Fentanyl (Transdermal)

Generic name: Fentanyl
Drug class: Opioids (narcotic analgesics)

Usage of Fentanyl (Transdermal)

Fentanyl skin patch is used to treat severe pain, including acute pain following surgery. Ionsys® is applied by your healthcare provider in a hospital setting after surgery for the short-term management of acute pain. Duragesic® is used for pain severe enough to require around-the-clock pain relief for a long period of time. Fentanyl is a strong narcotic analgesic (pain medicine). It acts on the central nervous system (CNS) to relieve pain.

The Duragesic® skin patch should not be used if you need pain medicine for just a short time, such as after dental surgery or tonsil surgery. Do not use the patch for mild pain or pain that occurs only once in a while.

When a narcotic medicine is used for a long time, it may become habit-forming, causing mental or physical dependence. However, people who have continuing pain should not let the fear of dependence keep them from using narcotics to relieve their pain. Mental dependence (addiction) is not likely to occur when narcotics are used for this purpose. Physical dependence may lead to withdrawal side effects if treatment is stopped suddenly. However, severe withdrawal side effects can usually be prevented by gradually reducing the dose over a period of time before treatment is stopped completely.

This medicine is available only under a restricted distribution program called the Opioid Analgesic REMS (Risk Evaluation and Mitigation Strategy) program.

Fentanyl (Transdermal) side effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

Less common

Anxiety

bloating or swelling of the face, arms, hands, lower legs, or feet

burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings

confusion

decrease in urine volume

difficulty in breathing or swallowing

difficulty in passing urine (dribbling)

fast, irregular, pounding, or racing heartbeat or pulse

painful urination

rapid weight gain

seeing, hearing, or feeling things that are not there

skin itching, rash, or redness

swelling of the face, throat, or tongue

tremor

unusual weight gain or loss

upper stomach pain

Rare

Bluish color of the fingernails, lips, skin, palms, or nail beds

burning, itching, redness, skin rash, swelling, or soreness at the application site

confusion about identity, place, and time

false or unusual sense of well-being

irregular, fast or slow, or shallow breathing

Incidence not known

Agitation

blurred vision

chest pain or discomfort

cough

darkening of the skin

diarrhea

dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position

fever

headache

hives

lightheadedness, dizziness, or fainting

loss of appetite

mental depression

nausea

nervousness

overactive reflexes

poor coordination

pounding in the ears

restlessness

severe constipation

severe vomiting

shivering

sweating

talking or acting with excitement you cannot control

tightness in the chest

unusual tiredness or weakness

vomiting

Get emergency help immediately if any of the following symptoms of overdose occur:

Symptoms of overdose

Cold, clammy skin

drowsiness that is so severe you are not able to answer when spoken to or, if asleep, cannot be awakened

pinpoint (small) pupils in the eyes

seizures

slow heartbeat

very slow or troubled breathing

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Constipation

feeling cold

sleepiness or unusual drowsiness

trouble sleeping

Less common

Dry mouth

feeling of constant movement of self or surroundings

feeling of crawling, tingling, or burning of the skin

lack or loss of strength

memory loss

sensation of spinning

unusual dreams

Rare

Abnormal ejaculation

decreased interest in sexual intercourse

decreased sexual performance or desire

inability to have or keep an erection

loss in sexual ability, desire, drive, or performance

muscle twitching

Incidence not known

Belching

heartburn

indigestion

stomach discomfort or upset

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Before taking Fentanyl (Transdermal)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

Appropriate studies performed to date have not demonstrated pediatric-specific problems that would limit the usefulness of the Duragesic® patch in children 2 years of age and older. However, pediatric patients must be opioid-tolerant before using a fentanyl patch. Safety and efficacy have not been established in children younger than 2 years of age.

Appropriate studies have not been performed on the relationship of age to the effects of the Ionsys® patch in the pediatric population. Safety and efficacy have not been established.

