Products
Dexmethylphenidate is commercially available in the form of capsules with a modified release of active ingredient (Focalin XR). It was approved in many countries in 2009. Since it does not contain L-threo-methylphenidate, the strengths are correspondingly half less (5 mg, 10 mg, 15 mg, 20 mg) than Ritalin LA (10 mg, 20 mg, 30 mg, 40 mg). Both drugs contain the same amount of dexmethylphenidate. The drug is subject to strict control as a narcotic and is available only by prescription.
Structure
Methylphenidate has two chiral centers and consequently can exist in four isomers. However, in practice, the two D,L-threo forms are mainly used. Dexmethylphenidate (C14H19NO2, Mr = 233.3 g/mol) is the pure D-threo enantiomer of methylphenidate and does not contain an L-threo enantiomer like Ritalin. It is present in drugs as dexmethylphenidate hydrochloride, a white powder that is soluble in water. Methylphenidate is a piperidine derivative of the stimulant amphetamine and has a phenylethylamine structure.
Effects
Dexmethylphenidate (ATC N06BA04) has central stimulant and sympathomimetic properties. The effects in ADHD are thought to be due to increases in synaptic dopamine and norepinephrine in the central nervous system. The exact mechanism of action is unknown. Dexmethylphenidate appears to be the more active of the two enantiomers, which is why it is marketed separately.
Indications
For the treatment of attention-deficit/hyperactivity disorder (ADHD) in children six years of age and older, adolescents, and adults. Unlike methylphenidate, it has not yet been approved for the treatment of narcolepsy in many countries.
Dosage
According to the drug label. The drug is taken once daily in the morning, regardless of meals. The capsules may be swallowed whole or the contents may be sprinkled on some food. The food should not be too warm (see package leaflet).
Further information
See methylphenidate and ADHD.
