2.1 Proper Patient Selection

2.2 Dosing

2.3 Titration and Maintenance of Therapy

Once therapy is initiated, assess pain intensity and opioid adverse reactions frequently, especially respiratory depression [see Warnings and Precautions (5.2)]. Routinely monitor all patients for signs of misuse, abuse and addiction [see Warnings and Precautions (5.1)].

The initial fentanyl transdermal system dose may be increased after 3 days based on the daily dose of supplemental opioid analgesics required by the patient on the second or third day of the initial application.

It may take up to 6 days for fentanyl levels to reach equilibrium on a new dose [see Clinical Pharmacology (12.3)]. Therefore, evaluate patients for further titration after no less than two 3-day applications before any further increase in dosage is made.

Base dosage increments on the daily dosage of supplementary opioids, using the ratio of 45 mg/24 hours of oral morphine to a 12 mcg/hour increase in fentanyl transdermal system dose.

The majority of patients are adequately maintained with fentanyl transdermal system administered every 72 hours. Some patients may not achieve adequate analgesia using this dosing interval and may require systems to be applied at 48 hours rather than at 72 hours, only if adequate pain control cannot be achieved using a 72-hour regimen. An increase in the fentanyl transdermal system dose should be evaluated before changing dosing intervals in order to maintain patients on a 72-hour regimen. Dosing intervals less than every 72 hours were not studied in children and adolescents and are not recommended.

2.4 Administration of Fentanyl Transdermal System

Fentanyl transdermal system patches are for transdermal use, only.

Proper handling of fentanyl transdermal system is advised in order to prevent adverse reactions, including death, associated with accidental secondary exposure to fentanyl transdermal system [see Warnings and Precautions (5.3)].

2.5 Disposal Instructions

Proper disposal of fentanyl transdermal system is advised in order to prevent adverse reactions, including death, associated with accidental secondary exposure to fentanyl transdermal system [see Warnings and Precautions (5.3)].

Patients should dispose of used patches by folding the adhesive side of the patch to itself, then flush the patch down the toilet immediately upon removal.

Patients should dispose of any patches remaining from a prescription as soon as they are no longer needed. Unused patches should be removed from their pouches, fold so that the adhesive side of the patch adheres to itself, and flush down the toilet.

5.1 Abuse Potential

Fentanyl transdermal system contains fentanyl, an opioid agonist and a Schedule II controlled substance with an abuse liability similar to other opioid analgesics. Schedule II opioid substances which include hydromorphone, morphine, oxycodone, fentanyl, oxymorphone and methadone have the highest potential for abuse and risk of fatal overdose due to respiratory depression. Fentanyl transdermal system can be abused in a manner similar to other opioid agonists, legal or illicit. These risks should be considered when administering, prescribing, or dispensing fentanyl transdermal system in situations where the healthcare professional is concerned about increased risk of misuse, abuse, or diversion [see Drug Abuse and Dependence (9)].

Assess patients for their clinical risks for opioid abuse or addiction prior to being prescribed opioids. Routinely monitor all patients receiving opioids for signs of misuse, abuse and addiction since use of opioid analgesic products carries the risk of addiction even under appropriate medical use. Persons at increased risk for opioid abuse include those with a personal or family history of substance abuse (including drug or alcohol abuse or addiction) or mental illness (i.e., major depression). Patients at increased risk may still be appropriately treated with modified-release opioid formulations; however these patients will require intensive monitoring for signs of misuse, abuse, or addiction. Concerns about abuse, addiction, and diversion should not prevent the proper management of pain.

Contact local state professional licensing board or state controlled substances authority for information on how to prevent and detect abuse or diversion of this product.

5.2 Respiratory Depression and Death

Respiratory depression is the chief hazard of fentanyl transdermal system. Respiratory depression, if not immediately recognized and treated, may lead to respiratory arrest and death.

