The P-I-E-N-O Parkinsn's List Drug Database
methylphenidate / RitalinTM
STIMULANT / ANTIADD:
HIGH RISK
Description: Methylphenidate is an orally administered central nervous system stimulant that is chemically and pharmacologically similar to the amphetamines. Methylphenidate's CNS actions are milder than those of the amphetamines and have more noticeable effects on mental activities than on motor activities. Methylphenidate shares the abuse potential of the amphetamines and is also a DEA schedule II controlled substance. It is clinically used in the treatment of narcolepsy and as adjunctive treatment in children with attention-deficit hyperactivity disorder. Methylphenidate was approved by the FDA in 1955. Under the General Agreement on Tariffs and Trade (GATT), the patent for Ritalin-SRTM expires on August 20, 1996.
Mechanism of Action: Methylphenidate exhibits pharmacological activity similar to that of the amphetamines. Methylphenidate's exact mechanism of action in the CNS is not fully understood, but the primary sites of activity appear to be in the cerebral cortex and the subcortical structures including the thalamus. Methylphenidate blocks the reuptake mechanism present in dopaminergic neurons. As a result, sympathomimetic activity in the central nervous system and in the periphery increases. Methylphenidate-induced CNS stimulation produces a decreased sense of fatigue, an increase in motor activity and mental alertness, mild euphoria, and brighter spirits. In the periphery, the actions of methylphenidate are minimal at therapeutic doses.
In treating children with attention-deficit hyperactivity disorder, methylphenidate produces a calming effect. This action of methylphenidate results in a decrease in hyperactivity and an increase in the child's attention span.
Pharmacokinetics: Methylphenidate hydrochloride is orally administered and is well absorbed from the GI tract. Peak serum concentrations are achieved in about 1.9 hours and 4.7 hours for the regular and extended-release forms, respectively. The duration of action ranges from 3-6 hours with regular tablets and about 8 hours with the extended-release tablets. The distribution in humans is unknown. Metabolism of methylphenidate occurs in the liver via hydroxylation to ritolinic acid. Methylphenidate is almost completely eliminated in the urine, with approximately 95% of a dose being recovered as metabolites in urine within 90 hours.
CONTRAINDICATIONS/PRECAUTIONS: Methylphenidate is relatively contraindicated in patients who have or have a family history of Tourette's syndrome, because motor or vocal tics can be exacerbated. Some patients with Tourette's syndrome may actually benefit from methylphenidate therapy; only administer under close supervision.
Methylphenidate is contraindicated in patients with severe cases of anxiety disorder, tension, agitation, major depression, glaucoma, or motor tics other than Tourette's syndrome because the symptoms associated with these conditions can be aggravated. Methylphenidate can cause CNS stimulation and psychosis and should be used with caution in children with psychosis because symptoms of behavior disturbances and thought disorders can be exacerbated.
Methylphenidate should be used with caution in patients with hypertension because the methylphenidate can increase blood pressure. Blood pressure monitoring during therapy is recommended.
Methylphenidate is relatively contraindicated in patients with a history of a seizure disorder because the seizure threshold can be reduced. Concomitant use of methylphenidate and anticonvulsants has not been established. If seizures occur, methylphenidate therapy should be discontinued.
Methylphenidate should be used cautiously, if at all, in patients with a history of emotional instability, alcoholism, or substance abuse because the potential for abuse is increased.
Abrupt discontinuation of long-term administration of methylphenidate is not recommended. Discontinuation may unmask severe depression or the effect of chronic overactivity (e.g., dysphoric mood, suicidal and paranoid ideation). Supervision of withdrawal is recommended.
DRUG INTERACTIONS: The CNS stimulation effects of methylphenidate can be additive when used concurrently with other CNS stimulants. In addition to drugs with CNS stimulating effects, caffeine may also cause excessive CNS stimulation if used by patients receiving methylphenidate.
Methylphenidate can potentiate the actions of both exogenous (such as dopamine and epinephrine) and endogenous (such as norepinephrine) vasopressors. Because methylphenidate and MAOIs both potentiate the effects of catecholamine neurotransmitters, concomitant use of these agents should be avoided. A hypertensive crisis may occur, although data supporting this hypothesis are scanty. Methylphenidate should not be given to any patient within 14 days of receiving a MAO inhibitor.
Methylphenidate can provoke tics and can mask their cause. The drug should be withdrawn before treatment with pimozide begins.
Methylphenidate's secondary anticholinergic effect can be additive with other anticholinergics.
