Amphetamine and Methylphenidate for ADHD and Narcolepsy

Introduction to Medications

Amphetamine (dextroamphetamine) demonstrates clinically significant improvements in both excessive daytime sleepiness and cataplexy in narcolepsy, while methylphenidate primarily improves disease severity, making amphetamine the preferred choice for narcolepsy with cataplexy 1, 2, 3

Both medications work as CNS stimulants but through slightly different mechanisms—amphetamine inhibits dopamine and norepinephrine transporters, VMAT-2, and monoamine oxidase activity 4
Effect sizes for stimulants in ADHD are approximately 1.0, significantly higher than non-stimulant alternatives (effect size ~0.7) 5

Dextroamphetamine receives a CONDITIONAL recommendation for narcolepsy with demonstrated improvements in BOTH excessive daytime sleepiness AND cataplexy 1, 2, 3
Methylphenidate receives a CONDITIONAL recommendation but primarily improves disease severity, with less robust evidence for cataplexy control 1, 2, 3, 6

Black box warning: HIGH potential for abuse and prolonged administration of amphetamine may lead to dependence 1, 3
Common adverse effects of amphetamine: sweatiness, edginess, weight gain, loss of appetite, irritability 1, 2, 3
Black box warning: Methylphenidate should be given cautiously to patients with history of drug dependence or alcoholism 1, 2, 6, 3
Common adverse effects of methylphenidate: dry mouth, sweating, headache, loss of appetite, stomach discomfort 1, 2, 6, 3

If patient develops tachycardia or elevated blood pressure on amphetamines, discontinue or decrease dose per ACC/AHA guidelines 5
Consider switching to non-stimulant alternatives (atomoxetine, guanfacine, clonidine) if cardiovascular adverse effects occur 5

Both medications may cause fetal harm based on animal data; human data insufficient 1, 2, 6, 3
Therapeutic use of amphetamine (Adderall) during pregnancy does not appear associated with major congenital malformations or significant adverse developmental outcomes per ACOG 4

Choose amphetamine (dextroamphetamine) when patient has narcolepsy with cataplexy (superior efficacy for both symptoms) 1, 3
Choose methylphenidate when patient has ADHD as primary indication or history of drug dependence 1, 3
Switch to non-stimulants when cardiovascular adverse effects develop (tachycardia, hypertension) 5

Do NOT abruptly discontinue if switching from stimulants to alpha-2 agonists (can cause rebound hypertension) 5
Do NOT expect immediate effects from non-stimulant alternatives if switching—they require 2-12 weeks for therapeutic effect 5

The American Academy of Pediatrics recommends monitoring blood pressure and heart rate at baseline and regularly during methylphenidate treatment, as it causes statistically significant increases in both parameters 7, 8
The American Academy of Pediatrics suggests that average increases in heart rate and blood pressure are small, but 5-15% of patients may experience clinically significant cardiovascular changes 9

Methylphenidate is associated with dose-related increases in heart rate (1-2 beats per minute) and blood pressure (1-4 mm Hg), which can be particularly relevant in patients with preexisting cardiovascular disease 7, 8, 9
The American Heart Association recommends careful monitoring of cardiovascular status during methylphenidate treatment, especially in patients with preexisting cardiovascular disease 7, 8

The American Academy of Pediatrics states that methylphenidate is associated with statistically significant reductions in height and weight gain, requiring careful monitoring 7, 8
Reduced appetite plays a major role in growth suppression, and the effects are usually minor but can be clinically relevant in subgroups 7, 8

The National Institute of Mental Health suggests that the relationship between stimulant medication and serious adverse events such as sudden death or suicidality is unlikely, though cannot be completely excluded 7, 8
Recent evidence from the National Institute of Mental Health indicates that psychostimulants may actually decrease the risk of suicidal events in ADHD patients 7, 8