Fentanyl transdermal system has a narrow indication and should be prescribed only by healthcare professionals who are knowledgeable in the administration of potent opioids and management of chronic pain [see Indications and Usage (1)]. Fentanyl transdermal system is contraindicated for use in conditions in which the risk of life threatening respiratory depression is significantly increased, including use as an as-needed analgesic, use in non-opioid tolerant patients, acute pain, and postoperative pain [see Contraindications (4)]. Proper dosing and titration of fentanyl transdermal system are essential [see Dosage and Administration (2.3)]. Overestimating the fentanyl transdermal system dose when converting patients from another opioid medication, can result in fatal overdose with the first dose. However, respiratory depression has also been reported with use of fentanyl transdermal system in patients who are opioid-tolerant, even when fentanyl transdermal system has been used as recommended and not misused or abused.

The mean half-life of fentanyl when delivered by fentanyl transdermal system is approximately 20 to 27 hours. Serum fentanyl concentrations continue to rise for the first two system applications. In addition, significant amounts of fentanyl continue to be absorbed from the skin for 24 hours or more after the patch is removed [see Clinical Pharmacology (12.3)].

Respiratory depression from opioids is manifested by a reduced urge to breathe and a decreased rate of respiration, often associated with a “sighing” pattern of breathing (deep breaths separated by abnormally long pauses). Carbon dioxide retention from opioid-induced respiratory depression can exacerbate the sedating effects of opioids.

While serious, life threatening or fatal respiratory depression can occur at any time during the use of fentanyl transdermal system, the potential for serious, life threatening, or fatal respiratory depression is greatest during the first two applications following initiation of dosing, or following an increase in dosage. Closely monitor patients for respiratory depression when initiating therapy with fentanyl transdermal system, especially within the initial 24 to 72 hours when serum concentrations from the initial patch will peak, and following increases in dosage. Because significant amounts of fentanyl continue to be absorbed from the skin for 24 hours or more after the patch is removed, respiratory depression may persist beyond the removal of fentanyl transdermal system. Monitor patients for respiratory depression after patch removal to ensure that the patient’s respiration has stabilized for at least 24 to 72 hours or longer as clinical symptoms dictate.

Management of respiratory depression may include close observation, supportive measures, and use of opioid antagonists, depending on the patient’s clinical status [see Overdose (10.2)].

5.3 Accidental Exposure

A considerable amount of active fentanyl remains in fentanyl transdermal system even after use as directed. Death and other serious medical problems have occurred when children and adults were accidentally exposed to fentanyl transdermal system. Accidental or deliberate application or ingestion by a child or adolescent will cause respiratory depression that could result in death. Placing fentanyl transdermal system in the mouth, chewing it, swallowing it, or using it in ways other than indicated may cause choking or overdose that could result in death.

Advise patients about strict adherence to the recommended handling and disposal instructions in order to prevent accidental exposure to fentanyl transdermal system (see Dosage and Administration (2.4)(2.5)].

5.4 Elderly, Cachectic, and Debilitated Patients

Respiratory depression is more likely to occur in elderly, cachectic, or debilitated patients as they may have altered pharmacokinetics due to poor fat stores, muscle wasting, or altered clearance. Therefore, monitor these patients closely, particularly when initiating therapy with fentanyl transdermal system and when given in conjunction with other drugs that depress respiration [see Warnings and Precautions (5.2) and Use in Specific Populations (8.5)].

5.5 Chronic Pulmonary Disease

Monitor patients with significant chronic obstructive pulmonary disease or cor pulmonale, and patients having a substantially decreased respiratory reserve, hypoxia, hypercapnia, or pre-existing respiratory depression for respiratory depression, particularly when initiating therapy with fentanyl transdermal system, as in these patients, even usual therapeutic doses of fentanyl transdermal system may decrease respiratory drive to the point of apnea [see Warnings and Precautions (5.2)]. Consider the use of alternative non-opioid analgesics in these patients if possible.

