Pharmacokinetics of Epinephrine

Epinephrine is well absorbed and has rapid onset of action following parenteral administration, e.g., when injected in combination with LAs or when administered IM into the vastus lateralis muscle (i.e., anterolateral aspect of the thigh) using an auto-injector.4 Following administration with LAs, epinephrine reaches peak plasma concentrations in 5-10 minutes; when using an auto-injector, it reaches peak plasma concentrations in 8±2 minutes.4,10-13

Epinephrine is distributed to most tissues: it crosses the placenta, it is secreted into milk, but it does not cross the blood-brain barrier.4 Epinephrine is rapidly cleared from the extracellular fluid by uptake into sympathetic postganglionic neurons, where it is mainly stored; and by uptake into liver cells, where it is inactivated primarily by catechol-O-methyltransferase and monoamine oxidase and excreted in the urine.4 The elimination half-life of epinephrine is ≈2 minutes.14