Updated March 25, 2015.
Written or reviewed by a board-certified physician. See About.com's Medical Review Board.
If you are thinking about taking a prescription diet pill, there are several medications that your doctor might prescribe. One of the most widely used weight loss medications is Adipex-P (phentermine hydrochloride). But just because the product is popular, doesn't necessarily mean that it is the right diet pill for you.
What Is Adipex-P?
Adipex-P is the brand name for a medication called phentermine.
Phentermine works to decrease appetite and speed weight loss in people who are also following a low-calorie diet and exercise program. The diet pill is generally prescribed for people with a body mass index (BMI) of 30 or more or for those with a BMI of 27 or more and who also have a weight-related risk factor like diabetes, high cholesterol or controlled high blood pressure.
Many patients who take Adipex-P to lose weight take one 37.5 mg tablet or capsule in the morning before breakfast. But your doctor will recommend the best dose for you based on your personal health profile. According to the National Institutes of Health, the average weight loss for patients on medications like Adipex-P is 5.8 pounds. But they also note that not everyone loses weight with the diet pill and most people will regain the weight if they don't make permanent changes to their diet and lifestyle.
Adipex-P: Side Effects and Risks
Dieters who take Adipex-P may experience side effects including depression, nervousness, problems sleeping, dry mouth, constipation, unpleasant taste, diarrhea or vomiting.
The NIH also reports that some patients taking Adipex-P may experience more serious problems including increased blood pressure, heart palpitations, dizziness, tremors, shortness of breath, chest pain, swelling of the legs and ankles or difficulty doing exercises that you can usually do.
Some people should not take Adipex-P including patients with a history of cardiovascular disease, hyperthyroidism, glaucoma, drug abuse or agitation, or a known sensitivity to sympathomimetic amines. Women who are pregnant or nursing should also avoid taking Adipex-P to lose weight.
Should I Buy Adipex-P Online?
Because Adipex-P is one of the more popular drugs to lose weight, you'll find many online sources that claim to sell Adipex-P or drugs like Adipex-P. Keep in mind that you need a prescription to get this medication. Many of the companies that sell pills "like Adipex-P" without a prescription have not been verified by the FDA for safety or effectiveness.
Because this drug can be habit-forming and because you may experience side effects while taking Adipex-P, you should visit your own doctor and review your full health history before you decide to use the medication. If you decide to try the diet medication buy it from a trusted pharmacy. Then communicate with your doctor about any side effects you experience and about whether or not the Adipex-P is helping you to lose weight.
Sources
Adipex-P Prescribing Information. U.S. Food and Drug Administration. Accessed: March 17, 2015. http://www.accessdata.fda.gov/drugsatfda_docs/label/2012/088023s037lbl.pdf
MedlinePlus. Phentermine. U.S. National Library of Medicine National Institutes of Health. Accessed: March 17, 2015. http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682187.html
MedlinePlus. Weight Loss Medications. U.S. National Library of Medicine National Institutes of Health. Accessed: March 17, 2015. http://www.nlm.nih.gov/medlineplus/ency/patientinstructions/000346.htm