5.6 Head Injuries and Increased Intracranial Pressure

Avoid use of fentanyl transdermal system in patients who may be particularly susceptible to the intracranial effects of CO2 retention such as those with evidence of increased intracranial pressure, impaired consciousness, or coma [see Warnings and Precautions (5.2)]. In addition, opioids may obscure the clinical course of patients with head injury. Monitor patients with brain tumors who may be susceptible to the intracranial effects of CO2 retention for signs of sedation and respiratory depression, particularly when initiating therapy with fentanyl transdermal system, as fentanyl transdermal system may reduce respiratory drive and CO2 retention can further increase intracranial pressure.

5.7 Interactions with Other CNS Depressants, Alcohol, and Drugs of Abuse

The concomitant use of fentanyl transdermal system with  other central nervous system depressants, including, but not limited to, other opioids, sedatives, hypnotics, tranquilizers (i.e., benzodiazepines), general anesthetics, phenothiazines, skeletal muscle relaxants, and alcohol, may cause respiratory depression, hypotension, and profound sedation or coma. Monitor patients prescribed concomitant CNS active drugs for signs of sedation and respiratory depression, particularly when initiating therapy with fentanyl transdermal system, and reduce the dose of one or both agents [see Warnings and Precautions (5.2)].

5.8 Interactions with CYP3A4 Inhibitors

The concomitant use of fentanyl transdermal system with a CYP3A4 inhibitors (such as ritonavir, ketoconazole, itraconazole, troleandomycin, clarithromycin, nelfinavir, nefazadone, amiodarone, amprenavir, aprepitant, diltiazem, erythromycin, fluconazole, fosamprenavir, verapamil) may result in an increase in fentanyl plasma concentrations, which could increase or prolong adverse drug effects and may cause potentially fatal respiratory depression. Carefully monitor patients receiving fentanyl transdermal system and any CYP3A4 inhibitor for signs of sedation and respiratory depression for an extended period of time, and make dosage adjustments if warranted [see Warnings and Precautions (5.2), Drug Interactions (7.1) and Clinical Pharmacology (12.3)].

5.9 Application of External Heat

Exposure to heat may increase fentanyl absorption and there have been reports of overdose and death as a result of exposure to heat.  A clinical pharmacology study conducted in healthy adult subjects has shown that the application of heat over the fentanyl transdermal system  increased fentanyl exposure [see Clinical Pharmacology (12.3)].

Warn patients to avoid exposing the fentanyl transdermal system application site and surrounding area to direct external heat sources [see Dosage and Administration (2.4)].

5.10 Patients with Fever

Based on a pharmacokinetic model, serum fentanyl concentrations could theoretically increase by approximately one-third for patients with a body temperature of 40°C (104°F) due to temperature-dependent increases in fentanyl released from the system and increased skin permeability. Monitor patients wearing fentanyl transdermal systems who develop fever closely for opioid side effects and reduce the fentanyl transdermal system dose if necessary. Warn patients to avoid strenuous exertion that leads to increased core body temperature while wearing fentanyl transdermal system to avoid the risk of potential overdose and death.

5.11 Cardiac Disease

Fentanyl transdermal system may produce bradycardia. Monitor patients with bradyarrhythmias closely for changes in heart rate, particularly when initiating therapy with fentanyl transdermal system.

5.12 Hepatic Impairment

A clinical pharmacology study with fentanyl transdermal system in patients with cirrhosis has shown that systemic fentanyl exposure increased in these patients. Because of the long half-life of fentanyl when administered as fentanyl transdermal system and hepatic metabolism of fentanyl, avoid use of fentanyl transdermal system in patients with severe hepatic impairment. Insufficient information exists to make precise dosing recommendations regarding the use of fentanyl transdermal system in patients with impaired hepatic function. Therefore, to avoid starting patients with mild to moderate hepatic impairment on too high of a dose, start with one half of the usual dosage of fentanyl transdermal system. Closely monitor for signs of sedation and respiratory depression, including at each dosage increase. [see Dosing and Administration (2.2),Use in Specific Populations (8.6) and Clinical Pharmacology (12.3)].

