MND: Memory issues can be a problem for some MS patients. A team of researchers from New Jersey/ New York studied the effect of from L-amphetamine on MS patients and found it to improve their memory.
MND: Amphetamines are serious drugs used for medical [ADHD, Narcolepsy], or illegal recreational use in the same class as cocaine or morphine 
MND: MSers are not foreign to medical/recreational controversies…see post s  about MS , spasticity and marijuanaThe risks are substantial:
“typical side effects on the body include dry mouth, heart rhythm alterations (palpitations and arrhythmias), hypertension, stomach cramps, and decreased urinary frequency. The central nervous system side effects include dizziness, dysphoria, headache, tremor, restlessness, insomnia, decreased appetite, increased aggressiveness, anxiety, and paranoid panic states. Extreme overdosage can result in convulsions, cerebral hemorrhaging, coma, and death.” 
Read more: http://www.answers.com/topic/amphetamine#ixzz1MeqvR8GH
MND: Seems that MSrs should probably let the dust settle on this one; Issues of efficacy, dosages, side effects need large clinical trials..
Talk to your Doctor