Pharmacodynamics

Methylphenidate HCl is a central nervous system (CNS) stimulant. The mode of therapeutic action in Attention Deficit Hyperactivity Disorder (ADHD) is not known. Methylphenidate is thought to block the reuptake of norepinephrine and dopamine into the presynaptic neuron and increase the release of these monoamines into the extraneuronal space. Methylphenidate is a racemic mixture comprised of the d- and l-threo enantiomers. The d-threo enantiomer is more pharmacologically active than the l-threo enantiomer.

Pharmacokinetics

The pharmacokinetics of the Methylphenidate HCl Extended-Release Capsules CD methylphenidate hydrochloride formulation have been studied in healthy adult volunteers and in children with Attention Deficit Hyperactivity Disorder (ADHD).

Absorption And Distribution

Methylphenidate is readily absorbed. Methylphenidate HCl Extended-Release Capsules CD has a plasma/time concentration profile showing two phases of drug release with a sharp, initial slope similar to a methylphenidate immediate-release tablet, and a second rising portion approximately three hours later, followed by a gradual decline. (See Figure 1 below.)

Comparison Of Immediate Release (IR) And Methylphenidate HCl Extended-Release Capsules CD Formulations After Repeated Doses Of Methylphenidate HCl In Children With ADHD

Methylphenidate HCl Extended-Release Capsules CD was administered as repeated once-daily doses of 20 mg or 40 mg to children aged 7-12 years with ADHD for one week. After a dose of 20 mg, the mean (±SD) early Cmax was 8.6 (±2.2) ng/mL, the later Cmax was 10.9 (±3.9)1 ng/mL and AUC0-9h was 63.0 (±16.8) ng∙h/mL. The corresponding values after a 40 mg dose were 16.8 (±5.1) ng/mL, 15.1 (±5.8)1 ng/mL and 120 (±39.6) ng∙h/mL, respectively. The early peak concentrations (median) were reached about 1.5 hours after dose intake, and the second peak concentrations (median) were reached about 4.5 hours after dose intake. The means for Cmax and AUC following a dose of 20 mg were slightly lower than those seen with 10 mg of the immediate-release formulation, dosed at 0 and 4 hours.

FIGURE 1 Comparison of Immediate Release (IR) and Methylphenidate HCl Extended-Release Capsules CD Formulations After Repeated Doses of Methylphenidate HCl in Children with ADHD

Dose Proportionality

Following single oral doses of 10-60 mg methylphenidate free base as a solution given to ten healthy male volunteers, Cmax and AUC increased proportionally with increasing doses. After the 60 mg dose, tmax was reached 1.5 hours post-dose, with a mean Cmax of 31.8 ng/mL (range 24.7-40.9 ng/mL).

Following one week of repeated once-daily doses of 20 mg or 40 mg Methylphenidate HCl Extended-Release Capsules CD to children aged 7-12 years with ADHD, Cmax and AUC were proportional to the administered dose.

Food Effects

In a study in adult volunteers to investigate the effects of a high-fat meal on the bioavailability of a dose of 40 mg, the presence of food delayed the early peak by approximately 1 hour (range -2 to 5 hours delay). The plasma levels rose rapidly following the food-induced delay in absorption. Overall, a high-fat meal increased the Cmax of Methylphenidate HCl Extended-Release Capsules CD by about 30% and AUC by about 17%, on average (see DOSAGE AND ADMINISTRATION).

After a single dose, the bioavailability (Cmax and AUC) of methylphenidate in 26 healthy adults was unaffected by sprinkling the capsule contents on applesauce as compared to the intact capsule. This finding demonstrates that a 20 mg Methylphenidate HCl Extended-Release Capsules CD capsule, when opened and sprinkled on one tablespoon of applesauce, is bioequivalent to the intact capsule.

Metabolism And Excretion

In humans, methylphenidate is metabolized primarily via deesterification to alpha-phenyl-piperidine acetic acid (ritalinic acid). The metabolite has little or no pharmacologic activity.

