Benzphetamine (Oral)

Benzphetamine is a drug prescribed to help reduce body weight and is recommended to be taken along with a healthy diet plan.


Benzphetamine is taken as a tablet that works by suppressing the appetite, leading to less caloric intake.

Benzphetamine is also marketed and sold under its brand name Didrex in the United States. It is popular as a treatment for those suffering from long-term obesity and can be an effective treatment before more drastic measures are introduced.

More than one in three people in the United States are considered to be overweight, and two in three are considered overweight or obese. Obesity is the most extreme form of being overweight and the condition can lead to poor quality of life, as well as increasing the patient's chance of developing conditions such as type 2 diabetes, heart problems, infections and breathing problems. In its most severe form, obesity can be life-threatening. One in 13 adults in the United States is also considered to be morbidly obese.

Benzphetamine can be prescribed to patients before they reach the extreme phase of becoming obese, helping the body to require less food. Reducing the daily caloric intake to below that of calories consumed causes the body to burn its fat reserves, leading to weight loss. The drug is most effective when used alongside a healthy meal plan and an exercise regime.

Appetite suppressants such as Benzphetamine are stimulants with effects similar to amphetamines. As a result, it impacts the central nervous system, causing a number of possible side effects.

Conditions treated

Type of medicine

  • Oral - in the form of a tablet


The usual dosage of benzphetamine is 50 mg taken orally once to twice per day. The drug should be taken with meals and at the same time each day.

The minimum dosage prescribed is 25 mg, to be taken orally once or twice per day. If you miss a dose, take it as soon as you remember. Do not take it if it is closer to your next dose. Do not attempt to double up on doses to make up for missed doses.

Side effects

There are various side effects that patients taking Benzphetamine may experience. It is therefore important that patients report any side effects that are persistent or particularly unpleasant to their doctor. Most side effects are normal and minor and will go away after the body has adapted to the drug, but there are those that can be more severe. In these cases, this drug may not be the right treatment for the patient, and an alternative may be prescribed.

These are some of the common side effects:

  • restless or hyperactive feeling
  • Excess sweating
  • Dryness in the mouth
  • Nausea
  • Stomachache
  • Diarrhea
  • headache
  • dizziness
  • Rashes or spots on the skin
  • tremors
  • Insomnia
  • increased sweating

There are some side effects that, if you experiment, you should stop taking benzphetamine straight away. These are:

  • Difficulty catching your breath, even after mild movements
  • swelling of any part of the body
  • Pain in your chest
  • Faintness
  • Sudden and fast weight gain
  • Increase or pounding heartbeat
  • Irritability
  • Confusion and forgetfulness
  • Signs of high blood pressure, such as a severe headache, anxiety, blurred vision, difficulty catching breath, irregular heartbeat, buzzing sensation in the ears
  • Seizure

Major drug interactions

Patients should always tell their doctors if they are taking any other medication. This may affect the drug and treatment methods that your doctor or pharmacist will prescribe to treat obesity. There are some drugs that, if taken with benzphetamine, can cause serious interactions. This can mean unknown and unpleasant side effects, or it can also impair the effectiveness of either drug, even making your conditions worse.

There are 562 drugs that are known to interact with benzphetamine, including 10 minor interactions, 462 moderate interactions and 90 major interactions. [ref 1] The major ones are listed below, and should not be taken alongside benzphetamine:

