Avil

# Avil ## Overview - **Classification**: First-generation antihistamine, alkylamine derivative. - **Mechanism**: Competitively blocks H1-receptors, reducing histamine's effects. Also has significant anticholinergic and moderate sedative properties. ## Primary Indications 1. **Allergic Conditions**: Symptomatic relief of allergic rhinitis, conjunctivitis, urticaria, angioedema. 2. **Pruritus**: Relief of itching associated with various dermatological conditions. 3. **Motion Sickness**: Prophylaxis and treatment. 4. **Adjunct in Anaphylaxis**: Used *after* epinephrine to control cutaneous symptoms. ## Adult Dosing ### Standard Dosing **Allergic Conditions/Pruritus** - **Dose**: **25-50 mg** - **Frequency**: Every **4-6 hours** as needed - **Route**: Oral, IM, or slow IV injection - **Maximum**: Oral **300 mg/day**, Parenteral **100 mg/day** **Motion Sickness** - **Dose**: **25-50 mg** - **Frequency**: **30-60 minutes before travel**, then every **6-8 hours** as needed. - **Route**: Oral **Adjunct in Anaphylaxis** - **Dose**: **10-20 mg** - **Frequency**: Single dose (after epinephrine) - **Route**: Slow IV injection or IM ### Dose Adjustments - **Renal Impairment**: Use with caution. Consider reduced frequency/dose for **CrCl < 30 mL/min**. - **Hepatic Impairment**: Use with caution. Dose reduction may be necessary due to impaired metabolism. - **Elderly Patients**: More susceptible to anticholinergic and CNS effects. Start with lower doses (e.g., **12.5 mg**) and titrate carefully. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: **Contraindicated**. - **Special Notes**: Risk of respiratory depression and severe CNS effects. ### Infants (1-12 months) - **Not generally recommended**: Limited data and high risk of adverse effects. - **If used under strict medical supervision**: **1 mg/kg/day** divided **3-4 times/day**. - **Maximum**: **20 mg/day**. ### Children (1-12 years) - **Allergic Conditions/Pruritus** - **Dose**: **0.5-1 mg/kg/day** - **Frequency**: Divided into **3-4 doses** (e.g., every **6-8 hours**). - **Maximum**: **25 mg/dose** or **75 mg/day**. - **Special Notes**: Oral solution/syrup preferred for dosing. ### Adolescents (13-18 years) - **Dose**: Follow **adult dosing** (**25-50 mg**). - **Frequency**: Every **4-6 hours** as needed. - **Maximum**: Initially **75 mg/day**, can approach adult max of **300 mg/day** based on tolerance. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to pheniramine. - **Absolute**: Newborns, premature infants. - **Absolute**: Acute asthma attacks, lower respiratory tract symptoms. - **Relative**: Angle-closure glaucoma, prostatic hypertrophy with urinary retention. - **Relative**: Concurrent use with MAO inhibitors. ### Common Adverse Effects - **Very Common (>10%)**: Drowsiness, sedation, dizziness. - **Common (1-10%)**: Dry mouth, blurred vision, urinary retention, constipation. - **Common (1-10%)**: Thickening of bronchial secretions. - **Serious but Rare**: Paradoxical excitation (children), seizures, arrhythmias, blood dyscrasias. ### Key Drug Interactions - **CNS Depressants (Alcohol, Opioids, Benzodiazepines)**: Potentiated sedation and CNS depression. Avoid concomitant use. - **Anticholinergics (TCAs, Atropine, MAOIs)**: Increased risk of anticholinergic side effects (e.g., dry mouth, urinary retention). - **MAO Inhibitors**: Prolongs and intensifies anticholinergic and CNS depressant effects. Contraindicated. ## Monitoring & Follow-up - **Before Treatment**: Assess for history of glaucoma, prostatic hypertrophy, or respiratory disease. - **During Treatment**: Monitor for excessive sedation, dizziness, or paradoxical excitation. - **Clinical Signs**: Observe for blurred vision, difficulty urinating, or severe drowsiness. ## Clinical Pearls - 💡 **Sedation**: Warn patients about significant drowsiness; avoid driving or operating machinery. - 💡 **Timing for Motion Sickness**: Administer **30-60 minutes** before anticipated travel. - 💡 **Alcohol Avoidance**: Advise patients to avoid alcohol due to additive CNS depression. - 💡 **Pediatric Caution**: Use extreme caution in young children due to unpredictable CNS effects, including paradoxical excitation. - 💡 **Anticholinergic Effects**: Counsel on managing dry mouth, e.g., sips of water, sugar-free candies. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.