What is Amfexa (Dexamfetamine Sulfate)?
Amfexa is dexamfetamine sulfate (also called dextroamphetamine), a central nervous system stimulant medication primarily used to treat Attention-Deficit/Hyperactivity Disorder (ADHD) and narcolepsy. It works by inhibiting the reuptake of dopamine and norepinephrine, enhancing prefrontal cortex activity to improve attention, focus, and impulse control 1.
Medical Uses
ADHD Treatment
Dexamfetamine is a first-line pharmacological treatment for ADHD in children (age 6+), adolescents, and adults 1. Guidelines recommend stimulants like dexamfetamine as the initial medication choice due to their large effect sizes in reducing core ADHD symptoms—larger than non-stimulant alternatives 1.
Typical dosing:
- Starting dose: 2.5 mg once or twice daily (morning and noon) 2
- Titration: Increase by 2.5-5 mg weekly increments 2
- Maximum dose: 40 mg total daily dose (though clinical practice sometimes exceeds this in rare cases) 2
- Duration of action: Approximately 6.5 hours for immediate-release formulations 3
Narcolepsy Treatment
Dexamfetamine is also used to treat excessive daytime sleepiness in narcolepsy, with typical starting doses of 5 mg twice daily, titrated up to a maximum of 50 mg daily 4.
Mechanism and Formulations
Dexamfetamine enhances dopaminergic and noradrenergic neurotransmission by:
- Inhibiting dopamine and norepinephrine transporters
- Blocking vesicular monoamine transporter 2
- Inhibiting monoamine oxidase activity 1
Available as immediate-release tablets requiring 2-3 times daily dosing, or as the prodrug lisdexamfetamine (Vyvanse), which provides once-daily extended-release effects 1.
Clinical Considerations
Monitoring Requirements
Before starting treatment, obtain 2, 5:
- Baseline blood pressure and pulse
- Height and weight measurements
- Physical examination including cardiac history
During treatment, monitor quarterly:
- Blood pressure and pulse (stimulants cause small but statistically significant increases) 1
- Height and weight (stimulants can slow growth velocity, though effects are typically minor) 1
Common Adverse Effects
- Decreased appetite (most common)
- Sleep disturbances
- Increased blood pressure and heart rate
- Headaches
- Irritability
- Stomach pain 1
Important: Dexamfetamine is an FDA Schedule II controlled substance with high abuse potential 5, 4. However, evidence suggests therapeutic use in ADHD patients may actually decrease risk of suicidal events rather than increase it 1.
Special Populations
Pregnancy: Limited data suggest amphetamines do not appear associated with major congenital malformations, though possible small increased risks for gastroschisis and preeclampsia have been reported 6.
Preschool children (ages 4-5): Methylphenidate is preferred over dexamfetamine due to more robust evidence in this age group, though dexamfetamine has FDA approval 5.
Clinical Effectiveness
Studies demonstrate dexamfetamine produces:
- Rapid onset of action (approximately 36 minutes) 3
- Significant reductions in ADHD symptoms (mean ADHD-RS-IV score reduction of 11.9 points) 3
- Clinical response rates of 78% (defined as ≥30% symptom reduction) 3
- Effectiveness maintained over 12 months of treatment 3
Cost-effectiveness data: Economic modeling suggests dexamfetamine as first-line treatment is more cost-effective than methylphenidate or atomoxetine, driven primarily by lower drug costs with comparable efficacy 7.