Drug Details
Therapeutic Class:
Sympathomimetic amines (anorectics)
Forms:
Capsule, tablet
Administration:
By mouth
Therapeutic Uses:
Short-term add-on treatment for exogenous obesity along with exercise and diet
Controlled Status:
Schedule IV controlled substance
Phentermine Drug Class
Phentermine (fen-ter-meen) is a sympathomimetic amine anorectic.
Phentermine Age Range
Phentermine is approved for use in adults and children 16 years of age and older.
Uses
Phentermine Uses
Phentermine is used for the short-term (a few weeks), along with caloric restriction and exercise, to help speed up weight loss in obese individuals. It is prescribed to individuals with exogenous obesity (a body mass index (BMI) of 30 or higher).
There may be other uses of phentermine. Your healthcare professionals or health system pharmacists can give you further phentermine drug information.
Phentermine Mechanism of Action
Phentermine works by decreasing appetite to help you lose weight. It works in conjunction with a reduced-calorie diet and exercise.
Phentermine Doses
Phentermine is available as 37.5 mg tablets and 37.5 mg capsules. Your doctor will give you an individualized dosage. The goal is to obtain an adequate response at the lowest effective dose. The usual dose of phentermine is 8 mg, 15 mg, or 37.5 mg per day in 1-3 divided doses. The maximum dose of phentermine is 37.5 mg per day.
Directions
How To Use Phentermine
Phentermine is available as an oral capsule and oral tablet to take by mouth 1-3 times a day as prescribed. You can take phentermine with or without food. Your doctor may ask you to take phentermine as a single daily dose in the morning or up to 3 times a day before meals.
You should avoid taking phentermine in the late evening as it can lead to insomnia (difficulty falling asleep and staying asleep).
If you are taking the extended-release phentermine tablets, do not cut, crush, or chew these tablets.
Read the prescription label carefully and take phentermine in the exact way as instructed by your doctor. Phentermine can be habit-forming. Do not take a higher or lower dose of this medicine or take it more or less frequently than prescribed. Most people are prescribed phentermine for 3-6 weeks, depending on their initial body mass index.
This medication works best with a diet and exercise program. Follow the calorie-restricted diet and exercise program your doctor recommends to have phentermine work.
Missed dose: If you forget to take a dose of phentermine, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and take the next dose according to your regular dosing schedule. Do not take two doses together to make up for a missed dose.
Storage: Store phentermine at room temperature (between 15-30° C or 59-86° F) away from moisture, heat, and direct light in a tightly closed container. Do not store medications in the bathroom, where they can be exposed to moisture and heat. Keep all medications safely out of reach of children and pets.
Unused medicine: Unused or expired phentermine should be disposed of in a way that children, other people, and pets cannot get to them. Do not throw phentermine in the trash or flush it down the toilet. The best way to dispose of expired or unneeded phentermine is through your local waste disposal company or a drug take-back program. Learn more about proper medication disposal.
NOTE: This medication guide is a summary and may not contain all possible drug information on phentermine. The information contained here may not be up-to-date. This sheet is for information purposes only. If you have questions about phentermine, talk to your healthcare professionals for medical advice.
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Side Effects
Phentermine Side Effects
Possible side effects of phentermine are listed below. Tell your doctor if these side effects are severe or do not go away in a few days.
- Unpleasant taste
- Dry mouth
- Diarrhea
- Vomiting
- Constipation
- Dizziness
- Headache
- Changes in sex drive
Rarely, more serious side effects of phentermine can occur and require immediate medical attention. Call your doctor without delay or seek emergency medical care if you experience the following symptoms:
- Increased blood pressure
- Heart palpitations
- Restlessness
- Tremors (shakiness)
- Insomnia (trouble sleeping)
- Chest pain
- Shortness of breath
- Swelling of the lower legs and ankles
- Decreased ability to exercise compared to previously
The above list may not include all the potential adverse effects of phentermine. Contact your healthcare professional if your side effects are unusual or severe or they do not get better over time. You can also report unusual side effects to the Food and Drug Administration at 1-800-FDA-1088.
