What is the recommended dosage of Avil (Pheniramine) injection?

Dosage of Avil (Pheniramine) Injection

For acute hypersensitivity reactions and dystonic reactions, administer pheniramine (Avil) at 1-2 mg/kg IV or IM, with a maximum initial dose of 50 mg. 1, 2

Administration Guidelines

Standard Dosing

• Adults and children: 1-2 mg/kg per dose IV or IM 1, 2
• Maximum initial dose: 50 mg 1, 2
• Route preference: Both IV and IM routes are acceptable; IM may be used when IV access is not immediately available 2

IV Administration Technique

• Administer slowly over 2-3 minutes to avoid pain at the injection site and reduce seizure risk 2
• Maintain IV access after administration for potential additional interventions 1

Clinical Context and Role in Therapy

Pheniramine serves as adjunctive second-line therapy, never as monotherapy for anaphylaxis. 2 Epinephrine must always be administered first in anaphylactic reactions, followed by fluid resuscitation, before considering antihistamines 1, 2.

Combination Therapy

• When used with H2-blockers (ranitidine 50 mg IV or 1 mg/kg in children), the combination is superior to H1-antihistamines alone 1, 2
• Ranitidine should be diluted in 5% dextrose to 20 mL total volume and injected IV over 5 minutes 1

Critical Safety Considerations

Common and Serious Adverse Effects

• Sedation: Most common side effect; anticipate and monitor 2
• Respiratory suppression: Particularly when combined with other sedative agents; be prepared to provide respiratory support 1, 2
• Hypotension: May occur, especially with rapid administration 1, 2
• Paradoxical excitement or agitation: Especially in younger children 1, 2

Monitoring Requirements

• Monitor vital signs and oxygen saturation continuously during and after administration 2
• Be prepared to support ventilation if respiratory depression occurs 1, 2
• Watch for paradoxical agitation, particularly in pediatric patients 2

Contraindications and Precautions

Absolute Contraindications

• Angle-closure glaucoma 2, 3
• Prostatic hypertrophy with urinary retention 2, 3
• Severe hepatic disease (sedative effects may precipitate hepatic coma) 2, 3

Drug Interactions to Avoid

• MAOIs: Avoid concomitant use 2, 3
• Other anticholinergic medications: Risk of additive toxicity 2, 3
• Other sedative agents: Increased risk of respiratory suppression 1, 2

Special Populations

• Pregnancy: Avoid, especially during first trimester 2, 3
• Lactation: Should be avoided 2, 3
• Elderly: Start with lower doses due to increased sensitivity to anticholinergic effects 2
• Renal impairment: Consider dose reduction in moderate renal insufficiency 3

Common Clinical Pitfalls

• Never use as monotherapy for anaphylaxis - epinephrine is the first-line treatment 2
• Avoid rapid IV push - increases risk of seizures and injection site pain 2
• Do not combine with multiple sedating agents without preparation for respiratory support 1, 2
• Monitor for delayed respiratory depression - effects may persist beyond initial administration 2