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The student media organization of California State University Northridge

Daily Sundial

The student media organization of California State University Northridge

Daily Sundial

Phentermine Reviews for Weight Loss – Phentermine 37.5 How It Works for Losing Weight, Pros and Cons


Branded Content by Cosmic Press

The rising obesity epidemic has led to an urgent need for safe and effective weight loss aids. In the United States alone, over 70% of adults are overweight or obese. The health risks and reduced quality of life associated with excess weight have created huge demand for solutions.

One of the most well-known and commonly prescribed anti-obesity medications is phentermine. It has been used since the late 1950s as a short-term treatment for weight loss. Even with the development of newer competitors, phentermine remains widely used for its potent effects.

However, there is also controversy around phentermine’s potential for side effects and abuse. This necessitates a thoughtful risk vs benefit analysis by patients and doctors considering its use.

The aim of this piece is to provide a comprehensive review of phentermine. It will examine how phentermine works as an appetite suppressant and metabolism booster. The pros and cons around effectiveness, safety, contraindications, dosing, and legality will be explored. We also review the best alternatives to phentermine for weight loss.

The goal is to equip readers with the full set of facts around phentermine to support informed decisions about whether it may be an appropriate weight loss option depending on individual circumstances and health status. Weighing the potential benefits versus the possible risks is key.

What is Phentermine?

Metabolism: Liver

Other names: ?-methyl-amphetamine; ?,?-dimethylphenethylamine

Pregnancy category: AU: B3

Protein binding: Approximately 96.3%

Addiction liability: Low

AHFS/ Monograph

ATC code: A08AA01 (WHO)

Phentermine Over the Counter Brands

Here are 3 of the most effective and popular Phentermine over the counter diet pills. These brands are a combination of natural appetite suppressants and fat burners.

PhenQ – arguably the most successful over the counter diet pill in circulation. PhenQ is a multi action appetite suppressant, fat burner and fat blocker that is documented as helping over 200,000 people lose weight. It is naturally formulated and classed as safe. Read more about PhenQ multi action diet pills

Phen24 – a night time fat burner that works to combat weight gain while you are asleep. Phen24 is completely natural and free from side effects. Read more about Phen24 nighttime diet pills

PhenGold – another non-prescription Phentermine 37.5 brand that has a high level of success for helping users shift gained weight. Read more about PhenGold natural diet pills

Phentermine 37.5 mg Prescription Only Brands

Here are 8 common brand name versions of prescribed phentermine diet pill brands

  1. Adipex-P – The most well-known brand name of phentermine, comes in 37.5mg tablets for short-term weight loss. Made by Teva Pharmaceuticals.
  2. Lomaira – Low dose phentermine tablets containing 8mg designed for long-term use. Made by KVK Tech.
  3. Duromine – Popular branded phentermine product in Australia and New Zealand, comes in 15mg, 30mg, and 40mg capsules.
  4. Suprenza – Orally disintegrating phentermine 37.5mg tablets that dissolve on the tongue. Made by Akrimax Pharmaceuticals.
  5. Qsymia – Doctor prescribed combination drug containing phentermine and topiramate for weight loss, available as 3.75/23 mg or 15/92 mg capsules. Made by Vivus.
  6. Razin – Generic form of phentermine hydrochloride capsules in strengths of 15mg, 30mg, and 37.5mg. Manufactured in India by Dankos Laboratories.
  7. Oseni – Extended release Phen capsule combining low doses of phentermine 15mg and topiramate ER 45 mg or 92mg. Made by Eisai.
  8. Panbesy – Branded European phentermine product made in Belgium by Omega Pharma, contains 37.5mg phentermine hydrochloride.

Brief history of phentermine:

Phentermine first received FDA approval in 1959 as an appetite suppressant for short-term obesity treatment. It became part of the fen-phen drug combination that was popular in the 1990s until being pulled from the market due to safety issues. Phentermine itself continued to be prescribed in low doses for a few weeks use. With obesity rates climbing, it remains one of the most widely prescribed weight loss medications.

Mechanism of action:

Phentermine primarily works as an appetite suppressant. It increases neurotransmitters like norepinephrine in the brain that activate the sympathetic nervous system, reducing hunger signals. It may also increase resting metabolic rate slightly. However, the main driver of weight loss is the reduced calorie intake facilitated by appetite suppression.