5.13 Renal Impairment

A clinical pharmacology study with intravenous fentanyl in patients undergoing kidney transplantation has shown that patients with high blood urea nitrogen level had low fentanyl clearance. Because of the long half-life of fentanyl when administered as fentanyl transdermal system, avoid the use of fentanyl transdermal system in patients with severe renal impairment. Insufficient information exists to make precise dosing recommendations regarding the use of fentanyl transdermal system in patients with impaired renal function. Therefore, to avoid starting patients with mild to moderate renal impairment on too high of a dose, start with one half of the usual dosage of fentanyl transdermal system. Closely monitor for signs of sedation and respiratory depression, including at each dosage increase [see Dosing and Administration (2.2), Use in Specific Populations (8.7) and Clinical Pharmacology (12.3)].

5.14 Use in Pancreatic/Biliary Tract Disease

Fentanyl transdermal system may cause spasm of the sphincter of Oddi. Monitor patients with biliary tract disease, including acute pancreatitis for worsened symptoms. Fentanyl transdermal system may cause increases in the serum amylase concentration.

5.15 Avoidance of Withdrawal

Opioid withdrawal symptoms (such as nausea, vomiting, diarrhea, anxiety, and shivering) are possible in some patients after conversion to another opioid or when decreasing or discontinuing fentanyl transdermal system. Gradual reduction of the dose of fentanyl transdermal system is recommended [see Dosage and Administration (2.3) and Drug Abuse and Dependence (9)].

5.16 Driving and Operating Machinery

Strong opioid analgesics impair the mental or physical abilities required for the performance of potentially dangerous tasks, such as driving a car or operating machinery. Warn patients not to drive or operate dangerous machinery unless they are tolerant to the effects of the fentanyl transdermal system.

6.1 Clinical Trial Experience

The safety of fentanyl transdermal system  was evaluated in 216 patients who took at least one dose of fentanyl transdermal system in a multicenter, double-blind, randomized, placebo-controlled clinical trial of fentanyl transdermal system. This trial examined patients over 40 years of age with severe pain induced by osteoarthritis of the hip or knee and who were in need of and waiting for joint replacement.

The most common adverse reactions (≥5%) in a double-blind, randomized, placebo-controlled clinical trial in patients with severe pain were nausea, vomiting, somnolence, dizziness, insomnia, constipation, hyperhidrosis, fatigue, feeling cold, and anorexia. Other common adverse reactions (≥5%) reported in clinical trials in patients with chronic malignant or nonmalignant pain were headache and diarrhea.  Adverse reactions reported for ≥1% of fentanyl transdermal system-treated patients and with an incidence greater than placebo-treated patients are shown in Table 3.

The most common adverse reactions that were associated with discontinuation in patients with pain (causing discontinuation in ≥1% of patients) were depression, dizziness, somnolence, headache, nausea, vomiting, constipation, hyperhidrosis, and fatigue.

Adverse reactions not reported in Table 1 that were reported by ≥1% of fentanyl transdermal system-treated adult and pediatric patients (N = 1,854) in 11 controlled and uncontrolled clinical trials of fentanyl transdermal system used for the treatment of chronic malignant or nonmalignant pain are shown in Table 4.

The following adverse reactions occurred in adult and pediatric patients with an overall frequency of <1% and are listed in descending frequency within each System/Organ Class:

Cardiac disorders: cyanosis

Eye disorders: miosis

Gastrointestinal disorders: subileus

General disorders and administration site conditions: application site reaction, influenza-like illness, application site hypersensitivity, drug withdrawal syndrome, application site dermatitis

Musculoskeletal and connective tissue disorders: muscle twitching

Nervous system disorders: hypoesthesia

Psychiatric disorders: disorientation, euphoric mood

Reproductive system and breast disorders: erectile dysfunction, sexual dysfunction

Respiratory, thoracic and mediastinal disorders: respiratory depression

Skin and subcutaneous tissue disorders: eczema, dermatitis allergic, dermatitis contact

6.2 Post-Marketing Experience

The following adverse reactions have been identified during post-approval use of fentanyl transdermal system. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency.

