What is fentanyl?
Fentanyl (brand name: Duragesic®) is an opioid medication used to treat moderate to severe pain. In the United States, fentanyl is considered a Schedule II controlled substance, which means there are strict rules about how it is prescribed, dispensed, and used. It is illegal to use fentanyl patches on any animal or human for which they have not been prescribed.
The use of fentanyl in cats and dogs to treat pain is “off label” or “extra label”. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully, as their directions may be significantly different from those on the label.
How is fentanyl given?
Fentanyl is given in the form of a transdermal patch. This is a medicated patch that sticks to the skin, slowly releasing medication through the skin into the blood. It may also be given as an injection in the hospital setting.
It is important to apply a fentanyl transdermal patch properly to ensure efficacy and safety, so it is usually applied by trained veterinary professionals. After application, patches must be kept away from other pets or people (children). Accidental exposure, either through touch or ingestion, may lead to a dangerous overdose of fentanyl. For that reason, fentanyl patches must be used with caution in households with other animals, children, or vulnerable adults.
"Accidental exposure, either through touch or ingestion, may lead to a dangerous overdose of fentanyl."
Your veterinarian may recommend that they remove the patch themselves or they will instruct you on the correct method of removal and disposal. Proper disposal is important to prevent exposure to other pets or people. Fold the patch in half with the sticky sides together and flush it down the toilet. Always wear gloves when handling patches.
After application, this medication takes effect in about 6 hours in cats and 12 hours in dogs and continues to provide pain relief for approximately 3 days. Other pain medications will be recommended or administered to provide pain relief during the time it takes for the fentanyl patch to take effect.
What if I miss giving my pet the medication?
Consult your veterinarian for instructions on whether additional fentanyl patches are needed. If your veterinarian has recommended you change a patch, remove it, apply a new patch when you remember, and then wait for the recommended amount of time between patch changes. Due to the time needed for the drug to take effect, your veterinarian may recommend additional pain control in the interim. Never apply two doses at once, cut patches, or give extra doses more frequently than recommended by your veterinarian.
Are there any potential side effects?
Mild side effects include lethargy, wobbly gait, skin rash at the site of application, constipation, difficulty urinating, mild agitation, dilated pupils in cats, and mildly decreased breathing rate and heart rate. Dogs use panting as a cooling mechanism, so they are at increased risk of overheating when using this medication. Notify your veterinarian if you see any possible side effects.
"Notify your veterinarian if you see any possible side effects."
More serious side effects that warrant immediate veterinary consultation include respiratory depression (reduced breathing), inability to wake up, and extreme agitation. Side effects are more likely and more pronounced if the patient has a high temperature, if the patch is applied to an area that the pet lies on, if the patch is exposed to heat like an electric blanket, or if the patch is inadvertently swallowed.
This short-acting medication should stop working within 24-48 hours of the patch being removed, although effects can be longer in pets with liver or kidney disease.
Are there any risk factors for this medication?
Fentanyl transdermal patches should not be used in pets that are allergic to fentanyl or other opioids, have severe liver or kidney disease, or have known or suspected gastrointestinal obstruction. Fentanyl should be used cautiously in very small breed dogs, pregnant animals, cats that are geriatric or frail, and pets with the following health conditions: mild or moderate liver or kidney disease, a history of seizures, head injury, low blood pressure, fever, or respiratory disease. Fentanyl should also be used cautiously in households where the risk of accidental exposure to other pets or humans cannot be avoided.
Are there any drug interactions I should be aware of?
Several medications should be used with caution when given with fentanyl patches, including: any medications that may have sedative effects, acepromazine, atropine, antidepressants (clomipramine, fluoxetine), telmisartan, antifungals, barbiturates (phenobarbital), benzodiazepines (diazepam, midazolam, alprazolam), beta blockers (atenolol, propranolol), calcium channel blockers (amlodipine, diltiazem), cannabidiol (CBD), cimetidine (Tagamet®), certain antibiotics (clarithromycin, erythromycin), MAO inhibitors (selegiline), metoclopramide, ondansetron and tramadol.
Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.
Does any monitoring need to be done with this medication?
Fentanyl patches should be checked regularly to ensure they are secure. Your pet should be assessed for signs of pain regularly to ensure the product is working. Monitor your pet at home for serious side effects.
How do I store fentanyl patches?
Fentanyl and other opioids have human abuse potential; any patches not already on your pet need to be kept in a safe place and ideally in a locked cabinet.
Fentanyl transdermal patches should be stored at room temperature, less than 25°C (77°F), in their original packaging. The patch must be applied immediately after it is removed from its sealed package.
Fentanyl is a controlled substance, which means that it has been designated by the Drug Enforcement Administration (DEA) as having a potential for diversion to people other than the patient it was prescribed for. Use of a controlled substance in any person or animal other than that for which it is prescribed is illegal. Therefore, this medication should be stored in a locked cabinet or safe that cannot be easily moved, with access limited to only those that need to administer the medication. Monitor the amount of medication remaining to ensure the expected amount is present.
What should I do in case of emergency?
If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. If you suspect any exposure to a human, seek emergency medical assistance.
