Dosing and uses of Didrex, Regimex (benzphetamine)
Adult dosage forms and strengths
tablet: Schedule III
- 25mg (Regimex)
- 50mg (Didrex)
Obesity
Indicated in the management of exogenous obesity as a short term (a few weeks) adjunct in a regimen of weight reduction based on caloric restriction in patients with an initial body mass index (BMI) of ≥30 kg/m² who have not responded to appropriate weight reducing regimen (diet and/or exercise) alone
25-50 mg PO qDay initially; may increase dose or frequency according to response up to TId
Pediatric dosage forms and strengths
tablet: Schedule III
- 25mg (Regimex)
- 50mg (Didrex)
Obesity
Indicated in the management of exogenous obesity as a short term (a few weeks) adjunct in a regimen of weight reduction based on caloric restriction in patients with an initial body mass index (BMI) of ≥30 kg/m² who have not responded to appropriate weight reducing regimen (diet and/or exercise) alone
<12 years: Safety and efficacy not established
≥12 years: 25-50 mg PO qDay initially; may increase dose or frequency according to response up to TId
Didrex, Regimex (benzphetamine) adverse (side) effects
Frequency not defined
Abdominal pain
Blood pressure incr
Constipation
Diarrhea
Dizziness
Dry mouth
Headache
Insomnia
Ischemic cardiac events associated with chronic amphetamine use
Libido changes
Nausea
Palpitations
Psychotic episodes (rare)
Restlessness
Tachycardia
Tremor
Warnings
Contraindications
Advanced arteriosclerosis
Symptomatic cardiovascular disease including arrhythmias
Hyperthyroidism
Moderate to severe hypertension
Hypersensitivity to sympathomimetic amines
Glaucoma
Agitated state
History of drug abuse
Pregnancy/lactation; women planning to get pregnant
Use within 14 days of MAOIs
Do not use in combination with other anorectic agents including prescription, OTC, or herbaL
Use of anorectic agents associated with increased risk of developing pulmonary hypertension (PH) (rare, but often fatal disorder); use >3 months associated with 23-fold increased risk of developing PH (benzphetamine not specifically studied)
Immediately discontinue if onset or aggravation of exertional dyspnea, or unexplained symptoms of angina pectoris, syncope, or lower extremity edema emerge suggesting possible PH
Valvular heart disease associated with use of some anorectics (no cases reported with benzphetamine monotherapy)
Not recommended for patients who used any anorectic agents within prior year
Cautions
Discontinue when tolerance develops - DO NOT EXCEED recommended dose
Diabetics: insulin requirements may be altered
Mild hypertension
May impair ability to drive &/or operate heavy machinery
Alkaline urine will increase half-life
Pregnancy and lactation
Pregnancy category: X
Lactation: enters breast milk/not recommended
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Didrex, Regimex (benzphetamine)
Mechanism of action
Amphetamine anorexigenic agent
Pharmacokinetics
Metabolism: by cytochrome P450 enzymes
Excretion: 5-30% unchanged in urine, highly dependent on pH