Cardiac Disorders: Tachycardia, Bradycardia

Eye Disorders: Vision blurred

Gastrointestinal Disorders: Ileus, Dyspepsia

General Disorders and Administration Site Conditions: Feeling of body temperature change

Immune System Disorders: Anaphylactic shock, Anaphylactic reaction, Anaphylactoid reaction

Investigations: Weight decreased

Nervous System Disorders: Convulsions (including Clonic convulsions and Grand mal convulsion), Amnesia

Psychiatric Disorders: Agitation

Respiratory, Thoracic, and Mediastinal Disorders: Respiratory distress, Apnea, Bradypnea, Hypoventilation, Dyspnea

Vascular Disorders: Hypotension, Hypertension

7.1 Agents Affecting Cytochrome P450 3A4 Isoenzyme System

Fentanyl is metabolized mainly via the human cytochrome P450 3A4 isoenzyme system (CYP3A4). Coadministration with agents that induce CYP3A4 activity may reduce the efficacy of fentanyl transdermal system. The concomitant use of fentanyl transdermal system with a CYP3A4 inhibitor (such as ritonavir, ketoconazole, itraconazole, troleandomycin, clarithromycin, nelfanivir, nefazadone, amiodarone, amprenavir, aprepitant, diltiazem, erythromycin, fluconazole, fosamprenavir, verapamil, or grapefruit juice) may result in an increase in fentanyl plasma concentrations, which could increase or prolong adverse drug effects and may cause fatal respiratory depression. Closely monitor patients receiving fentanyl transdermal system and any CYP3A4 inhibitor and reduce the dosage of fentanyl transdermal system if warranted [see Clinical Pharmacology (12.3)].

7.2 Central Nervous System Depressants

The concomitant use of fentanyl transdermal system with other central nervous system depressants, including but not limited to other opioids, sedatives, hypnotics, tranquilizers (i.e., benzodiazepines), general anesthetics, phenothiazines, skeletal muscle relaxants, and alcohol, may cause respiratory depression, hypotension, and profound sedation, or potentially result in coma or death. Monitor patients closely when central nervous system depressants are used concomitantly with fentanyl transdermal system and reduce the dose of one or both agents.

7.3 MAO Inhibitors

Avoid use of fentanyl transdermal system in the patient who would require the concomitant administration of a monoamine oxidase (MAO) inhibitor, or within 14 days of stopping such treatment because severe and unpredictable potentiation by MAO inhibitors has been reported with opioid analgesics.

8.1 Pregnancy

8.2 Labor and Delivery

Fentanyl readily passes across the placenta to the fetus; therefore, fentanyl transdermal system is not recommended for analgesia during labor and delivery.

8.3 Nursing Mothers

Fentanyl is excreted in human milk; therefore, fentanyl transdermal system is not recommended for use in nursing women because of the possibility of effects in their infants.

8.4 Pediatric Use

The safety of fentanyl transdermal system was evaluated in three open-label trials in 289 pediatric patients with chronic pain, 2 years of age through 18 years of age. Starting doses of 25 mcg/hr and higher were used by 181 patients who had been on prior daily opioid doses of at least 45 mg/day of oral morphine or an equianalgesic dose of another opioid. Initiation of fentanyl transdermal system therapy in pediatric patients taking less than 60 mg/day of oral morphine or an equianalgesic dose of another opioid has not been evaluated in controlled clinical trials.

The safety and effectiveness of fentanyl transdermal system in children under 2 years of age have not been established.

To guard against excessive exposure to fentanyl transdermal system by young children, advise caregivers to strictly adhere to recommended fentanyl transdermal system application and disposal instructions [see Dosage and Administration (2.4)(2.5) and Warnings and Precautions (5.3)].

8.5 Geriatric Use

Clinical studies of fentanyl transdermal system did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Data from intravenous studies with fentanyl suggest that the elderly patients may have reduced clearance and a prolonged half-life. Moreover, elderly patients may be more sensitive to the active substance than younger patients. A study conducted with the fentanyl transdermal system in elderly patients demonstrated that fentanyl pharmacokinetics did not differ significantly from young adult subjects, although peak serum concentrations tended to be lower and mean half-life values were prolonged to approximately 34 hours [see Clinical Pharmacology (12.3)].