In vitro studies showed that methylphenidate was not metabolized by cytochrome P450 isoenzymes, and did not inhibit cytochrome P450 isoenzymes at clinically observed plasma drug concentrations.

The mean terminal half-life (t½) of methylphenidate following administration of Methylphenidate HCl Extended-Release Capsules CD (t½=6.8h) is longer than the mean terminal (t½) following administration of methylphenidate hydrochloride immediate-release tablets (t½=2.9h) and methylphenidate hydrochloride sustained-release tablets (t½=3.4h) in healthy adult volunteers. This suggests that the elimination process observed for Methylphenidate HCl Extended-Release Capsules CD is controlled by the release rate of methylphenidate from the extended-release formulation, and that the drug absorption is the rate-limiting process.

Alcohol Effect

An in vitro study was conducted to explore the effect of alcohol on the release characteristics of methylphenidate from the Methylphenidate HCl Extended-Release Capsules CD 60 mg capsule dosage form. At an alcohol concentration of 40% there was an increase in the release rate of methylphenidate in the first hour, resulting in 84% of the methylphenidate being released. The results with the 60 mg capsule are considered to be representative of the other available capsule strengths. Patients should be advised to avoid alcohol while taking Methylphenidate HCl Extended-Release Capsules CD.

Special Populations

Attention Deficit Hyperactivity Disorder (ADHD)

Methylphenidate HCl Extended-Release Capsules CD are indicated for the treatment of Attention Deficit Hyperactivity Disorder (ADHD).

The efficacy of Methylphenidate HCl Extended-Release Capsules CD in the treatment of ADHD was established in one controlled trial of children aged 6 to 15 who met DSM-IV criteria for ADHD (see CLINICAL PHARMACOLOGY).

A diagnosis of Attention Deficit Hyperactivity Disorder (ADHD; DSM-IV) implies the presence of hyperactive-impulsive or inattentive symptoms that caused impairment and were present before age 7 years. The symptoms must cause clinically significant impairment, e.g., in social, academic, or occupational functioning, and be present in two or more settings, e.g., school (or work) and at home. The symptoms must not be better accounted for by another mental disorder. For the Inattentive Type, at least six of the following symptoms must have persisted for at least 6 months: lack of attention to details/careless mistakes; lack of sustained attention; poor listener; failure to follow through on tasks; poor organization; avoids tasks requiring sustained mental effort; loses things; easily distracted; forgetful. For the Hyperactive-Impulsive Type, at least six of the following symptoms must have persisted for at least 6 months: fidgeting/squirming; leaving seat; inappropriate running/climbing; difficulty with quiet activities; "on the go;" excessive talking; blurting answers; can't wait turn; intrusive. The Combined Types requires both inattentive and hyperactive-impulsive criteria to be met.

Special Diagnostic Considerations

Specific etiology of this syndrome is unknown, and there is no single diagnostic test. Adequate diagnosis requires the use not only of medical but of special psychological, educational, and social resources. Learning may or may not be impaired. The diagnosis must be based upon a complete history and evaluation of the child and not solely on the presence of the required number of DSM-IV characteristics.

Need For Comprehensive Treatment Program

Methylphenidate HCl Extended-Release Capsules CD is indicated as an integral part of a total treatment program for ADHD that may include other measures (psychological, educational, social) for patients with this syndrome. Drug treatment may not be indicated for all children with this syndrome. Stimulants are not intended for use in the child who exhibits symptoms secondary to environmental factors and/or other primary psychiatric disorders, including psychosis. Appropriate educational placement is essential and psychosocial intervention is often helpful. When remedial measures alone are insufficient, the decision to prescribe stimulant medication will depend upon the physician's assessment of the chronicity and severity of the child's symptoms.

Long-Term Use

The effectiveness of Methylphenidate HCl Extended-Release Capsules CD for long-term use, i.e., for more than 3 weeks, has not been systematically evaluated in controlled trials. Therefore, the physician who elects to use Methylphenidate HCl Extended-Release Capsules CD for extended periods should periodically re-evaluate the long-term usefulness of the drug for the individual patient (see DOSAGE AND ADMINISTRATION).

