Generic Name: benzphetamine (benz-FET-a-meen) (Oral route)
Medically reviewed by Drugs.com. Last updated on Sep 22, 2020.
The Didrex brand name has been discontinued in the U.S. If generic versions of this product have been approved by the FDA, there may be generic equivalents available.
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
Therapeutic Class: Appetite Suppressant, Centrally Acting
Chemical Class: Amphetamine (class)
Uses for Didrex
Benzphetamine is used for weight reduction in obese patients. This medicine works by suppressing your appetite.
This medicine is available only with your doctor's prescription.
Before using Didrex
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies have not been performed on the relationship of age to the effects of benzphetamine in children. Use of this medicine is not recommended in children younger than 17 years of age.
Appropriate studies have not been performed on the relationship of age to the effects of benzphetamine in the elderly. However, elderly patients are more likely to have age-related liver, kidney, or heart problems, which may require caution and an adjustment in the dose for patients receiving benzphetamine.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
- Methylene Blue
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Abiraterone Acetate
- Calcium Carbonate
- Dihydroxyaluminum Aminoacetate
- Iobenguane I 131
- Magnesium Carbonate
- Morphine Sulfate Liposome
- Opium Alkaloids
- Sodium Bicarbonate
- St John's Wort
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other medical problems
The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:
- Agitation or anxiety, severe or
- Drug abuse or dependence, history of or
- Glaucoma or
- Heart or blood vessel disease or
- Heart rhythm problems or
- High blood pressure, moderate or severe or
- Overactive thyroid—Should not be used in patients with these conditions.
- Diabetes or
- High blood pressure, mild or
- Lung or breathing problems or
- Mental illness—Use with caution. This medicine may make these conditions worse.
Proper use of Didrex
Take this medicine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. If too much of this medicine is taken, it may become habit-forming. If you feel that the medicine is not working properly after using it for a few weeks, check with your doctor first and do not increase the dose.
It is best to take this medicine in the mid-morning or mid-afternoon.
Carefully follow your doctor's instructions about a special diet plan that will help you lose weight.
The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For oral dosage form (tablets):
- For weight loss:
- Adults—At first, 25 to 50 milligrams (mg) once a day. Your doctor may increase your dose as needed. However, the dose is usually not more than 25 to 50 mg 3 times a day.
- Children—Use and dose must be determined by your doctor.
- For weight loss:
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Precautions while using Didrex
It is very important that your doctor check your progress at regular visits to make sure the medicine is working properly. Blood and blood pressure tests may be needed to check for unwanted effects.
Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant during treatment with this medicine. If you think you have become pregnant while using the medicine, tell your doctor right away.
If you will be taking this medicine for a long time, do not stop taking it without first checking with your doctor. Your doctor may want you to gradually reduce the amount you are taking before stopping completely.
This medicine may cause pulmonary hypertension (increased blood pressure in the lungs). Serious heart or blood vessel problems (eg, valvular heart disease) may also occur if you take more of it, if you take it for a longer time, or if you are taking other medicine that reduces appetite (eg, dexfenfluramine, fenfluramine). Check with your doctor right away if you have chest pain, decreased ability to exercise, fainting, swelling of the feet or lower legs, or trouble breathing.
Do not use this medicine if you are taking or if you took other medicine that reduces appetite within the past year.
You should not use this medicine if you have used an MAO inhibitor (MAOI) within the past 14 days or if you are also taking any other stimulants.
Unusual changes in behavior or moods may occur during treatment with this medicine together with a special diet plan that will help you lose weight. Tell your doctor right away if you or your family notice an increase in aggression, hostility, agitation, or irritability. Tell your doctor if you have hallucinations or any unusual thoughts, especially if they are new or getting worse quickly.
This medicine may cause some people to become dizzy or drowsy. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines, and herbal or vitamin supplements.
Didrex side effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- fast, irregular, pounding, or racing heartbeat or pulse
- feeling lightheaded or faint
- hives, welts, itching, skin rash
- mood or other mental changes
- numbness or tingling in the arms or legs
- redness of the skin
- shakiness or trembling in the legs, arms, hands, or feet
- trouble sleeping
- trouble thinking, speaking, or walking
- unusual feeling of excitement
- Chest discomfort or pain
- feeling sad or empty
- lack of appetite
- loss of interest or pleasure
- severe mental changes
- swelling of the feet or lower legs
- trouble breathing
- trouble concentrating
- unusual tiredness or weakness
Get emergency help immediately if any of the following symptoms of overdose occur:
Symptoms of overdose
- Blurred vision
- change in consciousness
- dark-colored urine
- dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
- loss of consciousness
- muscle cramps, spasms, pain, or stiffness
- physical attempt to injure oneself
- pounding in the ears
- rapid, shallow breathing
- severe anxiety or feeling of panic
- stomach cramps
- violent actions
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- Decrease in sexual ability, desire, drive, or performance
- decreased interest in sexual intercourse
- dry mouth
- inability to have or keep an erection
- increase in sexual ability, desire, drive, or performance
- increased interest in sexual intercourse
- unpleasant taste
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
More about Didrex (benzphetamine)
- Side Effects
- During Pregnancy
- Dosage Information
- Drug Images
- Drug Interactions
- En Español
- 11 Reviews
- Drug class: anorexiants
- Other brands
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