Phentermine Overdose: In case of an accidental or intentional overdose of phentermine, call your doctor immediately. You can also call the local poison control center or national poison control center at 1-800-222-1222. If a person cannot be awakened, has trouble breathing, has collapsed, or has had a seizure, call 911.
Source: FDA
Warnings
Phentermine Risks, Warnings, and Complications
Phentermine can cause serious medical problems in certain people. You may want to opt-out of taking this medicine if you are at a high risk of complications. Some of the risks of phentermine use include:
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Precautions Before Starting Phentermine
Tell your doctor if you have ever had an allergic reaction to phentermine, any of the active or inactive ingredients in phentermine capsules or tablets, other weight loss drugs, or any other drugs. Your pharmacy can give you a list of ingredients.
Give your doctor a complete medical history. Phentermine may not be right for people with certain health conditions, such as coronary artery disease, heart arrhythmias, stroke, congestive heart failure, heart valve disease, uncontrolled hypertension (high blood pressure), hyperthyroidism (overactive thyroid gland), glaucoma, diabetes, or a history of drug abuse. Women who are pregnant or breastfeeding should not take phentermine.
Give your doctor or pharmacist a complete list of your other medications, including prescription drugs, over-the-counter medicines, vitamins, supplements, and herbal products. This can help avoid possible drug interactions between phentermine and your other drugs. People who are taking certain medications called monoamine oxidase inhibitors (MAO inhibitors) or have taken them within the last 14 days should not take phentermine.
Tell your doctor if you are pregnant, could be pregnant, or are planning a pregnancy. Also, tell your doctor if you are breastfeeding.
If you are an older adult (age 65 and above), talk to your doctor about the safety of taking phentermine. There may be other safer alternatives available.
Precautions During Use of Phentermine
Keep all your healthcare appointments during treatment with phentermine. Your doctor may want to adjust your dose and keep an eye on any side effects of phentermine.
Tell your doctor if phentermine is not working for you. Do not increase the dose of phentermine without talking to your healthcare professional.
Taking phentermine can cause drowsiness and dizziness. Do not drive or operate heavy machinery until you know how this medicine affects you.
Alcohol can make the side effects of phentermine worse. Do not drink alcohol while on this medicine.
If you have diabetes and take insulin, you may need to reduce your dose of insulin while on phentermine. Talk to your healthcare professional about blood sugar control while taking phentermine.
Tell your doctor if you become pregnant while on phentermine. This medication can cause harm to an unborn baby.
Phentermine Drug Interactions
Certain other medicines can affect how phentermine works. Possible interactions between phentermine and other medicines can also increase the risk of severe adverse effects. Your doctor may change the dose of your medications or monitor you carefully for side effects if there are known interactions between phentermine and your other medicines.
The following medications can have possible interactions with phentermine:
- Antidepressants like fluvoxamine (Luvox), fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft)
- Other medications for weight loss
- Medications used to treat high blood pressure such as guanethidine
- Insulin
You should not take phentermine if you are on monoamine oxidase inhibitors or have taken them within the past 14 days. Examples of MAO inhibitors include isocarboxazid (Marplan), selegiline (Eldepryl, Zelapar, Emsam), phenelzine (Nardil), and tranylcypromine (Parnate).
The above list may not include all the possible interactions of phentermine. Give your doctor or pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, dietary supplements, and herbal remedies. Also, tell your healthcare provider if you smoke, drink alcohol, or use recreational drugs because some of these substances can cause serious health complications when used with prescription and over-the-counter medicines.
Pros & Cons
Phentermine Pros and Cons
- Phentermine is an FDA-approved weight loss drug that can reduce appetite and help with weight loss.
- The extended-release (long-acting) formulation of phentermine only needs to be taken once a day.
- You can take this medicine with or without food.
- Phentermine is available in a low-cost generic form.
