Lomaira, Adipex-p

Phentermine (FEN ter meen) oral tablet is prescribed for weight loss, as a short-term treatment along with lifestyle changes. It’s a generic version of the brand-name drugs Adipex-P and Lomaira. Phentermine belongs to a group of drugs called anorectics.

Medically reviewed by Purva Singla, April 20, 2023
Written by Alex Brewer, PharmD, MBA

Specifically, the Food and Drug Administration (FDA) has approved phentermine oral tablet as a short-term treatment to help with weight management. It’s used with other strategies such as lifestyle and habit changes. For this purpose, phentermine may be prescribed to adults with:

• a body mass index (BMI) of 30 or less, or
• a BMI of 27 or less, and certain health conditions, such as high blood pressure, high cholesterol, or diabetes

This article describes phentermine oral tablet’s uses and dosage, ways to save on cost, and more. Below you’ll find coupon options for phentermine.

Side effects of phentermine

Phentermine may cause mild or serious side effects. More common mild side effects of phentermine oral tablet and its serious side effects are listed below. This article doesn’t include all possible side effects of the drug. Side effects can vary based on your age, overall health, and any other medications you take.

To learn more about phentermine oral tablet’s side effects, see this article or ask your doctor or pharmacist. You can also read the prescribing information for the phentermine 37.5-milligram (mg) oral tablet and the 8-mg oral tablet.

Mild side effects

More common mild side effects reported with phentermine oral tablet are listed below.

With many drugs, mild side effects may go away within a few days or a couple of weeks. If the side effects are bothersome, tell your doctor or pharmacist. They may be able to suggest ways to manage them.

Phentermine oral tablet’s mild side effects include:

• constipation
• diarrhea
• dizziness
• dry mouth
• feeling restless or overstimulated
• headache
• insomnia (sleep problems)
• tremors (shaking you can’t control)
• mild allergic reaction*

* For details about this side effect, see the “Warnings for phentermine” section below.

Serious side effects

Serious side effects of phentermine oral tablet are listed below. With many drugs, serious side effects are possible but not common.

If you have serious side effects from this drug, call your doctor right away. If you’re having severe symptoms or a medical emergency, call 911 or a local emergency number.

Phentermine oral tablet’s serious side effects include:

• heart valve disease
• pulmonary hypertension (high blood pressure in your lungs)
• high blood pressure
• mood changes or psychosis (loss of touch with reality)
• sexual side effects, including erectile dysfunction, decreased sex drive, or loss of sex drive
• severe allergic reaction*

* For details about this side effect, see the “Warnings for phentermine” section below.

Common questions about phentermine

Below you’ll find answers to a few commonly asked questions about phentermine oral tablet.

Is there a difference in side effects of phentermine for females vs. males?

Yes, but barely. Side effects of phentermine for females* and males* are expected to be the same, except that males are at risk of erectile dysfunction as a side effect.

Talk with your doctor or pharmacist if you have more questions or concerns about phentermine and erectile dysfunction.

* Sex and gender exist on spectrums. In this article, we use the terms “male” and “female” to refer to a person’s sex assigned at birth.

How does phentermine compare with other similar drugs, such as Contrave or Qsymia?

Here are some brief facts on how phentermine compares with other drugs taken for weight loss:

• Contrave contains two drugs: bupropion and naltrexone. It’s prescribed to help with weight management along with lifestyle changes, like phentermine.
• Qsymia contains two drugs: phentermine and topiramate. It’s prescribed to help with weight management along with lifestyle changes, like phentermine. But unlike phentermine, Qsymia is also approved for this use in certain adolescents ages 12 years and older.
• Topamax contains the drug topiramate. Topamax isn’t approved to help with weight management but may be prescribed off-label for this purpose. Off-label use is when a drug is prescribed for a purpose that it’s not approved for.

Like phentermine, it’s not fully understood exactly how these drugs work to help with weight management.

Whether phentermine or a different treatment is best for you depends on several factors, including your health history, health goals, and your age. Talk with your doctor or pharmacist if you’d like to learn more about how phentermine compares with other treatments.

Is phentermine similar to Adderall, in that it can be taken for ADHD?

No, phentermine is not approved for treating attention deficit hyperactivity disorder (ADHD). Adderall is approved for ADHD treatment, as well as narcolepsy. Phentermine is only approved as a short-term weight-management aid along with lifestyle changes.

Talk with your doctor if you have questions about other medications, including medications that may be taken for ADHD.

How does phentermine work? And how long does it take to start working?