Agitation

Methylphenidate HCl Extended-Release Capsules CD is contraindicated in patients with marked anxiety, tension and agitation, since the drug may aggravate these symptoms.

Hypersensitivity To Methylphenidate Or Other Excipients

Methylphenidate HCl Extended-Release Capsules CD is contraindicated in patients known to be hypersensitive to methylphenidate or other components of the product.

Methylphenidate HCl Extended-Release Capsules CD contains sucrose. Therefore, patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption, or sucrase-isomaltase insufficiency should not take this medicine.

Glaucoma

Methylphenidate HCl Extended-Release Capsules CD is contraindicated in patients with glaucoma.

Tics

Methylphenidate HCl Extended-Release Capsules CD is contraindicated in patients with motor tics or with a family history or diagnosis of Tourette's syndrome (see ADVERSE REACTIONS).

Monoamine Oxidase Inhibitors

Methylphenidate HCl Extended-Release Capsules CD is contraindicated during treatment with monoamine oxidase inhibitors, and also within a minimum of 14 days following discontinuation of a monoamine oxidase inhibitor (hypertensive crises may result).

Hypertension And Other Cardiovascular Conditions

Methylphenidate HCl Extended-Release Capsules CD is contraindicated in patients with severe hypertension, angina pectoris, cardiac arrhythmias, heart failure, recent myocardial infarction, hyperthyroidism or thyrotoxicosis (see WARNINGS).

Halogenated Anesthetics

There is a risk of sudden blood pressure increase during surgery. If surgery is planned, Methylphenidate HCl Extended-Release Capsules CD should not be taken on the day of the surgery.

Serious Cardiovascular Events

Psychiatric Adverse Events

Long-Term Suppression Of Growth

Careful follow-up of weight and height in children ages 7 to 10 years who were randomized to either methylphenidate or non-medication treatment groups over 14 months, as well as in naturalistic subgroups of newly methylphenidate-treated and non-medication treated children over 36 months (to the ages of 10 to 13 years), suggests that consistently medicated children (i.e., treatment for 7 days per week throughout the year) have a temporary slowing in growth rate (on average, a total of about 2 cm less growth in height and 2.7 kg less growth in weight over 3 years), without evidence of growth rebound during this period of development. Published data are inadequate to determine whether chronic use of amphetamines may cause a similar suppression of growth, however, it is anticipated that they likely have this effect as well. Therefore, growth should be monitored during treatment with stimulants, and patients who are not growing or gaining height or weight as expected may need to have their treatment interrupted.

Seizures

There is some clinical evidence that stimulants may lower the convulsive threshold in patients with prior history of seizures, in patients with prior EEG abnormalities in absence of seizures, and, very rarely, in patients without a history of seizures and no prior EEG evidence of seizures. In the presence of seizures, the drug should be discontinued.

Priapism

Prolonged and painful erections, sometimes requiring surgical intervention, have been reported with methylphenidate products in both pediatric and adult patients. Priapism was not reported with drug initiation but developed after some time on the drug, often subsequent to an increase in dose. Priapism has also appeared during a period of drug withdrawal (drug holidays or discontinuation). Patients who develop abnormally sustained or frequent and painful erections should seek immediate medical attention.

Peripheral Vasculopathy, including Raynaud's phenomenon

Stimulants, including Methylphenidate HCl Extended-Release Capsules CD, used to treat ADHD are associated with peripheral vasculopathy, including Raynaud's phenomenon. Signs and symptoms are usually intermittent and mild; however, very rare sequelae include digital ulceration and/or soft tissue breakdown. Effects of peripheral vasculopathy, including Raynaud's phenomenon, were observed in post-marketing reports at different times and at therapeutic doses in all age groups throughout the course of treatment. Signs and symptoms generally improve after reduction in dose or discontinuation of drug. Careful observation for digital changes is necessary during treatment with ADHD stimulants. Further clinical evaluation (e.g., rheumatology referral) may be appropriate for certain patients.

