DIDREX Tablets contain the anorectic agent benzphetamine hydrochloride. Benzphetamine hydrochloride is a white crystalline powder readily soluble in water and 95% ethanol. The chemical name for benzphetamine hydrochloride is d-N,α-Dimethyl-N- (phenylmethyl)-benzeneethanamine hydrochloride and its molecular weight is 275.82.

The structural formula (dextro form) is represented below:

Each DIDREX Tablet, for oral administration, contains 50 mg of benzphetamine hydrochloride.

Inactive Ingredients: Calcium Stearate, Corn Starch, Erythrosine Sodium. FD & C Yellow No. 6, Lactose, Povidone, Sorbitol.

Last updated on RxList: 4/10/2008

DIDREX Tablets are indicated in the management of exogenous obesity as a short term adjunct (a few weeks) in a regimen of weight reduction based on caloric restriction. The limited usefulness of agents of this class (See CLINICAL PHARMACOLOGY) should be weighed against possible risks inherent in their use such as those described below.

Dosage should be individualized according to the response of the patient. The suggested dosage ranges from 25 to 50 mg one to three times daily. Treatment should begin with 25 to 50 mg once daily with subsequent increase in individual dose or frequency according to response. A single daily dose is preferably given in mid-morning or mid-afternoon, according to the patient's eating habits. In an occasional patient it may be desirable to avoid late afternoon administration. Use of benzphetamine hydrochloride is not recommended in individuals under 12 years of age.

DIDREX Tablets are supplied as follows:

50 mg (peach, round, imprinted with DIDREX 50, scored)

Bottles of 100................................NDC 0009-0024-01
Bottles of 500................................NDC 0009-0024-02

Store at controlled room temperature 20° to 25° C (68° to 77° F). [see USP]

Manufactured by: MOVA Pharmaceuticals Manati, PR 00674. Revised December 2005. FDA Rev date: 7/8/2000

Last updated on RxList: 4/10/2008

The following have been associated with the use of benzphetamine hydrochloride:

Cardiovascular

Palpitation, tachycardia, elevation of blood pressure. There have been isolated reports of cardiomyopathy associated with chronic amphetamine use.

CNS

Overstimulation, restlessness, dizziness, insomnia, tremor, sweating, headache; rarely, psychotic episodes at recommended doses; depression following withdrawal of the drug.

Gastrointestinal

Dryness of the mouth, unpleasant taste, nausea, diarrhea, other gastrointestinal disturbances.

Allergic

Urticaria and other allergic reactions involving the skin.

Endocrine

Changes in libido.

Drug Abuse And Dependence

Benzphetamine is a controlled substance under the Controlled Substance Act by the Drug Enforcement Administration and has been assigned to Schedule III.

Benzphetamine hydrochloride is related chemically and pharmacologically to the amphetamines. Amphetamines and related stimulant drugs have been extensively abused, and the possibility of abuse of DIDREX Tablets should be kept in mind when evaluating the desirability of including a drug as part of a weight reduction program. Abuse of amphetamines and related drugs may be associated with intense psychological dependence and severe social dysfunction. There are reports of patients who have increased the dosage to many times that recommended. Abrupt cessation following prolonged high dosage administration results in extreme fatigue and mental depression; changes are also noted on the sleep EEG. Manifestations of chronic intoxication with anorectic drugs include severe dermatoses, marked insomnia, irritability, hyperactivity, and personality changes. The most severe manifestation of chronic intoxication is psychosis, often clinically indistinguishable from schizophrenia.

Hypertensive crises have resulted when sympathomimetic amines have been used concomitantly or within 14 days following use of monoamine oxidase inhibitors. DIDREX should not be used concomitantly with other CNS stimulants.

Amphetamines may decrease the hypotensive effect of antihypertensives. Amphetamines may enhance the effects of tricyclic antidepressants.

Urinary alkalinizing agents increase blood levels and decrease excretion of amphetamines. Urinary acidifying agents decrease blood levels and increase excretion of amphetamines.

Last updated on RxList: 4/10/2008

When tolerance to the anorectic effect develops, the recommended dose should not be exceeded in an attempt to increase the effect; rather, the drug should be discontinued.

General: Insulin requirements in diabetes mellitus may be altered in association with use of anorexigenic drugs and the concomitant dietary restrictions.

