Dexmethylphenidate Hydrochloride (Page 4 of 7)

8.5 Geriatric Use

Dexmethylphenidate hydrochloride tablets has not been studied in the geriatric population.

9 DRUG ABUSE AND DEPENDENCE

9.1 Controlled Substance

Dexmethylphenidate hydrochloride tablets contains dexmethylphenidate hydrochloride, a Schedule II controlled substance.

9.2 Abuse

CNS stimulants, including dexmethylphenidate hydrochloride tablets, other methylphenidate-containing products, and amphetamines have a high potential for abuse. Abuse is characterized by impaired control over drug use despite harm, and craving.

Signs and symptoms of CNS stimulant abuse include increased heart rate, respiratory rate, blood pressure, and/or sweating, dilated pupils, hyperactivity, restlessness, insomnia, decreased appetite, loss of coordination, tremors, flushed skin, vomiting, and/or abdominal pain. Anxiety, psychosis, hostility, aggression, and suicidal or homicidal ideation have also been observed. Abusers of CNS stimulants may chew, snort, inject, or use other unapproved routes of administration which may result in overdose and death [see Overdosage (10)].

To reduce the abuse of CNS stimulants, including dexmethylphenidate hydrochloride tablets, assess the risk of abuse prior to prescribing. After prescribing, keep careful prescription records, educate patients and their families about abuse and on proper storage and disposal of CNS stimulants [see How Supplied/Storage and Handling (16)] , monitor for signs of abuse while on therapy, and reevaluate the need for dexmethylphenidate hydrochloride tablets use.

9.3 Dependence

Tolerance

Tolerance (a state of adaptation in which exposure to a drug result in a reduction of the drug’s desired and/or undesired effects over time) can occur during chronic therapy with CNS stimulants, including dexmethylphenidate hydrochloride tablets.

Dependence

Physical dependence (which is manifested by a withdrawal syndrome produced by abrupt cessation, rapid dose reduction, or administration of an antagonist) can occur in patients treated with CNS stimulants, including dexmethylphenidate hydrochloride tablets. Withdrawal symptoms after abrupt cessation following prolonged high-dosage administration of CNS stimulants include dysphoric mood; fatigue; vivid, unpleasant dreams; insomnia or hypersomnia; increased appetite; and psychomotor retardation or agitation.

10 OVERDOSAGE

Human Experience

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, and dryness of mucous membranes, and rhabdomyolysis.

Overdose Management

Consult with a Certified Poison Control Center (1-800-222-1222) for latest recommendations.

11 DESCRIPTION

Dexmethylphenidate hydrochloride tablets contains dexmethylphenidate hydrochloride, a CNS stimulant. Dexmethylphenidate hydrochloride is the d-threo enantiomer of racemic methylphenidate hydrochloride. Dexmethylphenidate hydrochloride tablets is available as 2.5 mg, 5 mg, and 10 mg strength tablets for oral administration.

Chemically, dexmethylphenidate hydrochloride is methyl α-phenyl-2-piperidineacetate hydrochloride, (R, R’)- (+)-. Its molecular formula is C14H19NO2•HCl. Its structural formula is:

Note: * = asymmetric carbon centers

Dexmethylphenidate hydrochloride is a white to off-white powder. Its solutions are acid to litmus. It is freely soluble in water and in methanol, soluble in alcohol, and slightly soluble in chloroform and in acetone. Its molecular weight is 269.77 g/mol.

Inactive ingredients: Dexmethylphenidate hydrochloride tablets also contains the following inert ingredients: lactose anhydrous, magnesium stearate, microcrystalline cellulose and pregelatinized starch. Additionally, 5 mg tablets contain D&C Yellow #10 aluminum lake; 2.5 mg tablets contains FD&C Blue #1 aluminum lake.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Dexmethylphenidate hydrochloride is a CNS stimulant. The mode of therapeutic action in ADHD is not known.

12.2 Pharmacodynamics

Pharmacodynamics

Dexmethylphenidate is the more pharmacologically active d- enantiomer of racemic methylphenidate. Methylphenidate blocks the reuptake of norepinephrine and dopamine into the presynaptic neuron and increase the release of these monoamines into the extraneuronal space.

Cardiac Electrophysiology

A formal QT study has not been conducted in patients taking dexmethylphenidate hydrochloride tablets; however, a large QT effect is not expected. At the recommended maximum total daily dosage of 40 mg, dexmethylphenidate hydrochloride extended-release capsule does not prolong the QTc interval to any clinically relevant extent.

