
• Subclass: First-generation alkylamine-type antihistamine

• Hypersensitivity to chlorpheniramine or any component of the formulation
• Narrow-angle glaucoma
• Symptomatic prostatic hypertrophy
• Severe hypertension or coronary artery disease
• Concurrent use with or within 14 days of MAO inhibitors

• Use with extreme caution in the elderly due to increased risk of sedation, confusion, and falls
• May cause CNS depression—avoid driving or operating heavy machinery
• Anticholinergic effects (dry mouth, urinary retention, constipation, blurred vision) may worsen in patients with BPH, asthma, or peptic ulcer
• Avoid alcohol and other CNS depressants
• Monitor closely in patients with hepatic or renal dysfunction
• Risk of paradoxical excitation in young children

Common:

• Central nervous system: Drowsiness, dizziness, sedation, headache
• Gastrointestinal: Dry mouth, nausea, vomiting, constipation, loss of appetite
• Ophthalmic: Blurred vision
• Respiratory: Thickened bronchial secretions

Serious / Rare:

• Allergic reaction, rash, or anaphylaxis
• Palpitations, tachycardia, or arrhythmia
• Seizures (especially with overdose)
• Urinary retention
• Confusion or hallucinations (especially in the elderly or pediatric patients)

• MAO inhibitors: Potentiation of anticholinergic and CNS depressant effects
• CNS depressants (e.g., alcohol, benzodiazepines, opioids): Increased sedation risk
• Anticholinergics (e.g., atropine, tricyclic antidepressants): Additive anticholinergic effects
• CYP2D6 inhibitors (e.g., fluoxetine, quinidine): May reduce metabolism and increase toxicity

• Recent clinical guidance suggests second-generation antihistamines as first-line agents due to fewer sedative effects. However, chlorpheniramine remains a cost-effective option, especially in resource-limited settings.
• Pediatric safety guidelines emphasize avoiding use in children under 2 years due to risk of serious respiratory depression.

• Store at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C–30°C
• Protect from excessive heat, humidity, and light
• Keep container tightly closed
• Oral liquid formulations: Shake well before use
• Keep out of reach of children