Phendimetrazine (Oral)

Part of the family of medications known as anorectics, phendimetrazine is a sympathomimetic amine that works as an appetite suppressant that is used in the treatment of obesity.


Phendimetrazine has been available in various forms for the treatment of obesity in adults since 1976. It is a sympathomimetic amine, which has much the same impact on the body as amphetamines. It affects the central nervous system, increasing both heart rate and blood pressure, but also decreasing the appetite. It has been marketed under many different brand names including Melfiat, Bontril, and Adipost, but has been available in generic form since 2010. It is used to treat patients whose body mass index (BMI) is 30 or greater. It may also be used for people whose BMI is at 27 or greater if they also suffer from other health conditions that increase their morbidity, including diabetes, high blood pressure or cardiovascular disease.

However, patients who suffer from com/health/coma/">glaucoma, Parkinson's disease, thyroid disease, kidney disease, liver disease or who have a history of stroke or pulmonary hypertension should not be prescribed phendimetrazine as it may make those conditions worse and may interact negatively with the medications used to treat those conditions. This is especially true for patients taking MAOI medications for Parkinson's or anxiety disorders. The interaction between phendimetrazine and MAOIs is particularly severe.

For patients with anxiety or other nervous disorders, phendimetrazine may not be an effective choice. Because this drug acts on the central nervous system and increases heart rate, it can exacerbate the symptoms of those conditions. Patients who are being treated for anxiety, panic disorder, psychotic behaviors, or other nervous conditions should only be prescribed phendimetrazine with careful and regular monitoring by their physician.

This medication should not be taken by pregnant women. Women who are pregnant should not attempt to lose weight. There is no definitive data on the impact phendimetrazine may have on the fetus. However, there have been known cases of infants born to mothers using phendimetrazine exhibiting symptoms of withdrawal. This medication is in Category C for pregnancy risk, which would contraindicate its use. It is not known how much phendimetrazine may be excreted through breast milk, but it is known that amphetamines may transfer that way, and phendimetrazine behaves in much the same way pharmacologically in the body as amphetamines. Nursing mothers should not use phendimetrazine.

Phendimetrazine interacts with a host of other medications, including common over the counter medications used to treat pain, inflammation and cold symptoms. It also can alter the effectiveness of drugs used to treat diabetes, high cholesterol and hyperthyroidism.

Patients with a history of drug abuse should not take this medication as it carries the risk of dependency and addiction. It is also classified as a Schedule III medication, indicating that its risk of dependency is high. Because it affects and metabolizes in the body in much the same way that amphetamines do, those addictive qualities that are present with those drugs are also present when using phendimetrazine. Patients are likely to develop a substantial tolerance for phendimetrazine after several weeks of use. Withdrawal from this medication can also be very difficult for patients and should be medically managed as well. Abrupt discontinuation of use can lead to debilitating fatigue and serious depression which carries its own risk.

Phendimetrazine is available by prescription in three different formulations. It may be prescribed as a slow release capsule of 105 mg that is taken once daily. It can also come as an extended release capsule of 105 mg taken once a day. It is also available in tablet form at 35 mg that may be taken two or three times a day. When prescribed for weight loss, phendimetrazine should be used alone. This medication should not be used in combination with other appetite suppressants as concomitant use increases the risk and intensity of side effects. It can lead to dangerously high blood pressure and significantly increase the risk of developing pulmonary hypertension, which can be fatal.