  • acetaminophen, aspirin, phenylpropanolamine
  • acetaminophen, brompheniramine, phenylpropanolamine
  • acetaminophen, caffeine, chlorpheniramine, phenylpropanolamine
  • acetaminophen, caffeine, phenylpropanolamine, salicylamide
  • acetaminophen, chlorpheniramine, dextromethorphan, phenylpropanolamine
  • acetaminophen, chlorpheniramine, guaifenesin, phenylpropanolamine
  • acetaminophen, chlorpheniramine, phenylephrine, phenylpropanolamine, pyrilamine
  • acetaminophen, chlorpheniramine, phenylpropanolamine
  • acetaminophen, dextromethorphan, guaifenesin, phenylpropanolamine
  • acetaminophen, dextromethorphan, phenylpropanolamine
  • acetaminophen, tramadol
  • aspirin, brompheniramine, dextromethorphan, phenylpropanolamine
  • aspirin, chlorpheniramine, dextromethorphan, phenylpropanolamine
  • aspirin, chlorpheniramine, phenylpropanolamine
  • aspirin, diphenhydramine, phenylpropanolamine
  • atropine, chlorpheniramine, hyoscyamine, phenylephrine, phenylpropanolamine, scopolamine
  • benzocaine, phenylephrine, phenylpropanolamine
  • benzoic acid, hyoscyamine, methenamine, methylene blue, phenyl salicylate
  • brompheniramine, codeine, phenylpropanolamine
  • brompheniramine, dextromethorphan, guaifenesin, phenylpropanolamine
  • brompheniramine, dextromethorphan, phenylpropanolamine
  • brompheniramine, phenylephrine, phenylpropanolamine
  • brompheniramine, phenylpropanolamine
  • bupropion
  • bupropion, naltrexone
  • caramiphen, phenylpropanolamine
  • carbetapentane, phenylephrine, phenylpropanolamine, potassium guaiacolsulfonate
  • chlorpheniramine, codeine, phenylephrine, phenylpropanolamine
  • chlorpheniramine, dextromethorphan, phenylpropanolamine
  • chlorpheniramine, dihydrocodeine, phenylephrine, phenylpropanolamine
  • chlorpheniramine, methscopolamine, phenylpropanolamine
  • chlorpheniramine, phenindamine, phenylpropanolamine
  • chlorpheniramine, phenylephrine, phenylpropanolamine
  • chlorpheniramine, phenylephrine, phenylpropanolamine, phenyltoloxamine
  • chlorpheniramine, phenylephrine, phenylpropanolamine, pyrilamine
  • chlorpheniramine, phenylpropanolamine
  • citalopram
  • clemastine, phenylpropanolamine
  • codeine, guaifenesin, phenylpropanolamine
  • desvenlafaxine
  • dexfenfluramine
  • dextromethorphan, guaifenesin, phenylpropanolamine
  • dextromethorphan, phenylpropanolamine
  • diethylpropion
  • duloxetine
  • escitalopram
  • fenfluramine
  • fluoxetine
  • fluoxetine, olanzapine
  • fluvoxamine
  • furazolidone
  • guaifenesin, hydrocodone, pheniramine, phenylephrine, phenylpropanolamine
  • guaifenesin, hydrocodone, pheniramine, phenylpropanolamine, pyrilamine
  • guaifenesin, phenylephrine, phenylpropanolamine
  • guaifenesin, phenylpropanolamine
  • hydrocodone, pheniramine, phenylephrine, phenylpropanolamine, pyrilamine
  • hydrocodone, phenylpropanolamine
  • hyoscyamine, methenamine, methylene blue, phenyl salicylate
  • hyoscyamine, methenamine, methylene blue, phenyl salicylate, sodium biphosphate
  • hyoscyamine, methenamine, methylene blue, sodium biphosphate
  • iohexol
  • iopamidol
  • isocarboxazid
  • levomilnacipran
  • linezolid
  • lorcaserin
  • ma huang
  • mazindol
  • methamphetamine
  • methylene blue
  • metrizamide
  • milnacipran
  • paroxetine
  • phendimetrazine
  • phenelzine
  • pheniramine, phenylpropanolamine, phenyltoloxamine, pyrilamine
  • pheniramine, phenylpropanolamine, pyrilamine
  • phentermine
  • phentermine, topiramate
  • phenylpropanolamine
  • procarbazine
  • selegiline
  • sertraline
  • sibutramine
  • tapentadol
  • tramadol
  • tranylcypromine
  • venlafaxine
  • vilazodone
  • vortioxetine



Do not take benzphetamine if you are pregnant. This drug has been found to cause harm to unborn babies, resulting in defects and abnormalities.

Recreational drug abuse

Do not take benzphetamine if you have a history of drug or alcohol addiction. This is because benzphetamine has an addictive nature similar to that of recreational drugs.

Food and drink interactions

Patients should avoid alcohol while taking benzphetamine. Alcohol taken together with this medication can seriously increase the risk of the patient developing headaches, drowsiness, blurred vision, depression, insomnia, bloatedness, confusion, impaired judgment, nausea and vomiting. It can also increase the risk of the patient suffering a cardiac arrest.

CPD supplements must be avoided when taking benzphetamine.

Other conditions

Always tell your doctor about any other conditions you have or have had in the past. Benzphetamine can make other conditions worse, so a safer treatment can be found for you if you suffer from any of the following:

There are 15 disease interactions with benzphetamine which include:


Benzphetamine should be stored at room temperature (between 15 and 25 degrees centigrade).

The drugs should always be stored in their original packaging. Any lockable tubs should be kept and fastened tightly shut when not in use. This prevents children from accessing the medication. All medicines should be kept out of the reach of children, ideally in a cupboard or a high shelf. More than 60,000 children are admitted to hospital each year due to taking prescription medications that have not been stored away properly.

Always dispose of unwanted or expired medication responsibly. If there are no drug take-back schemes in your area, you should dispose of the tablets by mixing them with an inedible substance such as soil or used coffee beans, put them in a sealed plastic bag, and then put them into the trash can. Do not flush or ground your tablets. [ref 2]


Benzphetamine is an effective treatment for those that are overweight or obese and is used by patients from a range of backgrounds and age groups. [ref 3] It is a relatively safe drug, with only very rare reports of serious side effects. However, the main risk to be aware of with benzphetamine is its addictive nature, meaning that it may be unsuitable for those with a history of addictive behavior.

Patients taking this drug should be occasionally monitored to check for any signs of addiction, and also for reactions with other drugs or conditions. If serious side effects are experienced, the patient should stop taking the medication immediately and seek another prescription.

These drugs are not to be used as slimming tablets on a recreational basis. This is a prescription only medication and is only to be used by those that are suffering from obesity, for which dietary and exercise planned have failed on their own. Care should be taken to ensure that this prescription is not mistaken for an over the counter slimming medication and that it is only used for the person to whom it was prescribed.

Benzphetamine is most effective when it is used as part of a holistic treatment for obesity of being overweight. This means that the patient has a responsibility to make positive and proactive lifestyle changes, including a change in diet, healthy eating plan, and a full exercise regime. The drug is not to be relied upon to be the sole cure for obesity, particularly those that are morbidly obese.

Patients should also commit to cutting out or cutting back on alcohol when taking this medication, and be upfront and honest with their doctors about their full medical history. There are a large number of drugs that can interact with this one, impeding its effectiveness and potentially leading to harm for the patient if taken at the same time.

If all instructions are followed and the patient takes the drug as recommended, it can be a very effective solution to obesity, often cutting out the need for surgery.

Last Reviewed:
December 24, 2017
Last Updated:
April 04, 2018
Content Source: