Taffy Makaya, Rebecca Poole and Kavitha Rozario
96
12 weeks), due to concerns regarding the potential addictiveness of
Phentermine [79]. Although approval of Phentermine preceded the FDA’s
requirements for obesity drugs published in 2007, Phentermine remains
approved and is used widely in the USA, where it is the most commonly
prescribed obesity medication in adults [80]. Despite being only approved by
the FDA for short term use in obesity, Phentermine is commonly taken by
patients for longer periods off label. However, despite its widespread use,
there are limited studies investigating the long-term effects of Phentermine on
weight and risk factors for cardiovascular disease. Meta-analysis of the results
of 6 separate studies following patients up from 2 to 24 weeks showed that
taking 15-30mg of Phentermine per day could reduce weight by an average of
3.6 kg compared to placebo [80]. One study investigating the use of
Phentermine either continuously or intermittently for a longer period of 36
weeks in obese adult female patients, showed a weight loss of 12.2kg in
participants taking the drug continuously and 13.0kg in participants taking
Phentermine intermittently, compared to weight loss of 4.8kg with placebo.
However this study was widely criticised for potentially misleading analysis,
presenting data for only participants completing the trial [81]. Side effects of
Phentermine include insomnia, irritability and anxiety, altered taste, dizziness,
tremors and restlessness, as well as changes in pulse and blood pressure [43,
81].
Diethylpropion
Diethylpropion has been shown to have a similar effect to Phentermine,
but is less commonly prescribed. A meta-analysis of 9 small studies
investigating Diethylpropion use for 6-52 weeks found that use of
Diethylpropion 75mg/day was associated with an average weight loss of 3.0kg
compared to placebo [82].
Phendimetrazine
Although there is poorer trial data supporting use of Phendimetrazine, it is
used more widely than Diethylpropion for treatment of obesity in adults.
Observations of Phendimetrazine in the 1960s showed a comparable weight
loss to other noradrenergic drugs [83, 84].
Benzphetamine
Benzphetamine is the least commonly prescribed FDA approved
noradrenergic drug in the treatment of adult obesity in the USA.
Benzphetamine is also the least investigated, with a poor evidence base for its