Pheniramine Maleate (Avil) Intramuscular Dosing
For intramuscular administration of pheniramine maleate (Avil), the recommended dose is 1-2 mg/kg per dose with a maximum of 50 mg for both adults and children. 1
Dosing Specifications
- Standard IM dose: 1-2 mg/kg per dose (maximum initial dose: 50 mg) 1
- This dosing applies to acute hypersensitivity reactions and allergic conditions 1
- The same dose range is used whether administering intramuscularly or intravenously 1
Critical Safety Considerations
Pheniramine maleate should NEVER be used as monotherapy in anaphylaxis. 1 The following hierarchy must be followed:
- Epinephrine is always first-line for anaphylaxis treatment 2, 1
- Pheniramine serves only as second-line adjunctive therapy after epinephrine has been administered 1
- Intramuscular epinephrine into the lateral thigh (vastus lateralis) achieves peak plasma concentrations in 8 ± 2 minutes, making it the preferred route for anaphylaxis 2
Enhanced Efficacy Strategy
Combination therapy with H2-blockers is superior to H1-antihistamine alone for acute hypersensitivity reactions. 1 Consider adding:
- Ranitidine 1 mg/kg diluted in 20 mL D5W administered over 5 minutes 1
- This combination approach provides more comprehensive histamine receptor blockade 1
Monitoring Requirements
Continuous monitoring is mandatory during and after pheniramine administration:
- Monitor oxygen saturation continuously 1
- Assess respiratory effort closely, as respiratory suppression and apnea can occur 1
- Watch for paradoxical excitement or agitation 1
- Be particularly vigilant when pheniramine is combined with benzodiazepines or opioids, as respiratory depression risk increases 1
Common Pitfalls to Avoid
- Never use pheniramine as sole treatment in anaphylaxis - epinephrine must be given first 1
- Never combine with other CNS depressants without enhanced respiratory monitoring 1
- Be aware that while IM administration avoids the seizure risk associated with rapid IV push, the same dose range applies to both routes 1
Route Comparison Context
While the question specifically asks about IM dosing, it's worth noting that IM administration generally provides safer administration compared to IV for pheniramine, as it avoids the risks of rapid IV push (seizures, hypotension) while still achieving therapeutic effect. 1, 3 The absorption from IM sites occurs over hours rather than minutes, providing a more gradual onset. 4