Monitor geriatric patients closely for signs of sedation and respiratory depression, particularly when initiating therapy with fentanyl transdermal system and when given in conjunction with other drugs that depress respiration [see Warnings and Precautions (5.2)(5.4)].

8.6 Hepatic Impairment

The effect of hepatic impairment on the pharmacokinetics of fentanyl transdermal system has not been fully evaluated. A clinical pharmacology study with fentanyl transdermal system in patients with cirrhosis has shown that systemic fentanyl exposure increased in these patients. Because there is in vitro and in vivo evidence of extensive hepatic contribution to the elimination of fentanyl transdermal system, hepatic impairment would be expected to have significant effects on the pharmacokinetics of fentanyl transdermal system. Avoid use of fentanyl transdermal system in patients with severe hepatic impairment [see Dosing and Administration (2.2), Warnings and Precautions (5.12) and Clinical Pharmacology 12.3)].

8.7 Renal Impairment

The effect of renal impairment on the pharmacokinetics of fentanyl transdermal system has not been fully evaluated. A clinical pharmacology study with intravenous fentanyl in patients undergoing kidney transplantation has shown that patients with high blood urea nitrogen level had low fentanyl clearance. Because there is in vivo evidence of renal contribution to the elimination of fentanyl transdermal system, renal impairment would be expected to have significant effects on the pharmacokinetics of fentanyl transdermal system. Avoid the use of fentanyl transdermal system in patients with severe renal impairment [see Dosing and Administration (2.2), Warnings and Precautions (5.13) and Clinical Pharmacology (12.3)].

8.8 Neonatal Opioid Withdrawal Syndrome

Chronic maternal use of fentanyl can affect the neonate with subsequent withdrawal signs. Neonatal withdrawal syndrome presents as irritability, hyperactivity, and abnormal sleep pattern, high pitched cry, tremor, vomiting, diarrhea, and failure to gain weight. The onset, duration and severity of neonatal withdrawal syndrome vary based on the drug used, duration of use, the dose of last maternal use, and rate of elimination of drug by the newborn. Neonatal opioid withdrawal syndrome, unlike opioid withdrawal syndrome in adults, may be life threatening and should be treated according to protocols developed by neonatology experts.

9.1 Controlled Substance

Fentanyl transdermal system contains fentanyl, a potent Schedule II opioid agonist. Schedule II opioid substances, which include hydromorphone, methadone, morphine, oxycodone, and oxymorphone, have the highest potential for abuse and risk of fatal overdose due to respiratory depression. Fentanyl transdermal system can be abused and is subject to criminal diversion [see Warnings and Precautions (5.1)].

9.2 Abuse

Addiction is a primary, chronic, neurobiologic disease, with genetic, psychosocial, and environmental factors influencing its development and manifestations. It is characterized by behaviors that include one or more of the following: impaired control over drug use, compulsive use, continued use despite harm, and craving. Drug addiction is a treatable disease, utilizing a multidisciplinary approach, but relapse is common.

“Drug seeking” behavior is very common in addicts and drug abusers. Drug-seeking tactics include emergency calls or visits near the end of office hours, refusal to undergo appropriate examination, testing or referral, repeated “loss” of prescriptions, tampering with prescriptions and reluctance to provide prior medical records or contact information for other treating physician(s). “Doctor shopping” to obtain additional prescriptions is common among drug abusers and people suffering from untreated addiction.

Abuse and addiction are separate and distinct from physical dependence and tolerance. Physicians should be aware that addiction may be accompanied by concurrent tolerance and symptoms of physical dependence. In addition, abuse of opioids can occur in the absence of true addiction and is characterized by misuse for non-medical purposes, often in combination with other psychoactive substances. Since fentanyl transdermal system may be diverted for non-medical use, careful recordkeeping of prescribing information, including quantity, frequency, and renewal requests is strongly advised.