Psychological disturbances have been reported in patients who receive an anorectic agent together with a restrictive dietary regime.

Caution is to be exercised in prescribing amphetamines for patients with even mild hypertension. The least amount feasible should be prescribed or dispensed at one time in order to minimize the possibility of overdosage.

Carcinogenesis, Mutagenesis, Impairment of Fertility: Animal studies to evaluate the potential for carcinogenesis, mutagenesis or impairment of fertility have not been performed by Pharmacia & Upjohn Company.

Pregnancy: Pregnancy Category X (see CONTRAINDICATIONS section).

Nursing Mothers: Amphetamines are excreted in human milk. Mothers taking amphetamines should be advised to refrain from nursing.

Pediatric Use: Use of benzphetamine hydrochloride is not recommended in individuals under 12 years of age.

Geriatric Use: Clinical studies of DIDREX Tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Last updated on RxList: 4/10/2008

Manifestations of Overdosage: Acute overdosage with amphetamines may result in restlessness, tremor, tachypnea, confusion, assaultiveness and panic states. Fatigue and depression usually follow the central stimulation. Cardiovascular effects include arrhythmias, hypertension or hypotension, and circulatory collapse. Gastrointestinal symptoms include nausea, vomiting, diarrhea, and abdominal cramps. Hyperpyrexia and rhabdomyolysis have been reported and can lead to a number of associated complications. Fatal poisoning is usually preceded by convulsions and coma.

Treatment of Overdosage: (See WARNINGS)- Information concerning the effects of overdosage with DIDREX Tablets is extremely limited. The following is based on experience with other anorexiants.

Management of acute amphetamine intoxication is largely symptomatic and includes sedation with a barbiturate. If hypertension is marked, the use of a nitrite or rapidly acting alpha receptor blocking agent should be considered. Experience with hemodialysis or peritoneal dialysis is inadequate to permit recommendations in this regard.

Acidification of the urine increases amphetamine excretion.

The oral LD₅₀ is 174 mg/kg in mice and 104 mg/kg in rats. The intraperitoneal LD50 in mice is 153 mg/kg.

DIDREX Tablets are contraindicated in patients with advanced arteriosclerosis, symptomatic cardiovascular disease, moderate to severe hypertension, hyperthyroidism, known hypersensitivity or idiosyncrasy to sympathomimetic amines, and glaucoma. Benzphetamine should not be given to patients who are in an agitated state or who have a history of drug abuse.

Hypertensive crises have resulted when sympathomimetic amines have been used concomitantly or within 14 days following use of monoamine oxidase inhibitors. DIDREX should not be used concomitantly with other CNS stimulants.

DIDREX may cause fetal harm when administered to a pregnant woman. Amphetamines have been shown to be teratogenic and embryotoxic in mammals at high multiples of the human dose. DIDREX is contraindicated in women who are or may become pregnant. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to the fetus.

Last updated on RxList: 4/10/2008

Benzphetamine hydrochloride is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, the amphetamines. Actions include central nervous system stimulation and elevation of blood pressure. Tachyphylaxis and tolerance have been demonstrated with all drugs of this class in which these phenomena have been looked for.

Drugs of this class used in obesity are commonly known as "anorectics" or "anorexigenics". It has not been established, however, that the action of such drugs in treating obesity is primarily one of appetite suppression. Other central nervous system actions, or metabolic effects, may be involved.

Adult obese subjects instructed in dietary management and treated with "anorectic" drugs, lose more weight on the average than those treated with placebo and diet, as determined in relatively short-term clinical trials.

The magnitude of increased weight loss of drug-treated patients over placebo-treated patients is only a fraction of a pound a week. The rate of weight loss is the greatest in the first weeks of therapy for both drug and placebo subjects and tends to decrease in succeeding weeks. The possible origins of the increased weight loss due to the various drug effects are not established. The amount of weight loss associated with the use of an "anorectic" drug varies from trial to trial, and the increased weight loss appears to be related in part to variables other than the drug prescribed, such as the physician- investigator, the population treated, and the diet prescribed. Studies do not permit conclusions as to the relative importance of the drug and non-drug factors on weight loss.

The natural history of obesity is measured in years, whereas the studies cited are restricted to a few weeks duration; thus, the total impact of drug-induced weight loss over that of diet alone must be considered to be clinically limited.

Pharmacokinetic data in humans are not available.