Geriatric

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of fentanyl skin patch in the elderly. However, elderly patients are more likely to have drowsiness and age-related lung, kidney, liver, or heart problems, which may require caution and an adjustment in the dose for patients receiving fentanyl skin patch.

Breast Feeding

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Interactions with Medicines

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

Levoketoconazole

Mifepristone

Nalmefene

Naltrexone

Safinamide

Samidorphan

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

Abametapir

Acepromazine

Adagrasib

Alefacept

Alfentanil

Almotriptan

Alprazolam

Amifampridine

Amineptine

Amiodarone

Amitriptyline

Amitriptylinoxide

Amobarbital

Amoxapine

Amphetamine

Amprenavir

Anileridine

Aprepitant

Aripiprazole

Armodafinil

Asciminib

Asenapine

Atazanavir

Avacopan

Baclofen

Belzutifan

Benperidol

Benzhydrocodone

Benzphetamine

Berotralstat

Boceprevir

Bosentan

Bromazepam

Bromopride

Brompheniramine

Buprenorphine

Bupropion

Buspirone

BUTAbarbital

Butorphanol

Calcium Oxybate

Cannabidiol

Cannabis

Carbamazepine

Carbinoxamine

Cariprazine

Carisoprodol

Carphenazine

Ceritinib

Cetirizine

Chloral Hydrate

Chlordiazepoxide

Chlorpheniramine

Chlorpromazine

Chlorzoxazone

Ciprofloxacin

Citalopram

Clarithromycin

Clobazam

Clomipramine

Clonazepam

Clopidogrel

Clorazepate

Clozapine

Cobicistat

Cocaine

Codeine

Conivaptan

Crizotinib

Cyclobenzaprine

Cyclosporine

Dabrafenib

Daridorexant

Darunavir

Delavirdine

Desipramine

Desmopressin

Desvenlafaxine

Dexamethasone

Dexmedetomidine

Dextroamphetamine

Dextromethorphan

Dezocine

Diazepam

Dibenzepin

Dichloralphenazone

Difenoxin

Dihydrocodeine

Diltiazem

Diphenhydramine

Diphenoxylate

Dolasetron

Donepezil

Doxepin

Dronedarone

Droperidol

Duloxetine

Efavirenz

Eletriptan

Eluxadoline

Enflurane

Enzalutamide

Erdafitinib

Erythromycin

Escitalopram

Esketamine

Eslicarbazepine Acetate

Estazolam

Eszopiclone

Ethchlorvynol

Ethopropazine

Ethylmorphine

Etravirine

Fedratinib

Fenfluramine

Fexinidazole

Flibanserin

Fluconazole

Fluoxetine

Fluphenazine

Flurazepam

Fluspirilene

Fluvoxamine

Fosamprenavir

Fosaprepitant

Fosnetupitant

Fosphenytoin

Fospropofol

Frovatriptan

Furazolidone

Gabapentin

Gabapentin Enacarbil

Gepirone

Granisetron

Halazepam

Haloperidol

Halothane

Hexobarbital

Hydrocodone

Hydromorphone

Hydroxyamphetamine

Hydroxytryptophan

Hydroxyzine

Idelalisib

Imatinib

Imipramine

Indinavir

Iproniazid

Isocarboxazid

Isoflurane

Itraconazole

Ivacaftor

Ketamine

Ketobemidone

Ketoconazole

Lacosamide

Lanreotide

Lasmiditan

Lefamulin

Lemborexant

Lenacapavir

Levocetirizine

Levomilnacipran

Levorphanol

Linezolid

Lisdexamfetamine

Lithium

Lofepramine

Lofexidine

Lomitapide

Lopinavir

Lorazepam

Lorcaserin

Lorlatinib

Loxapine

Lumacaftor

Magnesium Oxybate

Mavacamten

Meclizine

Melitracen

Melperone

Meperidine

Mephobarbital

Meprobamate

Meptazinol

Mesoridazine

Metaxalone

Methadone

Methamphetamine

Methdilazine

Methocarbamol

Methohexital

Methotrimeprazine

Methylene Blue