Available formulations:

Phentermine is available under brand names like Lomaira, Adipex-P, Suprenza in immediate-release tablets of 37.5mg, the most common dosage. An extended release formulation called Oseni comes in capsules containing 15mg or 30mg of phentermine in a 12-hour controlled release, taken once daily. The 37.5mg immediate release dose has faster absorption and effects.

In summary, phentermine is an older anorectic medication that remains commonly prescribed for short-term weight loss, mainly operating through appetite suppression mechanisms. It comes in several branded immediate and extended release formulations.

Related content: Which is the strongest appetite suppressant available over the counter?

How Phentermine Helps With Weight Loss

Here is how phentermine suppresses appetite to promote weight loss:

Suppresses appetite significantly

Of all phentermine’s weight loss mechanisms, appetite suppression is arguably the most impactful. Many users report a profoundly reduced appetite within just a few doses of starting treatment. Food cravings become less frequent and easier to resist.

How does phentermine work and smash hunger so effectively? The diet drug increases norepinephrine levels in the brain. This neurotransmitter stimulates the sympathetic nervous system into overdrive, mimicking the ‘fight or flight’ state. When the body senses danger, hunger signals are suppressed to prioritize survival.

By chemically recreating this process via norepinephrine, taking phentermine dulls the appetite and desire to eat, ultimately helping users to lose weight. Food seems unappealing or downright unpalatable, especially calorie-dense junk foods. Smaller portion sizes become satisfying. Users often remind themselves to eat instead of needing to be reminded.

One study tested obese patients on 37.5mg phentermine daily versus placebo. The phentermine group reported a 3-fold decrease in overall hunger levels. Food journals also showed phentermine reduced daily calorie intake by up to 1000 calories. This powerful appetite suppression makes it much easier to comply with the reduced calorie diet needed for weight loss success.

However, experts warn phentermine’s hunger blunting effects diminish after several weeks as the body adapts. This is why long-term use requires periodically cycling off under medical supervision. But for a kickstart to compliance with dietary changes, phentermine’s profound appetite suppression can be a real game changer.

Increases resting metabolic rate

In addition to suppressing appetite, phentermine mobilizes fat from storage by increasing resting metabolic rate (RMR). This is the number of calories burned daily by non-exercise activity.

Phentermine stimulates the sympathetic nervous system just like the ‘fight or flight’ response. This ramps up RMR by increasing fat breakdown and thermogenesis – heat production in the body.

Clinical studies using indirect calorimetry show phentermine can boost RMR by over 5% compared to placebo. For someone with a 2000 calorie daily RMR, that translates to around 100 extra calories burned per day without any exercise.

This might not seem like much, but those extra calories burned around the clock really add up over months. Plus, the increase in resting metabolism is stackable with additional calorie burning from exercise and activity.

However, experts caution the metabolic boost is temporary. Phentermine’s effects on metabolism peak within the first 4 weeks before plateauing as the body adapts. Tolerance can develop over longer-term use.

To maximize results, phentermine is best utilized short-term to jumpstart weight loss through appetite suppression and spiking calorie expenditure. Maintaining long-term metabolic boosts requires permanent lifestyle changes like more physical activity and muscle-building exercise.

Provides extra energy expenditure through thermogenesis

Phentermine ramps up thermogenesis in the body – the production of heat energy. This process burns extra calories above the body’s normal metabolic rate.

There are two forms of thermogenesis stimulated by phentermine. The first is fat thermogenesis. Phentermine activates the enzymes responsible for breaking down triglycerides stored in fat cells. This lipolysis generates heat and expends energy.

The second form is muscle thermogenesis. Phentermine causes specialized proteins called uncoupling proteins to activate in muscle tissue. This makes the muscles less efficient at storing energy from nutrients. More calories are wasted as heat rather than stored as fat.

Studies show phentermine can increase fat thermogenesis by over 30%. This equates to burning around 50 extra calories daily. Muscle thermogenesis bumps expenditure by 7-10% or 25 calories per day. That’s potentially 75 bonus calories burned around the clock without any physical activity.

While a 75 calorie increase might appear minimal, the cumulative impact over months significantly accelerates weight loss. Thermogenic effects also stack with the metabolic boost and appetite suppression. The combination can create the 500-1000 daily calorie deficit needed for shedding excess pounds.

