Why Fentanyl Is Showing Up in Other Drugs Now

When OxyContin was reformulated in 2010 to be abuse-deterrent, it did not eliminate demand. It pushed people toward heroin, igniting the next wave of the epidemic [5].

Fentanyl is about 50 to 100 times stronger than many prescription opioids, so a tiny amount can replace a much larger quantity of other opioids while producing a similar effect [7].

It is purely synthetic, which means it can be made easily and cheaply in a lab, and it is easy to press into counterfeit pills or mix with other drugs [5] [7]. Its low cost, ease of transport and extreme potency made it highly attractive to traffickers [5].

Because it is compact and potent, it is easier to ship than bulkier plant-based opioids like heroin. That helped drive a shift from heroin and prescription opioids to illicitly manufactured fentanyl in the U.S. street supply since around 2015 or 2016 [7].

By the end of 2024, the annual rate of fatal fentanyl overdoses had fallen by over a third, according to statistics from the Centers for Disease Control and Prevention [1].

The study mentioned above found that this reversal was likely driven not by changes in domestic treatment or prevention efforts, but by a disruption in the global supply of illicit fentanyl. The most likely cause was restrictions on precursor chemicals used in its production in China [1]. How long the decline will last is uncertain [1].

Meanwhile, illicit drug makers keep adapting. Fentanyl is increasingly showing up mixed with other drugs, particularly veterinary tranquilizers like xylazine and medetomidine, not by accident, but as a direct result of market forces [5] [6].

Crackdowns on one substance tend to push traffickers to substitute a new, often more potent compound in a continuous "whack-a-mole" cycle [5]. When one substance is banned, regulated or made scarce, another fills its place [5]. That is how veterinary sedatives entered the supply.

Dealers are increasingly mixing fentanyl into all kinds of drugs, including heroin, cocaine and methamphetamine [7].

Counterfeit prescription pills are made to look like real medications such as oxycodone, Xanax (alprazolam) or Adderall, but they may contain lethal amounts of fentanyl or methamphetamine instead [2] [3]. In one drug checking study of pills bought at tourist-oriented pharmacies in northern Mexico, 8 of 27 pills sold as oxycodone contained fentanyl, and 7 of 11 sold as Adderall contained methamphetamine [4]. People think they are taking a known dose of a legitimate pill but may actually be consuming fentanyl.

The share of U.S. overdose deaths with evidence of counterfeit pill use more than doubled between mid-2019 and late 2021, from 2.0% to 4.7% [2].

Because fentanyl does not depend on poppy crops and can be made in clandestine labs, it was able to fill demand as other opioid sources tightened [5] [7]. As it became the main opioid in the market, it spread into many street drug categories, and there are no quality control mechanisms in the labs that produce these products [3].

Xylazine, known as "tranq," was the first major adulterant. It extended fentanyl's short high, but it also caused extended sedation, tissue necrosis (dead tissue in skin wounds) and severe withdrawal [5].

After Pennsylvania classified xylazine as a controlled substance in mid-2023, its presence in the local drug supply began to drop. By May 2024 it was being replaced by medetomidine, a veterinary sedative that is 100 to 200 times more potent than xylazine [5]. Medetomidine is also known as "rhino tranq" [6].

In Toronto, Canada, for example, medetomidine was found in 80% of fentanyl samples tested by the city's Drug Checking Service, according to a February 2026 report [6]. Reports out of the U.S., particularly Philadelphia, show the drug has increased hospitalizations, including stays in intensive care units [6].

There are several reasons:

• Profit. Today's illicit supply chain is unregulated and built for potency and profit [5]. Cheap, potent additives fit that model.
• Extending the high. Fentanyl's effects are intense but short. Xylazine stretched fentanyl's high from 30 to 60 minutes to as long as 8 to 72 hours [5], and medetomidine is being mixed in because of the belief that it enhances fentanyl's sedative effects [6]. That longer, deeper sedation sharply raises health risks.
• Staying ahead of the rules. Xylazine spread in part because it was unregulated, and once it was scheduled, medetomidine quickly took its place [5].

There are numerous very serious consequences for people who use these drugs [5] [6].

• The unpredictable cocktail. People who buy what they think is fentanyl, cocaine or a prescription pill may be consuming a mix of potent opioids and veterinary sedatives without knowing it [6] [7].
• New health crises. In a CDC investigation of 165 patients with a new withdrawal syndrome linked to fentanyl and medetomidine, 91% required ICU-level care and 24% were intubated [5]. Medetomidine can cause a deep state of unconsciousness, lower blood pressure and heart rate, and slow breathing [6].

The very features that make fentanyl attractive to illicit markets, high potency and low cost, also dramatically raise overdose risk. Someone might misjudge the amount of fentanyl in their supply and get two or three times as much as they expected [7].

Core harm reduction responses to this new supply reality include:

• Drug checking. Fentanyl test strips and drug checking services help people know what is in their drugs [2] [7]. Test strips are not foolproof, since one corner of a pill may test differently from another [7].
• Naloxone on hand. Keeping naloxone available and never using alone are core overdose prevention steps [2].
• Clear messaging. Pills obtained illicitly or without a prescription might contain highly potent drugs [2]. The only safe medications are ones prescribed to you and dispensed by a licensed pharmacist.