Pheniramine

# Pheniramine ## Overview - **Classification**: First-generation antihistamine, alkylamine derivative - **Mechanism**: Competitively blocks H1 receptors, reducing histamine effects. Also has anticholinergic, sedative, and mild local anesthetic properties. ## Primary Indications 1. **Allergic Rhinitis** - Symptomatic relief of sneezing, rhinorrhea, pruritus. 2. **Allergic Conjunctivitis** - Relief of itchy, watery eyes. 3. **Urticaria** - Management of allergic skin reactions and itching. ## Adult Dosing ### Standard Dosing **Allergic Symptoms (Rhinitis, Conjunctivitis, Urticaria)** - **Dose**: **25 mg** - **Frequency**: Every 4 to 6 hours - **Route**: Oral - **Maximum Dose**: **150 mg/day** ### Dose Adjustments - **Renal Impairment**: Use with caution. Consider reduced dose or extended interval due to renally cleared metabolites. - **Hepatic Impairment**: Use with caution. Consider lower doses due to hepatic metabolism. - **Elderly Patients**: More sensitive to anticholinergic effects (sedation, confusion, urinary retention). Start with **12.5 mg** every 4-6 hours, titrate cautiously. Max **75 mg/day**. ## Pediatric Dosing ### Neonates (0-28 days) - **Contraindicated**: Not recommended for use due to high risk of serious adverse effects including respiratory depression. ### Infants (1-12 months) - **Contraindicated**: Not recommended. Increased risk of respiratory depression, paradoxical excitation, and other serious CNS effects. ### Children (1-12 years) - **Note**: Generally **not recommended** for children under **2 years** for any indication, and caution advised for children under **6 years** in cold/cough products. If used for allergic symptoms in older children, use with extreme caution. - **Children (2-5 years)** (If specifically indicated by provider for allergy) - **Dose**: **6.25 mg** - **Frequency**: Every 4 to 6 hours - **Maximum**: **37.5 mg/day** - **Children (6-12 years)** - **Dose**: **12.5 mg** - **Frequency**: Every 4 to 6 hours - **Maximum**: **75 mg/day** ### Adolescents (13-18 years) - **Dose**: **25 mg** - **Frequency**: Every 4 to 6 hours - **Maximum**: **150 mg/day** ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to pheniramine or similar antihistamines - **Absolute**: Narrow-angle glaucoma - **Absolute**: Prostatic hypertrophy with urinary retention - **Absolute**: Acute asthma attack - **Absolute**: Not for use in neonates or infants (<2 years) ### Common Adverse Effects - **Very Common (>10%)**: Drowsiness, sedation, dizziness - **Common (1-10%)**: Dry mouth, blurred vision, urinary retention, constipation, headache - **Serious but Rare**: Paradoxical excitation (especially in children), seizures, arrhythmias, agranulocytosis ### Key Drug Interactions - **CNS Depressants (alcohol, opioids, benzodiazepines)**: Increased sedation and respiratory depression. - **Anticholinergics (TCAs, atropine)**: Potentiates anticholinergic effects (dry mouth, urinary retention). - **MAOIs**: May prolong and intensify anticholinergic effects of pheniramine. Avoid concurrent use. ## Monitoring & Follow-up - **Before Treatment**: Assess for contraindications (e.g., glaucoma, prostatic hypertrophy). - **During Treatment**: Monitor for symptom improvement and adverse effects (sedation, anticholinergic symptoms). - **Clinical Signs**: Watch for excessive drowsiness, confusion, difficulty urinating, or paradoxical excitation. ## Clinical Pearls - 💡 **Tip 1**: Advise patients to take at bedtime to minimize daytime sedation. - 💡 **Tip 2**: Counsel patients to avoid driving or operating heavy machinery until they know how the drug affects them. - 💡 **Tip 3**: Avoid alcohol and other CNS depressants due to additive sedative effects. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.