Benefits, Side Effects, and Dosage

Consuming a well-balanced, reduced-calorie weight loss program and exercising usually are the cornerstones of weight reduction, however sure medication can present highly effective help.

One such drug is phentermine — one of the vital widespread weight reduction medication on the planet.

It has been confirmed efficient for short-term weight reduction when used alongside a reduced-calorie weight loss program and train.

Nonetheless, utilizing phentermine for weight reduction is just not with out dangers and unintended effects.

This text explains all the things it’s essential to learn about phentermine, together with its advantages, dosage, and doable unintended effects.

Phentermine is a prescription weight reduction remedy.

The Meals and Drug Administration (FDA) authorized it in 1959 for short-term use of as much as 12 weeks for folks older than 16 (1).

Within the Nineteen Nineties, drug makers mixed phentermine with different weight reduction medication. This drug mixture was generally referred to as fen-phen.

After stories of serious coronary heart issues in customers, the FDA pulled the opposite two medication that had been used within the therapy — fenfluramine and dexfenfluramine — from the market (2).

At this time, phentermine can be utilized by itself and goes by the model names Adipex-P, Lomaira, and Suprenza. You too can discover it together drugs for weight reduction, similar to Qsymia, which mixes phentermine and one other drug referred to as topiramate.

Phentermine is a stimulant and is obtainable in case you have a prescription. As a result of taking phentermine comes with a threat of dependence, it’s thought-about a managed substance. It’s chemically just like the stimulant amphetamine, which can be a managed substance (3).

A healthcare skilled could prescribe phentermine in case you have weight problems, outlined by a physique mass index (BMI) of 30 or higher.

Healthcare professionals may prescribe it in case you have extra weight with a BMI higher than or equal to 27 and have no less than one weight-related situation, similar to hypertension, excessive ldl cholesterol, or sort 2 diabetes (4, 5).

Nonetheless, a healthcare skilled will possible advocate different weight reduction methods first, similar to train and a calorie-reduced weight loss program.


Phentermine is an FDA-approved drug supposed for weight reduction. Its chemical construction is just like that of the stimulant drug amphetamine, and it’s obtainable solely with a prescription.

Phentermine belongs to a category of medicine referred to as anorectics, also referred to as urge for food suppressants.

Taking phentermine helps suppress your urge for food, thereby limiting what number of energy you eat. Over time, this could result in weight reduction.

Whereas the precise manner phentermine reduces urge for food stays unclear, the drug is assumed to behave by growing neurotransmitter ranges in your mind (6, 7).

Neurotransmitters — the chemical compounds norepinephrine, serotonin, and dopamineare — are your physique’s chemical messengers (6, 7).

When your ranges of those three chemical compounds enhance, your feeling of starvation decreases.

Nonetheless, you could construct a tolerance to the appetite-suppressing results of phentermine inside just a few weeks. If that occurs, communicate with the healthcare skilled who prescribed it.


Phentermine is assumed to lower your urge for food by growing neurotransmitter ranges in your mind.

Phentermine is most frequently used for weight reduction, however may be utilized in mixture with the remedy topiramate to assist with sure consuming problems, similar to binge consuming dysfunction (BED) (8).

Efficient for weight reduction

A number of medical research have proven that phentermine can help significant weight reduction.

Although the FDA authorized it just for short-term use of lower than 12 weeks, healthcare professionals typically prescribe phentermine off-label for longer use.

Docs could prescribe it intermittently, which means you’re taking a break from the remedy for a set time frame earlier than resuming it (5, 9).

The common weight reduction when taking phentermine is 3% of your preliminary physique weight after 3 months and 5–7% after 6 months. Some folks report much more weight reduction than this (5, 6, 9, 10).

To place this into perspective, a 5–7% weight reduction is 10–14 kilos (4.5–6.4 kg) for an individual who weighs 200 kilos (90.7 kg).

Nonetheless, not everybody responds the identical approach to this remedy. In case you haven’t misplaced a lot weight after 3 months of utilizing it, a healthcare skilled could advocate discontinuing the remedy.

Additional, its effectiveness seems to steadily lower after extended use of greater than a 12 months (5, 6, 9, 10).

Whereas phentermine has been proven to be efficient for weight reduction, it could work higher when mixed with topiramate.

Topiramate is a drug that has been used by itself to deal with seizures however, like phentermine, additionally has appetite-reducing properties (6, 11, 12).

