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Methylphenidate (MPH) is an amphetamine-like prescription stimulant commonly used to treat Attention Deficit Hyperactivity Disorder (ADHD) in children and adults. It is also one of the primary drugs used to treat the daytime drowsiness symptoms of narcolepsy. Brand names of drugs that contain methylphenidate include Ritalin, Concerta (a timed-release capsule), Metadate, Methylin, and Focalin (containing only dextro-methylphenidate, rather than the usual racemic dextro- and laevo-methylphenidate mixture of other formulations).
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Methylphenidate
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IUPAC name:
methyl a-phenyl-2-piperi-dylacetate
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CAS number
113-45-1 |
ATC code
N06B A04 |
| Chemical formula |
C14H19NO2 |
| Molecular weight |
233.31 |
| Bioavailability [1] |
11 to 52% (Oral) |
| Metabolism |
Liver |
| Elimination half life |
2 - 4 hours |
| Excretion |
Urine |
| Pregnancy category |
C |
| Legal status |
Schedule II USA |
| Delivery |
Ritalin: 5mg, 10mg, and 20mg tablets;
Ritalin SR: 20mg tablets;
Ritalin LA: 20mg, 30mg, and 40mg capsules;
Methylin: 5mg, 10mg, and 20mg tablets;
Methylin ER: 10mg and 20mg tablets;
Metadate ER: 10mg and 20mg tablets;
Metadate CD: 10mg, 20mg, and 30mg capsules;
Concerta: 18mg, 27mg, 36mg, 54mg and 72mg tablets
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History
Methylphenidate was patented in 1950 by the Ciba Pharmaceutical Company (a precursor to Novartis) and was initially prescribed as a treatment for depression, chronic fatigue, and narcolepsy, among other ailments. Beginning in the 1960s, it was used to treat children with ADHD, known at the time as hyperactivity or minimal brain dysfunction (MBD). Today methylphenidate is the medication most commonly prescribed to treat ADHD around the world. According to most estimates, more than 75 percent of methylphenidate prescriptions are written for children, with boys being about four times as likely to take methylphenidate as girls. Production and prescription of methylphenidate rose significantly in the 1990s, especially in the United States, as the ADHD diagnosis came to be better understood and more generally accepted within the medical and mental health communities.
Most brand-name Ritalin is produced in the United States, although methylphenidate is also produced in Mexico and Argentina by respective contract pharmaceutical manufacturers and is marketed under the brand name "Ritalin" for Novartis. In the United States, various generic forms of methylphenidate are also produced by several pharmaceutical concerns (such as Methylin, etc.), and Ritalin is also sold in the United Kingdom, Germany, and other European countries (although in much lower volumes than the United States).
Effects
Methylphenidate is a central nervous system (CNS) stimulant. It has a "calming" effect on many children who have ADHD, reducing impulsive behavior and the tendency to "act out", and helps them concentrate on schoolwork and other tasks. Adults who have ADHD often find that MPH increases their ability to focus on tasks and organize their lives.
The means by which methylphenidate helps people with ADHD are not well understood. Some researchers have theorized that ADHD is caused by a dopamine imbalance in the brains of those affected. MPH is a dopamine reuptake inhibitor, which means that it increases the level of the dopamine neurotransmitter in the brain by partially blocking the transporters that remove it from the synapses. [2]
In the United States, methylphenidate is classified as a Schedule II controlled substance, the designation used for substances that have a recognized medical value but which have a high potential for abuse. Internationally, methylphenidate is a Schedule II drug under the Convention on Psychotropic Substances[3]. Some people abuse MPH by crushing the tablets and snorting them, which produces a "high" similar to that of cocaine or amphetamine and can lead to addiction. When taken orally in prescribed doses, MPH is less addictive and may not produce a "high". After taking the drug or resuming it after going a month or more without it, the effects of dependence will tend to level off after a week, and again, after a month.
Methylphenidate is also used by some university students as a stimulant to assist with coursework and examinations. [4] [5]. It is also done recreationally in combination with alcohol to counter the downing effects of excessive drinking, allowing the user to stay fairly awake and social while being heavily intoxicated late into the night. Users often prefer to crush and snort the pills nasally for a more intense rush, rather than swallowing them.
Formulations
Most products containing methylphenidate contain a racemic mixture of dextro-methylphenidate and laevo-methylphenidate, although it is only dextro-methylphenidate which is considered to provide the pharmacologically useful effects of mental focus. However, with the introduction of Focalin, pure dextro-methylphenidate is available - described as a fast-acting form of the drug, it is absorbed more quickly by the body, with a shorter time to peak concentration (and excretion) than with the heterogeneous compound.
The pharmacological profiles and relative usefulness of dextro- and laevo-methylphenidate is analogous to what is found in amphetamine, where dextro-amphetamine is considered to have a more beneficial effect than laevo-amphetamine.
Criticism
Treating children with stimulant medication, and methylphenidate in particular, has become controversial as the number of children taking them has increased dramatically over the years. Critics contend that MPH is extensively overprescribed in the United States, especially among children; that the drug is used primarily to control or sedate "problem" schoolchildren so that they will not disrupt class; that it transforms healthy children into "zombies", stifling their creativity and intellectual energy; and that it can lead children into dangerous drug addictions later in life. State laws have been passed to prevent school districts from requiring students to undergo any kind of treatment for ADHD as a pre-requisite for attending school. And in the cases of abused and neglected children, who regularly 'act out' within a classroom situation, false diagnoses and subsequent medication can mask the real problems and thus prevent Child Protective Services from getting involved in what could be a serious child abuse or child neglect situation.
However, criticism that methylphenidate is overprescribed may be unfounded; the incidence of ADHD is believed to be between three and five percent of the population, while the number of children in America taking Ritalin is estimated at one to two percent. [6] Recent research [7] suggests that ADHD boys who are treated with stimulants like MPH are actually less likely to abuse drugs including alcohol later in life. Also, the only time when the usage of the drug is known to induce zombie-like effects (known to parents and those familiar with the drug as "zombie syndrome" or "zombification") is in an overdose situation. When prescribed in the correct amount, MPH only creates a zombie-like effect in the first 2-4 days of use when beginning the drug, or resuming it after going without it for a month, and even that effect is significantly less than the effect produced in overdoses.
As long-term use of methylphenidate was relatively uncommon before the 1990s, the long-term neurological effects are not well researched. As documented for amphetamines, the potential of methylphenidate use over many years causing permanent neurological damage to dopaminergic systems exists at least in theory.
Although not common, Ritalin has been found by coroners to be the cause of a few deaths among children.[8]
Potential Carcinogen
In February 2005, researches from The University of Texas M.D. Anderson Cancer Center announced that a small scale study 1 of 12 children indicated that methylphenidate may be carcinogenic. In the study, 12 children were given standard therapeutic doses of methylphenidate. At the conclusion of the 3 month study, all 12 children displayed significant, treatment induced chromosomal aberrations. The researches indicated that while their study was too small to derive meaningful conclusions, they indicated more studies should be done as the link between chromosomal aberrations and cancer is well documented.
Reference
See also
External links
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