Visual Disturbance

Difficulties with accommodation and blurring of vision have been reported with stimulant treatment.

Use In Children Under Six Years Of Age

Methylphenidate HCl Extended-Release Capsules CD should not be used in children under six years, since safety and efficacy in this age group have not been established.

Hematologic Monitoring

Periodic CBC, differential, and platelet counts are advised during prolonged therapy.

Drug Testing

Methylphenidate HCl Extended-Release Capsules CD contains methylphenidate which may result in a positive result during drug testing.

Information For Patients

Patients should be instructed to take one dose in the morning before breakfast. The patients should be instructed that the capsule may be swallowed whole, or alternatively, the capsule may be opened and the capsule contents sprinkled onto a small amount (tablespoon) of applesauce and given immediately, and not stored for future use. The capsules and the capsule contents must not be crushed or chewed.

Patients should be advised to avoid alcohol while taking Methylphenidate HCl Extended-Release Capsules CD. Consumption of alcohol while taking Methylphenidate HCl Extended-Release Capsules CD may result in a more rapid release of the dose of methylphenidate.

Drug Interactions

Monoamine Oxidase Inhibitors (MAOI)

Concomitant use of MAOIs and CNS stimulants, including Methylphenidate HCl Extended-Release Capsules CD can cause hypertensive crisis. Potential outcomes include death, stroke, myocardial infarction, aortic dissection, ophthalmological complications, eclampsia, pulmonary edema, and renal failure (see CONTRAINDICATIONS). Concomitant use of Methylphenidate HCl Extended-Release Capsules CD with MAOIs or within 14 days after discontinuing MAOI treatment is contraindicated.

Antihypertensive Drugs

Methylphenidate HCl Extended-Release Capsules CD may decrease the effectiveness of drugs used to treat hypertension. Monitor blood pressure and adjust the dosage of the antihypertensive drug as needed.

Because of possible effects on blood pressure, Methylphenidate HCl Extended-Release Capsules CD should be used cautiously with pressor agents.

Human pharmacologic studies have shown that methylphenidate may inhibit the metabolism of coumarin anticoagulants, anticonvulsants (e.g., phenobarbital, phenytoin, primidone), phenylbutazone and some antidepressants (tricyclics and selective serotonin reuptake inhibitors). Downward dose adjustment of these drugs may be required when given concomitantly with methylphenidate. It may be necessary to adjust the dosage and monitor plasma drug concentrations (or, in the case of coumarin, coagulation times), when initiating or discontinuing concomitant methylphenidate.

In theory, there is a possibility that the clearance of methylphenidate might be affected by urinary pH, either being increased with acidifying agents or decreased with alkalizing agents. This should be considered when methylphenidate is given in combination with agents that alter urinary pH.

Carcinogenesis, Mutagenesis, And Impairment Of Fertility

In a lifetime carcinogenicity study carried out in B6C3F1 mice, methylphenidate caused an increase in hepatocellular adenomas and, in males only, an increase in hepatoblastomas, at a daily dose of approximately 60 mg/kg/day. This dose is approximately 30 times and 4 times the maximum recommended human dose of Methylphenidate HCl Extended-Release Capsules CD on a mg/kg and mg/m2 basis, respectively. Hepatoblastoma is a relatively rare rodent malignant tumor type. There was no increase in total malignant hepatic tumors. The mouse strain used is sensitive to the development of hepatic tumors, and the significance of these results to humans is unknown.

Methylphenidate did not cause any increases in tumors in a lifetime carcinogenicity study carried out in F344 rats; the highest dose used was approximately 45 mg/kg/day, which is approximately 22 times and 5 times the maximum recommended human dose of Methylphenidate HCl Extended-Release Capsules CD on a mg/kg and mg/m2 basis, respectively.

In a 24-week carcinogenicity study in the transgenic mouse strain p53+/-, which is sensitive to genotoxic carcinogens, there was no evidence of carcinogenicity. Male and female mice were fed diets containing the same concentration of methylphenidate as in the lifetime carcinogenicity study; the high-dose groups were exposed to 60 to 74 mg/kg/day of methylphenidate.

