Ephedrine is primarily an indirect sympathomimetic that causes the release of endogenous catecholamines (i.e., norepinephrine). Its uses extend from traditional Chinese medicine as an anti-asthmatic to recreational use due to its structural similarity to methamphetamine. I administer ephedrine boluses of 5-10 mg intravenously to offset hypotension in the ICU and OR. Often this medication is given in addition to or as a substitute for phenylephrine when the heart rate is “low” as ephedrine tends to increase the blood pressure and heart rate.

Because of its mechanism, prolonged use of ephedrine can result in diminished efficacy over time (tachyphylaxis). This is due to a depletion of norepinephrine-containing vesicles from their usual storage sites at the neuronal synaptic cleft.

I also give 20-30 mg of intramuscular ephedrine before spinal anesthetics to promote hemodynamic stability as the neuraxial anesthetic knocks out parts of the sympathetic outflow. I always give this injection in the thigh since any residual discomfort should disappear once the spinal is in place.

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