Both attention deficit hyperactivity disorder (ADHD) and narcolepsy can be treated with methylphenidate hydrochloride (Ritalin®). (Hydrochloride is often abbreviated as HCl.) Why can this drug treat two very different conditions? When taken in low doses, methylphenidate HCl has a calming effect on people with ADHD; when higher amounts are taken, the medicine has a stimulating effect, which makes it useful for people with narcolepsy.
This medication is considered a controlled substance because it has such a high potential for abuse. As a result, special rules and guidelines are in place for prescribing it.
(Click Methylphenidate to learn more about this drug, including possible side effects, signs of an overdose, if there is a generic version, and if women can take it when pregnant or breastfeeding.)