Usage
Chlorpheniramine maleate, an antihistamine, is used to relieve symptoms associated with allergic conditions such as rhinitis (hay fever), urticaria (hives), conjunctivitis, and common cold. Citric acid is often included as a buffering agent to adjust and maintain the pH of the formulation. The combination primarily addresses allergy symptoms.
- Pharmacological Classification: Antihistamine (first-generation alkylamine).
- Mechanism of Action: Chlorpheniramine competitively antagonizes histamine at H1 receptors, reducing the effects of histamine release in allergic reactions.
Alternate Names
Chlorphenamine, Chlorpheniramine. Brand names vary depending on the specific formulation and region. One example from the UK is “Piriton.”
How It Works
- Pharmacodynamics: Chlorpheniramine binds to H1 receptors, preventing histamine from binding and exerting its effects like vasodilation, increased vascular permeability, and smooth muscle contraction. It also possesses anticholinergic properties which contribute to some of its side effects.
- Pharmacokinetics:
- Absorption: Readily absorbed from the gastrointestinal tract.
- Metabolism: Extensively metabolized in the liver, primarily by CYP450 enzymes.
- Elimination: Excreted primarily in urine, with some elimination through feces.
- Mode of Action: Competitive inhibition of histamine at H1 receptors.
- Receptor Binding: Binds to H1 histamine receptors.
- Elimination Pathways: Primarily renal excretion with hepatic metabolism.
Dosage
Dosage information provided below pertains specifically to chlorpheniramine maleate. The presence of citric acid as a buffering agent doesn’t usually impact the standard dosing of chlorpheniramine.
Standard Dosage
Adults:
Tablets: 4 mg every 4-6 hours, not to exceed 24 mg in 24 hours. Extended-release formulations have varying dosages (e.g., 8-12 mg every 8-12 hours). Liquid formulations typically contain 2 mg/5 mL, with a recommended adult dose of 10 mL every 4-6 hours, not exceeding 60 mL in 24 hours.
Children:
Dosing depends on age and weight and should always be guided by a doctor’s recommendation. Not generally recommended for children under 2. Children aged 2-5 years: 1 mg every 4-6 hours, not exceeding 6 mg daily. Children aged 6-11 years: 2 mg every 4-6 hours, not exceeding 12 mg daily.
Special Cases:
- Elderly Patients: Reduced doses are often recommended due to increased sensitivity to side effects. Start with a lower dose (e.g., 4 mg every 6-8 hours) and titrate up if needed, not exceeding 12 mg daily.
- Patients with Renal Impairment: Dose adjustment may be necessary. Consult a doctor for specific recommendations.
- Patients with Hepatic Dysfunction: Dose reduction may be needed. Consult a doctor for specific recommendations.
- Patients with Comorbid Conditions: Use with caution in patients with cardiovascular disease, hypertension, glaucoma, prostatic hypertrophy, or urinary retention.
Clinical Use Cases
The combination of chlorpheniramine maleate and citric acid isn’t typically used in specific medical settings like intubation, surgery, or intensive care. Chlorpheniramine is primarily used for symptom relief in outpatient settings.
Dosage Adjustments
Dose modifications should be based on individual patient factors including renal and hepatic function, age, and other medical conditions.
Side Effects
Common Side Effects
Drowsiness, dry mouth, blurred vision, constipation, dizziness.
Rare but Serious Side Effects
Severe allergic reactions (anaphylaxis), seizures, difficulty urinating, heart palpitations.
Long-Term Effects
Chronic use may lead to tolerance and reduced efficacy.
Adverse Drug Reactions (ADR)
Severe allergic reactions, cardiac arrhythmias, hepatotoxicity (rare).
Contraindications
Hypersensitivity to chlorpheniramine, narrow-angle glaucoma, urinary retention, severe hypertension or coronary artery disease, concomitant or recent MAOI use.
Drug Interactions
Alcohol, other CNS depressants (sedatives, tranquilizers, hypnotics), MAOIs, anticholinergic drugs (atropine).
Pregnancy and Breastfeeding
Limited data exists on the effects during pregnancy. Should only be used if the potential benefit outweighs the potential risk to the fetus. Small, occasional doses of chlorpheniramine are considered acceptable during breastfeeding, though non-sedating antihistamines are preferred.
Drug Profile Summary
- Mechanism of Action: Competitive H1 receptor antagonist.
- Side Effects: Drowsiness, dry mouth, blurred vision, constipation, dizziness.
- Contraindications: Hypersensitivity, glaucoma, urinary retention, severe hypertension, MAOI use.
- Drug Interactions: Alcohol, CNS depressants, MAOIs, anticholinergics.
- Pregnancy & Breastfeeding: Use with caution.
- Dosage: Adult: 4 mg every 4-6 hours (max 24mg/day). Child: age-dependent.
- Monitoring Parameters: Monitor for side effects, especially drowsiness.
Popular Combinations
Chlorpheniramine is sometimes combined with decongestants (like phenylephrine) or analgesics (like paracetamol) in cold and flu medications.
Precautions
Caution in patients with cardiovascular disease, hypertension, glaucoma, prostatic hypertrophy, urinary retention, hepatic or renal impairment. Avoid alcohol. May impair alertness; caution advised when operating machinery.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Chlorpheniramine Maleate + Citric Acid?
A: The dosage of chlorpheniramine is not usually affected by the presence of citric acid. Adults: 4 mg every 4-6 hours (max 24mg/day). Child: age-dependent.
Q2: What are the common side effects?
A: Drowsiness, dry mouth, blurred vision, constipation, dizziness.
Q3: Can I take this medication while pregnant or breastfeeding?
A: Consult a doctor before use during pregnancy or breastfeeding.
Q4: What are the potential drug interactions?
A: Alcohol, CNS depressants, MAOIs, anticholinergic drugs.
Q5: Is it safe to drive after taking this medication?
A: May cause drowsiness. Use caution when driving or operating machinery.
Q6: How should this medication be stored?
A: Store at room temperature, away from moisture and heat.
Q7: What should I do if I miss a dose?
A: Take the missed dose as soon as you remember, unless it is close to the time for the next dose.
Q8: What are the signs of an allergic reaction to chlorpheniramine?
A: Rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
Q9: Can children take this medication?
A: Yes, but with dosage adjustments based on age and weight. Not recommended for children under 2 years.
Q10: Can I take this medication if I have glaucoma?
A: No, chlorpheniramine is contraindicated in patients with narrow-angle glaucoma.