Metoclopramide

Mibefradil

Midazolam

Milnacipran

Mirtazapine

Mitotane

Mobocertinib

Moclobemide

Modafinil

Molindone

Moricizine

Morphine

Morphine Sulfate Liposome

Nafcillin

Nalbuphine

Naratriptan

Nefazodone

Nelfinavir

Netupitant

Nevirapine

Nialamide

Nicardipine

Nicomorphine

Nifedipine

Nilotinib

Nirmatrelvir

Nitrazepam

Nitrous Oxide

Nortriptyline

Octreotide

Olanzapine

Omaveloxolone

Ondansetron

Opipramol

Opium

Opium Alkaloids

Orphenadrine

Oxazepam

Oxcarbazepine

Oxycodone

Oxymorphone

Ozanimod

Palbociclib

Palonosetron

Papaveretum

Paregoric

Paroxetine

Pazopanib

Pentazocine

Pentobarbital

Perampanel

Perazine

Periciazine

Perphenazine

Phenelzine

Phenobarbital

Phenytoin

Pimozide

Piperacetazine

Pipotiazine

Piritramide

Pirtobrutinib

Posaconazole

Potassium Oxybate

Prazepam

Prednisone

Pregabalin

Primidone

Procarbazine

Prochlorperazine

Promazine

Promethazine

Propofol

Protriptyline

Quazepam

Quetiapine

Ramelteon

Ranitidine

Ranolazine

Rasagiline

Remifentanil

Remimazolam

Remoxipride

Ribociclib

Rifabutin

Rifampin

Rifapentine

Ritlecitinib

Ritonavir

Rizatriptan

Ropeginterferon Alfa-2b-njft

Saquinavir

Scopolamine

Secobarbital

Selegiline

Selpercatinib

Sertindole

Sertraline

Sibutramine

Sodium Oxybate

Sotorasib

St John's Wort

Sufentanil

Sulpiride

Sumatriptan

Suvorexant

Tacrolimus

Tapentadol

TaurUrsodiol

Telaprevir

Telithromycin

Temazepam

Thiethylperazine

Thiopental

Thiopropazate

Thioridazine

Tianeptine

Tilidine

Tizanidine

Tocilizumab

Tolonium Chloride

Topiramate

Tramadol

Tranylcypromine

Trazodone

Triazolam

Trifluoperazine

Trifluperidol

Triflupromazine

Trimeprazine

Trimipramine

Trofinetide

Tryptophan

Tucatinib

Venlafaxine

Verapamil

Vilazodone

Voriconazole

Vortioxetine

Voxelotor

Zaleplon

Ziprasidone

Zolmitriptan

Zolpidem

Zopiclone

Zotepine

Zuranolone

Interactions with Food/Tobacco/Alcohol

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following is usually not recommended, but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco.

Ethanol

Grapefruit Juice

Relate drugs

How to use Fentanyl (Transdermal)

Use this medicine only as directed by your doctor. Do not use more of it, do not use it more often, and do not use it for a longer time than your doctor ordered. This is especially important for elderly patients, who may be more sensitive to the effects of pain medicines. If too much of this medicine is used for a long time, it may become habit-forming (causing mental or physical dependence) or cause an overdose.

The fentanyl skin patch is only used for opioid-tolerant patients. A patient is opioid-tolerant if oral narcotics have already been used for severe pain. Check with your doctor if you have questions about this.

It is very important that you understand the rules of the Opioid Analgesic REMS program to prevent addiction, abuse, and misuse of fentanyl. This medicine should also come with a Medication Guide and patient instructions. Read and follow these instructions carefully. Read it again each time you refill your prescription in case there is new information. Ask your doctor if you have any questions.

