Exelon (Page 3 of 6)

7 DRUG INTERACTIONS

No specific interaction studies have been conducted with Exelon Patch (rivastigmine transdermal system).

7.1

Effect of Exelon on the Metabolism of Other Drugs

Rivastigmine is primarily metabolized through hydrolysis by esterases. Minimal metabolism occurs via the major cytochrome P450 isoenzymes. Based on in-vitro studies, no pharmacokinetic drug interactions with drugs metabolized by the following isoenzyme systems are expected: CYP1A2, CYP2D6, CYP3A4/5, CYP2E1, CYP2C9, CYP2C8, or CYP2C19.

No pharmacokinetic interaction was observed between rivastigmine taken orally and digoxin, warfarin, diazepam or fluoxetine in studies in healthy volunteers. The increase in prothrombin time induced by warfarin is not affected by administration of rivastigmine.

7.2

Effect of Other Drugs on the Metabolism of Exelon

Drugs that induce or inhibit CYP450 metabolism are not expected to alter the metabolism of rivastigmine.

Population PK analysis with a database of 625 patients showed that the pharmacokinetics of rivastigmine taken orally were not influenced by commonly prescribed medications such as antacids (n=77), antihypertensives (n=72), ß-blockers (n=42), calcium channel blockers (n=75), antidiabetics (n=21), nonsteroidal anti-inflammatory drugs (n=79), estrogens (n=70), salicylate analgesics (n=177), antianginals (n=35) and antihistamines (n=15).

7.3

Use with Anticholinergics

,

C

holinomimetics and

O

ther

Cholinesterase I

nhibitors

In view of its pharmacodynamic effects, rivastigmine should not be given concomitantly with other cholinomimetic drugs and might interfere with the activity of anticholinergic medications. A synergistic effect may be expected when cholinesterase inhibitors are given concurrently with succinylcholine, similar neuromuscular blocking agents or cholinergic agonists such as bethanechol.

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

8.1.1

Pregnancy Category B

There are no adequate or well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, Exelon Patch should be used during pregnancy only if the potential benefit outweighs the potential risk to the fetus. No dermal reproduction studies in animals have been conducted. Oral reproduction studies conducted in pregnant rats at doses up to 2.3 mg base/kg/day and in pregnant rabbits at doses up to 2.3 mg base/kg/day revealed no evidence of teratogenicity. Studies in rats showed slightly decreased fetal/pup weights, usually at doses causing some maternal toxicity.

8.

3

Nursing Mothers

Milk transfer studies in animals have not been conducted with dermal rivastigmine. In rats given rivastigmine orally, concentrations of rivastigmine plus metabolites were approximately two times higher in milk than in plasma. It is not known whether rivastigmine is excreted in human breast milk. Exelon Patch (rivastigmine transdermal system) has no indication for use in nursing mothers.

8.

4

Pediatric Use

There are no adequate and well-controlled trials documenting the safety and efficacy of Exelon in any illness occurring in children.

8.

5

Geriatric Use

Age had no impact on the exposure to rivastigmine in Alzheimer’s disease patients treated with Exelon Patch.

8.

6

Hepatic Disease

No pharmacokinetic study was conducted with Exelon Patch in subjects with hepatic impairment. Following a single 3-mg dose, mean oral clearance of rivastigmine was 60% lower in hepatically impaired patients (n=10, biopsy proven) than in healthy subjects (n=10). After multiple 6-mg BID oral dosing, the mean clearance of rivastigmine was 65% lower in mild (n=7, Child-Pugh score 5-6) and moderate (n=3, Child-Pugh score 7-9) hepatically impaired patients (biopsy proven, liver cirrhosis) than in healthy subjects (n=10). Dosage adjustment is not necessary in hepatically impaired patients as the dose of drug is individually titrated to tolerability.

8.

7

Renal Disease

No study was conducted with Exelon Patch in subjects with renal impairment. Following a single 3-mg dose, mean oral clearance of rivastigmine is 64% lower in moderately impaired renal patients (n=8, GFR=10-50 mL/min) than in healthy subjects (n=10, GFR greater than or equal to 60 mL/min); Cl/F=1.7 L/min (cv=45%) and 4.8 L/min (cv=80%), respectively. In severely impaired renal patients (n=8, GFR less than 10 mL/min), mean oral clearance of rivastigmine is 43% higher than in healthy subjects (n=10, GFR greater than or equal to 60 mL/min); Cl/F=6.9 L/min and 4.8 L/min, respectively. For unexplained reasons, the severely impaired renal patients had a higher clearance of rivastigmine than moderately impaired patients. However, dosage adjustment may not be necessary in renally impaired patients as the dose of the drug is individually titrated to tolerability.

