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What is it?

Fentanyl is an opioid drug that is medically prescribed for chronic pain conditions. It’s a depressant, which means that it slows down the messages between the brain and the body – basically, we are a few steps behind the beat! Fentanyl can be extremely dangerous as it is about 80 to 100 times stronger than morphine. It can come in many forms including patches, lozenges or lollipops, and as a liquid.

Fentanyl can be dissolved in the mouth and swallowed, or absorbed through the skin via patches, or through intravenous injection. With injecting, there is a risk of contracting blood-borne viruses, such as hepatitis B & C and HIV if needles are shared and the risk of infection at the injecting site.

What are the effects?


  • Euphoria
  • Pain relief
  • Nausea, vomiting
  • Constipation and/or diarrhoea
  • Reduced appetite
  • Wind, indigestion, cramps
  • Drowsiness, confusion
  • Weakness or fatigue
  • Dizziness
  • Headache
  • Incoherent or slurred speech
  • Impaired balance
  • A slow pulse and lowered blood pressure
  • A rash, inflammation, or swelling at the patch site
  • Mood instability
  • Reduced libido
  • Constipation
  • Menstrual problems
  • Respiratory impairment


If we take a large amount of fentanyl or have a strong batch, it’s possible to overdose. Knowing the signs of overdose helps keeps us and others safe, and when we might need to call an ambulance. Watch out for these symptoms and call 000 in an emergency:


Chest pain


Slowed breathing




Greyish lips and complexion (in darker skin people)




Passing out


Bluish lips and complexion (in lighter skin people)

Naloxone is an over the counter drug used to temporarily reverse an overdose on opioids. It can be purchased at local pharmacies and anyone can administer it. It’s handy to have around, just in case! It can be used as a nose spray or injected – and no, it’s not like Pulp Fiction! Even after naloxone has been used, medical attention should be sought immediately.

Mixing with other drugs

The effects of mixing fentanyl with other drugs – including over the counter or prescribed medications can be unpredictable and dangerous. Do not mix fentanyl with the following medications as it increases the risk of overdose, and even death:

  • Ketamine
  • Cocaine
  • Alcohol
  • GHB
  • Benzos

There are a range of unsafe interactions to be cautious of when mixing fentanyl and other drugs, and they can be found at TripSit.

HIV Medications

The interactions between fentanyl and antiretroviral medications are not well known. There’s currently no evidence to suggest that fentanyl use directly reduces the efficacy of antiretroviral medications. If some new research comes to light, then we’ll update this section and let you know.

We did find that protease inhibitors and some other medications, including Efavirenz, Etravirine, Nevirapine and Cobicistat can have fatal consequences when mixed with fentanyl. Some of these drugs can increase the effects of fentanyl, amplify any withdrawal symptoms, result in increased bleeding or risk potentially fatal respiratory depression.

The interactions between fentanyl and PrEP and PEP are not well known. There’s currently no evidence to suggest that fentanyl use directly interacts with these medications or reduces their efficacy. We’ll keep looking and update you if any new research comes to light.

To learn about the interactions between specific HIV medications and fentanyl head to Liverpool HIV Drug Interactions Checker.


There’s currently no evidence to suggest that fentanyl use directly reduces the efficacy of HRT. We’ll keep looking and update this information if something new comes to light.

Fentanyl is an opioid and Oestradiol can affect our opioid receptors, and therefore how the body processes it, so it’s best to chat with a healthcare professional about whether our dosage needs to be adjusted.

Spironolactone and opioids can potentially lead to a build-up of toxicity and affect our kidneys.

Progesterone and Cyproterone Acetate can have sedative effects and cause tiredness and fatigue, so taking these along with other depressants may lead to feeling more exhausted during or after using opioids.

Both testosterone and opioids can cause water retention, which means we may experience constipation and bloating when taking both.

We don’t yet know enough about how opioid-induced androgen deficiency (OPIAD) may impact bodies that are taking testosterone, including whether it may impact our absorption or processing of our HRT.

For more information about fentanyl head to the Australian Drug Foundation or TripSit.

The information given on this page is not medical advice and should not be relied upon in that way.