However, phentermine’s thermogenic effects decrease over time as the body adapts. So it works best as a short-term aid alongside lifestyle changes. Sustained thermogenic response requires adopting permanent habits like strength training to build metabolically active muscle mass.

Alters neurochemistry in brain to reduce hunger and cravings

One of phentermine’s main weight loss mechanisms is the way it alters neurotransmitters and hormonal signals in the brain that control hunger and food cravings.

It primarily works by increasing the activity of norepinephrine. This neurotransmitter stimulates the sympathetic nervous system, signaling the ‘fight or flight’ response which suppresses appetite.

Phentermine also elevates serotonin levels which regulates food intake. Serotonin creates feelings of satiety and satisfaction after eating. Higher levels reduce cravings and the urge to overeat.

There is also evidence that phentermine may reduce levels of the hunger hormone ghrelin. Ghrelin communicates hunger signals from the gut to the brain. Suppressing ghrelin leads to feeling less hungry more often.

In effect, phentermine chemically tricks the appetite control centers in the brain, dulling reactions to food cues and hunger pangs. Signals to seek out and consume high-calorie foods occur less frequently. Willpower is enhanced to resist cravings and overeating.

However, the brain adapts to phentermine’s effects within several weeks, diminishing results. This is why phentermine is only recommended for short-term use. Permanent hunger and craving control requires making lasting lifestyle changes in nutrition, activity levels, sleep, and stress management.

Enhances willpower and control over eating behaviors

In addition to chemically suppressing hunger signals, phentermine also enhances willpower and self-control when it comes to making healthier food choices.

By reducing cravings and desire for calorie-dense foods, phentermine makes it easier for users to resist temptation and overeating. Food becomes fuel for the body rather than a source of pleasure or emotional comfort.

Many users report feeling more motivated and empowered to say no to junk food, fast food, and sugary treats while on phentermine. They have greater discipline to choose nutritious foods in proper portions that align with their weight loss goals.

Phentermine also gives users energy and focus to implement lifestyle changes like cooking healthy meals at home and exercising daily. It enhances the ability to develop new positive habits that support weight loss.

However, experts caution that phentermine is not a “magic pill” for self-control. Lasting results require putting in the work to modify behaviors and adopt permanent healthy eating habits. Stopping phentermine usually leads to appetite and cravings returning.

But used short-term alongside coaching, phentermine can provide a powerful push to get motivated, break bad habits, and establish new weight-supporting routines. The mental clarity and energy from phentermine makes implementing major lifestyle changes more achievable.

Phentermine Clinical Study Evidence

Phentermine is one of the most studied weight loss medications, with numerous clinical trials examining its efficacy and safety.

Major Clinical Trials on Phentermine

Numerous clinical trials have been conducted on Phentermine. One of the most significant is a systematic review and meta-analysis published in “Obesity Reviews” in 2016, which analyzed 28 randomized clinical trials involving Phentermine.

Average Weight Loss Over Placebo

According to the aforementioned meta-analysis, individuals using Phentermine lost an average of 3.6 kg (about 7.9 lbs) more than those given a placebo over 3 months. This demonstrates Phentermine’s effectiveness in promoting weight loss beyond what can be achieved with no treatment.

Combination with Lifestyle Modifications

Clinical studies consistently show that the best results with Phentermine occur when it is used in combination with lifestyle modifications, like a low-calorie diet and regular exercise. A study published in “Obesity” in 2017 found that participants who combined lifestyle modifications with Phentermine treatment lost significantly more weight than those who only made lifestyle modifications.

Limitations of Studies

While these studies provide evidence for Phentermine’s efficacy, they also have limitations. Many of the trials have been relatively short in duration, often only a few months long, which doesn’t provide data on long-term efficacy and safety. Also, many studies have small sample sizes, limiting their statistical power.

Additionally, some studies may be industry-funded, which could potentially introduce bias. Industry funding doesn’t automatically invalidate the results of a study, but it’s a factor that should be considered when evaluating the evidence.

Given these limitations and the potential side effects of Phentermine, it’s essential to discuss with a healthcare provider to determine whether it’s an appropriate option for individual weight loss goals.