You will receive the Ionsys® patch while you are in a hospital. A nurse or other trained health professional will give you this medicine after surgery. You will be taught how to use this medicine in the hospital, but the patch will be removed by your healthcare provider before you leave the hospital. Do not leave the hospital with the patch on your skin.

To use the Duragesic® patch:

Use this medicine exactly as directed by your doctor. It will work only if it has been applied correctly.

This medicine should only be used on skin that is not irritated or injured. Do not put the patch in your mouth, chew it, or swallow it.

Fentanyl skin patches are packaged in sealed pouches. Do not remove the patch from the sealed pouch until you are ready to apply it.

When handling the skin patch, be careful not to touch the adhesive (sticky) surface with your hand. The adhesive part of the system contains some fentanyl, which can be absorbed into your body too fast through the skin of your hand. If any of the medicine does get on your hand, rinse the area right away with a lot of clear water. Do not use soap or other cleansers.

Be careful not to tear the patch or make any holes in it. Damage to a patch may allow fentanyl to pass into your skin too quickly. This can cause an overdose.

Apply the patch to a dry, flat skin area on your upper arm, chest, or back. Choose a place where the skin is not very oily and is free of scars, cuts, burns, or irritation. Do not apply this medicine to areas that have received radiation treatment.

The patch will stay in place better if it is applied to an area with little or no hair. If you need to apply the patch to a hairy area, you may first clip the hair with scissors, but do not shave it off.

If you need to clean the area before applying the medicine, use only plain water. Do not use soaps, other cleansers, lotions, or anything that contains oils or alcohol. Be sure that the skin is completely dry before applying the medicine.

Remove the liner covering the sticky side of the skin patch. Then press the patch firmly in place, using the palm of your hand, for a minimum of 30 seconds. Make sure that the entire adhesive surface is attached to your skin, especially around the edges.

If the patch becomes loose, tape the edges with first aid tape.

If the patch falls off after applying it, throw it away and apply a new patch in a different area.

If you need to apply more than 1 patch at a time, place the patches far enough apart so that the edges do not touch or overlap each other.

Wash your hands with a lot of clear water after applying the medicine. Do not use soap or other cleansers.

Remove the patch after 3 days (72 hours), or as directed by your doctor. Choose a different place on your skin to apply the next patch. If possible, use a place on the other side of your body. Wait at least 3 days before using the first area again.

In young children or persons with decreased mental alertness, the Duragesic® patch should be put on the upper back to decrease the chance that the patch will be removed and placed in the mouth.

After a Duragesic® patch is applied, fentanyl passes into the skin a little at a time. A certain amount of the medicine must build up in the skin before it is absorbed into the body. Up to a full day (24 hours) may pass before the first dose begins to work. Your doctor may need to adjust the dose during the first few weeks before finding the amount that works best for you. Even if you feel that the medicine is not working, do not increase the amount of fentanyl skin patch that you apply. Instead, check first with your doctor.

You will probably need to take a faster-acting narcotic by mouth to relieve pain during the first few days of using fentanyl skin patch. You may also need another narcotic while your dose of fentanyl is being adjusted, and to relieve any "breakthrough" pain that occurs later on. Be sure you do not take more of the other narcotic, and do not take it more often than directed. Taking 2 narcotics together can increase the chance of serious side effects.

Grapefruit and grapefruit juice may increase the effects of fentanyl skin patch by increasing the amount of the medicine in your body. You should not consume grapefruit products while you are using this medicine.

Dosing

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For transdermal dosage form (Duragesic® skin patch):

For relief of chronic pain:

Adults and children 2 years of age and older—Your doctor will decide which dose of the patch you need based on your present daily narcotic dose. The patch is applied to the skin and left in place for 3 days (72 hours). Your doctor may adjust your dose as needed.

Children younger than 2 years of age—Use and dose must be determined by your doctor.

