a chemical closely resembling amphetamine which is used in some over-the counter appetite control products. Although it has milder side effects that amphetamine, phenylpropanolamine can, after prolonged use, cause depletion of brain norepinephrine (NE) and possible depression. Phenylalanine is a natural precursor to NE, and its use as an appetite inhibitor does not result in NE depletion.