Expected Weight Loss Results On Phentermine

Phentermine is a prescription medication used to suppress appetite and help with weight loss. It’s typically prescribed for individuals who have a high body mass index (BMI) and whose weight may cause serious health concerns.

Average Weight Loss

While Phentermine results can vary significantly between individuals, studies show that the average weight loss with Phentermine is around 5-10% of the initial total body weight over 12 weeks to 6 months. For instance, a person who weighs 200 pounds at the start of Phentermine treatment might expect to lose between 10 to 20 pounds on average.

Initial Weight Loss Period

The greatest weight loss typically occurs during the first six months of treatment. This is when the body is most responsive to the appetite-suppressing effects of the medication, leading to reduced calorie intake and subsequent weight loss.

Factors That Influence Results

Several factors can influence weight loss results with Phentermine:

  1. Dosage: The prescribed dose of Phentermine can affect the amount of weight loss. Higher doses may lead to more significant weight loss but may also increase the risk of side effects.
  2. Diet: Phentermine is intended to be used in combination with a reduced-calorie diet. The types and amounts of food consumed can greatly impact weight loss results.
  3. Exercise: Regular physical activity can enhance weight loss and improve overall health. The type, duration, and intensity of exercise can influence results.
  4. Genetics: Individual genetic factors can influence how the body responds to Phentermine and how much weight is lost.

Weight Loss Plateau

Many people find that their weight loss plateaus after several months of taking Phentermine. This is a common occurrence in weight loss journeys and can be due to several reasons, such as the body adapting to the lower calorie intake and slowing down the metabolic rate to conserve energy. It could also be due to the body becoming tolerant to the appetite-suppressing effects of Phentermine over time.

Remember, Phentermine is meant to be part of a complete weight loss program that includes diet, exercise, and behavior change. It’s important to consult with a healthcare professional for personalized advice and to monitor progress regularly.

Phentermine Side Effects and Safety

Common side effects

Like all medications, phentermine can cause some undesirable side effects. However, most are mild and temporary. The most frequently reported include:

  • Dry mouth – Phentermine reduces saliva production which can leave the mouth feeling parched. Sipping water regularly can provide relief. Sugar-free gum or lozenges also stimulate saliva flow.
  • Insomnia – Phentermine can make it harder to fall and stay asleep, especially if taken late in the day. Taking the dose earlier in the morning minimizes sleep disruption. Avoiding stimulants close to bedtime helps too. Melatonin supplements can also improve sleep quality.
  • Constipation – Phentermine slows digestion which can lead to constipation. Drinking more liquids, adding fiber, and exercising regularly can prevent and relieve this effect. Occasional stool softeners may also be used.
  • Headache – Some users report headaches when starting phentermine, likely from vasoconstriction in the brain. Staying well hydrated and limiting caffeine reduces headache occurrence. Over-the-counter pain relievers like acetaminophen can provide relief.

While uncomfortable, these common side effects of phentermine are temporary and subside with the body’s adaptation to the medication. Preventative strategies can reduce incidence and severity. Seeking medical advice is recommended if any severe, troublesome, or long-lasting side effects occur.

Contraindicated with heart disease, glaucoma, hyperthyroidism

Due to its stimulant properties, phentermine is contraindicated (advised against) in certain medical conditions as it may exacerbate risks:

  • Heart disease – Phentermine can increase heart rate, blood pressure, and cardiac workload. Those with conditions like coronary artery disease, arrhythmias, or uncontrolled hypertension are at higher risk of heart attack or stroke if using phentermine.
  • Glaucoma – Phentermine may worsen glaucoma by further increasing intraocular pressure. This damage to the optic nerve can lead to vision loss. Those with narrow-angle glaucoma are especially contraindicated.
  • Hyperthyroidism – Excess thyroid hormone already increases metabolism so combining phentermine can over-stimulate the sympathetic nervous system. Thyroid hormone production needs stabilization first before considering phentermine use.

Phentermine also requires caution in those with a history of substance abuse, anxiety, and diabetes among other conditions. Screening by a medical professional determines if potential benefits outweigh the risks given a patient’s full health profile. Monitoring is required to watch for signs of adverse reactions. While effective for weight loss, phentermine is not suitable for everyone due to concerns about dangerous side effects.