For transdermal dosage form (Ionsys® skin patch):

For short-term relief of acute pain after surgery:

Adults—Your doctor will decide which dose of the patch you need based on your present daily narcotic dose. The patch is applied by your healthcare provider to your upper outer arm or chest. Your doctor will show you how to adjust your dose as needed while in the hospital.

Missed Dose

If you forget to wear or change a patch, put one on as soon as you can. If it is almost time to put on your next patch, wait until then to apply a new patch and skip the one you missed. Do not apply extra patches to make up for a missed dose.

Remove the Duragesic® patch 3 days (72 hours) after applying it.

Your healthcare provider will remove the Ionsys® patch before you leave the hospital. The Ionsys® patch is not for use at home.

Storage

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.

Fentanyl can cause serious unwanted effects or a fatal overdose if taken by children, pets, or adults who are not used to strong narcotic pain medicines. Make sure you store the medicine in a safe and secure place to prevent others from getting it.

To dispose of the Duragesic® patch, fold the patch in half with the sticky side inside. If the patch has not been used, take it out of the pouch and remove the liner that covers the sticky side of the patch before folding it in half. Ask your pharmacist about the best way to dispose of patches you do not use. Do not flush the pouch or the protective liner down the toilet. Put them in a trash can.

Your healthcare provider will dispose of the Ionsys® patch after removing it.

Drop off any unused narcotic medicine at a drug take-back location right away. If you do not have a drug take-back location near you, flush any unused narcotic medicine down the toilet. Check your local drug store and clinics for take-back locations. You can also check the DEA web site for locations. Here is the link to the FDA safe disposal of medicines website: www.fda.gov/drugs/resourcesforyou/consumers/buyingusingmedicinesafely/ensuringsafeuseofmedicine/safedisposalofmedicines/ucm186187.htm

Warnings

It is very important that your doctor check your or your child's progress while using this medicine. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it. Blood and urine tests may needed to check for unwanted effects.

Do not touch the sticky side of the patch or the gel. Fentanyl can be quickly absorbed through the eyes and mouth and can be extremely dangerous. If you do touch the sticky side of the patch or gel, let your nurse or doctor know right away and rinse the area with large amounts of water. Do not use soaps or other cleansers.

Check with your doctor at regular times while using fentanyl. Be sure to report any side effects.

After you have been using this medicine for awhile, "breakthrough" pain may occur more often than usual, and it may not be relieved by your regular dose of medicine. If this occurs, do not increase the amount of fentanyl skin patch or other narcotic that you are using without first checking with your doctor.

This medicine will add to the effects of alcohol and other CNS depressants. CNS depressants are medicines that slow down the nervous system, which may cause drowsiness or make you less alert. Some examples of CNS depressants are antiHistamines or medicine for hay fever, other allergies, or colds, sedatives, tranquilizers, or sleeping medicine, other prescription pain medicine or narcotics, benzodiazepines, medicine for seizures or barbiturates, muscle relaxants, or anesthetics, including some dental anesthetics. This effect may last for a few days after you stop using this medicine. Check with your doctor before taking any of the medicines listed while you are using this medicine.

The Ionsys® patch must be removed before a procedure called a magnetic resonance imaging (MRI) scan. It may cause skin burns if left in place during the procedure.

The Ionsys® patch may cause serious skin reactions. Call you doctor right away if you have blistering, lesions, a rash, redness, or swelling of the skin, especially at the site of application.

Fentanyl may cause some people to become drowsy, dizzy, or lightheaded, or to feel a false sense of well-being. Do not drive or do anything else that could be dangerous until you know how this medicine affects you. These effects usually go away after a few days of treatment, when your body gets used to the medicine. However, check with your doctor if drowsiness that is severe enough to interfere with your activities continues for more than a few days.

Dizziness, lightheadedness, or even fainting may occur when you get up suddenly from a lying or sitting position. Getting up slowly may help lessen this problem. Also, lying down for a while may relieve dizziness or lightheadedness.