It’s not known exactly how phentermine works to help with weight loss. One thought is that phentermine reduces appetite. Another thought is that phentermine may have effects on your metabolism (your body’s major processes that create and use energy).

Phentermine begins working after you take your first dose. But it may take several weeks before you notice an effect on your weight. Your doctor can provide more information about when you can expect to notice changes in weight during phentermine treatment.

Is there a best time of day to take phentermine? What should I do if I miss a dose?

Yes. It’s recommended to take phentermine in the morning about 30 minutes before eating. Be sure to follow your doctor’s instructions. It’s best to avoid taking a dose close to bedtime, as it may increase your risk of sleep problems as a side effect.

If you miss a phentermine dose, take it as soon as you remember. But if it’s nearly time for your next dose, skip the missed dose. Take your next scheduled dose at the regular time. Do not take more than one dose of phentermine at once.

If you aren’t sure what to do after missing a dose, you can ask your doctor or pharmacist.

Can phentermine tablets be crushed, split, or chewed?

Yes, phentermine tablets may be split along the score (line) in the middle of the tablet. But you should not crush or chew phentermine tablets.

Talk with your pharmacist or doctor if you’re having trouble swallowing phentermine tablets. They may suggest switching to phentermine disintegrating tablets. Disintegrating tablets dissolve in your mouth without water and may be easier to swallow.

Uses of phentermine

The Food and Drug Administration (FDA) approves prescription drugs such as phentermine for certain conditions. Approved uses for phentermine oral tablet are described below.

Use for weight loss

Doctors may prescribe phentermine oral tablet for weight loss. It’s taken for this purpose in adults with:

• a body mass index (BMI) of 30 or less, or
• a BMI of 27 or less, and certain health conditions, such as high blood pressure, high cholesterol, or diabetes

Phentermine is prescribed along with lifestyle changes, such as a nutritious diet and an exercise plan. It’s not approved to be taken for weight management on its own. It’s usually prescribed as a short-term treatment for a few weeks.

For adults, having a BMI of 30 or above meets the criteria for obesity. Your doctor or another healthcare professional will calculate your BMI using your weight and height.

Excess weight raises your risk of certain health conditions, including type 2 diabetes, high blood pressure, and heart disease. Long lasting weight management is usually a result of long-term dietary and lifestyle changes.

Dosage of phentermine

The dosage of phentermine oral tablet your doctor prescribes may vary based on your condition and certain other factors. Talk with your doctor about the dosage you should take.

Taking phentermine

Phentermine oral tablet is taken by mouth.

Your doctor will talk with you about how to take phentermine. They’ll explain how much to take and how often. Always follow your doctor’s recommendation.

Phentermine oral tablet should be taken about 30 minutes before a meal, usually in the morning.

See the “Common questions about phentermine” section for information on missed doses and the best time to take this drug.

Overdose of phentermine

You should not take more phentermine than your doctor prescribes. For some drugs, doing so may lead to serious side effects or overdose.

If you think you’ve taken too much phentermine, call your doctor or pharmacist right away. Or you could call 800-222-1222 to speak with someone at America’s Poison Centers. You can also use its online resource. If you have concerning symptoms, call 911 or a local emergency number immediately. You can also go to the closest emergency room.

Misuse, withdrawal, or dependence of phentermine

Phentermine is a controlled substance, meaning it has a risk of misuse. Misuse is when a drug is taken in a way other than how it’s prescribed.

A controlled substance is a medication with special regulations that doctors and pharmacists must follow. It’s illegal to sell or give your prescribed controlled substance, such as phentermine, to another person.

Although phentermine is not considered addictive, it may lead to dependence and withdrawal symptoms. Dependence means the body needs the drug to function like usual. Withdrawal symptoms can occur when you stop taking a drug your body is dependent on.

Withdrawal symptoms reported when people have suddenly stopped taking phentermine include:

• extreme fatigue (low energy)
• severe insomnia (sleep problems)
• feeling irritable or overstimulated
• personality or mood changes, including psychosis (loss of touch with reality)

Dependence and withdrawal symptoms can occur even when phentermine is taken as prescribed. But the risk is higher when the drug is taken long term and in doses higher than recommended by your doctor.

For this reason, it’s very important that you only take phentermine at the dose and for the length of time recommended by your doctor. It’s used as a short-term treatment. And do not suddenly stop taking phentermine. Following these tips lowers your risk of dependence and withdrawal when you stop treatment.

Your doctor will likely ask about your health history before prescribing phentermine, including any history of substance use disorder (formerly called drug abuse). Depending on your health history, they may decide that a weight-loss treatment other than phentermine is safer for you.

