Sympathetic alpha-adrenergic agonist with actions like PHENYLEPHRINE. It is used as a vasoconstrictor in circulatory failure, asthma, nasal congestion, and glaucoma. Synephrine (or oxedrine) is a drug commonly used for weight loss. While its effectiveness is widely debated, synephrine has gained significant popularity as an alternative to ephedrine, a related substance which has been made illegal or restricted in many countries due to its use as a precursor in the illicit manufacture of methamphetamine. Products containing bitter orange or synephrine: suspected cardiovascular adverse reactions [citation needed]. Synephrine is derived primarily from the fruit of Citrus aurantium, a relatively small citrus tree, of which several of its more common names include Bitter Orange, Sour Orange, and Zhi shi.; There has been some confusion surrounding synephrine and phenylephrine (neosynephrine), one of its positional isomers. The chemicals are similar in structure; the only difference is the location of the aromatic hydroxyl group. In synephrine, the hydroxyl is at the para position, whereas, in neosynephrine, it is at the meta position. Each compound has differing biological properties.; p-Synephrine is an endogenous amine in plasma, in variable levels with a tendency to be higher in hypertensive patients (PMID 8255371)