Proper assessment of the patient, proper prescribing practices, periodic reevaluation of therapy, and proper dispensing and storage are appropriate measures that help to limit abuse of opioid drugs.

9.3 Dependence

Tolerance is a state of adaptation in which exposure to a drug induces changes that result in a diminution of one or more of the drug’s effects over time. Tolerance may occur to both the desired and undesired effects of drugs, and may develop at different rates for different effects.

Physical dependence is a state of adaptation that is manifested by an opioid specific withdrawal syndrome that can be produced by abrupt cessation, rapid dose reduction, decreasing blood concentration of the drug, and/or administration of an antagonist. The opioid abstinence or withdrawal syndrome is characterized by some or all of the following: restlessness, lacrimation, rhinorrhea, yawning, perspiration, chills, piloerection, myalgia, mydriasis, irritability, anxiety, backache, joint pain, weakness, abdominal cramps, insomnia, nausea, anorexia, vomiting, diarrhea, or increased blood pressure, respiratory rate, or heart rate. In general, opioids should not be abruptly discontinued [see Dosage and Administration (2.3)].

10.1 Clinical Presentation

Acute overdosage with opioids can be manifested by respiratory depression, somnolence progressing to stupor or coma, skeletal muscle flaccidity, cold and clammy skin, constricted pupils, and sometimes bradycardia, hypotension and death. The pharmacokinetic characteristics of fentanyl transdermal system must also be taken into account when treating the overdose. Even in the face of improvement, continued medical monitoring is required because of the possibility of extended effects. Deaths due to overdose have been reported with abuse and misuse of fentanyl transdermal system.

10.2 Treatment

Give primary attention to the reestablishment of a patent airway and institution of assisted or controlled ventilation. Employ supportive measures (including oxygen and vasopressors) in the management of circulatory shock and pulmonary edema accompanying overdose as indicated. Cardiac arrest or arrhythmias will require advanced life support techniques. Remove all fentanyl transdermal systems.

The pure opioid antagonists, such as naloxone, are specific antidotes to respiratory depression from opioid overdose. Since the duration of reversal is expected to be less than the duration of action of fentanyl, carefully monitor the patient until spontaneous respiration is reliably reestablished. After fentanyl transdermal system removal, serum fentanyl concentrations decline gradually, falling about 50% in approximately 20 to 27 hours. Therefore, management of an overdose must be monitored accordingly, at least 72 to 96 hours beyond the overdose.

Only administer opioid antagonists in the presence of clinically significant respiratory or circulatory depression secondary to hydromorphone overdose. In patients who are physically dependent on any opioid agonist including fentanyl transdermal system, an abrupt or complete reversal of opioid effects may precipitate an acute abstinence syndrome. The severity of the withdrawal syndrome produced will depend on the degree of physical dependence and the dose of the antagonist administered. Please see the prescribing information for the specific opioid antagonist for details of their proper use.

12.1 Mechanism of Action

Fentanyl is an opioid analgesic. Fentanyl interacts predominately with the opioid mu-receptor. These mu-binding sites are distributed in the human brain, spinal cord, and other tissues.

12.2 Pharmacodynamics

12.3 Pharmacokinetics

Absorption

Fentanyl transdermal system is a drug-in-adhesive matrix designed formulation. Fentanyl is released from the matrix at a nearly constant amount per unit time. The concentration gradient existing between the matrix and the lower concentration in the skin drives drug release. Fentanyl moves in the direction of the lower concentration at a rate determined by the matrix and the diffusion of fentanyl through the skin layers. While the actual rate of fentanyl delivery to the skin varies over the 72-hour application period, each system is labeled with a nominal flux which represents the average amount of drug delivered to the systemic circulation per hour across average skin.

While there is variation in dose delivered among patients, the nominal flux of the systems (12.5 mcg, 25 mcg, 50 mcg, 75 mcg, and 100 mcg of fentanyl per hour) is sufficiently accurate as to allow individual titration of dosage for a given patient.

