There is no single experience that describes how fentanyl "feels."

A patient receiving fentanyl under medical supervision may primarily notice reduced pain and sleepiness. Some people may experience warmth, relaxation, dizziness, nausea, or itching.

When fentanyl is misused, people may experience opioid intoxication, including euphoria and sedation. However, attempting to reproduce or intensify these effects is extremely dangerous because the difference between a desired effect and life-threatening respiratory depression can be difficult to predict.

Fentanyl was first developed in 1959 and introduced during the 1960s as an intravenous anesthetic.

The development of synthetic opioids was driven partly by the search for powerful analgesic and anesthetic medicines that could be used in medical settings.

Over subsequent decades, fentanyl became available in several pharmaceutical formulations, including injectable products and transdermal patches, as well as specialized transmucosal and nasal products in certain markets.

The medical history of fentanyl is therefore very different from the modern history of illicitly manufactured fentanyl.

Pharmaceutical fentanyl has a long-standing role in medicine. The contemporary overdose crisis, meanwhile, has been driven largely by illicitly manufactured fentanyl and fentanyl analogs, particularly because illegally produced products can have unpredictable composition and may be incorporated into counterfeit pills.

There are two very different answers depending on whether someone means pharmaceutical fentanyl or illicit fentanyl.

Pharmaceutical fentanyl

Pharmaceutical fentanyl is manufactured by regulated pharmaceutical manufacturers and distributed through controlled medical supply chains.

It is prescribed or administered by healthcare professionals according to applicable laws and medical standards.

Illicitly manufactured fentanyl

Illicit fentanyl is manufactured outside the regulated pharmaceutical system.

In the United States, authorities have reported that much illicit fentanyl is manufactured clandestinely and trafficked through international criminal networks. Because illicit products are not subject to pharmaceutical quality control, the amount and composition can vary substantially.

This distinction should always be made when discussing the "origin" of fentanyl.

Fentanyl has been marketed under various brand names and formulations.

Examples historically or currently associated with pharmaceutical fentanyl include:

• Duragesic — transdermal fentanyl patch
• Actiq — oral transmucosal fentanyl product
• Fentora — buccal fentanyl
• Abstral — sublingual fentanyl
• Lazanda — nasal fentanyl
• Subsys — sublingual spray

Availability and approved indications can vary by country and may change over time. DEA materials identify several of these formulations, including transdermal patches, injectable formulations, nasal sprays, and transmucosal products.

Fentanyl is the generic name of the active drug.

The generic medication may appear as fentanyl or as a specific salt or formulation depending on the product.

For example, hospital injectable products are commonly identified as fentanyl citrate.

Fentanyl Names and Other Names

Fentanyl may be referred to by:

• Fentanyl
• Fentanyl citrate
• Transdermal fentanyl
• Fentanyl patch
• Pharmaceutical fentanyl
• Illicitly manufactured fentanyl
• Synthetic opioid

Illicit-market slang names are not reliable indicators of what a substance contains.

The DEA lists several historical or street terms associated with illicit fentanyl, but terminology varies considerably between locations and drug markets.

Fentanyl is classified pharmacologically as a synthetic opioid analgesic.

In the United States, pharmaceutical fentanyl is a Schedule II controlled substance.

Its opioid classification means that it shares pharmacological characteristics with medicines such as morphine, oxycodone, hydromorphone, and other opioid analgesics.

However, each opioid differs in potency, pharmacokinetics, metabolism, formulation, and clinical use.

Searches for "fentanyl to morphine conversion" are common because clinicians sometimes need to transition patients between opioids.

However, fentanyl-to-morphine conversion is not a simple mathematical equivalence.

The appropriate calculation depends on:

• Formulation
• Route
• Patient opioid tolerance
• Current opioid regimen
• Clinical condition
• Duration of treatment
• Other medications
• Whether the patient is switching from or to a transdermal formulation

Published conversion tables can also differ.

For these reasons, patients should never attempt to calculate or change fentanyl and morphine doses independently.

Intravenous fentanyl conversion is particularly dependent on the clinical context.

An anesthesiologist or other qualified clinician must consider the patient's current opioid exposure, timing, response, monitoring requirements, and the pharmacology of the replacement opioid.

A generic internet conversion number is not an appropriate substitute for professional assessment.

"Dilaudid" is a brand name for hydromorphone.

Fentanyl-to-hydromorphone conversion is clinically complex because both drugs are potent opioids but have different pharmacokinetic and pharmacodynamic characteristics.

The safest approach is for a prescriber or pharmacist experienced in opioid conversion to calculate the appropriate regimen and account for incomplete cross-tolerance.

For safety reasons, an online article should not provide an individualized fentanyl-to-Dilaudid dose.

Hydromorphone and fentanyl are both opioids, but their doses are not interchangeable on a simple one-to-one basis.

When a patient changes opioids, clinicians may reduce the calculated equivalent dose because a person's response to a new opioid cannot be predicted perfectly from the previous opioid dose.

This is known as incomplete cross-tolerance and is one reason professional supervision is essential.