Methylphenidate was not mutagenic in the in vitro Ames reverse mutation assay or in the in vitro mouse lymphoma cell forward mutation assay. Sister chromatid exchanges and chromosome aberrations were increased, indicative of a weak clastogenic response, in an in vitro assay in cultured Chinese Hamster Ovary cells. Methylphenidate was negative in vivo in males and females in the mouse bone marrow micronucleus assay.

Methylphenidate did not impair fertility in male or female mice that were fed diets containing the drug in an 18-week Continuous Breeding study. The study was conducted at doses up to 160 mg/kg/day, approximately 80-fold and 8-fold the highest recommended human dose of Methylphenidate HCl Extended-Release Capsules CD on a mg/kg and mg/m2 basis, respectively.

Pregnancy

Nursing Mothers

It is not known whether methylphenidate is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised if Methylphenidate HCl Extended-Release Capsules CD is administered to a nursing woman.

Pediatric Use

The safety and efficacy of Methylphenidate HCl Extended-Release Capsules CD in children under 6 years old have not been established. Long-term effects of methylphenidate in children have not been well established (see WARNINGS).

Adverse Findings In Clinical Trials With Methylphenidate HCl Extended-Release Capsules CD

Adverse Events Occurring At An Incidence Of 5% Or More Among Methylphenidate HCl Extended-Release Capsules CD-Treated Patients

Table 1 enumerates, for a pool of the three studies in pediatric patients with ADHD, at Methylphenidate HCl Extended-Release Capsules CD doses of 20, 40, or 60 mg/day, the incidence of treatment-emergent adverse events. One study was a 3-week placebo-controlled, parallel-group trial, one study was a controlled, crossover trial, and the third study was an open titration trial. The table includes only those events that occurred in 5% or more of patients treated with Methylphenidate HCl Extended-Release Capsules CD where the incidence in patients treated with Methylphenidate HCl Extended-Release Capsules CD was greater than the incidence in placebo-treated patients.

The prescriber should be aware that these figures cannot be used to predict the incidence of adverse events in the course of usual medical practice where patient characteristics and other factors differ from those which prevailed in the clinical trials. Similarly, the cited frequencies cannot be compared with figures obtained from other clinical investigations involving different treatments, uses, and investigators. The cited figures, however, do provide the prescribing physician with some basis for estimating the relative contribution of drug and non-drug factors to the adverse event incidence rate in the population studied.

1: Events, regardless of causality, for which the incidence for patients treated with Methylphenidate HCl Extended-Release Capsules CD was at least 5% and greater than the incidence among placebo-treated patients. Incidence has been rounded to the nearest whole number.

Adverse Events With Other Marketed Methylphenidate HCl Products

Nervousness and insomnia are the most common adverse reactions reported with other methylphenidate products. Other reactions include hypersensitivity (including skin rash, urticaria, fever, arthralgia, exfoliative dermatitis, erythema multiforme with histopathological findings of necrotizing vasculitis, and thrombocytopenic purpura); anorexia; nausea; dizziness; palpitations; headache; dyskinesia; drowsiness; blood pressure and pulse changes, both up and down; tachycardia; angina; cardiac arrhythmia; abdominal pain; weight loss during prolonged therapy. There have been rare reports of Tourette's Syndrome and obsessive-compulsive disorder. Toxic psychosis has been reported. Although a definite causal relationship has not been established, the following have been reported in patients taking this drug: instances of abnormal liver function, ranging from transaminase elevation to severe hepatic injury; isolated cases of cerebral arteritis and/or occlusion; leucopenia and/or anemia; transient depressed mood; a few instances of scalp hair loss. Very rare reports of neuroleptic malignant syndrome (NMS) have been reported, and, in most of these, patients were concurrently receiving therapies associated with NMS. In a single report, a ten year old boy who had been taking methylphenidate for approximately 18 months experienced an NMS-like event within 45 minutes of ingesting his first dose of venlafaxine. It is uncertain whether this case represented a drug-drug interaction, a response to either drug alone, or some other cause.

