Phentermine is an appetite suppressant generally prescribed to obese patients, whose weight puts them at increased medical risk, for short-term use. It is meant to be combined with exercise and healthy dieting. Phentermine was approved by the FDA in 1959 and is currently sold as a generic drug; since it was originally approved, almost no clinical studies have tested its effectiveness.
Phentermine works by releasing norepinephrine in the brain, a neurotransmitter which reduces hunger by signaling a “fight of flight” response. The FDA recommends taking phentermine for up to twelve weeks.
Patients with certain conditions should consult a doctor before using phentermine: women who are breast-feeding, pregnant, or plan to become pregnant; anyone with an allergy to ingredients used in phentermine or other sympathomimetics, like pseudoephedrine; those with glaucoma, heart or blood vessel disease, high blood pressure, diabetes, high cholesterol, or an overactive thyroid; and those with a history of substance abuse. Americans are able to buy phentermine online from select websites that are permitted to resale the diet pill.
Side effects associated with phentermine are generally understood to be relatively mild and tolerable. The most common side effects include the possibility of insomnia, hypertension, nervousness, irritability, euphoria, clumsiness, increased libido in women, confusion, headache, nausea or vomiting, dizziness, stomach pain, diarrhea, and fatigue.
Meridia is a brand name for sibutramine; like phentermine, it was also, until recently, an appetite suppressant used in conjunction with exercise and diet for over-weight patients. The FDA approved Sibutramine as a treatment for obesity in 1997 but it has since been linked with strokes and increased cardiovascular events. Sibutramine has been removed from the market in the US, the EU, the UK, Canada, and Australia.
While phentermine is an oral anorexiant of the amphetamine class, sibutramine is a serotonin-norepinephrine reuptake inhibitor. Structurally, sibutramine is related to amphetamines, but its mechanism of action is different. While amphetamines, such as phentermine, force the release of neurotransmitters, as indicated above, sibutramine works by affecting the neurotransmitter’s reuptake. Sibutramine reduces the reuptake of dopamine by 16%, serotonin by 53%, and norepinephrine by 54%.
Sibutramine was sold under a variety of brand names; along with Meridia, it was sold as Sibutrex and Reductil. Abbott Laboratories was the sibutramine manufacturer at the point of its market withdrawal but, originally, sibutramine was marketed by Knoll Pharmaceuticals.
The most frequently observed side effects of sibutramine include dry mouth, increased appetite, nausea, constipation, joint and/or muscle pain, headache, and menstrual cramps. Sibutramine may also trigger more serious side effects, though these have been noted less commonly: these include a substantial increase in blood pressure and pulse, serious mood changes including depression and thoughts of suicide, and seizures.
Sibutramine has also been found to contraindicate in certain patients, including patients with serious depression or manias, patients with bulimia nervosa or anorexia nervosa, patients with a history of drug or alcohol abuse, patients who exhibit an insufficiently controlled hypertension, patients who have had or are at risk of seizures, patients with a history of coronary artery disease, pregnant or breast-feeding women, patients below 18 years old, and patients older than 65.