Last updated on RxList: 4/10/2008

Amphetamines may impair the ability of the patient to engage in potentially hazardous activities such as operating machinery or driving a motor vehicle; the patient should therefore be cautioned accordingly.

Last updated on RxList: 4/10/2008

IMPORTANT NOTE: This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your health care professional. Always seek the advice of your health care professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your health care professional. This information does not contain any assurances that this product is safe, effective, or appropriate for you.

BENZPHETAMINE - ORAL

(benz-FET-uh-meen)

COMMON BRAND NAME(S): Didrex

USES: Benzphetamine is used along with a doctor-approved, reduced-calorie diet, exercise, and behavior change program to help you lose weight. It is used in people who are significantly overweight (obese) and have not been able to lose enough weight with diet and exercise alone. Losing weight and keeping it off can reduce the many health risks that come with obesity, including heart disease, diabetes, high blood pressure, and a shorter life.

It is not known how this medication helps people to lose weight. It may work by decreasing your appetite, increasing the amount of energy used by your body, or by affecting certain parts of the brain. This medication is an appetite suppressant and belongs to a class of drugs called sympathomimetic amines.

HOW TO USE: Take this medication by mouth, usually 1-3 times a day as directed by your doctor. Taking this medication late in the day may cause trouble sleeping (insomnia).

The dosage is based on your medical condition and response to therapy. Your doctor will adjust the dose to find the best dose for you. Use this medication regularly and exactly as prescribed in order to get the most benefit from it. To help you remember, take it at the same time(s) each day.

Benzphetamine is usually taken for only a few weeks at a time. It should not be taken with other appetite suppressants (see also Drug Interactions section). The possibility of serious side effects increases with longer use of this medication and use of this drug along with certain other diet drugs.

This medication may cause dependence, especially if it has been used regularly for an extended time or if it has been used in high doses. In such cases, withdrawal reactions (e.g., depression, severe tiredness) may occur if you suddenly stop this drug. To prevent withdrawal when stopping extended/regular treatment with this drug, gradually reduce the dosage as directed. Consult your doctor or pharmacist for more details, and report any withdrawal reactions immediately.

Rarely, abnormal drug-seeking behavior (addiction) is possible with this medication. Do not increase your dose, take it more frequently, or use it for a longer time than prescribed. Properly stop the medication when so directed.

This medication may stop working well after you have been taking it for a while. Talk with your doctor if this medication stops working well. Do not increase the dose unless directed by your doctor. Your doctor may direct you to stop taking this medication.

SIDE EFFECTS: Dizziness, dry mouth, difficulty sleeping, irritability, nausea, vomiting, diarrhea, or constipation may occur. If these effects persist or worsen, notify your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: fast/irregular/pounding heartbeat, mental/mood changes (e.g., agitation, uncontrolled anger, hallucinations, nervousness), uncontrolled muscle movements, change in sexual ability/interest.

Stop taking this medication and seek immediate medical attention if any of these rare but very serious side effects occur: severe headache, slurred speech, seizure, weakness on one side of the body, vision changes (e.g., blurred vision).

This drug may infrequently cause serious (sometimes fatal) lung or heart problems (pulmonary hypertension, heart valve problems). The risk increases with longer use of this medication and use of this drug along with other appetite-suppressant drugs/herbal products. If you notice any of the following unlikely but very serious side effects, stop taking this medication and consult your doctor or pharmacist immediately: chest pain, difficulty breathing with exercise, decreased ability to exercise, fainting, swelling of the legs/ankles/feet.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any of the following symptoms of a serious allergic reaction: rash, itching, swelling, severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

Contact your doctor for medical advice about side effects. The following numbers do not provide medical advice, but in the US you may report side effects to the Food and Drug Administration (FDA) at 1-800-FDA-1088. In Canada, you may call Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking benzphetamine, tell your doctor or pharmacist if you are allergic to it; or to any other sympathomimetic amines (e.g., decongestants such as pseudoephedrine, stimulants such as amphetamine, appetite suppressants such as phentermine); or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using benzphetamine, consult your doctor or pharmacist if you have: uncontrolled high blood pressure, glaucoma, history of alcohol/drug abuse, vascular heart disease (e.g., chest pain, heart attack), mental/mood problems (e.g., severe anxiety, bipolar disorder, psychosis, schizophrenia), high blood pressure in the lungs (pulmonary hypertension), stroke, overactive thyroid (hyperthyroidism).

