Generic Name: phendimetrazine (fen-dye-MET-ra-zeen TAR-trate) (Oral route)
Medically reviewed by Drugs.com. Last updated on Nov 29, 2020.
The Prelu-2 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.
- Bontril PDM
- Bontril Slow-Release
Available Dosage Forms:
- Capsule, Extended Release
Therapeutic Class: Appetite Suppressant, Centrally Acting
Chemical Class: Phendimetrazine
Uses for Prelu-2
Phendimetrazine is used as part of a short-term plan, along with a low calorie diet, for weight reduction. It is used in obese patients who have not been able to lose weight with diet and exercise alone. Phendimetrazine belongs to the group of medicines known as appetite suppressants.
This medicine is available only with your doctor's prescription.
Before using Prelu-2
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 phendimetrazine extended-release capsules in children younger than 17 years of age. Safety and efficacy have not been established.
Appropriate studies have not been performed on the relationship of age to the effects of phendimetrazine tablets in the pediatric population. Safety and efficacy have not been established.
Use of phendimetrazine slow-release capsules is not recommended in children younger than 12 years of age.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of phendimetrazine extended-release capsules in the elderly. However, elderly patients are more likely to have age-related kidney problems, which may require caution and an adjustment in the dose for patients receiving phendimetrazine extended-release capsules.
No information is available on the relationship of age to the effects of phendimetrazine slow release capsules and tablets in geriatric patients.
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.
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.
- Iobenguane I 131
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:
- Agitated state or
- Arteriosclerosis (hardening of the arteries), advanced or
- Drug abuse or dependence, history of or
- Glaucoma or
- Heart or blood vessel disease (e.g., arrhythmia, congestive heart failure, coronary artery disease, stroke), history of or
- Heart problems (e.g., heart murmur, valvular heart disease) or
- Hypertension (high blood pressure), uncontrolled or
- Hyperthyroidism (overactive thyroid) or
- Pulmonary hypertension, history of—Should not be used in patients with these conditions.
- Diabetes or
- Hypertension (high blood pressure), controlled—Use with caution. May make these conditions worse.
- Kidney disease—Use with caution. The effects may be increased because of slower removal of the medicine from the body.
Proper use of Prelu-2
This section provides information on the proper use of a number of products that contain phendimetrazine. It may not be specific to Prelu-2. Please read with care.
Take this medicine only 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 is taken, it may become habit-forming (causing mental or physical dependence).
This medicine is available in 3 forms: extended-release capsules, slow-release capsules, and tablets. Ask your doctor which dosage form is right for you.
Swallow the extended-release capsule whole. Do not crush, break, or chew it.
Carefully follow your doctor's instructions for a reduced-calorie diet plan and regular exercise. Talk with your doctor before starting any exercise program.
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 weight loss:
- For oral dosage form (extended-release capsules):
- Adults and teenagers 17 years of age and older—One capsule or 105 milligrams (mg) once a day, taken 30 to 60 minutes before the morning meal.
- Children younger than 17 years of age—Use and dose must be determined by your doctor.
- For oral dosage form (slow-release capsules):
- Adults and teenagers—One capsule or 105 milligrams (mg) once a day, taken 30 to 60 minutes before the morning meal.
- Children younger than 12 years of age—Use is not recommended.
- For oral dosage form (tablets):
- Adults—One tablet or 35 milligrams (mg) two or three times a day, taken one hour before meals. Your doctor may adjust your dose as needed. However, the dose is usually not more than 2 tablets three times a day.
- Children—Use and dose must be determined by your doctor.
- For oral dosage form (extended-release capsules):
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 Prelu-2
It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly and does not cause any unwanted effects.
Do not use phendimetrazine if you are also using similar medicines, such as benzphetamine, diethylpropion, mazindol, phentermine, Didrex®, or Suprenza™. Also, do not use this medicine if you have used an MAO inhibitor (MAOI) such as Eldepryl®, Marplan®, Nardil®, or Parnate® within the past 14 days. Using these medicines together may cause serious 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. If you think you have become pregnant while using the medicine, tell your doctor right away.
This medicine may be habit-forming. If you think this medicine is not working properly after you have taken it for a few weeks, do not increase the dose. Instead, check with your doctor.
Stop using this medicine and check with your doctor right away if you notice a decrease in your ability to exercise, if you faint, or if you have chest pain, swelling of your feet or lower legs, or trouble with breathing. These may be symptoms of a very serious heart or lung problem.
This medicine may cause some people to become dizzy, lightheaded, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or not alert.
Do not stop using this medicine unless your doctor tells you to. If you suddenly stop using this medicine, you may feel very tired and depressed.
For diabetic patients: This medicine may affect blood sugar levels. If you notice a change in the results of your blood or urine sugar tests or if you have any questions, check with your doctor.
Avoid drinking alcohol while you are using this medicine.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription and nonprescription (over-the-counter) medicines, dietary supplements, herbal remedies, or medicines for appetite control, asthma, colds, cough, hay fever, and sinus problems.
Prelu-2 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:
- Seeing, hearing, or feeling things that are not there
- severe mental changes
Incidence not known
- burning while urinating
- chest pain or discomfort
- decreased ability to exercise
- difficult or painful urination
- dry mouth
- fast, irregular, pounding, or racing heartbeat or pulse
- feeling of warmth
- increased need to urinate
- numbness or tingling in the arms or legs
- pain or discomfort in the arms, jaw, back, or neck
- passing urine more often
- redness of the face, neck, arms, and occasionally, upper chest
- shakiness in the legs, arms, hands, or feet
- shortness of breath
- swelling of the feet or lower legs
- trembling or shaking of the hands or feet
- trouble with breathing
- trouble with sleeping
- trouble with thinking, speaking, or walking
Get emergency help immediately if any of the following symptoms of overdose occur:
Symptoms of overdose
- Abdominal or stomach cramps
- blurred vision
- change in consciousness
- dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
- fast, slow, or irregular heartbeat
- feeling sad or empty
- lack of appetite
- loss of consciousness
- loss of interest or pleasure
- overactive reflexes
- physical attempt to injure
- pounding in the ears
- rapid breathing
- trouble with concentrating
- unusual tiredness or weakness
- 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:
Incidence not known
- Decreased interest in sexual intercourse
- difficulty having a bowel movement (stool)
- inability to have or keep an erection
- increased in sexual ability, desire, drive, or performance
- increased interest in sexual intercourse
- loss in sexual ability, desire, drive, or performance
- stomach pain
- unable to sleep
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 Prelu-2 (phendimetrazine)
- Side Effects
- During Pregnancy
- Dosage Information
- Drug Images
- Drug Interactions
- Drug class: anorexiants
Related treatment guides
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.