Label Changes for:

Didrex (benzphetamine hydrochloride) tablets

February 2010

Changes have been made to the WARNINGS, PRECAUTIONS and ADVERSE REACTIONS sections of the safety label.

Detailed View: Safety Labeling Changes Approved By FDA Center for Drug Evaluation and Research (CDER) – February 2010

WARNINGS

  • Didrex tablets should not be used in combination with other anorectic agents, including prescribed drugs, over-the-counter preparations and herbal products.
  • In a case-control epidemiological study, the use of anorectic agents was associated with an increased risk of developing pulmonary hypertension, a rare, but often fatal disorder. The use of anorectic agents for longer than three months was associated with a 23-fold increase in the risk of developing pulmonary hypertension. Increased risk of pulmonary hypertension with repeated courses of therapy cannot be excluded. It should be noted that benzphetamine was not specifically studied in this case-control study.
  • The onset or aggravation of exertional dyspnea, or unexplained symptoms of angina pectoris, syncope, or lower extremity edema suggest the possibility of occurrence of pulmonary hypertension. Under these circumstances, Didrex tablets should be immediately discontinued, and the patient should be evaluated for the possible presence of pulmonary hypertension.
  • Valvular heart disease associated with the use of some anorectic agents such as fenfluramine and dexfenfluramine has been reported. Possible contributing factors include use for extended periods of time, higher than recommended dose, and/or use in combination with other anorectic drugs. However, no cases of this valvulopathy have been reported when benzphetamine has been used alone.
  • The potential risk of possible serious adverse effects such as valvular heart disease and pulmonary hypertension should be assessed carefully against the potential benefit of weight loss. Baseline cardiac evaluation should be considered to detect pre-existing valvular heart diseases or pulmonary hypertension prior to initiation of benzphetamine treatment. Didrex tablets are not recommended in patients with known heart murmur or valvular heart disease. Echocardiogram during and after treatment could be useful for detecting any valvular disorders which may occur. To limit unwarranted exposure and risks, treatment with Didrex tablets should be continued only if the patient has satisfactory weight loss within the first 4 weeks of treatment (i.e., weight loss of at least 4 pounds, or as determined
    by the physician and patient).
  • Didrex tablets are not recommended for severely hypertensive patients or for patients with symptomatic cardiovascular disease including arrhythmias.
  • Didrex tablets are not recommended for patients who used any anorectic agents within the prior year.

PRECAUTIONS

Drug Interactions
  • Efficacy of Didrex tablets in combination with other anorectic agents has not been studied and the combined use may have the potential for serious cardiac problems.
Pediatric Use 
  • Safety and effectiveness in pediatric patients have not been established
Geriatric Use
  • Clinical studies of Didrex tablets did not include sufficient numbers of subjects aged 65 and over to establish safety and efficacy in this population.

ADVERSE REACTIONS

Cardiovascular
  • There have been isolated reports of ischemic cardiac events associated with chronic amphetamine use
  • Valvular heart disease associated with the use of some anorectic agents such as fenfluramine and dexfenfluramine, both independently and especially when used in combination with other anorectic drugs, have been reported. However, no cases of this valvulopathy have been reported when Didrex tablets have been used alone.
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