Definitions

bleeding dry

Methylphenidate

[meth-uhl-fen-i-deyt, -fee-ni-]

Indicated for:

Other uses:

Contraindications:
  • Use of tricyclic antidepressants (e.g. desipramine), as methylphenidate may dangerously increase their plasma concentrations, leading to potential toxic reactions (mainly, cardiovascular effects).
  • Use of MAO Inhibitors, such as phenelzine (Nardil) or tranylcypromine (Parnate), and certain other drugs.
  • methylphenidate should not be given to patients who suffer from the following conditions: Severe Arrhythmia, Hypertension or Liver damage.
  • Drug-seeking behaviour
  • Pronounced agitation or nervousness. Other side effects include drowsiness, and mood swings

Side effects: Atypical sensations: *

Cardiovascular:

Ear, nose, and throat: *

Endocrinal:

  • Appetite loss

Eye:

  • Blurred vision

Gastrointestinal:

  • Nausea/vomiting, abdominal pain

Hematological: *

Musculoskeletal:

  • Muscle twitches

Neurological:

Psychological:

Respiratory:

  • Increased respiration rate

Skin: *

Urogenital and reproductive: *

Miscellaneous:

  • Fever

Methylphenidate (MPH) is a prescription stimulant commonly used to treat Attention-deficit hyperactivity disorder, or ADHD. It is also one of the primary drugs used to treat the daytime drowsiness symptoms of narcolepsy and chronic fatigue syndrome. The drug is seeing early use to treat cancer-related fatigue. Brand names of drugs that contain methylphenidate include Ritalin (Ritalina, Rilatine, Attenta, Methylin, Penid, Rubifen); and the sustained release tablets Concerta, Metadate CD, Methylin ER, Ritalin LA, and Ritalin-SR. Focalin is a preparation containing only dextro-methylphenidate, rather than the usual racemic dextro- and levo-methylphenidate mixture of other formulations. A newer way of taking methylphenidate is by using a transdermal patch (under the brand name Daytrana), similar to those used for hormone replacement therapy (HRT), nicotine release and pain relief (Fentanyl or Morphine).

History

Methylphenidate was patented in 1954 by the CIBA pharmaceutical company (now Novartis) as a potential cure for Mohr's disease. Beginning in the 1960s, it was used to treat children with ADHD or ADD, known at the time as hyperactivity or minimal brain dysfunction (MBD). Today methylphenidate is the most commonly prescribed medication to treat ADHD around the world. 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, and methylphenidate is produced in the United States, Mexico, Argentina and Pakistan. Other generic forms, such as "methylin", are produced by several U.S. pharmaceutical companies. Ritalin is also sold in the United Kingdom, Germany and other European countries (although in much lower volumes than in the United States). These generic versions of methylphenidate tend to outsell brand-name Ritalin four to one. In Belgium the product is sold under the name "Rilatine".

Another medicine is Concerta, a once-daily extended-release form of methylphenidate, which was approved in April 2000. Studies have demonstrated that long-acting methylphenidate preparations such as Concerta are just as effective, if not more effective, than IR (instant release) formulas. Time-release medications are also harder to misuse.

In April 2006, the FDA approved a transdermal patch for the treatment of ADHD called Daytrana.

Indications

Methylphenidate is a central nervous system (CNS) stimulant, reducing impulsive behavior, and facilitating concentration on work and other tasks. Adults who have ADHD often report that methylphenidate increases their ability to focus on tasks and organize their lives.

Methylphenidate has been found to have a lower incidence of side effects than dextroamphetamine, a less commonly prescribed medication. When prescribed at the correct dosage, methylphenidate is usually well tolerated by patients.

A 2006 review assessing the safety of methylphenidate on the developing brain found that in animals with psychomotor impairments, structural and functional parameters of the dopamine system were improved with treatment. This indicates that in subjects with ADHD, methylphenidate treatment may positively support brain development.

Pharmacology

Methylphenidate has binding affinity for both the dopamine transporter and norepinephrine transporter, with the Dextromethylphenidate enantiomers displaying a prominent affinity for the norepinephrine transporter. Both the dextro- and levorotary enantiomers displayed receptor affinity for the serotonergic 5HT1A and 5HT2B subtypes, though direct binding to the serotonin transporter was not observed.

