Pharmacy Author: Emmanuel Saltiel, PharmD, FASHP, FCCP
Pharmacy and Medical Editor: Jay W. Marks, MD

GENERIC NAME: fentanyl transdermal system

BRAND NAME: Duragesic

DRUG CLASS AND MECHANISM: Fentanyl is a potent synthetic (man-made) narcotic. A 100 µg dose of fentanyl is approximately equal to 10 mg of morphine. Fentanyl stimulates receptors on nerves in the brain to increase the threshold to pain (the amount of discomfort that a person must feel in order to be considered painful) and reduce the perception of pain (the perceived importance of the pain). Fentanyl is available in transdermal (for application to the skin), transmucosal (for application to mucus membranes) and parenteral (injectable) forms. When applied to the skin of the upper torso, fentanyl is well absorbed. The amount of fentanyl in the blood increases gradually after topical application, reaching a peak after 12-24 hours. Once this concentration is achieved, blood concentrations remain constant over the 72 hours that the patch is worn. After removal of the patch, blood concentrations of fentanyl decrease slowly due to ongoing absorption of fentanyl remaining on the skin. Fentanyl was originally approved by the FDA for injection in 1968.

GENERIC AVAILABLE: Yes

PRESCRIPTION: Yes

PREPARATIONS: Transdermal systems labeled as delivering 50, 75, or 100 µg/hour.

STORAGE: Patches should be stored at room temperature below 30°C (86°F). Used patches should be folded in half with the sticky sides together, and then flushed down the toilet. Patients must avoid exposing the patches to excessive heat as this promotes the release of fentanyl from the patch and increases the absorption of fentanyl through the skin which can result in fatal overdose.

PRESCRIBED FOR: Fentanyl transdermal system is used for patients with severe chronic pain, for example, the pain of cancer.

DOSING: Patches should be applied to a flat, non-irritated area on the upper torso. The area of application should be clean and washed with water only prior to application. The patch should be applied immediately after removing it from the package and pressed firmly against the skin for 10 to 20 seconds especially around the edges. Patches should never be cut or otherwise damaged. Doses vary widely among patients. The manufacturer considers a fentanyl transdermal dose of 100 µg/hour approximately equivalent to 360 mg/day of oral morphine.

DRUG INTERACTIONS: The use of fentanyl with other central nervous system (CNS) depressants can intensify the effects of fentanyl to depress breathing, depress the brain, sedate, and lower blood pressure. Other drugs that should be used cautiously with fentanyl include: antipsychotics [for example, Thorazine; Stelazine, haloperidol (Haldol)], anxiolytics [for example, diazepam (Valium), lorazepam (Ativan), zolpidem (Ambien)], certain antihistamines [for example, diphenhydramine (Benadryl),  hydroxyzine (Vistaril), clemastine (Tavist)], barbiturates [for example, phenobarbital (Donnatal)], tricyclic antidepressants [for example, amitriptyline (Elavil), doxepin (Sinequan)], ethanol, and skeletal muscle relaxants [for example, carisoprodol (Soma), cyclobenzaprine (Flexeril), baclofen (Lioresal)]. The use fentanyl with amiodarone (Cordarone) may result in slow heart rates. Cimetidine (Tagamet) when used with fentanyl can cause confusion, disorientation, or seizures due to impairment in breathing and brain function.

PREGNANCY: Fentanyl can cross the placenta and enter the fetus. Effects on the developing fetus are not known; however, fentanyl can slow breathing in newborn infants whose mothers were exposed to fentanyl. Routine use of fentanyl by pregnant women can lead to withdrawal reactions in the newborn. Thus, caution should be used if fentanyl is administered near the time of delivery.

NURSING MOTHERS: The effects of fentanyl on the infants of mothers who nurse is unknown. Since most drugs are concentrated in breast milk, it is advisable that women requiring fentanyl bottle-feed their infants.

SIDE EFFECTS: Mild physical dependence occurs commonly during therapy with opiate agonists such as fentanyl. Abruptly stopping the drug in patients can precipitate a withdrawal reaction. Symptoms of withdrawal include nausea, diarrhea, coughing, tearing, nasal discharge, profuse sweating, twitching muscles, and yawning.

Fentanyl can cause respiratory depression (decreased rate or depth of breathing). Nausea or vomiting, constipation, and itching can occur during treatment with fentanyl. Transdermal fentanyl can cause a variety of skin reactions. Commonly, redness occurs at the site of application and can last for 6 hours following removal of the patch.

Other side effects include a decrease in sexual drive, hypothyroidism (low thyroid hormone concentrations), dry mouth, abdominal pain, loss of appetite, drowsiness, confusion, headache, dizziness, nervousness, hallucinations, anxiety, depression and euphoria. The FDA is investigating reports of deaths and other serious side effects from the use of the fentanyl transdermal system as well as overdoses.

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