empowered to put pressure on manufacturers, who voluntarily withdrew it from the market. Amphetamines (marketed as Benzedrine) became popular for weight loss during the late 1930s. They worked primarily by suppressing appetite, and had other beneficial effects such as increased alertness. Use of amphetamines increased over the subsequent decades, including Obetrol and culminating in the "rainbow diet pill" regime. This was a combination of multiple pills, all thought to help with weight loss, taken throughout the day. Typical regimens included stimulants, such as amphetamines, as well as thyroid hormone, diuretics, digitalis, laxatives, and often a barbiturate to suppress the side effects of the stimulants. In 1967/1968 a number of deaths attributed to diet pills triggered a Senate investigation and the gradual implementation of greater restrictions on the market. While rainbow diet pills were banned in the US in the late 1960s, they reappeared in South America and Europe in the 1980s. Eventually rainbow diet pills were re-introduced into the US by the 2000s and led to additional adverse health effects. In 1959, phentermine had been FDA approved and fenfluramine in 1973. The two were no more popular than other medications until in 1992 a researcher reported that when combined the two caused a 10% weight loss which was maintained for more than two years. Fen-phen was born and rapidly became the most commonly prescribed diet medication. Dexfenfluramine (Redux) was developed in the mid-1990s as an alternative to fenfluramine with fewer side-effects, and received regulatory approval in 1996. However, this coincided with mounting evidence that the combination could cause valvular heart disease in up to 30% of those who had taken it, leading to withdrawal of Fen-phen and dexfenfluramine from the market in September 1997. Medical complications included fatal pulmonary hypertension and heart valve damage due to Redux and Fen-phen, and hemorrhagic stroke due to phenylpropanolamine. Since the introduction of medicines for the management of obesity in the 1930s, many compounds have been tried. Most of them reduce body weight by small amounts, and several of them are no longer marketed for obesity because of their side effects. Out of 25 anti-obesity medications withdrawn from the market between 1964 and 2009, 23 acted by altering the functions of chemical neurotransmitters in the brain. The most common side effects of these drugs that led to withdrawals were mental disturbances, cardiac side effects, and drug abuse or drug dependence. Deaths were reportedly associated