Chlorpheniramine

 

1. Generic Name & Brand Names

• Generic Name: Chlorpheniramine Maleate

• Common Brands:

  • Chlor-Trimeton® (US)

  • Piriton® (UK)

  • Allergex® (South Africa)

  • Cadistin® (India)

  • Generic/store brands ("Allergy Relief," "Cold Tablets")

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2. Dosage Forms

• Oral:

  • Tablets (4 mg)

  • Extended-release tablets (8 mg, 12 mg)

  • Syrup/Liquid (0.4 mg/mL)

• Injectable: IV/IM (hospital use)

• Combination Products:

  • With decongestants (e.g., chlorpheniramine + pseudoephedrine)

  • With analgesics (e.g., cold/flu multisymptom formulas)

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3. Drug Class

• First-Generation H₁ Antihistamine

• Sedating, potent anticholinergic effects

• Anti-allergic, antipruritic (anti-itch)

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4. Uses

• Allergic Conditions:

  • Hay fever, urticaria (hives), allergic conjunctivitis

• Common Cold Symptoms:

  • Sneezing, runny nose, itchy eyes/throat

• Adjunct in Anaphylaxis (with epinephrine)

• Motion Sickness (off-label)

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5. Side Effects

Common (>10%)	Serious (Require Discontinuation)
Drowsiness (50%)	Seizures
Dry mouth/nose	Severe hypotension
Dizziness	Urinary retention
Blurred vision	Glaucoma exacerbation
Constipation	Cardiac arrhythmias

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6. Critical Warnings

• 🚫 Contraindications:

  • Newborns/premature infants

  • Narrow-angle glaucoma

  • Severe hypertension, prostate enlargement

  • MAOI use (within 14 days)

• High-Risk Groups:

  • Elderly (>65 yrs): ↑ Delirium/fall risk

  • Asthma/COPD: Thickens secretions

  • Pregnancy: Category B (avoid in 3rd trimester)

• Drug Interactions:

  • ⚠️ CNS Depressants: Alcohol, opioids, benzodiazepines (↑ sedation)

  • ⚠️ Anticholinergics: Scopolamine, TCAs (↑ toxicity)

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7. How to Take

Form	Adults Dose	Max Daily	Timing
Standard Tablet	4 mg every 4-6 hrs	24 mg	With/without food
ER Tablet	8-12 mg every 8-12 hrs	24 mg	Avoid crushing
Syrup (≥6 yrs)	2-4 mg every 4-6 hrs	24 mg	Measure carefully

• Key Notes:

  • Avoid driving/operating machinery

  • Take evening doses 30 min before bedtime for allergy relief

  • Duration: ≤7 days for cold symptoms

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8. Pediatric Use

Age	Dose (Syrup)	Frequency
2-5 years	1 mg (2.5 mL)	Every 4-6 hrs
6-11 years	2 mg (5 mL)	Every 4-6 hrs

• 🚫 Infants <2 yrs: Contraindicated (respiratory depression risk)

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9. Overdose

• Symptoms:

  Extreme drowsiness, hallucinations, tachycardia, seizures, coma

• Action:

  • Call emergency services

  • Activated charcoal + IV physostigmine (for anticholinergic crisis)

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10. Storage

• Temperature: 15-30°C (59-86°F)

• Syrup: Discard after 1 year of opening

• Keep away from children (sweet syrup = ingestion risk)

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Critical Safety Alerts:

⚠️ Sedation Hazard:

• Impairs coordination as much as 0.1% blood alcohol - avoid driving entirely during use.
  ⚠️ Cold Medication Risks:

• Found in 80+ multisymptom products (e.g., Tylenol Cold®) - check labels to avoid duplicate dosing.
  ⚠️ Elderly Vulnerability:

• ↑ Risk of falls, confusion, and urinary retention - avoid in dementia patients.
  ⚠️ Asthma Warning:

• Dries respiratory secretions - not recommended during acute asthma attacks.

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Comparison to Newer Antihistamines

Feature	Chlorpheniramine	Cetirizine
Generation	1st	2nd
Sedation	High (50%)	Low (10-15%)
Dosing Frequency	4-6 hourly	Once daily
Pediatric Use	≥2 years	≥6 months
Decongestant Effect	Yes (mild)	No

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Clinical Tips:

✅ Best For:

• Nighttime allergy/cold symptoms (sedation beneficial)

• Acute itching (hives, insect bites)
  ❌ Avoid For:

• Daytime use in active adults

• Chronic allergies (use 2nd-gen agents instead)
  💡 Combination Therapy:

• Often paired with pseudoephedrine (e.g., Deconamine®) for congestion - monitor BP.

OTC Status: Available without prescription, but high-risk populations require medical consultation.

📊 Efficacy Note:

• 4 mg chlorpheniramine ≈ 10 mg cetirizine for allergy relief (Ann Pharmacother), but sedation limits utility.

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