In children, loss of appetite, abdominal pain, weight loss during prolonged therapy, insomnia and tachycardia may occur more frequently; however, any of the other adverse reactions listed above may also occur.

Postmarketing Experience

In addition to the adverse events listed above, the following have been reported in patients receiving Methylphenidate HCl Extended-Release Capsules CD worldwide. The list is alphabetized: abnormal behavior, aggression, anxiety, bruxism, cardiac arrest, depression, fixed drug eruption, hyperactivity, irritability, libido changes, migraine, obsessive-compulsive disorder, peripheral coldness, Raynaud's phenomenon, reversible ischaemic neurological deficit, rhabdomyolysis, serotonin syndrome in combination with serotonergic drugs, sudden death, suicidal behavior (including completed suicide), and thrombocytopenia. Data are insufficient to support an estimation of incidence or establish causation.

Controlled Substance Class

Methylphenidate HCl Extended-Release Capsules CD, like other methylphenidate products, is classified as a Schedule II controlled substance by federal regulation.

Abuse, Dependence, And Tolerance

See WARNINGS for boxed warning containing drug abuse and dependence information.

Signs And Symptoms

Signs and symptoms of acute methylphenidate overdosage, resulting principally from overstimulation of the CNS and from excessive sympathomimetic effects, may include the following: vomiting, agitation, tremors, hyperreflexia, muscle twitching, convulsions (may be followed by coma), euphoria, confusion, hallucinations, delirium, sweating, flushing, headache, hyperpyrexia, tachycardia, palpitations, cardiac arrhythmias, hypertension, mydriasis, dryness of mucous membranes, and rhabdomyolysis.

Recommended Treatment

Treatment consists of appropriate supportive measures. The patient must be protected against self-injury and against external stimuli that would aggravate overstimulation already present. Gastric contents may be evacuated by gastric lavage as indicated. Before performing gastric lavage, control agitation and seizures if present and protect the airway. Other measures to detoxify the gut include administration of activated charcoal and a cathartic. Intensive care must be provided to maintain adequate circulation and respiratory exchange; external cooling procedures may be required for hyperpyrexia.

Efficacy of peritoneal dialysis or extracorporeal hemodialysis for Methylphenidate HCl Extended-Release Capsules CD overdosage has not been established.

The prolonged release of methylphenidate from Methylphenidate HCl Extended-Release Capsules CD should be considered when treating patients with overdose.

Poison Control Center

As with the management of all overdosage, the possibility of multiple drug ingestion should be considered. The physician may wish to consider contacting a poison control center for up-to-date information on the management of overdosage with methylphenidate.

Initial Treatment

The recommended starting dose of Methylphenidate HCl Extended-Release Capsules CD is 20 mg once daily. Dosage may be adjusted in weekly 10-20 mg increments to a maximum of 60 mg/day taken once daily in the morning, depending upon tolerability and degree of efficacy observed. Daily dosage above 60 mg is not recommended.

Maintenance/Extended Treatment

There is no body of evidence available from controlled trials to indicate how long the patient with ADHD should be treated with Methylphenidate HCl Extended-Release Capsules CD. It is generally agreed, however, that pharmacological treatment of ADHD may be needed for extended periods. Nevertheless, the physician who elects to use Methylphenidate HCl Extended-Release Capsules CD for extended periods in patients with ADHD should periodically re-evaluate the long-term usefulness of the drug for the individual patient with trials off medication to assess the patient's functioning without pharmacotherapy. Improvement may be sustained when the drug is either temporarily or permanently discontinued.

Dose Reduction And Discontinuation

If paradoxical aggravation of symptoms or other adverse events occur, the dosage should be reduced, or, if necessary, the drug should be discontinued.

If improvement is not observed after appropriate dosage adjustment over a one-month period, the drug should be discontinued.

Store at 25°C (77°F); excursions permitted to 15°-30°C (59°-86°F) [See USP Controlled Room Temperature].

Keep out of the reach of children.