Risk of pulmonary hypertension and valvular heart disease

Phentermine use has been associated with an increased risk of pulmonary hypertension, a rare but serious condition where blood pressure rises in the arteries of the lungs. This can damage the right side of the heart over time.

There are also concerns that phentermine may contribute to valvular heart disease by causing inflammation and fibrosis in the heart valves, leading to restriction of normal blood flow. However, the risk appears low when phentermine is used short-term and discontinued if any cardiac side effects emerge.

Though the correlation is not fully proven, the structural similarities between phentermine and amphetamines known to cause these heart conditions necessitates caution. Patients on phentermine require monitoring for pulmonary hypertension and valvular heart disease signs. The medication is contraindicated in those with pre-existing cardiovascular conditions.

Drug interactions

Phentermine can interact with other medications, especially antidepressants like SSRIs leading to serotonin syndrome. It also should not be combined with other stimulants due to risk of excessive cardiovascular effects.

DEA schedule IV

Phentermine is classified as a schedule IV controlled substance by the DEA due to its potential for abuse and dependence. While lower than schedule II drugs, the risk exists of psychological and physical dependence from improper phentermine use.

Phentermine weight loss drugs can interact dangerously with certain medications so all co-administered drugs should be evaluated. Its DEA schedule IV designation means while its abuse potential is lower, care should still be exercised with long-term use due to risks of dependence. Patients require appropriate screening and monitoring by a medical professional when using phentermine.

Lifestyle Changes Needed for Best Phentermine Results

While phentermine can help jumpstart weight loss, it does not lead to sustained results on its own. The effects diminish within several weeks as the body adapts. True long-term weight management requires making permanent lifestyle changes.

Follow a reduced-calorie diet while taking Phentermine

Phentermine makes it easier to lower caloric intake, but a structured meal plan based on expert nutrition advice should be followed. Cutting at least 500 calories daily from maintenance needs through portion control and balanced macronutrients sets the stage for ongoing weight loss.

Exercise regimen

Adding cardio, strength training, and flexibility workouts accelerates fat burning. Building metabolism-boosting muscle also enables maintaining a caloric deficit without hunger. A program customized to your physical abilities by a trainer helps ensure adherence.

Behavioral counseling

Counseling teaches strategies to promote self-motivation, build healthy habits, manage stress, and overcome the emotional factors that may trigger overeating. Cognitive behavioral therapy combined with phentermine or other weight loss medications is ideal.

Adopting permanent changes

The skills learned through dietary, physical activity, and behavioral plans must become regular habits. For example, cooking weekly nutritious meals, exercising 5x a week, and practicing mindful eating. Phentermine facilitates implementing these changes which must then be sustained.

In summary, phentermine should be combined with therapeutic lifestyle modifications under medical supervision for lasting weight reduction. The medication jumpstarts weight loss progress while the lifestyle changes sustain it over the long term.

Pros and Cons of Using Phentermine

Here are some positives and negatives of using Phentermine 37.5 mg


  • Significant appetite suppression – Phentermine curbs hunger and cravings more strongly than many other weight loss medications. The reduced calorie intake it facilitates accelerates weight loss.
  • Rapid initial weight loss – Many see over 5-10% body weight loss in the first months of phentermine use, faster than diet and exercise alone. This motivates users to stick to their regimen.
  • Inexpensive – Phentermine is typically inexpensive, especially compared to newer prescription anti-obesity drugs. Most insurance plans cover phentermine making it affordable.


  • Short-term effects – Tolerance builds within 6-12 weeks as the brain adapts to phentermine. This leads to its weight loss effects diminishing over time. Cycling off periods are required.
  • Side effects – Various side effects like dry mouth, insomnia, headaches, and constipation are common. Though usually mild, some users experience more troubling reactions.
  • Contraindications – Phentermine cannot be used safely by those with a history of cardiovascular disease, hyperthyroidism, glaucoma and other conditions.
  • Abuse potential – There is a risk of growing dependence on phentermine resulting in addiction and withdrawal. It must be used cautiously under medical supervision.

In summary, when used short-term under guidance, phentermine can effectively jumpstart weight loss. But disadvantages like diminishing results, side effects, contraindications, and abuse potential limit its suitability for all patients.