Topiramate and phentermine is a mix remedy bought underneath the model identify Qsymia. The FDA authorized it in 2012 as an addition to wholesome way of life behaviors similar to elevated train and a calorie-reduced weight loss program.

In comparison with three different generally prescription drugs for weight reduction, the mixture of phentermine and topiramate was related to the best odds of shedding no less than 5% of preliminary physique weight (13).

What’s extra, a current evaluation of research discovered that individuals who took a medicine that mixed phentermine and topiramate misplaced 16 kilos (7.3 kg) on common in contrast with a placebo.

For many who took the remedy for greater than 56 weeks, this quantity elevated to 17.8 kilos (8 kg) (14).

Moreover, the diploma of weight reduction elevated with the dose. Common weight reduction was (14):

  • 7.8 kilos (3.55 kg) for a 3.75/23 mg (phentermine/topiramate) dose
  • 16 kilos (7.27 kg) for a 7.5/46 mg dose
  • 18 kilos (8.25 kg) for a 15/92 mg dose

In customers of phentermine-topiramate, weight reduction translated to a major lower in waist circumference in addition to improved insulin sensitivity, improved blood sugar administration, and discount in blood strain (15, 16).

Could also be useful for sure consuming problems

The mixture of phentermine and topiramate could assist scale back binge consuming in folks with BED and bulimia nervosa.

BED is characterised by consuming massive quantities of meals, typically shortly and to the purpose of discomfort. It’s additionally related to a sense of shedding management in the course of the binge, in addition to emotions of disgrace or guilt afterward (17).

Bulimia nervosa includes the identical binge-eating habits as with BED but additionally consists of behaviors folks use to compensate for the consequences of binge consuming, similar to self-induced vomiting (17).

In a small 12-week examine in folks with BED who had extra weight, individuals who took a phentermine and topiramate drug mixture skilled important reductions in binge-eating episode frequency (18).

In one other 12-week examine, folks with BED or bulimia nervosa acquired the drug mixture or a placebo (19).

Over 28 days, therapy with the phentermine and topiramate mixture decreased the members’ variety of binge-eating days from 16.2 to 4.2. The identical outcomes weren’t noticed within the placebo group (19).

Whereas these outcomes are promising, bigger research are nonetheless wanted.

In case you assume you have got BED, bulimia nervosa, or disordered consuming, it’s necessary to talk with a healthcare skilled.


Phentermine mixed with topiramate has been proven to advertise important weight reduction and should assist scale back the incidence of binge-eating episodes.

Dosages for phentermine differ relying on its kind and focus.


Previous to 2016, the one obtainable doses of phentermine had been 15, 30, and 37.5 mg (7, 9).

Nonetheless, because it’s a finest follow for docs to prescribe the bottom efficient dose, the FDA authorized an 8-mg formulation (Lomaira) in 2016, which may be taken as much as thrice day by day no less than half-hour earlier than meals.

In case you’re prescribed a better dose (15, 30, or 37.5 mg), you’ll be able to take it as soon as per day within the morning earlier than breakfast or 1–2 hours after breakfast.

To forestall insomnia or issue falling or staying asleep, you need to keep away from taking the final dose too late within the day.

Phentermine and topiramate

The mixture of phentermine and topiramate — bought underneath the model identify Qsymia — is a medicine used for weight reduction.

This remedy is obtainable in 4 doses, ranging in energy from 3.75–15 mg of phentermine and 23–92 mg of topiramate. It’s provided in an extended-release capsule that ought to be taken within the morning (7, 9, 20).

After you’re taking the bottom dose for 14 days, your physician can select to progress you to a better dose (9, 20).

In accordance with the FDA, you need to cease utilizing the remedy when you don’t lose 3% of your physique weight after 12 weeks on the best day by day dose (20).


The dosage of phentermine differs, relying on whether or not it’s used alone or alongside topiramate.

Phentermine alone is designed for short-term use solely, as there are few long-term research on its security.

One examine noticed that folks skilled no important unintended effects once they took phentermine for as much as 24 months (10).

Nonetheless, the FDA has authorized phentermine together with topiramate for long-term use, for the reason that doses of the 2 substances are decrease than the utmost doses of the person medication (20).