Conditions Treated

  • Obesity (BMI of 30 or greater)
  • Controlled weight reduction for patients with a BMI of 27 or over in combination with other risk factors such as diabetes or high blood pressure

Type Of Medication

  • Amine, phenylalkylamine sympathomimetic

Side Effects

Phendimetrazine has many known side effects. These side effects are relatively common, and may not require medical attention. Patients may suffer from one or more of the following:

  • Headache
  • Unusual irritability
  • Loss of libido
  • Insomnia
  • Vomiting
  • Back pain
  • Painful or burning urination
  • More frequent urination
  • Increased anxiety levels
  • Constipation or difficult bowel movements
  • Hyperactivity
  • Dry mouth
  • Stomach ache
  • Unexplained tremor
  • Dizziness or lightheadedness
  • Feeling faint
  • Increased libido
  • Sexual dysfunction, impotence
  • Nausea
  • Flushing, hot flashes

The following symptoms/side effects require immediate medical attention as they can indicate allergic reaction or overdose.

  • Hallucinations
  • Irregular heartbeat (arrhythmia)
  • Increased agitation
  • Abrupt mood changes, altered personality
  • Seizure, uncontrolled muscle spasms
  • Swelling of the lower extremities
  • Disorientation
  • Depression
  • Blurred vision
  • Intense feeling of sadness or depression
  • Hyperventilation
  • Blurry or hazy vision, double vision
  • Attempts to self-harm or harm others
  • Panic attacks
  • Severe abdominal cramping

Phendimetrazine is a Schedule III controlled substance according to the US Drug Enforcement Administration and has been associated with dependence and addiction, especially when used for an extended period of time. It has a similar pharmacologic effect in the body as amphetamines. Some signs of dependence are social dysfunction, chronic insomnia, skin conditions and rashes, and in its most extreme form, mental psychosis that may resemble schizophrenia.

It can be dangerous to abruptly discontinue use of phendimetrazine, particularly if the patient has been using it for more than four weeks. Withdrawal symptoms can include severe depression and extreme fatigue.


Phendimetrazine is available in three different forms. It is available in slow release capsule form with a dosing strength of 105 mg. There is also the option of an extended release capsule at 105 mg. Phendimetrazine also comes in tablet form with a dosing level of 35 mg.

For patients taking the 105 mg capsule, regular dosing is once daily at least 30 minutes before breakfast.

For patients taking the 35 mg tablet, regular dosing is twice or three times a day at least an hour before meals. The maximum dose daily for immediate release medication is 70 mg, so tablets may be divided in half.

Capsules should be swallowed whole. Any effort to break it or chew it will result in medication being released too quickly into the body which could lead to overdose or exacerbated side effects.

The normal length of treatment with this medication is four to eight weeks under the supervision of a physician for controlled weight loss. Phendimetrazine may be taken over a longer period of time, but the patient should be closely monitored for chemical or psychological dependence. Patients prescribed this medication should take it exactly as directed by the prescribing physician.

For patients with liver or kidney conditions, this medication should be used with caution, and maximum dosing levels should not be exceeded.

Patients under 17 should not be prescribed the extended release form of this medication. Patients under 12 should not be prescribed the immediate release form of this medication. It should not be taken by women who are pregnant or breastfeeding.


Phendimetrazine interacts with many other medications. Patients who are prescribed this drug should insure that their physician is aware of any and all other medications they are taking to avoid negative interactions, exacerbation of symptoms or lessening the efficacy of one or all medications. Major drug interactions include:

  • Atropine
  • Aspirin
  • Dextromethorphan
  • Acetaminophen
  • Salicylamide
  • Tramadol
  • Guaifenesin
  • Phenylpropanolamine
  • Scopolamine
  • Bupropion
  • Benzocaine
  • Benzphetamine
  • Brompheniramine
  • Chlorpheniramine
  • Caramiphen
  • Citalopram
  • Codeine
  • Dihydrocodeine
  • Carbetapentane
  • Clemastine
  • Duloxetine
  • Dexfenfluramine
  • Diethylpropion
  • Desvenlafaxine
  • Escitalopram
  • Furazolidone
  • Fenfluramine
  • Olanzapine
  • Fluvoxamine
  • Fluoxetine
  • Hydrocodone
  • Methylene blue
  • Hyoscyamine
  • Isocarboxazid
  • Lorcaserin
  • Iohexol
  • Levomilnacipran
  • Iopamidol
  • Linezolid
  • Metrizamide
  • Ma huang
  • Methamphetamine
  • Mazindol
  • Milnaciprin
  • Phenelzine
  • Procarbazine
  • Topiramate
  • Paroxetine
  • Phentermine
  • Pyrilamine
  • Sertraline
  • Tapentadol
  • Selegiline
  • Tranylcypromine
  • Sibutramine
  • Vilazodone
  • Venlafaxine
  • Vortioxetine

