Answer to Question 1
Ritalin reduces the core symptoms of ADHD (impulsivity, distractibility, excessive fidgetiness) in about 60-80 of ADHD children and improves most aspects of their classroom behavior and performance and interactions with their teachers and peers, but does not seem to induce substantial longterm benefits in overall cognitive functioning (e.g., I.Q.). Elimination of potential allergens like food additives and salicylates (e.g., the Feingold diet) seems to benefit a small minority (approximately 5) of ADHD children. Barbiturates (sedative-hypnotics) are not effective at all and may actually be worse than placebo in ADHD children.
Answer to Question 2
Virtually none in terms of clinical efficacy regarding the target symptoms of ADHD or their side effects, although pemoline rarely may induce hepatic toxicity that potentially can be lethal. They differ in potency (d>m>p in terms of potency), but this is of little relevance clinically. The primary advantage of pemoline over the immediate release forms of dextroamphetamine and methylphenidate was its slower onset of action, longer duration of action and lower likelihood of abuse; however, since several sustained release formulations of dextroamphetamine or methylphenidate have been developed, this is no longer a significant factor. The particular type of psychostimulant, particularly the specific sustained release formulation of dextroamphetamine and methylphenidate that is most effective for an individual patient is determined largely on the basis of trial and error.