Phentermine Alternatives

  • Overview of prescription and OTC alternatives
  • Phentermine vs. Contrave, Belviq, phentermine OTC supplements

Getting a Prescription and Dosage Info

Here is an overview of getting a phentermine prescription and dosage information:

Phentermine Prescription Duration

  • Phentermine is only approved by the FDA for short-term use of around 12 weeks or less
  • Prescriptions typically cover 1 month and can be renewed for up to 3 months total
  • Longer use requires approval and close monitoring for side effects

Doctor Visits

  • Requires an in-person exam by a licensed medical provider at doctor surgery or weight loss clinic
  • Weight, height, blood pressure, and other health markers are checked
  • Medical history, medications, and contraindications are reviewed
  • An individualized dosage is determined based on health profile

Phentermine Dosage Range

  • Phentermine diet pill starting doses range from 15mg to 37.5mg per day
  • Phentermine 37.5mg is the most common and effective dosage
  • Doses are taken once daily in the morning to prevent sleep disruption
  • Extended release doses are taken once while immediate release may be divided

Purchasing Phentermine Online Warnings

  • Phentermine is only available with a valid prescription
  • It is illegal to purchase without a prescription or doctor supervision
  • Illicit online pharmacies often sell counterfeit or unsafe products
  • Only obtain phentermine from licensed medical professionals

Careful medical oversight is important when using phentermine short-term for weight loss support. Attempting to purchase it without a proper prescription and monitoring is unsafe.

Conclusion and Recommendation

In summary, Phentermine offers notable pros as a short-term weight loss aid, including potent appetite suppression and rapid initial weight loss. However, disadvantages like tolerance buildup, side effects, contraindications, and abuse potential warrant caution. Phentermine is not a standalone solution but rather an adjunct to permanent lifestyle modifications.

Phentermine can help jumpstart weight loss through strong appetite control. Yet its effects diminish after several weeks as the body adapts. Lasting success requires dietary changes, increased physical activity, and behavior modifications. Phentermine facilitates implementing these changes but does not replace the need for them.

Given the pros and cons, phentermine is best suited for those struggling with severe obesity alongside other life-threatening conditions. Realistic expectations are key – phentermine provides a powerful nudge but the hard work must still be put in. I recommend speaking to a doctor to have an honest discussion about whether phentermine is appropriate given your health profile and weight loss goals.

For those seeking similar appetite and metabolism boosting benefits without the risks of phentermine, natural alternatives such as PhenQ could be considered. Under medical guidance, PhenQ may provide phentermine-like weight loss acceleration without side effects or potential harm. As always, adopting healthy eating habits combined with more exercise remains the bedrock for long-term weight control.

Phentermine Reviews FAQ

Here are 5 common frequently asked questions about phentermine:

How much weight can I expect to lose on phentermine?

Most people lose 5-10% of their body weight over 3-6 months on phentermine. However, results vary widely depending on dosage, diet, exercise, and adherence. Realistic goals are 1-2 lbs per week.

How long should I take phentermine for?

Phentermine is only approved for short-term use of around 12 weeks. Effects diminish after this as tolerance builds. Taking breaks helps regain effectiveness.

What are the side effects of phentermine?

Common side effects include dry mouth, insomnia, constipation, headache and elevated heart rate. Phentermine may also increase anxiety for some. More serious cardiac risks exist.

Is phentermine addictive?

While less addictive than amphetamines, phentermine has some potential for psychological and physical dependence with improper use. Addiction is rare when taken as prescribed short-term.

Can I take phentermine if I have high blood pressure?

Phentermine typically should not be used if uncontrolled high blood pressure is present. But some forms may be prescribed if blood pressure is well-managed and monitoring occurs.

Phentermine Resources

  1. FDA Drug Label Info
  2. Mayo Clinic Overview
  3. WebMD Phentermine Facts
  4. American Academy of Family Physicians
  5. Obesity Medicine Association Guidance
  6. International Journal of Obesity Review

These reputable medical organizations and peer-reviewed journals provide evidence-based information on phentermine’s mechanisms, effectiveness, dosage, safety risks, side effects, and clinical recommendations that validate the key facts covered in our Phentermine review.

Branded content furnished by our promotional partners. The Daily Sundial editorial staff is not involved in its production. Content does not reflect the views or opinions of the editorial staff.
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