Methylphenidate metabolism is inhibited by anticonvulsants (particularly phenytoin, phenobarbital, and primidone) and warfarin, which can lead to increased serum concentrations. Dosage reduction of methylphenidate may be necessary.
Serum concentrations of tricyclic antidepressants (desipramine, imipramine) can be increased by concurrent use with methylphenidate due to inhibition of antidepressant metabolism. Data supporting this interaction, however, are scanty.
Methylphenidate reduces the hypotensive effect of antihypertensive agents and/or diuretics. The antihypertensive effects of bretylium and guanethidine can be reduced by concurrent use with methylphenidate.
ADVERSE REACTIONS: Nervousness (agitation, anxiety) and insomnia are the most common adverse reactions to methylphenidate. These reactions can be limited by dosage reduction and administering the drug before noon, omitting afternoon or evening doses.
A hypersensitivity reaction to methylphenidate can include skin rash, urticaria, fever, arthralgia, exfoliative dermatitis, and erythema multiforme, with histopathological findings of necrotizing vasculitis and thrombocytopenic purpura.
Other adverse effects of methylphenidate include anorexia, nausea/vomiting, dizziness, palpitations, headache, dyskinesia, drowsiness, angina, sinus tachycardia, hypertension, hypotension, abdominal pain, weight loss, and toxic psychosis. There have been rare reports of Tourette's syndrome.
For children being treated for attention deficit hyperactivity disorder the most commonly reported adverse reactions are loss of appetite, abdominal pain and weight loss. During prolonged therapy insomnia and sinus tachycardia are the most frequently reported reactions.
Abrupt discontinuation of methylphenidate can produce a withdrawal syndrome manifested as severe mental depression, unusual behavior, tiredness, and weakness.
A causal relationship between use of methylphenidate and anemia, thrombocytopenia, leukopenia and other blood dyscrasias has not been established.
PATIENT INFORMATION:
What do methylphenidate tablets do?
Methylphenidate (RitalinTM ) is a stimulant that can increase or stimulate some aspect of brain activity. Methylphenidate helps improve attention in children who cannot concentrate or who are easily distracted. Methylphenidate can also help a condition called narcolepsy. Narcolepsy makes people fall into a sudden deep sleep at odd times. Federal law prohibits the transfer of methylphenidate to any person other than the patient for whom it was prescribed. Do not share this medicine with anyone else. Generic methylphenidate tablets are available.
What should my doctor, dentist, or pharmacist know before I take methylphenidate?
They need to know if you have any of these conditions:
How should I take this medicine?
Take methylphenidate tablets by mouth. Follow the directions on the prescription label. Swallow the tablets with a drink of water. It is best to take methylphenidate 30 to 45 minutes before meals, unless directed otherwise by your doctor. Take your doses at regular intervals. Do not take your medicine more often than directed.
Special precautions for use in children:
This medicine is not for children under 6 years old.
What if I miss a dose?
If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.
What other medicines can interact with methylphenidate?
Tell your doctor or pharmacist: about all other medicines you are taking, including non-prescription medicines; if you are a frequent user of drinks with caffeine or alcohol; if you smoke; or if you use illegal drugs. These may affect the way your medicine works. Check before stopping or starting any of your medicines.
What side effects may I notice from taking methylphenidate?
Serious side effects with methylphenidate include:
Call your doctor as soon as you can if you get any of these side effects.
Minor side effects with methylphenidate include:
Let your doctor know about these side effects if they do not go away or if they annoy you.
What do I need to watch for while I take methylphenidate?
The use of methylphenidate needs careful supervision. Visit your doctor for regular checks on your progress. Tell your doctor if you feel a need to take more tablets than prescribed, or to take them more often; you can develop a dependence on this medicine. If you have been taking methylphenidate regularly for some time, do not suddenly stop taking it. You must gradually reduce the dose or you may feel withdrawal effects. Ask your doctor for advice.
Methylphenidate may affect your concentration, hide signs of tiredness, or make you feel drowsy or dizzy. Until you know how methylphenidate affects you, do not drive, ride a bicycle, use machinery, or do anything that needs mental alertness.
If methylphenidate keeps you awake, or interferes with your normal sleep, do not take the last dose after 6 p.m., (or later than 4-6 hours before your normal bedtime.)
Where can I keep my medicine?
Keep out of the reach of children in a container that small children cannot open.
Store at room temperature below 30C (86F). Protect from light and moisture. Keep container tightly closed. Throw away any unused medicine after the expiration date.
Parkinsn's Archive Treasures Page
The elements and images found in these pages are copyrighted and all rights are retained by the author.
John Cottingham is the webmaster of this site.
