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Fentanyl Signs Withdrawal Symptoms & Side-effects

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The fentanyl crisis in the United States is a continuing public health issue. Since 2013, the number of overdose deaths involving fentanyl has skyrocketed, increasing 18-fold between then and 2020. Most of these deaths occur among people aged 25-54, with men being twice as likely to die from an overdose as women.

There are numerous contributing factors to this alarming trend, including illicitly manufactured fentanyl or counterfeit pills made with the drug, increased levels of availability due to international supply chains, and the co-use of substances such as cocaine and methamphetamine.

If you or someone close to you is struggling with opioid dependence or any substance use disorder, Guardian Recovery can help. We will work with you to develop an individualized and effective program to help you recover from addiction and get you started on the road to long-term recovery. We believe in the benefits of a full curriculum of clinical care, beginning with medical detoxification, transitioning into a higher level of treatment, and concluding with personalized aftercare planning. Contact us today to learn more about our treatment options in your area.

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Side Effects of Fentanyl Use & Other Opioid Analgesics

Opioid pain relievers, such as fentanyl, and other prescription pain medications like oxycodone, morphine, and codeine can cause strong side effects that impair your ability to think, function, operate machinery, and even breathe. Furthermore, fentanyl is highly addictive and has a high potential for misuse due to its euphoric effects. As with any opioid analgesic, it is crucial to take it exactly as your doctor prescribes and never exceed the recommended dosage.

Short-Term Side Effects

The short-term side effects of fentanyl use can include the following:

  • Drowsiness.
  • Nausea.
  • Confusion,
  • Constipation.
  • Dizziness.
  • Difficulty breathing or swallowing.

Fentanyl can also cause a decrease in blood pressure and heart rate which may lead to fainting if not appropriately managed.

Longer-Term Adverse Effects

The long-term side effects of using opioids, including fentanyl, can include tolerance, physical dependence, and a higher risk of overdose. Prolonged use may also lead to depression or anxiety, reduced sexual function, and increased susceptibility to infections. One study also reported that long-term opioid therapy led to:

  • Serious fractures.
  • Breathing problems during sleep.
  • Increased sensitivity and extreme response to pain (hyperalgesia).
  • Chronic constipation and bowel obstruction.
  • Heart attack.
  • Tooth decay caused by dry mouth.

Can Medical Fentanyl Use Cause Negative Side Effects?

Fentanyl is a powerful synthetic opioid originally used to provide comfort and symptom relief to cancer patients. Its use in medical settings gradually expanded to pain relief, sedation, and anesthesia.

Fentanyl can be administered as an intramuscular injection, intravenous infusion, or transdermal patch to treat moderate to severe acute pain, such as post-operative pain or chronic pain conditions. It is also sometimes used to reduce symptoms of opioid withdrawal and help with addiction recovery.

Because of its potency, fentanyl and other opioid analgesics have a high potential for misuse, giving rise to new clinical practice guidelines in prescribing them. Despite its potential therapeutic benefits, fentanyl should always be taken according to the instructions provided by your doctor, as misuse can lead to severe adverse reactions, health risks, and dependence.

Risk Factors for Fentanyl Administration

The primary risk factor for fentanyl administration is misuse or overdose. Fentanyl is a potent synthetic opioid that should only be taken as your doctor prescribes, never exceeding the recommended dosage. If you have existing medical conditions such as kidney or liver disease, breathing problems, or a history of substance use disorder, you may be at an increased risk of adverse reactions when using opioids. Discussing these risks with your doctor before taking any medication is essential.

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Dangerous Risks & Side Effects of Mixing Fentanyl with Other Medications

Mixing fentanyl with other medications can be dangerous and increases the risk of serious side effects. Fentanyl is a powerful opioid. When combined with other drugs, including alcohol or sedatives, it can significantly slow heart rate, breathing rate, and blood pressure, leading to coma or death.

Mixing fentanyl with drugs that interact with serotonin, including most anti-depressants, may increase the risk of serotonin syndrome, an often life-threatening condition caused by too much serotonin in the body. Symptoms of serotonin syndrome are:

  • Diarrhea.
  • Excessive sweating.
  • Agitation.
  • Tremors.
  • Increased blood pressure.
  • Irregular heartbeat.
  • Twitching and involuntary muscle movements.

What Symptoms Are Caused by an Overdose of Fentanyl?

The symptoms of a fentanyl overdose include shallow or stopped breathing, severe drowsiness, confusion and disorientation, cold or clammy skin, pinpoint pupils, extreme weakness or dizziness, seizures, coma, and death.

If you suspect someone has overdosed on fentanyl, seek medical help immediately. If there is an opioid reversal kit (naloxone) available, use it as soon as possible – do not wait for help to arrive.

Naloxone is a lifesaving medication that can reverse an opioid overdose. It is small, easy to use, and available at pharmacies in most states without a prescription.

Withdrawal Symptoms Caused by Fentanyl & Opioid Addiction & Dependence

If you are dependent on opioids such as fentanyl, you may experience withdrawal symptoms when trying to quit. These can include nausea and vomiting, muscle aches, agitation and restlessness, insomnia or difficulty sleeping, anxiety and depression, chills and sweating, diarrhea, and abdominal cramps. Additionally, you may experience cravings, making it difficult to stay off the drug. If you or someone you know is struggling with opioid dependence, seeking medical help right away is vital, as withdrawals can be very intense and dangerous if left untreated.

Fentanyl Withdrawal Timeline

The timeline for fentanyl withdrawal can vary depending on the individual but typically begins with mild symptoms appearing within 8-12 hours after the last use. These can include anxiety, agitation and restlessness, sweating, insomnia, difficulty sleeping, and cravings. During this time, drug dependence is at its highest risk of developing.

From days 2-4, symptoms may peak, including abdominal cramps or diarrhea, nausea or vomiting, muscle aches, and increased heart rate. The worst physical symptoms pass between days 5-7, although psychological discomfort such as depression may still exist. Over the following weeks to months, other withdrawal symptoms can manifest, including fatigue, nightmares, irritability, and mood swings. It is important to note that it is not safe to attempt detoxing from opioids without medical supervision.

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Fentanyl is a potent synthetic opioid that is highly addictive and widespread throughout the U.S. Its potency is 50 times that of heroin, making it easy to overdose, especially if mixed with another substance. If you or someone you know is struggling with opioid dependence, it is important to seek professional help right away. The experienced and compassionate medical, clinical, and administrative staff at Guardian Recovery are ready to help. We provide comprehensive treatment, including medically-assisted detox, therapy, specialty programs, and reintegration support. We will guide you through every step of your recovery from your first call and throughout your recovery. We provide a complimentary assessment and a free insurance benefits check and help coordinate local travel to our facility. All you have to do is ask for help; we will take care of the rest. Contact us today.


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Reviewed professionally for accuracy by:

Ryan Soave


Ryan Soave brings deep experience as a Licensed Mental Health Counselor, certified trauma therapist, program developer, and research consultant for Huberman Lab at Stanford University Department of Neurobiology. Post-graduation from Wake Forest University, Ryan quickly discovered his acumen for the business world. After almost a decade of successful entrepreneurship and world traveling, he encountered a wave of personal and spiritual challenges; he felt a calling for something more. Ryan returned to school and completed his Master’s Degree in Mental Health Counseling. When he started working with those suffering from addiction and PTSD, he found his passion. He has never looked back.

Written by:

Cayla Clark

Cayla Clark

Cayla Clark grew up in Santa Barbara, CA and graduated from UCLA with a degree in playwriting. Since then she has been writing on addiction recovery and psychology full-time, and has found a home as part of the Guardian Recovery team.

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