Before using this medication, tell your doctor or pharmacist your medical history, especially of: diabetes, controlled high blood pressure, other heart problems (e.g., heart murmur, fast/irregular heartbeat, heart valve problems), kidney disease, seizure problem.

This drug may make you dizzy or (rarely) drowsy or cause blurred vision. Use caution engaging in activities requiring alertness and clear vision such as driving or using machinery. Avoid alcoholic beverages.

Before having surgery, tell your doctor or dentist that you are using this medication.

Kidney function declines as you grow older. This medication is removed by the kidneys. Therefore, elderly people may be at greater risk for dizziness and high blood pressure while using this drug.

Benzphetamine must not be used during pregnancy. It may harm an unborn baby. If you become pregnant or think you may be pregnant, inform your doctor immediately. Infants born to mothers who have been using this medication for a long time or in high doses may have withdrawal symptoms such as irritability or extreme tiredness. Tell your doctor immediately if you notice any of these symptoms in your newborn.

This drug may pass into breast milk and could have undesirable effects on a nursing infant. Therefore, breast-feeding is not recommended while using this drug. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with them first.

This drug should not be used with certain medications because very serious interactions may occur. If you are taking or have taken other appetite-suppressant drugs in the past year (e.g., phentermine, sibutramine, ephedra/ma huang), tell your doctor or pharmacist before starting this medication.

Avoid taking MAO inhibitors (e.g., furazolidone, isocarboxazid, linezolid, moclobemide, phenelzine, procarbazine, rasagiline, selegiline, tranylcypromine) within 2 weeks before, during, and after treatment with benzphetamine. In some cases a serious (possibly fatal) drug interaction may occur.

If you are currently using any of these medications, tell your doctor or pharmacist before starting this medication.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially: drugs for depression (e.g., TCAs such as imipramine, SSRIs and SNRIs such as paroxetine, fluoxetine, venlafaxine, duloxetine), drugs for diabetes (e.g., insulin, sulfonylureas such as glipizide), drugs that affect the acid level of urine (e.g., sodium bicarbonate), high blood pressure medicine (e.g., guanethidine, methyldopa), phenothiazines (e.g., prochlorperazine, promethazine, chlorpromazine), other stimulants (e.g., amphetamines, methylphenidate, street drugs such as cocaine or MDMA/"ecstasy").

Tell your doctor or pharmacist if you also take drugs that cause dizziness or drowsiness such as: certain antihistamines (e.g., diphenhydramine), anti-seizure drugs (e.g., carbamazepine), medicine for sleep or anxiety (e.g., alprazolam, diazepam, zolpidem), muscle relaxants, narcotic pain relievers (e.g., codeine), psychiatric medicines (e.g., risperidone, amitriptyline, trazodone).

Also report the use of drugs which might increase seizure risk when combined with this medication such as isoniazid (INH), phenothiazines (e.g., thioridazine), theophylline, or tricyclic antidepressants (e.g., amitriptyline), among others.

Check the labels on all your medicines/herbal products (e.g., cough-and-cold products containing decongestants such as pseudoephedrine, diet aids such as phenylpropanolamine, ephedra/ma huang) because they may contain ingredients that could increase your heart rate or blood pressure. Ask your pharmacist about using those products safely.

Caffeine can increase the side effects of this medication. Avoid drinking large amounts of beverages containing caffeine (coffee, tea, colas) or eating large amounts of chocolate.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

OVERDOSE: If overdose is suspected, contact your poison control center or emergency room immediately. US residents can call the US National Poison Hotline at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: rapid breathing, unusual restlessness, fast/slow/irregular heartbeat, chest pain, hallucinations, seizures, loss of consciousness.

NOTES: Appetite suppressants should not be used in place of proper diet. For best results, this drug must be used along with a doctor-approved diet and exercise program.

Do not share this medication with others. It is against the law.

Laboratory and/or medical tests (e.g., blood pressure, heart tests, kidney tests) may be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is near the time of the next dose or late in the evening, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

STORAGE: Store in a tightly closed container at room temperature between 68-77 degrees F (20-25 degrees C) away from light and moisture. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

Information last revised July 2008 Copyright(c) 2008 First DataBank, Inc.