Chlorphenamine 

1. Introduction

Chlorphenamine, also known as chlorpheniramine, is an antihistamine commonly used to treat allergic conditions such as hay fever, urticaria, and allergic rhinitis. It works by blocking histamine receptors, thereby reducing symptoms like itching, swelling, and nasal congestion. Chlorphenamine is available in various formulations and is suitable for both acute and chronic allergic conditions.

2. Indications

  • Approved Indications:
    • Allergic rhinitis (seasonal and perennial).
    • Urticaria (hives) and angioedema.
    • Hay fever.
    • Food or drug allergies.
    • Insect bite or sting reactions.
    • Adjunct in anaphylaxis after adrenaline administration.
    • Cold symptoms (e.g., sneezing, runny nose).
  • Off-Label Uses:
    • Mild sedative in some cases due to its drowsiness-inducing effects.

3. Dosage

  • Adults and Children >12 years:
    • 4 mg every 4–6 hours (maximum: 24 mg/day).
  • Children (6–12 years):
    • 2 mg every 4–6 hours (maximum: 12 mg/day).
  • Children (2–6 years):
    • 1 mg every 4–6 hours (maximum: 6 mg/day).
  • Elderly:
    • Use lower doses due to increased susceptibility to side effects.

4. Administration

  • Take orally with or without food.
  • For liquid formulations, use a measuring spoon or cup for accurate dosing.
  • Extended-release tablets should not be crushed or chewed.

5. Forms Available

  • Tablets: 4 mg.
  • Oral solution: 2 mg/5 mL.
  • Syrup: 2 mg/5 mL.
  • Injectable solution: 10 mg/mL (used in emergencies such as anaphylaxis).

6. Side Effects

6.1. Common Side Effects

  • Drowsiness.
  • Dry mouth.
  • Dizziness.
  • Nausea.

6.2. Less Common Side Effects

  • Blurred vision.
  • Constipation.
  • Difficulty urinating.

6.3. Rare but Serious Side Effects

  • Severe allergic reactions (e.g., rash, swelling, difficulty breathing).
  • Confusion or hallucinations (more common in the elderly).

7. Warnings

  • May cause drowsiness; avoid driving or operating heavy machinery.
  • Use with caution in patients with narrow-angle glaucoma, enlarged prostate, or urinary retention.
  • Avoid use in patients with severe hepatic or renal impairment unless prescribed.

8. Precautions

  • Avoid alcohol and other central nervous system depressants, as they may increase sedation.
  • Use cautiously in elderly patients due to an increased risk of confusion and anticholinergic effects.
  • Do not exceed the recommended dosage to avoid severe side effects.

9. Interactions

  • Drug-Drug Interactions:
    • Sedatives, benzodiazepines, or opioids: Increased risk of sedation.
    • Monoamine oxidase inhibitors (MAOIs): May prolong and intensify the anticholinergic and sedative effects of chlorphenamine.
    • Alcohol: Enhanced sedative effects.
  • Drug-Food Interactions:
    • Avoid alcohol consumption during treatment.

10. Monitoring Parameters

  • Symptom relief for allergies (e.g., reduction in itching, swelling, and nasal congestion).
  • Watch for excessive drowsiness or confusion, especially in elderly patients.
  • Monitor for any signs of adverse reactions or overdose, such as severe drowsiness or agitation.

11. Use in Children

  • Approved for use in children over 2 years of age.
  • Dosages must be adjusted according to age and weight.

12. Use in Pregnancy

  • Category B: Considered safe in pregnancy when used at recommended doses.
  • Should only be used if clearly needed and prescribed by a healthcare provider.

13. Use in Elderly

  • Use with caution due to increased sensitivity to sedation and anticholinergic effects.
  • Start at a lower dose and monitor for side effects.

14. Use in Kidney Disease

  • Use cautiously in patients with renal impairment.
  • Dose adjustments may be required in severe kidney dysfunction.

15. Use in Liver Disease

  • Use cautiously in patients with hepatic impairment.
  • Dose adjustments may be required in severe liver dysfunction.

16. Patient Counselling Points

  • Explain that chlorphenamine may cause drowsiness, so avoid driving or using heavy machinery.
  • Take only the prescribed dose and avoid combining with alcohol or sedatives.
  • Inform patients that dry mouth is a common side effect and suggest sipping water or chewing sugar-free gum.
  • Advise patients to consult their doctor if symptoms persist beyond 7 days or worsen.
  • Store liquid formulations in a cool, dry place and keep out of reach of children.

17. Table of Brand Names, Manufacturers, and Prices

Brand NameManufacturerPrice (USD)
PiritonGSK$5–10 (30 tablets, 4 mg)
Chlor-TrimetonBayer$8–12 (30 tablets, 4 mg)
Generic OptionsVarious$3–8 (30 tablets, 4 mg)

18. FAQs (15 Questions)

  1. What is chlorphenamine used for?
    It is used to treat allergies, hay fever, hives, and cold symptoms.
  2. How does chlorphenamine work?
    It blocks histamine receptors, reducing allergic symptoms such as itching, swelling, and runny nose.
  3. Can chlorphenamine cause drowsiness?
    Yes, drowsiness is a common side effect.
  4. Can children take chlorphenamine?
    Yes, it is approved for use in children over 2 years, with age-appropriate dosing.
  5. Is chlorphenamine safe during pregnancy?
    Yes, it is generally considered safe when prescribed by a doctor.
  6. Can I take chlorphenamine with alcohol?
    No, combining it with alcohol can increase drowsiness and sedation.
  7. How often can I take chlorphenamine?
    Usually every 4–6 hours, depending on the prescribed dose.
  8. Can chlorphenamine cause dry mouth?
    Yes, dry mouth is a common side effect.
  9. What should I do if I miss a dose?
    Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double up.
  10. Can I drive after taking chlorphenamine?
    Avoid driving or operating machinery if you feel drowsy.
  11. Does chlorphenamine interact with other medications?
    Yes, it interacts with sedatives, MAOIs, and alcohol.
  12. How should chlorphenamine be stored?
    Store at room temperature, away from light and moisture.
  13. Can chlorphenamine treat cold symptoms?
    Yes, it can relieve sneezing and runny nose associated with colds.
  14. How long does it take for chlorphenamine to work?
    It usually starts working within 30 minutes to an hour.
  15. What should I do in case of an overdose?
    Seek immediate medical attention. Symptoms may include severe drowsiness, confusion, or seizures.