Nausea or vomiting may occur, especially during the first several days of treatment. Lying down for a while may relieve these effects. However, if they are especially bothersome or if they continue for more than a few days, check with your doctor. You may be able to take another medicine to help prevent these problems.

Using narcotics for a long time may cause severe constipation. To prevent this, your doctor may direct you to take laxatives, drink a lot of fluids, or increase the amount of fiber in your diet. Be sure to follow the directions carefully, because continuing constipation can lead to more serious problems.

Heat can cause the fentanyl in the patch to be absorbed into your body faster. This may increase the chance of serious side effects or an overdose. While you are using this medicine, do not use a heating pad, electric blanket, heat or tanning lamps, sauna, a sunlamp, or a heated water bed, and do not sunbathe, or take long baths or showers in hot water. Also, check with your doctor if you get a fever.

Be careful about letting other people come in contact with your patch. The patch could stick to someone else, such as when you hug them or if someone helps you put the patch on. If any medicine gets on another person, wash it off right away with clear water.

Before having any kind of surgery (including dental surgery) or emergency treatment, tell the medical doctor or dentist in charge that you are using this medicine. Serious side effects can occur if your medical doctor or dentist gives you certain other medicines without knowing that you are using fentanyl.

You may bathe, shower, or swim while wearing a fentanyl skin patch. However, be careful to wash and dry the area around the patch gently. Rubbing may cause the patch to get loose or come off. If this does occur, throw away the patch and apply a new one in a different place. Make sure the area is completely dry before applying the new patch.

If you have been using this medicine regularly for several weeks or more, do not suddenly stop using it without first checking with your doctor. You may be directed to gradually reduce the amount you are using before stopping treatment completely to lessen the chance of withdrawal side effects.

Using too much fentanyl skin patch, or taking too much of another narcotic with fentanyl skin patch, may cause an overdose. If this occurs, get emergency help right away. An overdose can cause severe breathing problems (breathing may even stop), unconsciousness, and death. Serious signs of an overdose include: very slow breathing (fewer than 8 breaths a minute) and drowsiness that is so severe that you are not able to answer when spoken to, or, if asleep, cannot be awakened. Other signs of an overdose may include: cold, clammy skin, low blood pressure, pinpoint pupils of the eyes, and slow heartbeat. It may be best to have a family member or a friend check on you several times a day when you start using a narcotic regularly, and whenever your dose is increased, so that he or she can get help for you if you cannot do so yourself.

This medicine may cause sleep-related breathing problems (eg, sleep apnea, sleep-related hypoxemia). Your doctor may decrease your dose if you have sleep apnea (stop breathing for short periods during sleep) while using this medicine.

Do not use a fentanyl patch if you have taken a monoamine oxidase (MAO) inhibitor in the past 2 weeks. Some examples of MAO inhibitors are isocarboxazid (Marplan®), phenelzine (Nardil®), selegiline (Eldepryl®), and tranylcypromine (Parnate®). If you use the 2 medicines close together it may cause serious side effects like confusion, agitation, restlessness, stomach or intestinal symptoms, a sudden high temperature, an extremely high blood pressure, or severe convulsions.

Check with your doctor right away if you have anxiety, restlessness, a fast heartbeat, fever, sweating, muscle spasms, twitching, nausea, vomiting, diarrhea, or see or hear things that are not there. These may be symptoms of a serious condition called serotonin syndrome. Your risk may be higher if you also take certain other medicines that affect serotonin levels in your body.

Using this medicine while you are pregnant may cause serious unwanted effects, including neonatal opioid withdrawal syndrome in your newborn baby. Tell your doctor right away if you think you are pregnant or if you plan to become pregnant while using this medicine.

Using too much of this medicine may cause reduced infertility (unable to have children). Talk with your doctor before using this medicine if you plan to have children.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

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