Drug Breakdown: Methylphenidate

Day 1: The mild CNS stimulant #methylphenidate was synthesised in the1940s & marketed as Ritalin by the 1950s, after recognition it improved concentration. Trialled for many conditions e.g chronic fatigue & chronic pain; it is now associated with its main licensed use for ADHD symptom management

Day 2: #methylphenidate is the 1st line drug treatment for ADHD 6-18yrs. Oral dose range 10-60 mg/day depending on age & response. If immediate release, divide doses 1-3/day. Long-acting preparations contain a mixture of immediate & modified release drug & may not be equivalent to each other (care if switching). Adults with ADHD may need indefinitely, although long-term use is not fully evaluated. Use is unlicensed in adults, except some brands if being continued post-initiation in childhood. #methylphenidate is a schedule 2 CD in UK & US. Careful titration & withdrawal needed

Day 3: Kinetics: good GI absorption (no effect from food), with effects in 4+ hrs (3-9 hrs if m.r). Metabolism via de-esterification to ritalinic acid (inactive). 80% excreted as ritalinic acid; no known effect of renal impairment. T½ 2-7 hrs. If #methylphenidate is used with alcohol the metabolite ethylphenidate is produced. This may contribute to toxicity & psychiatric symptoms eg agitation, psychosis & tachycardia, HTN, hyperthermia (not exhaustive)