8.

8

Low Body Weight

Rivastigmine exposure is higher in subjects with low body weight. Compared to a patient with a body weight of 65 kg, the rivastigmine steady-state concentrations in a patient with a body weight of 35 kg would be approximately doubled, while for a patient with a body weight of 100 kg the concentrations would be approximately halved. This suggests special attention should be given to patients with very low body weight during up-titration [see Dosage and Administration (2) ].

8.

9

Gender and Race

No specific pharmacokinetic study was conducted to investigate the effect of gender and race on the disposition of Exelon, but a population pharmacokinetic analysis indicates that gender (n=277 males and 348 females) and race (n=575 White, 34 Black, 4 Asian, and 12 Other) did not affect the clearance of Exelon administered orally. Similar results were seen with analyses of pharmacokinetic data obtained after the administration of Exelon Patch.

8.

10

Nicotine Use

Population pharmacokinetic analysis showed that nicotine use increases the oral clearance of rivastigmine by 23% (n=75 Smokers and 549 Nonsmokers). No dose adjustment is necessary as the dose of the drug is individually titrated to tolerability.

10 OVERDOSAGE

Because strategies for the management of overdose are continually evolving, it is advisable to contact a Poison Control Center to determine the latest recommendations for the management of an overdose of any drug. As in any case of overdose, general supportive measures should be utilized.

As rivastigmine has a plasma half-life of about 3.4 hours after patch administration and a duration of acetylcholinesterase inhibition of about 9 hours, it is recommended that in cases of asymptomatic overdose the patch should be immediately removed and no further patch should be applied for the next 24 hours.

As in any case of overdose, general supportive measures should be utilized. Overdosage with cholinesterase inhibitors can result in cholinergic crisis characterized by severe nausea, vomiting, salivation, sweating, bradycardia, hypotension, respiratory depression, collapse and convulsions. Increasing muscle weakness is a possibility and may result in death if respiratory muscles are involved. Atypical responses in blood pressure and heart rate have been reported with other drugs that increase cholinergic activity when coadministered with quaternary anticholinergics such as glycopyrrolate. Due to the short plasma elimination half-life of rivastigmine after patch administration, dialysis (hemodialysis, peritoneal dialysis, or hemofiltration) would not be clinically indicated in the event of an overdose.

In overdose accompanied by severe nausea and vomiting, the use of antiemetics should be considered. In a documented case of an oral 46-mg overdose with Exelon, the patient experienced vomiting, incontinence, hypertension, psychomotor retardation, and loss of consciousness. The patient fully recovered within 24 hours and conservative management was all that was required for treatment.

There are currently no data on overdose with Exelon Patch (rivastigmine transdermal system).

11 DESCRIPTION

Exelon Patch (rivastigmine transdermal system) is a reversible cholinesterase inhibitor and is known chemically as (S)- 3-[1-(dimethylamino) ethyl]phenyl ethylmethylcarbamate. It has an empirical formula of C14 H22 N2 O2 as the base and a molecular weight of 250.34 (as the base). Rivastigmine is a viscous, clear, and colorless to yellow to very slightly brown liquid that is sparingly soluble in water and very soluble in ethanol, acetonitrile, n-octanol and ethyl acetate.

The distribution coefficient at 37°C in n-octanol/phosphate buffer solution pH 7 is 4.27.

image of chemical structure

Exelon Patch is for transdermal administration. The patch comprises a four-layer laminate containing the backing layer, drug matrix, adhesive matrix and overlapping release liner. The release liner is removed and discarded prior to use. See Figure 1 for a detailed illustration.

image of Figure 1
Layer 1Backing Film
Layer 2Drug Product (Acrylic) Matrix
Layer 3Adhesive (Silicone) Matrix
Layer 4Release Liner (removed at time of use)

Excipients within the formulation include acrylic copolymer, poly(butylmethacrylate, methylmethacrylate), silicone adhesive applied to a flexible polymer backing film, silicone oil, and vitamin E.

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