- Phentermine only works in conjunction with exercise and a reduced-calorie diet.
- This medicine can be habit forming.
- You cannot take phentermine if you have heart disease, increased blood pressure, overactive thyroid gland, glaucoma, or a history of drug abuse.
- Insurance may not cover phentermine, and you may have to pay for this medicine out of pocket.
Pharmacist Tips
Phentermine Tips from Pharmacists
Avoid taking phentermine close to bedtime as it can cause problems with falling asleep and staying asleep.
Phentermine can make you feel dizzy and drowsy, especially when you first start taking it. Avoid driving or doing anything that requires your complete attention until you know how phentermine affects you.
Avoid alcohol while on phentermine as it can make the side effects worse.
Do not take phentermine if you are pregnant. It can harm an unborn baby.
Rx Savings Tips
Phentermine Rx Savings Tips
Phentermine is a generic medication and it is available at significantly lower prices than the brand name drugs. Brand name Adipex-P or Lomaira and generic phentermine contain the same medicine and are equally effective and safe. Like with most medications, the generic drug offers better value. A BuzzRx phentermine coupon can result in big savings on the brand names and generic form of the drug. With a BuzzRx discount card, savings card, or discount coupons, the medication could cost you a fraction of retail prices. Phentermine may be under $12 for 30 tablets of the 37.5 mg dose at Walmart, Walgreens, Rite Aid, CVS Pharmacy, and other participating pharmacies with a BuzzRx discount card or free coupon. For the biggest discounts on phentermine, give the checkout clerk your BuzzRx phentermine discount coupon when you drop off your prescriptions at the pharmacy counter.
Lowest Price for Phentermine | |
| Brand $66.81 | Generic $11.58 |
VIEW DISCOUNTS Pricing based on most commonly-filled versions. Select the strength and quantity of your medication for the most accurate pricing. | |
Common Questions
Common Questions about Phentermine
How fast does phentermine make you lose weight?Phentermine can lead to weight loss over a period of 3-6 months. Keep in mind that this medication works in conjunction with exercise and a calorie restricted diet. |
How much weight can you lose in a month on phentermine?Results vary from person to person. In general, phentermine can help you lose 3-7% of your body weight. You can expect to lose anywhere from 3 lbs to 5 lbs a month on phentermine. Remember that phentermine is for short-term use only (a few weeks). |
What does phentermine do to the body?Phentermine works on the brain and reduces appetite. However, it can only result in weight loss when combined with an exercise program and a calorie-reduced diet. |
Is phentermine the same as fen phen?No, fen phen contains phentermine and another drug called fenfluramine. Fen phen has been banned as it was found to cause heart problems. |
How long can I take phentermine?Phentermine is meant to be taken for the short term (a few weeks) to help speed up weight loss. Your doctor will advise you on how long to take this medicine. |
What is the price of phentermine without insurance?Without insurance, phentermine can be as high as $44.99, but with a free BuzzRx prescription discount coupon, you could pay as low as $11.58 for the most common version of this medication. Use the BuzzRx drug price look-up tool to find the lowest discounted price, and be sure to enter the correct dosage, form, and quantity for the most accurate pricing. While generics tend to have the best savings, you can also use your BuzzRx card and coupons to purchase brand-name versions. It never hurts to ask your pharmacist to try BuzzRx when filling or refilling any of your prescription drugs—whether you have insurance or not. |
What is the price of phentermine with insurance?Ask your pharmacist or insurance provider for your copay price on phentermine—copay amounts vary depending on the type of insurance plan you have and if there is a deductible to reach before prescription drug coverage begins. You could save up to 80% on your prescription medication with a free BuzzRx discount coupon for phentermine. When using the BuzzRx lookup tool to find the price of your medicine, be sure to enter the correct dosage, form, and quantity to receive the most accurate discounted pricing. It never hurts to ask your pharmacist to try BuzzRx when filling or refilling any of your prescriptions—whether you have insurance or not. |
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