Phendimetrazine interacts to a lesser extent with the following drugs:

  • Acarbose
  • Acetohexamide
  • Pseudoephedrine
  • Doxylamine
  • Acrivastine
  • Amitriptyline
  • Albuterol
  • Aminophylline
  • Alogliptin
  • Potassium iodide
  • Phenobarbital
  • Pioglitazone
  • Metformin
  • Albiglutide
  • Azatadine
  • Articaine
  • Arformoterol
  • Anhydrous calcium iodide
  • Amoxapine
  • Rauwolfia serpentine
  • Budesonide
  • Bitolterol
  • Formoterol
  • Bisacodyl
  • Bendroflumethiazide
  • Canagliflozin
  • Cetirizine
  • Chlophedianol
  • Methscopolamine
  • Carbetapentane
  • Tripolidine
  • Dapaglifozin
  • Desloratidine
  • Dopamine
  • Desipramine
  • Doxepin
  • Droxidopa
  • Dobutamine
  • Dulaglutide
  • Ethanol
  • Lidocaine
  • Empagliflozin
  • Exenatide
  • Umeclidinium
  • Fexofenadine
  • Gingko
  • Guanadrel
  • Glimeperide
  • Glycopyrrolate
  • Guanethidine
  • Glyburide
  • Haloperidol
  • Reserpine
  • Hydralazine
  • Ibuprofen
  • Isoprotenorol
  • Insulin regular
  • Insulin zinc
  • Imipramine
  • Insulin
  • Lixisenatide
  • Lindane topical
  • Levalbuterol
  • Linagliptin
  • Liraglutide
  • Levonordefrin
  • Midodrine
  • Methdilazine
  • Magnesium sulfate
  • Methoxamine
  • Miglitol
  • Methdilazine
  • Norepinephrine
  • Naproxen
  • Nortriptyline
  • Nateglinide
  • Olodaterol
  • Pramlintide
  • Terfenadine
  • Pirbuterol
  • Perphenazine
  • Polyethylene glycol 3350
  • Racepinephrine
  • Ritodrine
  • Rasagiline
  • Repaglinide
  • Rosiglitazone
  • Simvastatin
  • Salmeterol
  • Safinamide
  • Tolazamide
  • Terbutaline
  • Thyroid dessicated
  • Evening primrose
  • Bilberry

Phendimetrazine interacts negatively with alcohol. Patients taking this medication should not ingest alcohol. This can cause increased heart rate, blood pressure and chest pain. It can also lead to increased drowsiness and dizziness.

Patients should not take any sort of amphetamine in combination with phendimetrazine as it can lead to dangerously high heart rates and blood pressure.

Patients suffering from glaucoma should not be prescribed phendimetrazine as it can cause a condition called transient mydriasis and lead to worsening of the glaucoma.

Patients who are being treated for various disorders linked to agitation and hyperactivity should not be prescribed this medication as it interacts negatively with medications prescribed to treat those conditions and may also worsen the conditions themselves.

Patients who suffer from hepatic impairment should be prescribed phendimetrazine with great caution. Phendimetrazine is metabolized largely in the liver and can impact liver function even further.

Patients struggling with seizure disorder should only be prescribed phendimetrazine under close supervision as it interacts with those medications often prescribed to control seizures. Phendimetrazine has also been shown to trigger seizures. Should seizures occur, patients should discontinue use of phendimetrazine.