Essentially the most generally reported unintended effects of phentermine and mixed phentermine and topiramate are (6, 20, 21):

Whereas uncommon, some extreme unintended effects are doable, similar to elevated blood strain, suicidal ideation, metabolic acidosis, elevated creatinine ranges, fetal hurt, imaginative and prescient issues, cognitive impairment, and hypokalemia (6, 20, 21).

You shouldn’t take phentermine in case you have coronary heart illness, hyperthyroidism, glaucoma, or extreme kidney or liver illness or when you’re pregnant or nursing (6, 20, 21, 22).

Phentermine also needs to not be prescribed together with monoamine oxidase inhibitors (MAOIs), a category of medicines used to deal with despair.

Converse with a healthcare skilled when you’re taking different drugs, similar to antihypertensive or antiepileptic drugs (20).

Your healthcare skilled will decide whether or not phentermine is suitable and protected for you.


Whereas some frequent unintended effects are related to using phentermine and topiramate, most individuals tolerate it. Nonetheless, individuals who have sure circumstances or are pregnant or nursing mustn’t use phentermine and topiramate.

Most frequently, healthcare professionals prescribe phentermine and topiramate after you’ve tried different way of life modifications for weight reduction however haven’t seen important outcomes.

Whereas phentermine is usually a highly effective weight reduction support, the one confirmed approach to shed weight and hold it off in the long run is to have interaction in wholesome way of life behaviors (23, 24).

With out making these behavior adjustments, you could achieve again any weight you’ve misplaced — and probably extra — when you cease taking phentermine (25).

As a substitute, it’s finest to prioritize wholesome, sustainable way of life habits that promote well being past weight reduction.

In depth analysis has proven that train, a nutritious weight loss program, stress administration, and correct sleep are essential to selling higher well being and lowering your threat of illness (26, 27, 28, 29).

What’s extra, taking remedy long-term is just not with out dangers, and the associated fee can add up, particularly when you don’t have insurance coverage.

For these causes, a healthcare skilled will possible advocate that you simply make wholesome way of life adjustments earlier than recommending a weight reduction remedy.

Some examples of wholesome way of life adjustments you can also make embrace (23, 24, 30):

  • Consuming a reduced-calorie weight loss program. When you have extra weight to lose, you’ll be able to attempt to eat 300–500 fewer energy per day. A registered dietitian might help you tailor this vary based mostly in your preferences and objectives.
  • Prioritizing nutrient-dense meals. Nutrient-dense meals similar to vegetables and fruit are comparatively low in energy and excessive in vitamins similar to fiber, nutritional vitamins, and minerals.
  • Growing bodily exercise. The U.S. Division of Well being and Human Providers recommends getting a minimal of 150 minutes per week of reasonable cardio train similar to brisk strolling or operating.
  • Getting extra sleep. Although particular person wants differ, attempt to get 7–9 hours of sleep per evening.
  • Doing all your finest to handle your stress ranges. Managing stress might help scale back emotional consuming and irritation. You may strive methods similar to remedy, going for walks, socializing with family and friends, or talking with a educated skilled.
  • Attempting behavioral methods. Conduct adjustments that could be useful embrace self-monitoring your meals consumption, bodily exercise, and weight and making changes as wanted.

These way of life adjustments may be tough to make, and also you don’t should do them all of sudden. As a substitute, slowly incorporate new wholesome behaviors over time. This may assist promote long-term, sustainable outcomes.


Life-style and habits modifications are the cornerstones of profitable weight reduction and upkeep.

Phentermine is a prescription-only urge for food suppressant and weight reduction tablet authorized for short-term use.

The mixture of phentermine and topiramate seems to be much more efficient than phentermine alone, and it’s authorized for long-term use. It could additionally assist scale back bingeing episodes in folks with BED.

Frequent unintended effects embrace dry mouth, dizziness, fatigue, irritability, and constipation. You shouldn’t use this remedy in case you have coronary heart illness, hyperthyroidism, glaucoma, or extreme kidney or liver illness or when you’re pregnant or nursing.

Additionally, you’ll want to seek the advice of a healthcare skilled earlier than making an attempt phentermine when you’re taking sure drugs, similar to monoamine oxidase inhibitors (MAOIs).

Whereas phentermine is usually a helpful weight reduction software, it’s not really helpful as a first-line therapy. As a substitute, it’s finest to prioritize wholesome way of life adjustments for long-term success.

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