Phentermine is used to speed weight loss in overweight people. It is used together with diet and exercise to treat obesity, especially in people with risk factors such as high blood pressure, high cholesterol, or diabetes.

Phentermine is similar to an amphetamine. It stimulates the central nervous system (nerves and brain), which increases your heart rate and blood pressure and decreases your appetite.

Phentermine belongs to a class of medications called anorectics. It works by reducing your appetite.

Do not use phentermine if you are pregnant or breast-feeding a baby.

You should not use phentermine if you have glaucoma, overactive thyroid, severe heart problems, uncontrolled high blood pressure, advanced coronary artery disease, extreme agitation, or a history of drug abuse.

Do not use this medicine if you have used an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, or tranylcypromine. A dangerous drug interaction could occur.

Before taking this medicine

You should not use phentermine if you are allergic to it, or if you have:

• a history of heart disease (coronary artery disease, heart rhythm problems, congestive heart failure, stroke);

• severe or uncontrolled high blood pressure;

• overactive thyroid;

• glaucoma;

• extreme agitation or nervousness;

• a history of drug abuse; or

• if you take other diet pills.

Do not use phentermine if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others.

Weight loss during pregnancy can harm an unborn baby, even if you are overweight. Do not use phentermine if you are pregnant. Tell your doctor right away if you become pregnant during treatment.

You should not breast-feed while using this medicine.

To make sure this medicine is safe for you, tell your doctor if you have:

• heart disease or coronary artery disease;

• a heart valve disorder;

• high blood pressure;

• diabetes (your diabetes medication dose may need to be adjusted); or

• kidney disease.

Phentermine is not approved for use by anyone younger than 16 years old.

Take phentermine exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose.

Doses are normally taken before breakfast, or 1 to 2 hours after breakfast. Follow your doctor's dosing instructions very carefully.

Never use phentermine in larger amounts, or for longer than prescribed. Taking more of this medication will not make it more effective and can cause serious, life-threatening side effects.

This medicine is for short-term use only. The effects of appetite suppression may wear off after a few weeks.

Phentermine may be habit-forming. Misuse can cause addiction, overdose, or death. Selling or giving away this medicine is against the law.

Call your doctor at once if you think this medicine is not working as well, or if you have not lost at least 4 pounds within 4 weeks.

Do not stop using this medicine suddenly, or you could have unpleasant withdrawal symptoms. Ask your doctor how to safely stop using this medicine.

Store at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use.

Usual Adult Dose for Obesity:

8 mg orally 3 times a day 30 minutes before meals, OR
15 to 37.5 mg orally once a day before breakfast or 1 to 2 hours after breakfast.

Use: Short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification, and caloric restriction in the management of exogenous obesity in patients with an initial body mass index (BMI) of 30 kg/m2 or greater, or BMI of 27 kg/m2 or greater in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia).

Usual Pediatric Dose for Obesity:

Age 17 Years and Older:
8 mg orally 3 times a day 30 minutes before meals, OR
15 to 37.5 mg orally once a day before breakfast or 1 to 2 hours after breakfast.

Use: Short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification, and caloric restriction in the management of exogenous obesity in patients with an initial body mass index (BMI) of 30 kg/m2 or greater, or BMI of 27 kg/m2 or greater in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia).

You should not use phentermine if you are allergic to it, or if you have:

• a history of heart disease (coronary artery disease, heart rhythm problems, congestive heart failure, stroke);

• severe or uncontrolled high blood pressure;

• overactive thyroid;

• glaucoma;

• extreme agitation or nervousness;

• a history of drug abuse; or

• if you take other diet pills.

Do not use phentermine if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others.

Weight loss during pregnancy can harm an unborn baby, even if you are overweight. Do not use phentermine if you are pregnant. Tell your doctor right away if you become pregnant during treatment.

You should not breast-feed while using this medicine.

To make sure this medicine is safe for you, tell your doctor if you have:

• heart disease or coronary artery disease;

• a heart valve disorder;

• high blood pressure;

• diabetes (your diabetes medication dose may need to be adjusted); or

• kidney disease.

Phentermine is not approved for use by anyone younger than 16 years old.

Take the medicine as soon as you can, but skip the missed dose if it is late in the day. Do not take two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of phentermine can be fatal.

Overdose symptoms may include confusion, panic, hallucinations, extreme restlessness, nausea, vomiting, diarrhea, stomach cramps, feeling tired or depressed, irregular heartbeats, weak pulse, seizure, or slow breathing (breathing may stop).

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).

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Follow the diet and exercise program your doctor has given you. Phentermine works best in combination with a diet program.

Avoid driving or hazardous activity until you know how phentermine will affect you. Your reactions could be impaired.

Drinking alcohol with this medicine can cause side effects.

Get emergency medical help if you have signs of an allergic reaction to phentermine: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Phentermine may cause serious side effects. Call your doctor at once if you have:

• feeling short of breath, even with mild exertion;

• chest pain, feeling like you might pass out;

• swelling in your ankles or feet;

• pounding heartbeats or fluttering in your chest;

• tremors, feeling restless, trouble sleeping;

• unusual changes in mood or behavior; or

• increased blood pressure - severe headache, blurred vision, pounding in your neck or ears, anxiety, nosebleed.

Common side effects of phentermine may include:

• itching;
• dizzinessheadache;
• dry mouth;
• unpleasant taste;
• diarrhea;
• constipation;
• stomach pain; or
• increased or decreased interest in sex.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Taking phentermine together with other diet medications such as fenfluramine (Phen-Fen) or dexfenfluramine (Redux) can cause a rare fatal lung disorder called pulmonary hypertension. Do not take phentermine with any other diet medications without your doctor's advice.

Many drugs can interact with phentermine. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any medicine you start or stop using.

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 helps promote weight loss by lessening your appetite or making you feel fuller longer.

This medicine should be taken as part of a weight loss plan that also includes diet and exercise.

Phentermine should be used only by people who can’t lose enough weight with diet and exercise alone; it’s not recommended for individuals who want to lose only a few pounds.

Your dosage will depend on your age, your medical condition, and other factors.

A typical dose for adults with obesity is either of the following:

• 8 milligrams (mg) three times a day, about 30 minutes before meals
• 15 mg to 37.5 mg once a day, before breakfast or one to two hours after breakfast

Your doctor will try to keep you on the lowest effective dose possible.

Phentermine is sometimes prescribed “off-label” to treat other conditions, such as attention deficit hyperactivity disorder (ADHD).