12.3 Pharmacokinetics

Absorption

Dexmethylphenidate hydrochloride is readily absorbed following oral administration of dexmethylphenidate hydrochloride tablets. In patients with ADHD, plasma dexmethylphenidate concentrations increase rapidly, reaching a maximum in the fasted state at about 1 to 1.5 hours postdose. No differences in the pharmacokinetics of dexmethylphenidate hydrochloride tablets were noted following single and repeated twice daily dosing, thus indicating no significant drug accumulation in children with ADHD.

After single dose administration of dexmethylphenidate hydrochloride tablets to pediatric patients, dexmethylphenidate exposure (C _max and AUC _0-inf ) showed dose-proportional increase in the range of 2.5 mg to 10 mg. Comparable plasma dexmethylphenidate levels were achieved following single dl-threo -methylphenidate HCl doses given as capsules in twice the total mg amount (equimolar with respect to dexmethylphenidate hydrochloride tablets).

Approximately 90% of the dose is absorbed after oral administration of radiolabeled racemic methylphenidate. However, due to first pass metabolism the mean absolute bioavailability of dexmethylphenidate when administered in various formulations was 22% to 25%.

Effect of Food

High fat breakfast did not significantly affect C _max or AUC _0-inf of dexmethylphenidate when two 10 mg dexmethylphenidate hydrochloride tablets were administered, but delayed T _max from 1.5 hours post dose to 2.9 hours post dose.

Distribution

The plasma protein binding of dexmethylphenidate is not known; racemic methylphenidate is bound to plasma proteins by 12% to 15%, independent of concentration. Dexmethylphenidate shows a volume of distribution of 2.65 ± 1.11 L/kg.

Elimination

Plasma dexmethylphenidate concentrations declined exponentially following oral administration of dexmethylphenidate hydrochloride tablets. Intravenous dexmethylphenidate was eliminated with a mean clearance of 0.40 ± 0.12 L/hr/kg. The mean terminal elimination half-life of dexmethylphenidate was approximately 2.2 hours.

Metabolism

In humans, dexmethylphenidate is metabolized primarily via de-esterification to d-α- phenyl-piperidine acetic acid (also known as d- ritalinic acid). This metabolite has little or no pharmacological activity. There is little or no in vivo interconversion to the l-threo- enantiomer.

Excretion

After oral dosing of radiolabeled racemic methylphenidate in humans, about 90% of the radioactivity was recovered in urine. The main urinary metabolite of racemic dl -methylphenidate was dl- ritalinic acid, accountable for approximately 80% of the dose. Urinary excretion of parent compound accounted for 0.5% of an intravenous dose.

Studies in Special Populations

Male and Female Patients

Pharmacokinetic parameters were similar for boys and girls (mean age 10 years).

In a single dose study conducted in adults, the mean dexmethylphenidate AUC _0-inf values (adjusted for body weight) following single two 10 mg doses of dexmethylphenidate hydrochloride tablets were 25% to 35% higher in adult female volunteers (n = 6) compared to male volunteers (n = 9). Both T _max and t _1/2 were comparable for males and females.

Racial or Ethnic Groups

There is insufficient experience with the use of dexmethylphenidate hydrochloride tablets to detect ethnic variations in pharmacokinetics.

Pediatric Patients

The pharmacokinetics of dexmethylphenidate after dexmethylphenidate hydrochloride tablets administration have not been studied in children less than 6 years of age. When single doses of dexmethylphenidate hydrochloride tablets were given to children between the ages of 6 to 12 years and healthy adult volunteers, C _max of dexmethylphenidate was similar, however, pediatric patients showed somewhat lower AUCs compared to the adults.

Patients with Renal Impairment

There is no experience with the use of dexmethylphenidate hydrochloride tablets in patients with renal impairment. Since renal clearance is not an important route of methylphenidate clearance, renal impairment is expected to have little effect on the pharmacokinetics of dexmethylphenidate hydrochloride tablets.

Patients with Hepatic Impairment
There is no experience with the use of dexmethylphenidate hydrochloride tablets in patients with hepatic impairment.

Drug Interaction Studies

Methylphenidate is not metabolized by cytochrome P450 (CYP) isoenzymes to a clinically relevant extent. Inducers or inhibitors of CYPs are not expected to have any relevant impact on methylphenidate pharmacokinetics. Conversely, the d- and l- enantiomers of methylphenidate did not relevantly inhibit CYP1A2, 2C8, 2C9, 2C19, 2D6, 2E1, or 3A. Clinically, methylphenidate coadministration did not increase plasma concentrations of the CYP2D6 substrate desipramine.