EpiPen Dose for 222 lbs (100.91 kg) Adult
An adult weighing 222 lbs (100.91 kg) should use the 0.3 mg EpiPen (or 0.3-0.5 mg of intramuscular epinephrine 1:1000 solution). 1
Dosing Rationale
The FDA-approved dosing for epinephrine in anaphylaxis is straightforward for adults:
Adults and children ≥30 kg (66 lbs): 0.3 to 0.5 mg (0.3-0.5 mL of 1:1000 solution) administered intramuscularly in the anterolateral thigh, with a maximum of 0.5 mg per injection 1
Your patient at 100.91 kg far exceeds the 30 kg threshold, making the 0.3 mg autoinjector the appropriate choice, or up to 0.5 mg if using a manual syringe 1
Administration Details
Route and location matter significantly for efficacy:
Inject intramuscularly into the anterolateral aspect of the thigh (vastus lateralis), which achieves peak plasma concentrations in 8±2 minutes compared to 34±14 minutes with subcutaneous deltoid injection 2
The injection can be administered through clothing if necessary to avoid delay 1
Use a needle at least 1/2 to 5/8 inch long to ensure intramuscular delivery 1
Repeat Dosing Protocol
Be prepared to repeat the dose:
Repeat injection every 5-10 minutes if symptoms fail to resolve or worsen 2, 1
Approximately 6-28% of patients require a second dose 2
Do not inject repeatedly at the same site, as vasoconstriction may cause tissue necrosis 1
Monitor clinically for reaction severity and cardiac effects between doses 1
Critical Safety Points
The maximum single dose is capped despite body weight:
Even though the standard pediatric dose is 0.01 mg/kg (which would theoretically be 1.0 mg for a 100 kg patient), the maximum single dose for adults is 0.5 mg 1
This cap exists because higher doses increase cardiac adverse effects without improving outcomes 3
Common pitfall to avoid:
Never confuse epinephrine concentrations: Use 1:1000 (1 mg/mL) for intramuscular anaphylaxis treatment, NOT 1:10,000 which is reserved for IV cardiac arrest 4
Using the wrong concentration can lead to potentially fatal overdose or underdose 4
Concurrent Management
Epinephrine is first-line, but not the only intervention:
Call 911 immediately and position the patient supine with legs elevated; never allow standing or walking as this increases mortality risk 2
Supplemental oxygen, IV fluids (1000-2000 mL normal saline bolus for adults), antihistamines, and corticosteroids may be necessary as adjunctive therapy 2
Transport to emergency department via EMS for observation even if symptoms resolve 2
The intramuscular route is safer than IV epinephrine for first-line treatment, as IV administration carries significant risk of dilution/dosing errors and serious cardiac adverse effects 2