Some unwanted side effects caused by Fentanyl

In addition to its required benefits, some unwanted effects can be caused as a result of using Fentanyl. These side effects need immediate medical attention to avoid further complications.

Let us look at some major side effects that are noticed as a result of Fentanyl and need immediate medical attention

More common

  • Chest pain
  • Confusion
  • Cough
  • Dizziness
  • Tarry or black stools
  • Decreased urine
  • Dry mouth
  • Fainting
  • Chills or fever
  • Increased thirst
  • Difficulty in breathing
  • Appetite loss
  • Lightheadedness
  • Mood changes
  • Side or lower back pain
  • Vomiting
  • Nausea
  • Muscle cramps or muscle pain
  • Tingling or numbness in hands, lips and feet
  • Sneezing
  • Pale skin
  • Nervousness
  • Sunken eyes
  • Rapid breathing
  • Exertion and troubled breathing
  • Chest tightness
  • Unusual bruising or bleeding
  • Unusual weakness and tiredness
  • Sores, white spots or ulcers in mouth
  • Wrinkled skin


Less common

  • Thinking abnormalities
  • Severe sleepiness
  • Shakiness in feet, hands, arms and legs
  • Shaking or trembling feet or hands
  • Seizures
  • Muscle jerking or twitching
  • Unsteadiness and clumsiness
  • Change in balance or walking
  • Stomach or abdominal pain
  • Headache
  • Decreased responsiveness or awareness
  • Decreased urination
  • Unsteadiness or clumsiness
  • Severe constipation

Symptoms of overdose

  • Slow breathing or shallow breathing

If you notice any of the above symptoms of overdose while using Fentanyl, ask for emergency medical help immediately.

Side effects- Minor

Some side effects do not need medical help. As your body gets used to the medication, these side effects disappear with time. Your physician can tell you how to reduce the side effects and if any of these side effects continue for a longer period, contact your health care provider immediately. More common side effects are

  • Diarrhea
  • Irritability
  • Feeling empty or sad
  • Back pain
  • Tiredness
  • Loss of pleasure or interest
  • Joint pain
  • Unusual drowsiness
  • Weight loss
  • Trouble sleeping
  • Discouragement
  • Difficult in bowel movement
  • Muscle stiffness

Less Common side effects are

  1. Increased muscle tone
  2. Feeling heat or warmth
  3. Sweating
  4. Rash
  5. Itching skin
  6. Spinning sensation
  7. Redness or flushing of skin on neck or face


Post treatment- Side effects

After you stop using Fentanyl, you might experience side effects that need medical help. If you notice the side effects given below, contact your doctor immediately

  1. Weakness
  2. Stomach cramps
  3. Restlessness
  4. Speech disorder

Side effects can range from mild to severe, but if you think that they are troublesome, please seek medical help as some side effects if not treated in time can be life threatening too. Talk to your doctor to know about the possible side effects of the drug, so that it becomes easy for you to identify possible side effects and call for medical help if required.

With benefits Fentanyl also has side effects that might need change in dose. Your doctor is the right person to adjust your dose and help you use the medication safely.

Right dosage of Fentanyl can be helpful

Learning about the right dosage of Fentanyl can be helpful for you. Let us learn about the right dosage of Fentanyl so that it becomes easy for you to avoid overdose and related complications

Dosage strengths and forms

Surgery premedication

50-100 mcg/dose or IV (slow) of minimum 30 to 60 minutes before surgery

Addition to regional anesthesia- 24-100 mcg/dose or IV (slow) above 1-2minutes

General Anesthesia

Surgical procedures (minor) – 0.5 to 2 mcg/kg/dose IV

Chronic Pain (Severe)

To be used in patients tolerant to opioid for treating chronic pain. Daily doses, long term treatment through opioids are required for severe pain in case there are no alternative treatments available.


Due to the risk of abuse, addiction and misuse of opioids even in case of recommended doses and due to high risk of overdose and death with the use of extended release formulation of opioid,  limited to patients whom no other alternative          treatment method is effective, not tolerated or in cases where sufficient management of pain is not achieved.