Interactions of phentermine

For some medications, certain things may affect how the drug works. These include getting vaccines, consuming alcohol or certain foods, or taking the drug with other medications. This effect is called a drug interaction.

Before you take phentermine, ask your doctor to check for possible interactions. They can check for interactions these items may cause with phentermine. Be sure to tell them about any of the following you take or use:

• prescription medications
• over-the-counter medications
• vitamins, herbs, or supplements

To learn about drug-condition interactions, see the “Warnings for phentermine” section below.

Warnings for phentermine

Phentermine should not be taken or should be taken with caution by certain people. Precautions for taking this drug are described below.

Warnings

Phentermine could cause harm to people with certain health conditions. This effect is called a drug-condition interaction. Other factors can also affect whether phentermine oral tablet is a safe option for you.

Tell your doctor about your overall health and any past health conditions before you take phentermine oral tablet. Health conditions and other factors you and your doctor should discuss include:

• any cardiovascular (heart and blood vessel) condition, including coronary artery disease, heart failure, irregular heart rhythm, or a history of heart attack or stroke
• high blood pressure
• type 1 or type 2 diabetes
• hyperthyroidism
• glaucoma
• kidney conditions, such as chronic (long-term) kidney disease
• use of a monoamine oxidase inhibitor (MAOI) drug within the last 14 days, such as phenelzine (Nardil)
• history of substance use disorder

Allergic reaction

Phentermine can cause an allergic reaction in some people. Severe allergic reactions are rare but possible.

If you’ve had an allergic reaction to phentermine or any of its ingredients, your doctor will likely not prescribe phentermine. They can tell you about medications that are safer options for you.

A mild allergic reaction may cause the following symptoms:

• skin rash
• itchiness
• flushing (temporary warmth, redness, or deepening of skin color)

A severe allergic reaction may cause the following symptoms:

• swelling under your skin, usually in your hands, feet, eyelids, or lips
• swelling of your mouth, throat, or tongue, which can cause breathing problems

If you have an allergic reaction to phentermine, call your doctor right away. If you have severe symptoms, call 911 or a local emergency number.

Pregnancy or breastfeeding and phentermine

Information about phentermine and pregnancy and breastfeeding is described below.

Phentermine and pregnancy

Phentermine oral tablet should not be taken during pregnancy. If you’re planning a pregnancy or can become pregnant, talk with your doctor before taking this medication. Your doctor may suggest birth control options to use during treatment with phentermine.

Phentermine and breastfeeding

Phentermine oral tablet should not be taken while breastfeeding. If you’re currently breastfeeding or planning to do so, talk with your doctor before taking this medication. Your doctor may recommend other ways to feed your child during treatment with phentermine.

Phentermine coupon

You may be able to save money on your prescription for phentermine oral tablet by using our Perks discount coupons. These can be found at the end of this article.

If you have questions about how to pay for phentermine, talk with your doctor or pharmacist. You can also learn more about the cost of phentermine in this article.

Note: Optum Perks coupons cannot be used with insurance copays or benefits.

What to ask your doctor

This article describes phentermine oral tablet’s uses and dosage, ways to save on cost, and more. Let your doctor know if you have questions about phentermine or would like more details about it.

Here’s a list of some possible questions you may want to ask your doctor:

• Can phentermine cause long-term side effects?
• What are my treatment options if short-term phentermine isn’t effective for me?
• Does my health history raise my risk of side effects if I take phentermine?
• Since phentermine is a controlled substance, should I bring a copy of my prescription when traveling with my medication?

Article resources

• Contrave (naltrexone hydrochloride and bupropion hydrochloride) extended-release tablets, for oral use. (2021). https://contrave.com/storage/2022/02/Contrave_PI_CON-LC115.02_0222.pdf
• Food and Drug Administration. (2023). Orange Book: Approved drug products with therapeutic equivalence evaluations. https://www.accessdata.fda.gov/scripts/cder/ob/index.cfm
• Phentermine hydrochloride — phentermine hydrochloride tablet. (2023). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/c5d60a6d-2410-4a3c-88e1-a6126b56cf6a/spl-doc
• Phentermine hydrochloride — phentermine hydrochloride tablet. (2018). https://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/ff620c0b-aa99-4f63-9526-d094cedc8d19/spl-doc
• Qsymia (phentermine and topiramate extended-release capsules), for oral use, CIV. (2022). https://qsymia.com/patient/include/media/pdf/prescribing-information.pdf?v=0422

Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.