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Discontinued Warning IconPlease Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

Side Effects


Commonly Observed

The most commonly observed, treatment-emergent adverse events associated with the use of dexfenfluramine in double-blind, placebo-controlled clinical trials were diarrhea (17.5%), dry mouth (12.5%), and somnolence (7.1%). These and other commonly observed adverse reactions were generally mild and transient. (Commonly observed is defined as incidence of 5% or greater and incidence in dexfenfluramine group at least twice that of placebo group, as derived from the Table 3 below.)

Associated with Discontinuation of Treatment

Seven percent of the 1159 patients who received dexfenfluramine in double-blind, placebo-controlled clinical trials discontinued treatment because of an adverse event. The most common adverse events resulting in discontinuation included asthenia, insomnia, headache, and depression. Five percent of the 1138 placebo-treated patients discontinued because of an adverse event.

Incidence in Controlled Clinical Trials

The following Table 3 lists treatment-emergent adverse events from several double-blind, placebo-controlled trials that occurred at a frequency of 2% or more among patients treated with dexfenfluramine and occurred at least as frequently as the placebo group, regardless of relationship to study medication.

Other Events Observed in Controlled Clinical Trials

The events below are classified within body system categories and enumerated in order of decreasing frequency using the following definitions. Frequent adverse events are those occurring in more than 1/100 patients but were not described above because the frequency in dexfenfluramine-treated patients was less than that in placebo-treated patients or they occurred at a rate less than 2%. Infrequent adverse events are those occurring in 1/100 to 1/1000 patients, while rare adverse events are those occurring in only one patient during placebo-controlled clinical trials.

    Body as a whole:

      Frequent: infection, flu syndrome, pain,back pain, fever, allergic reaction.

      Infrequent: malaise, neck pain, chest pain, generalized edema, stress, face edema, neoplasm, pelvic pain.

      Rare: adenoma, immune system disorder, neck rigidity, suicide attempt.

    Cardiovascular System:

      Frequent: hypertension, angina pectoris, palpitation, vasodilation, migraine.

      Infrequent: cardiovascular disorder, tachycardia, postural hypotension, hypotension, peripheral vascular disorder, syncope, arrhythmia, extrasystoles, hemorrhage, thrombophlebitis, varicose vein.

      Rare: heart block, pulmonary embolus, thrombosis.

    Gastrointestinal system:

      Frequent: constipation, nausea, dyspepsia, increased appetite, rectal disorder, gastritis, gastroenteritis, flatulence.

      Infrequent: colitis, eructation, gastrointestinal hemorrhage, enteritis, peptic ulcer, hepatitis, hepatomegaly.

      Rare: appendicitis, cholelithiasis, fecal incontinence, melena, mouth ulceration, pancreatitis, rectal hemorrhage, sialoadenitis.


      Infrequent: goiter, diabetes mellitus, thyroid disorder.

      Rare: hypothyroidism.

    Hemic and lymphatic system:

      Infrequent: anemia, lymphedema.

      Rare: coagulation disorder, lymphadenopathy, polycythemia, thrombocythemia.

    Metabolic and nutritional:

      Infrequent: edema, gout, hypoglycemia, hypokalemia.

      Rare: hyperglycemia, hyperkalemia, hyperlipemia, hyperuricemia.

    Musculoskeletal system:

      Frequent: arthralgia, myalgia, arthritis.

      Infrequent: leg cramps, joint disorder, bone disorder, tenosynovitis, myasthenia, rheumatoid arthritis.

      Rare: bursitis, tetany.

    Nervous system:

      Frequent: nervousness, anxiety, increased libido, hypertonia, paresthesia.

      Infrequent: tremor, amnesia, euphoria, decreased libido, incoordination, neuralgia, speech disorder, ataxia, hypokinesia, sleep disorder, abnormal gait, agitation, confusion, depersonalization, diplopia, hostility, hyperesthesia, hyperkinesia, peripheral neuritis.

      Rare: apathy, dementia, hallucinations, hypotonia, neuritis, neurosis, paralysis.

    Respiratory system:

      Frequent: rhinitis, sinusitis. Infrequent: asthma, dyspnea, epistaxis, laryngitis.

      Rare: apnea, hyperventilation.

    Skin and appendages:

      Frequent: sweating, alopecia, urticaria, pruritus.

      Infrequent: skin disorder, fungal dermatitis, hirsutism, eczema, psoriasis.

      Rare: skin hypertrophy.

    Special senses:

      Frequent: taste perversion, amblyopia.

      Infrequent: abnormal vision, conjunctivitis, eye disorder, glaucoma, tinnitus, vestibular disorder, dry eyes, mydriasis.

      Rare: abnormality of accommodation, anisocoria, lacrimation disorder, miosis, parosmia, retinal disorder.

    Urogenital system:

      Frequent: menstrual disorder, urinary tract infection, nocturia, dysmenorrhea.

      Infrequent: amenorrhea, dysuria, oliguria, albuminuria, breast pain, kidney calculus, kidney pain.

      Rare: spontaneous abortion, threatened abortion, breast neoplasm, endometrial disorder, female lactation, hematuria, impotence, mastitis, nephritis, prostatic disorder, testis disorder, urinary incontinence, urinary retention, uterine hemorrhage.