Dosing restrictions

It is not recommended to treat acute pain or used as PRN analgesic


Treating overdose of Fentanyl

Treatment for overdose of Fentanyl should be started immediately, upon knowing that overdose has taken place. If the overdose occurs due to lozenge or patch, then the very first step should be flushing out Fentanyl and stop the absorption of Fentanyl in the body. This is where the medical professional consider Fentanyl as a strong poison.

Depending upon when Fentanyl dose was consumed last, user’s stomach is pumped to eliminate the drug that is being absorbed in the bloodstream. Activated charcoal is used to flush out the drug from the bloodstream. It helps preventing the damage caused due to absorption of drug in large amounts. If you notice someone losing consciousness suddenly and appear to be sleeping peacefully, it can be overdose symptoms that you cannot ignore. If you cannot manage to get antagonist drugs, turn the patient on one side and sometimes the patient vomits to throw out the medicine.

Overdose can happen in people who use this drug to get instant pain relief and as Fentanyl is quite effective in treating pain faster, people tend to depend on the drug or fall in prey for overdose. It is recommended that one should take Fentanyl in right doses as prescribed by the doctor.

The medication is strong enough to cause life threatening damage and to avoid such a situation; you need to be very careful about drug dependency. There are many rehabilitation centres that help people who get are victims of drug abuse to overcome addicition. To prevent Fentanyl overdose, you can educate yourself on the right dosage of Fentanyl.

You can ask your doctor for a suitable dose and if possible do not take Fentanyl for a long term or in high doses. Discuss with your doctor about other medications that you are using along with Fentanyl to avoid complications. Fentanyl drug interactions can also lead to overdose, which can be avoided by following your doctor’s instructions.

Fentanyl drug interactions that you might not be aware about

Some medicines can lead to dangerous and unwanted effects when taken with Fentanyl.  Tell your physician about all other medication you are using or medications that you started or stopped using.

After taking Fentanyl, using other drugs that make you feel drowsy or slow breathing can be quite dangerous and fatal too. Check with your doctor before you take pain medicine (narcotic), sleeping pill, medicines for seizures, depression or muscle relaxer.

Even other medications like OTP drugs, vitamins, herbal supplements can also interact with Fentanyl. So make sure you discuss with your doctor about the medicines that you are using now.

Let us have a look at some other Fentanyl drug interactions


Using Lorazepam and Fentanyl together can increase unwanted side effects like drowsiness, confusion, dizziness and breathing problems. Elderly people often experience impairment in judgment and thinking as well as motor co-ordination. Also you should avoid alcohol consumption while you are on these medications. Avoid engaging yourself in activities that need extra alertness and need you to be awake till the time you know how medication works for you.


Taking Fentanyl and Pregabalin together can lead to side effects like confusion, drowsiness, dizziness and difficulty in concentrating. Elderly people experience impairment in motor co-ordination, judgment etc.


Using Fentanyl and duloxetine together can lead to rare yet serious condition termed as  serotonin syndrome, that can result in symptoms like




Excessive sweating

Changes in blood pressure

Stomach cramp



Blurred vision


Sometimes in severe cases it can lead to coma or death. If you experience such symptoms while using these medications together, contact your health care provider immediately.

Fentanyl- furosemide

Fentanyl and Furosemide can have additional effects in decreasing your blood pressure. You may notice fainting, lightheadedness, headache, change in heart or pulse rate or dizziness. These side effects are observed in initial stages of treatment followed by an increase in dose or when the treatment is started again after a period of time. Do not operate hazardous machinery until you know the effects of medication.

It is always better to let your doctor know about the medication you are using as you are not aware about the possible drug interactions of Fentanyl. To be on the safer side consult your doctor. Checking the ingredients present in all other medications you are using can help you avoid drug interactions.

Avoid consuming alcohol with Fentanyl as it can lead to serious side effects. Alcohol consumption with Fentanyl can affect your nervous system and lead to difficulty in concentrating, low BP, lightheadedness, impairment in judgment and thinking ability. Also do not consume grapefruit juice or grapefruit as these increases the blood levels and efficacy of Fentanyl.

Avoid activities that need mental alertness as Fentanyl leads to drowsiness and dizziness. Once you know how your body reacts to Fentanyl, you can engage in activities that require mental alertness, only if you do not experience severe drowsiness, dizziness etc.

Always check with your doctor about the side effects and drug interactions so that Fentanyl doesn’t harm you.

1 2 3 6