Phendimetrazine is an effective appetite suppressant, but its pharmacological effects on the body carry a number of risks and warnings. It is a medication that should be prescribed cautiously and only when the benefits of the weight loss outweigh the risks inherent in the medication itself. For patients with some medical conditions, use of phendimetrazine is contraindicated altogether. These conditions include:

  • Congestive heart failure
  • Hyperthyroidism
  • History of stroke or heart attack
  • Glaucoma
  • Hypertension that is not well controlled
  • Any condition treated with monoamine oxidase inhibitors (MAOIs)
  • History of drug abuse or addiction
  • Certain psychoses
  • Pregnancy
  • Hypersensitivity to sympathomimetic amines

The use of phendimetrazine and other similar medications has been linked to a significant increase in risk of the development of pulmonary hypertension, a serious condition which can be fatal. This risk is much greater when the medication is used for more than three months.

Phendimetrazine should not be used in combination with any other appetite suppressants, whether through prescription or over the counter.

Patients typically develop a tolerance for the anorectic effects of phendimetrazine after a few weeks and it becomes less effective. Maximum doses should not be exceeded under any circumstances.

Sudden discontinuation of phendimetrazine is not recommended as withdrawal from this medication can be unpleasant and cause severe depression and fatigue.

While this medication carries the risk of causing cardiac issues, those risks must be weighed against the risks associated with obesity or being overweight. In a medically controlled weight loss program, this medication can be an effective tool in lowering some of those risks.

Phendimetrazine can interfere with and reduce the effectiveness of medications such as insulin in the treatment of diabetes mellitus. It may also reduce the efficacy of certain medications used to treat hypertension.

Pregnant women and nursing mothers should not use phendimetrazine as its effects on the fetus is not known.

Phendimetrazine should be prescribed to geriatric patients with great caution, particularly if they suffer from cardiovascular disease as this medication may exacerbate those conditions.

This medication should not be prescribed to pediatric patients under the age of seventeen.

There is real risk of patients developing an addiction to or dependence on this medication. Physicians should monitor patients carefully for this condition. It is also possible to overdose, fatally, on phendimetrazine, so following prescribed dosage levels are extremely important.


Phendimetrazine should be stored in its original container until it is used. It should be kept at room temperature, and kept out of direct sunlight, excessive heat or moisture. It must not be allowed to freeze.

This medication should not be kept past its expiration date and must be disposed of safely. Phendimetrazine should be kept safely and securely out of the reach of children or animals, particularly because of the possibility of overdose and addiction. If overdose is suspected, call 911 immediately and contact poison control.

Patients with phendimetrazine that they need to dispose of should contact a local pharmacist, physician's office or the FDA website regarding safe disposal of medications. A medical take-back program is the preferred method of disposal for this drug.


Phendimetrazine is an effective medication in the treatment of obesity. As the number of people struggling with serious weight issues increases globally, this medication is a viable tool to help in that effort. However, it carries some real risks and dangers. The list of side effects that patients may experience is long and varied. As a Schedule III drug, it is known to cause dependency and addiction. It behaves as an amphetamine, and so the risk of increased tolerance, physical and psychological dependency and addiction are similar. This medication should not be used for an extended period of time and maximum dosage levels should not be exceeded. The typical treatment period is four to eight weeks.

Patients who suffer from certain medical conditions including thyroid disease, glaucoma, Parkinson's, uncontrolled high blood pressure, certain nervous and psychotic conditions or have a history of stroke should not take this medication. It should not be taken by women who are pregnant or nursing. It is also not recommended for pediatric patients, particularly those under 17.

Overdose on this medication is possible, so it should be handled with care and kept in a safe and secure location out of the reach of children.

Patients who are prescribed phendimetrazine should follow this treatment under medical supervision, with regular monitoring for symptoms of elevated blood pressure, management of side effects and risk of addiction and dependence.