r/pharmacology • u/nowlistenhereboy • Jun 14 '21

What is the reason why intravenous epinephrine must be diluted more than intramuscular in the setting of cardiac arrest?

Just curious what the physiological reason is that 1:1000 epinephrine is not to be used for cardiac arrest/active CPR.

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u/[deleted] Jun 14 '21

A more concentrate formulation allows for a smaller volume in muscle which is easier to administer.

A long slower infusion is required IV to reduce fatal hypertension, pulmonary and cerebral edema. For example 0.5ml of 1:10,000 IV for anaphylaxis is easier to administer safely than 0.05ml 1:1000. For cardiac events approx 10ml 1:10,000 is infused slowly which is safer and easier than 1ml 1:1000, especially when dose volume isn't a concern.

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u/JustHere2CorrectYou Jun 14 '21

Why do you reference 0.5ml of 1:10,000 IV, which would be 50mcg, for anaphylaxis? Are you talking about it as a push dose pressor? The IM treatment dose is 0.3-0.5mg, 50mcg is off by an order of magnitude.

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u/[deleted] Jun 15 '21

IV administration of adrenaline is not recommended but can be an alternative if IM is ineffective. The recommendation is to slowly titrate 0.5mL 10,000. You are right if repeated doses are required then infusion should be performed.

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https://www.medicines.org.uk/emc/product/3675/smpc#gref

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u/JustHere2CorrectYou Jun 15 '21

Thanks for this. I’ve never seen recommendations regarding single push doses of IV epi in anaphylaxis before.