Synephrine is a drug that is deemed to selectively bind to and also activate alpha adrenergic receptors. Mainly used as a vasoconstrictor in asthma, glaucoma, circulatory failure and nasal congestion, this compound is currently propagated as a weight loss agent. The alleged function synephrine is providing include fat burning, energy level and metabolism increase and promotion of weight loss. Synephrine, also known as oxedrine, is the widely accepted replacement for ephedrine. The natural source of synephrine is the citrus aurantium fruit, better known as bitter orange. Bitter orange extracts, which contain synephrine, are known to stimulate the alpha-1 adrenergic receptor, thereby constricting blood vessels and increasing the heart rate as well as blood pressure, effecting in an increased energy use.