Stimulation of alpha-1-adrenergic smooth muscle receptors within vasculature results in a rise in systemic vascular resistance and, consequently, systolic and diastolic blood pressure. It is, therefore, effective in elevating central venous pressure when the patient is challenged with fluids. While the indirect effect is most profound on arterial blood pressure, the direct vasoconstricting action functions more on the venous system. Įphedrine’s indirect mechanism results in a sustained or even increased heart rate due to norepinephrine’s ability to bind alpha and beta receptors, whereas more direct sympathomimetics like phenylephrine results in reflex bradycardia. This action allows norepinephrine to remain in the synapse longer to bind postsynaptic alpha and beta receptors. It binds directly to both alpha and beta receptors however, its primary mode of action is indirectly achieved by inhibiting neuronal norepinephrine reuptake and displacing more norepinephrine from storage vesicles. Ephedrine acts as both a direct and indirect sympathomimetic. Įphedrine, a stereoisomer to better-known pseudoephedrine, is a sympathomimetic amine with unique effects due to its indirect mechanism than other sympathomimetic agents like pseudoephedrine and phenylephrine. Lastly, case reports demonstrate using ephedrine to alleviate bronchoconstriction during induction for patients on beta-blocker maintenance therapy. Patients with myasthenia gravis may also benefit from treatment with ephedrine however, evidence for its specific mechanism of action and benefit in this disease has not come from randomized controlled trials, and only observational and non-randomized trials are currently available. However, ephedrine lost favor as a supplement after research established links to ventricular arrhythmias, nausea, and psychiatric issues with use. In the early 2000s, the drug became very popular among over-the-counter supplements because it was found to work synergistically with caffeine to promote weight loss by stimulating metabolism. Other off-label indications include bronchoconstriction, myasthenia gravis, and weight loss(in the past). Oral formulations of ephedrine have been used historically to treat asthma via pulmonary vasoconstriction and reduction in airway edema along with beta-induced bronchodilation, but it is rarely used for this purpose in modern medicine due to unwanted cardiac effects and availability of more selective beta-agonists such as albuterol. Ephedrine is also available in a fixed-dose combination with guaifenesin to temporarily relieve mild asthma symptoms with an expectorant. Due to the constriction of smooth muscle via alpha receptor binding and bronchi dilation due to beta-2 receptor agonism, most sympathomimetics, including ephedrine, work effectively to decrease allergic symptoms. Most vasopressors used during anesthesia should be viewed as a temporizing measure while determining and addressing the source of hypotension.Īnother notable indication of ephedrine is for allergy relief. Since ephedrine results in both alpha and beta-adrenoreceptor stimulation, it is most beneficial in the setting of hypotension along with bradycardia or a low-normal heart rate, and caution is necessary for patients with hypotension and coexisting tachycardia. However, in the absence of maternal bradycardia, phenylephrine is preferred. According to the American Society of Anesthesiologists Committee Task Force on obstetric anesthesia, ephedrine or phenylephrine can be utilized to treat hypotension during neuraxial anesthesia. It is sometimes given intramuscularly to achieve a longer-lasting effect. Although phenylephrine selection is due to fewer effects on umbilical arterial acidity, ephedrine is a frequent choice due to less alpha-adrenergic action on the uterine vasculature, which preserves uterine blood flow. In obstetrics, sympathectomy during spinal anesthetics results in hypotension in 80% of patients. It is also frequently the agent of choice for hypotension induced by spinal or epidural anesthesia. Induction of general and ongoing anesthesia during operative cases results in vasodilatation and hypotension, requiring treatment with vasopressors. The FDA-approved primary indication for ephedrine is the treatment of clinically significant hypotension perioperatively.

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