One of the newly approved drugs, Qsymia, is a combination of phentermine and topirimax, a drug for easing seizures and migraines that also tends to make people feel full. The other, Belviq, works on brain receptors for serotonin, a neurotransmitter than triggers feelings of satisfaction.
Physicians can legally prescribe medications for uses not specifically approved by the FDA. But most obesity doctors do so cautiously given the history of diet pills removed from the market due to serious side effects including death.
While some experts argue that people who are obese should simply eat less and exercise more, many physicians who treat obesity say it is driven by biological changes in the body, not just lack of willpower.
In trials of 3,700 obese and overweight patients, those who took Qsymia for one year lost 6% to 9% more of their body weight than those on a placebo. Nearly 70% lost at least 5% of their weight. With Belviq, of nearly 8,000 patients studied, those on the drug lost about 4% more than those on placebo. All were also counseled to exercise and eat a reduced calorie diet. The FDA says people who don’t lose at least 5% of their weight in 12 weeks should discontinue the drugs.
People who eat for emotional reasons tend to benefit less, although drugs can help clarify their motivations. “If you give a medication that makes them feel full, but they still keep eating, it becomes very clear that it really is emotional,” says Dr. Kushner, chairman of the American Board of Obesity Medicine.
The new drugs are FDA approved for patients with a body mass index of 30 or higher, or with a BMI of 27 and high blood pressure, diabetes, high cholesterol or sleep apnea. People with very large amounts of weight to lose may benefit more from bariatric surgery, or a combination, doctors say. The drugs aren’t covered by most insurance companies. They are expected to be available this fall.
Most of the drugs currently prescribed for weight loss suppress appetite by affecting neurotransmitters, which send signals in the brain. Stimulant medications are among the most powerful. The FDA approved several stimulants—including phendimetrazine (marketed as Bontril) and diethylpropion (Tenuate)—specifically for weight loss in 1959. They remain on the market today.
Drugs sometimes prescribed for weight loss work in various ways. Stimulants rev up the central nervous system. Antidepressant drugs such as buproprion (Wellbutrin) affect brain chemistry. The diabetes drug metformin (Glucophage) reduces the impact of blood sugar. Liraglutide (Victoza) boosts a gut hormone to promote fullness. The FDA-approved obesity drug orlistat (Xenical, Alli) blocks fat absorption.
Naltrexone (Depade, ReVia) blocks opiod receptors and makes food less appealing.
The best known is phentermine, half of the popular fen-phen combination in the 1990s until fenfluramine was linked to heart-value damage and discontinued in 1997. Because they are potentially addictive, phentermine and the others are approved for short-term use only. “But all of us use it long-term,” says Dr. Kushner. Dr. Hendricks, who says he has treated 15,000 patients with phentermine, alone and in combinations, over 23 years, and says that patients who keep taking it tend to maintain their weight loss. Drs. Aronne, Hendricks and Kushner all consult for drug makers.
ADHD drugs including Ritalin and Adderall also suppress appetite in some patients, but most obesity doctors use older generic stimulants. Patients with heart disease, high blood pressure, hyperthyroidism or glaucoma should not use stimulants.
The diabetes drug Metformin helps decrease the amount of sugar the body absorbs from food and increases the body’s response to insulin. Some patients can experience dangerously low blood sugar.
Why is Phentermine medication prescribed?
Phentermine is used for a limited period of time to speed weight loss in overweight people who are exercising and eating a low-calorie diet. Phentermine is in a class of medications called anorectics. It works by decreasing appetite.
How should Phentermine medicine be used?
Phentermine comes as tablets and extended-release capsules. It usually is taken as a single daily dose in the morning or three times a day 30 minutes before meals. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take phentermine exactly as directed.
Most people takephentermine for 3-6 weeks; the length of treatment depends on how you respond to the medication. Phentermine can be habit-forming. Do not take a larger dose, take it more often, or take it for a longer period than your doctor tells you to.
If you are taking the extended-release (long-acting) tablets, do not split, chew, or crush them tablet. There are some tablets that can be crushed and mixed with food.
Other uses for Phentermine medicine
This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.
What special precautions should I follow?
Before taking phentermine,
- tell your doctor and pharmacist if you are allergic to phentermine, any other medications, or any of the ingredients in phentermine tablets. Ask your pharmacist for a list of the ingredients.
- tell your doctor and pharmacist what prescription and nonprescription medications, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: fluoxetine (Prozac), fluvoxamine (Luvox), guanethidine, insulin medications for weight loss and depression, paroxetine (Paxil), and sertraline (Zoloft). Also tell your doctor if you are taking monoamine oxidase (MAO) inhibitors such as isocarboxazid (Marplan), phenelzine (Nardil), selegiline (Eldepryl, Emsam, Zelapar) and tranylcypromine (Parnate), or if you have stopped taking one of these medications in the past 2 weeks. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
- tell your doctor if you have or have ever had heart disease, high blood pressure, arteriosclerosis (narrowing of the arteries), hyperthyroidism (overactive thyroid gland), diabetes, glaucoma, or a history of drug abuse.
- tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking phentermine, call your doctor.
talk to your doctor about the risks and benefits of taking phentermine if you are 65 years of age or older. Older adults should not usually take phentermine because it is not as safe as other medications that can be used to treat the same condition.
- you should know that this medication may make you drowsy. Do not drive a car or operate machinery until you know how this medication affects you.
- ask your doctor about the safe use of alcohol while you are taking phentermine. Alcohol can make the side effects of phentermine worse.
- if you have diabetes, you may need to decrease your dose of insulin while taking phentermine. Call your doctor if you have questions or problems.
What special dietary instructions should I follow?
Follow the diet and exercise program your doctor has given you. Phentermine works best in combination with a diet program.
What should I do if I forget a dose?
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
What side effects can Phentermine medication cause?
Phentermine may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- dry mouth
- unpleasant taste
Some side effects can be serious. If you experience any of the following symptoms, call your doctor immediately:
- increased blood pressure
- heart palpitations
- shortness of breath
- chest pain
- swelling of the legs and ankles
- difficulty doing exercise that you have been able to do
Phentermine may cause other side effects. Call your doctor if you have any unusual problems during your treatment with phentermine.
What storage conditions are needed for Phentermine medicine?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom). Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of emergency/overdose
In case of overdose, call your local poison control center. If the victim has collapsed or is not breathing, call local emergency services at 911.
What other information should I know?
Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to phentermine.
Do not let anyone else take your medication. Phenteramine is a controlled substance. Prescriptions may be refilled only a limited number of times; ask your pharmacist any questions you have about refilling your prescription.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.
Phentermine Brand names