The enantiomers and the relative psychoactive effects and CNS stimulation of dextro- and levo-methylphenidate is analogous to what is found in amphetamine, where dextro-amphetamine is considered to have a greater physchoactive and CNS stimulatory effect than levo-amphetamine (levamfetamine is sold legally OTC in Vick's inhalers).

Mode of action

The means by which methylphenidate affects people diagnosed with ADHD are not well understood. Some researchers have theorized that ADHD is caused by a dopamine imbalance in the brains of those affected. Methylphenidate is a norepinephrine and dopamine reuptake inhibitor, which means that it increases the level of the dopamine neurotransmitter in the brain by partially blocking the dopamine transporter (DAT) that removes dopamine from the synapses. This inhibition of DAT blocks the reuptake of dopamine and norepinephrine into the presynaptic neuron, increasing the amount of dopamine in the synapse. It also stimulates the release of dopamine and norepinephrine into the synapse. Finally, it increases the magnitude of dopamine release after a stimulus, increasing the salience of stimulus. The stimulants do not work paradoxically. They stimulate portions of the brain that are underactive by increasing dopamine and norepinephrine in the striatum and prefontal cortex. An alternate explanation which has been explored is that the methylphenidate affects the action of serotonin in the brain.

Side effects

Reported methylphenidate side effects include psychosis (abnormal thinking or hallucinations), difficulty sleeping, mood swings, mood changes, nervousness, stomach aches, diarrhea, headaches, decreased sex drive, lack of hunger (leading to weight loss), gum and skin bleeding, dry mouth, and irritability.

Less common side effects include palpitations, high blood pressure and tachycardia.

Known or suspected risks to health

Researchers have also looked into the role of methylphenidate in affecting stature, with some studies finding slight decreases in height acceleration. Other studies indicate height may normalize by adolescence. In a 2005 study, only "minimal effects on growth in height and weight were observed" after 2 years of treatment. "No clinically significant effects on vital signs or laboratory test parameters were observed.

A 2003 study tested the effects of dextromethylphenidate (Focalin), levomethylphenidate, and (racemic) detro-, levomethylphenidate (Ritalin) on mice to search for any carcinogenic effects. The researchers found that all three preparations were non-genotoxic and non-clastogenic; d-MPH, d, l-MPH, and l-MPH did not cause mutations or chromosomal aberrations. They concluded that none of the compounds present a carcinogenic risk to humans.

In February 2005, a team of researchers from The University of Texas M. D. Anderson Cancer Center led by R.A. El-Zein announced that a study 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 researchers indicated that their study was relatively small and their results needed to be reproduced in a bigger population for a definitive conclusion about the genotoxicity of methylphenidate to be drawn.

In response to the El-Zein study published in 2005, a team of six scientists from the Department of Child and Adolescent Psychiatry and Psychotherapy and the Department of Toxicology, University of Würzburg, Würzburg, Germany began a more in-depth study. They sought to respond to the challenge noted above to attempt to replicate the results of El-Zein et al. in a larger study. Their paper was completed in 2006 and published in 2007 in Environmental Health Perspectives (EHP), the peer-reviewed journal of the United States' National Institute of Environmental Health Sciences. This study used a larger cohort and a longer period of follow-up and included a small group of long-term users, but otherwise used what researchers believed to be an identical methodology to that used by El-Zein et al. (They note that El-Zein et al. published a short study report and did not publish detailed descriptions of methodology.) After follow-ups at six months, the researchers found no evidence that methylphenidate might cause cancer, stating "the concern regarding a potential increase in the risk of developing cancer later in life after long-term MPH treatment is not supported".

The effects of long-term methylphenidate treatment on the developing brains of children with ADHD is the subject of study and debate. Although the safety profile of short-term methylphenidate therapy in clinical trials has been well established, repeated use of psychostimulants such as methylphenidate is less clear.

