Phentermine
Phentermine (phenyl-tertiary-butylamine), with several brand names including Ionamin and Sentis, is a medication used together with diet and exercise to treat obesity. It is taken by mouth for up to a few weeks at a time, after which the benefits subside. It is also available as the combination phentermine/topiramate.
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| Trade names | Adipex-p, Duromine, Metermine, Suprenza, others |
| Other names | α-methyl-amphetamine α,α-dimethylphenethylamine |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682187 |
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| Dependence liability | Limited |
| Addiction liability | Low |
| Routes of administration | By mouth |
| Drug class | Appetite suppressant |
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| Pharmacokinetic data | |
| Bioavailability | High (almost complete) |
| Protein binding | Approximately 96.3% |
| Metabolism | Liver |
| Elimination half-life | 25 hours, urinary pH-dependent |
| Excretion | Urinary (62–85% unchanged) |
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| ECHA InfoCard | 100.004.112 |
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| Formula | C10H15N |
| Molar mass | 149.237 g·mol−1 |
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Common side effects include a fast heart beat, high blood pressure, trouble sleeping, dizziness, and restlessness. Serious side effects may include abuse, but do not include pulmonary hypertension or valvular heart disease, as the latter were caused by the fenfluramine component of the fen-phen drug combination. Use is not recommended during pregnancy or breastfeeding, or with SSRIs or MAO inhibitors. It works mainly as an appetite suppressant, likely as a result of being a CNS stimulant. Chemically, phentermine is a substituted amphetamine.
Phentermine was approved for medical use in the United States in 1959. It is available as a generic medication. In 2020, it was the 181st most commonly prescribed medication in the United States, with more than 3 million prescriptions. Phentermine was withdrawn from the market in the United Kingdom in 2000, while the combination medication fen-phen, of which it was a part, was withdrawn from the market in 1997 due to side effects of fenfluramine which caused increased levels of circulating serotonin which stimulated serotonin receptors on heart valves and thus causing valve insufficiency and leading to primary pulmonary hypertension (PPH). According to the NIH (National Institutes of Health) there is no evidence that phentermine causes PPH.