Following fentanyl transdermal system application, the skin under the system absorbs fentanyl, and a depot of fentanyl concentrates in the upper skin layers. Fentanyl then becomes available to the systemic circulation. Serum fentanyl concentrations increase gradually following initial fentanyl transdermal system application, generally leveling off between 12 and 24 hours and remaining relatively constant, with some fluctuation, for the remainder of the 72-hour application period. Peak serum concentrations of fentanyl generally occurred between 20 and 72 hours after initial application (see Table 6). Serum fentanyl concentrations achieved are proportional to the fentanyl transdermal system delivery rate. With continuous use, serum fentanyl concentrations continue to rise for the first two system applications. By the end of the second 72-hour application, a steady-state serum concentration is reached and is maintained during subsequent applications of a patch of the same size (see Figure 1). Patients reach and maintain a steady-state serum concentration that is determined by individual variation in skin permeability and body clearance of fentanyl.

The kinetics of fentanyl in normal subjects following application of a 25 mcg/hr fentanyl transdermal system were bioequivalent with or without either BIOCLUSIVE® or Askina®Derm overylay (polyurethane film dressing).

After system removal, serum fentanyl concentrations decline gradually, falling about 50% in approximately 20 to 27 hours. Continued absorption of fentanyl from the skin accounts for a slower disappearance of the drug from the serum than is seen after an IV infusion, where the apparent half-life is approximately 7 (range 3 to 12) hours.

A clinical pharmacology study conducted in healthy adult subjects has shown that the application of heat over the fentanyl transdermal system increased mean overall fentanyl exposure by 120% and average maximum fentanyl level by 61%.

TABLE 6: FENTANYL PHARMACOKINETIC PARAMETERS FOLLOWING FIRST 72 HOUR APPLICATION OF FENTANYL TRANSDERMAL SYSTEM

* Cmax values dose normalized from 4 x 12.5 mcg/hr: Study 2003-038 in healthy volunteers † Cmax values: Study C-2002-048 dose proportionality study in healthy volunteers
	Mean (SD) Time to Maximal  Concentration Tmax (hr)	Mean (SD) Maximal Concentration Cmax (ng/mL)
Fentanyl Transdermal System 12 mcg/hr	28.8 (13.7)	0.38 (0.13) *
Fentanyl Transdermal System 25 mcg/hr	31.7 (16.5)	0.85 (0.26)†
Fentanyl Transdermal System 50 mcg/hr	32.8 (15.6)	1.72 (0.53)†
Fentanyl Transdermal System 75 mcg/hr	35.8 (14.1)	2.32 (0.86)†
Fentanyl Transdermal System 100 mcg/hr	29.9 (13.3)	3.36 (1.28)†

NOTE: After system removal there is continued systemic absorption from residual fentanyl in the skin so that serum concentrations fall 50%, on average, in approximately 20 to 27 hours.

             Figure 1 Serum Fentanyl Concentrations
           Following Single and Multiple Applications of Fentanyl Transdermal System 100 mcg/hr

TABLE 7: RANGE OF PHARMACOKINETIC PARAMETERS OF INTRAVENOUS FENTANYL IN PATIENTS

TABLE 7: RANGE OF PHARMACOKINETIC PARAMETERS OF INTRAVENOUS FENTANYL IN PATIENTS

TABLE 7: RANGE OF PHARMACOKINETIC PARAMETERS OF INTRAVENOUS FENTANYL IN PATIENTS

* Estimated
	Clearance (L/hr) Range [70 kg]	Volume of Distribution VSS (L/kg) Range	Half-Life t1/2 (hr) Range
Surgical Patients	27 to 75	3 to 8	3 to 12
Hepatically Impaired Patients	3 to 80*	0.8 to 8*	4 to 12*
Renally Impaired Patients	30 to 78	-	-

NOTE: Information on volume of distribution and half-life not available for renally impaired patients.

13.1 Carcinogenesis, Mutagenesis, and Impairment of Fertility