The use of ADHD medication in children under the age of 6 has not been studied. Severe hallucinations may occur. ADHD symptoms include hyperactivity and difficulty holding still and following directions; these are also characteristics of a typical child under the age of 6. For this reason it may be more difficult to diagnose young children, and caution should be used with this age group.

On March 22, 2006 the FDA Pediatric Advisory Committee decided that medications using methylphenidate ingredients do not need black box warnings about their risks, noting that "for normal children, these drugs do not appear to pose an obvious cardiovascular risk. Previously, 19 possible cases had been reported of Cardiac arrest linked to children taking methylphenidate and the Drug Safety and Risk Management Advisory Committee to the FDA recommend a "black-box" warning in 2006 for stimulant drugs used to treat attention deficit/hyperactivity disorder.

According to a small study conducted by the Society of Nuclear Medicine, the use of methylphenidate in certain individuals for reasons outside of its intended clinical applications may adversely affect cognitive performance. Specifically, methylphenidate positively affected brain glucose metabolism in subjects who performed well at baseline on an accuracy-controlled cognitive task, but caused further deterioration of mental processing in subjects who performed poorly at baseline. In other words, certain individuals without ADHD who take the drug to enhance concentration and focus may inadvertently make things worse.

However, in a paper published in Biological Psychiatry (June 24, 2008 online), researchers report that methylphenidate fine-tunes the functioning of neurons in the prefrontal cortex - a brain region involved in attention, decision-making and impulse control - while having few effects outside it. The team studied PFC neurons in rats under a variety of methylphenidate doses, including one that improved the animals' performance in a working memory task of the type that ADHD patients have trouble completing. Using microelectrodes, the scientists observed both the random, spontaneous firings of PFC neurons and their response to stimulation of the hippocampus. When they listened to individual PFC neurons, the scientists found that while cognition-enhancing doses of methylphenidate had little effect on spontaneous activity, the neurons' sensitivity to signals coming from the hippocampus increased dramatically. Under higher, stimulatory doses, on the other hand, PFC neurons stopped responding to incoming information. Another study suggests that methylphenidate improves spatial orientation and working memory in rats on the radial arm maze.

Scheduling and abuse potential

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 present a high likelihood for abuse because of their addictive potential. Internationally, methylphenidate is a Schedule II drug under the Convention on Psychotropic Substances. Methylphenidate has been used illegally by students for whom the drug has not been prescribed, intended to assist with coursework and examinations.

Delivery formulations

All media are in milligrams.

Tablet

  • Ritalin: 5, 10 or 20mg tablets.
  • Ritalin SR: 20mg controlled-release tablets.
  • Attenta: 10mg tablets.
  • Methylin: 5, 10 or 20mg tablets.
  • Methylin ER: 10 and 20mg controlled-release tablets.
  • Metadate ER: 10 and 20mg controlled-release tablets.
  • Concerta: 18, 27, 36 and 54mg controlled-release tablets. (goes off patent in 2018)
  • Equasym: 5, 10, 20 or 30mg tablets.
  • Rubifen: 5, 10 or 20mg tablets.

Capsules

  • Ritalin LA: 10, 20, 30 or 40mg controlled-release capsules.
  • Metadate CD: 10, 20, 30, 40 or 60mg controlled-release capsules.

Patches

  • Daytrana 10, 15, 20 or 30mg controlled-release patches (1.1, 1.6, 2.2 or 3.3 mg/hour for 9 hours).

Criticism

Methylphenidate is frequently used in the treatment for ADHD, and as such criticism of the drug is typically related to the controversy about ADHD.

Generally criticism of methylphenidate revolves around the alleged or established side effects. There are also concerns about illicit use of the drug and the ethics of giving psychotropic drugs to children to reduce ADHD symptoms. Others wonder if the medication is a gateway drug to substance abuse although this contention has been discredited.

According to an article in the Los Angeles Times, "the uproar over Ritalin was triggered almost single-handedly by the Scientology movement." The Citizens Commission on Human Rights, an antipsychiatry group associated with Scientology, conducted a major campaign against Ritalin in the 1980s and lobbied Congress for an investigation of Ritalin. Though, some studies - namely by the U.S. government - concluded that side-effects often develop when starting this therapy at younger ages.

See also

References

External links

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