When an overdose is reported, the common assumption is that the counterfeit pills contained fentanyl. Now well-known throughout the U.S., fentanyl is a highly potent opioid—only a few grains can cause a deadly overdose. It mixes into pills unevenly, like chocolate chips into a cookie, making it unpredictable.
The positive news is that whereas at one point, seven out of ten pills contained a deadly amount of fentanyl, that ratio has gone down to three out of ten. However, the drugs that fentanyl has been mixed with to create counterfeit pills are dangerous in their own right.
Medetomidine
The Centers for Disease Control and Prevention (CDC), in conjunction with the White House Office of National Drug Control Policy (ONDCP) issued a Health Advisory about medetomidine in April 2026, as it was increasingly prevalent in the illegal fentanyl supply and resulting in an increasing risk for overdose. Also known as “rhino tranq” (because of its strength), “mede,” or “dex,” medetomidine is not approved for human use. It is used in veterinary practices as a sedation and analgesia in dogs.
According to the CDC, “Medetomidine can cause profound sedation, bradycardia, and hypotension.” Dependency and addiction are also possible, and stopping medetomidine following regular use may lead to severe withdrawal symptoms, including hypertension, anxiety, nausea, vomiting, and fluctuating alertness.
The prevalence of medetomidine varies greatly by region; in the Northeast, it has been found in nearly three-quarters of counterfeit pills that also contain fentanyl. In the South (which includes Virginia), that percentage drops to one-third.
Because medetomidine is frequently found in pills containing fentanyl and other opioids, naloxone should be administered immediately in the case of a suspected overdose. However, naloxone does not counter the effects of rhino tranq itself.
Nitazenes
Nitazenes are synthetic opioids that were developed in the 1950s. Because they carried a high risk of addiction, development was halted and they were never approved for human use. Nitazenes can be up to 500 times stronger than morphine. They have been detected in the drug supply of heroin and many counterfeit pills. Like other opioids, nitazenes can result in respiratory depression and even death. While naloxone will work on nitazenes, their potency seems to require multiple doses. (There are other factors that could potentially be impacting the amount of naloxone needed, such as the presence of xylazine or the doses not being given properly.)
Metamizole
Metamizole, also known as Dipryrone, is a controversial drug. It is actually available in many nations, but it is illegal in the United States due to its connection to adverse effects on bone marrow and the liver, including agranulocytosis (a disease that severely impairs the body’s ability to fight infections), acute hepatitis, and acute liver failure. It is referred to as an NSAID (non-steroidal anti-inflammatory drug, the same category as ibuprofen). While its side effects are reported to be lower than those of ibuprofen and aspirin, the occurrences of agranulocytosis and liver injury were of significant concern.
Most people will not see adverse effects from Metamizole if they are unknowingly taking it in counterfeit pills. However, you should be aware that even if you don’t have a reaction initially, the build-up of the drug in your system can have serious consequences, in particular liver injuries that may result in a need for a liver transplant or even death. If you are experiencing fatigue, nausea, anorexia, and right upper quadrant discomfort followed by dark urine and jaundice, your counterfeit pills may contain metamizole.
Acetaminophen
Acetaminophen, sometimes more well-known under the brand name of Tylenol and also called paracetamol or Panadol, is a pain-reliever and fever-reducer. It seems innocent enough, but excessive amounts of acetaminophen can result in liver injury or acute livery failure. Acetaminophen toxicity can even progress to multi-organ failure and death.
Because you don’t know what is in a counterfeit pill, it is easy to overdose on acetaminophen, especially if you are also taking cold medicine or Tylenol. More than 600 prescription and over-the counter medications contain acetaminophen.
What to watch for: Nausea, vomiting, excessive sweating, a sense of weakness, and/or loss of appetite are your early warning signs. Abdominal pain on the right side, confusion, and dark-colored urine show up as the disease progresses. If you allow it to continue, you could experience jaundice, blood clotting issues, and even loss of consciousness or coma.
Protect Yourself
Make sure you purchase your medications from a licensed pharmacy. Ordering online from unknown sources can be deadly. If you have a dealer, keep in mind that they have no knowledge of what is going into the drugs they are selling you.
Note: The heading for each substance is linked to an NIH, FDA, or CDC site where you can obtain more information.