In controlled clinical trials, there has been no consistent pattern of laboratory abnormalities in patients treated with dexfenfluramine.

Post-introduction Reports

Voluntary reports of adverse events temporally associated with dexfenfluramine that have been received since market introduction in countries other than the US, for which the association with the drug is unknown, and which are not included in descriptions of adverse events elsewhere in this labeling, include the following:

    Body as a whole: anaphylaxis, congenital anomaly, eventration, hypothermia, laryngeal edema, peritonitis, reaction aggravation, retroperitoneal fibrosis, scleroderma, sudden death.

    Cardiovascular system: pulmonary hypertension (see WARNINGS), atrial fibrillation, cardiomyopathy, cerebral vasculitis, ECG abnormal, heart arrest, heart failure, myocardial infarction, myocarditis, shock, tachycardia, ventricular fibrillation, ventricular tachycardia.

    Digestive system: dysphagia, gastrointestinal disorder, tongue disorder. Endocrine system--diabetic coma.

    Gastrointestinal system: hepatic failure, jaundice, liver damage.

    Hemic and lymphatic system: agranulocytosis, antinuclear antibody present, bone marrow depression, ecchymosis, hemolytic anemia, pancytopenia.

    Metabolic and nutritional: dehydration, elevated lipases, increased prolactin, thyroid disease, weight increase.

    Musculoskeletal: myopathy.

    Nervous system: antisocial reaction, apathy, cerebellar ataxia, cerebrovascular accident (including cerebral hemorrhage, cerebral infarction, cerebral ischemia and cochlear infarction), choreoathetosis, convulsions, decreased reflexes, delirium, drug dependence, dyslexia, encephalopathy, grand mal convulsions, Guillain-Barré syndrome, hemiplegia, hypoesthesia, manic-depressive psychosis, manic reaction, memory loss, meningism, meningitis, neuropathy, papilledema, paraplegia, personality disorder, reflexes increased, retrobulbar neuritis, schizophrenic reaction, stupor, subdural hematoma, twitch, withdrawal syndrome.

    Respiratory system: pulmonary hypertension (see WARNINGS), diffuse interstitial pneumonitis, dyspnea, hiccup, lung edema.

    Skin and appendages: angioedema, bullous eruption, erythema multiforme, lower extremity purpura, purpura annularis telangiectodes, Stevens-Johnson syndrome (erythema multiforme major).

    Special Senses: ophthalmoplegia, photophobia, transitory deafness, visual field defects.

    Urogenital system: breast enlargement, carcinoma (breast), carcinoma (cervix), ejaculation abnormal, gynecomastia, hypomenorrhea, kidney failure, placenta previa, urinary tract disorder.

Adverse Events Occurring After Discontinuation

In controlled clinical trials and/or in post-marketing reports, symptoms have been reported within a few days after discontinuation of dexfenfluramine. These include one or more of the following: abdominal pain, anxiety, asthenia, delusion, depression, diarrhea, dizziness, hypertension, insomnia, nausea and vomiting.


Controlled Substance Class

Dexfenfluramine is a controlled substance in Schedule IV.

Abuse and Physical and Psychological Dependence

Dexfenfluramine is not an amphetamine or a stimulant. There is no evidence of addictive or drug-seeking behavior in pre-marketing clinical studies. Dexfenfluramine was inactive in rat and monkey self-administration, drug-discrimination, and place-preference models of abuse potential.

Read the Redux (dexfenfluramine (fda removed from us market 9/15/97)) Side Effects Center for a complete guide to possible side effects


In patients receiving nonselective monoamine oxidase inhibitors (MAOIs) (e.g., selegiline hydrochloride) in combination with serotoninergic agents (e.g., fluoxetine, fluvoxamine, paroxetine, sertraline, venlafaxine), there have been reports of serious, sometimes fatal, reactions. Because dexfenfluramine is a serotonin releaser and reuptake inhibitor, dexfenfluramine should not be used concomitantly with a MAO inhibitor (see CONTRAINDICATIONS).

At least 14 days should elapse between discontinuation of a MAO inhibitor and initiation of treatment with dexfenfluramine. At least 3 weeks should elapse between discontinuation of dexfenfluramine and initiation of treatment with a MAO inhibitor.

A rare, but serious, constellation of symptoms, termed "serotonin syndrome," has been reported with the concomitant use of selective serotonin reuptake inhibitors (SSRIs) and agents for migraine therapy, such as Imitrex (sumatriptan succinate) and dihydroergotamine. The syndrome requires immediate medical attention and may include one or more of the following symptoms: excitement, hypomania, restlessness, loss of consciousness, confusion, disorientation, anxiety, agitation, motor weakness, myoclonus, tremor, hemiballismus, hyperreflexia, ataxia, dysarthria, incoordination, hyperthermia, shivering, pupillary dilation, diaphoresis, emesis, and tachycardia. Dexfenfluramine should not be administered with other serotoninergic agents. The appropriate interval between administration of these agents and dexfenfluramine has not been established. The use of dexfenfluramine with other CNS-active drugs has not been systematically evaluated; consequently, caution is advised if dexfenfluramine and such drugs are prescribed concurrently.

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 12/8/2004

Side Effects

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