Fentanyl vs. Heroin: An Opioid Comparison

3 min read · 5 sections

Heroin vs Fentanyl: Uses & Classifications

Heroin and fentanyl are both opioid drugs that bind to opioid receptors in the brain, reducing pain sensations and elevating pleasure and relaxation. Both are extremely potent, fast-acting, and can be lethal in as little as one dose.

Heroin is derived from morphine, which is a natural substance that is removed from the seed of the opium poppy plant. Heroin is distributed as a white or brown powder, or as a black, tacky substance known as “black tar” heroin. It is classified as an illegal drug with no accepted medicinal uses in the United States (Schedule I controlled substance) by the Drug Enforcement Administration (DEA). It is typically injected, smoked, or snorted when abused.

Fentanyl is a synthetic (manmade) opioid that is similar to morphine; however, the National Institute on Drug Abuse (NIDA) warns that it is 50-100 times more potent than morphine. The chemical structure of fentanyl is slightly different from that of heroin. Fentanyl was originally synthesized as a powerful analgesic (pain reliever), and it is still used medically to treat severe pain following surgery or for chronic pain in people who are opioid-tolerant, which means that other painkillers aren’t as effective. Unlike heroin, fentanyl does have some accepted medicinal uses, so it is classified as a Schedule II controlled substance by the DEA. Schedule II drugs still have a very high potential for abuse and addiction despite their specific medical uses.

Fentanyl is diverted from licit uses for abuse, and it is also manufactured in clandestine laboratories. Fentanyl is cheaper and easier to obtain than heroin and is often used as a cutting agent or filler for heroin.

Fentanyl can be absorbed through the skin and be lethal in very small doses, as little as 0.25 milligrams, CNN warns. Prescription fentanyl comes in lozenges, buccal and sublingual tablets, nasal or oral sprays, as an injectable, and in a transdermal patch form. When abused, fentanyl patches may be sucked on, chewed, inserted into the body, or the gel can be scraped off the patches and injected. Tablets may be ingested or crushed and snorted, smoked, or injected. Illegal fentanyl may be made into pills to look like other prescription opioid medications like Norco, be manufactured in powder form, or put on blotter paper to be placed under the tongue.

Comparing Heroin & Fentanyl


  • Illegal drug with no accepted medical uses
  • Manufactured in powder form
  • Injected, smoked, or snorted when abused
  • Fast-acting and creates a short but intense rush
  • Semi-synthetic opioid
  • Potential for rapid onset of overdose, leading to fatal respiratory depression
  • Highly addictive
  • Often requires medical detox and opioid replacement medications to safely process the drug out of the body
  • Comprehensive treatment ideal for long-term recovery


  • Available by prescription as a powerful painkiller and also manufactured illegally
  • Manufactured as a pill, patch, lozenge, tablet, injectable liquid, and powder
  • Ingested, snorted, smoked, or injected when abused
  • Fast-acting and creates a short but intense rush
  • Synthetic opioid
  • Lethal in much smaller doses and can be absorbed through the skin and incidental contact
  • Highly addictive
  • Often requires medical detox and opioid replacement medications to safely process the drug out of the body
  • Comprehensive treatment ideal for long-term recovery

Dependence and Addiction

Both fentanyl and heroin are considered to be extremely addictive drugs. They can produce an intense and euphoric “high,” and dependence can form quickly. Once the brain becomes used to the presence of an opioid drug, the body will require the drug in order to function optimally. Significant withdrawal symptoms can occur when the drug wears off. These effects include depression, anxiety, irritability, agitation, insomnia, and physical symptoms similar to those experienced with the flu. It may seem better to just keep taking the drug than deal with these painful withdrawal symptoms, and this can quickly lead to an inability to control how much and how often the drug is taken. Compulsive drug use caused by altered brain chemistry as the result of regular drug abuse is the definition of addiction.

The American Society of Addiction Medicine (ASAM) publishes that nearly a quarter of people who use heroin will suffer from opioid addiction, and over 2.5 million Americans battled addiction to opioids in 2015.

Both fentanyl and heroin are dangerous and powerful opioid drugs, and comprehensive addiction treatment is needed to address addiction to these substances. There are several medications that are FDA-approved to treat opioid dependence (suboxone, methadone, buprenorphine, naltrexone), and these pharmaceutical tools, combined with behavioral therapies, are often beneficial in managing the cravings and withdrawal symptoms of either substance.

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Overdose, Side Effects & Treatment

Overdose fatalities involving heroin or fentanyl are rising. The Centers for Disease Control and Prevention (CDC) reports that close to 30,000 Americans died from an opioid overdose in 2014. Overdose deaths from synthetic opioids like fentanyl nearly doubled from 2013 to 2014, and heroin overdose fatalities quadrupled from 2002 to 2013, the CDC publishes.

People may not even realize that the drug they are taking contains fentanyl, as it is often passed off as pure heroin. Fentanyl is more potent than heroin and can therefore cause a toxic buildup and lead to overdose faster and in lower doses. An opioid overdose becomes dangerous when breathing is slowed too much. Pulse also slows, body temperature drops, and individuals often become mentally confused, drowsy, and lethargic. Pinpoint pupils and potential loss of consciousness are further indicators of an opioid overdose.


Overdose on either fentanyl or heroin has the potential to be life-threatening, and overdoses on both substances can be reversed with the swift administration of the opioid antagonist naloxone (Narcan). Since fentanyl is more powerful in lower doses than heroin, it may take several doses of Narcan to reverse the toxic side effects.

Both heroin and fentanyl can cause long-term damage to the respiratory and cardiovascular systems as well as lead to potential brain damage and cognitive defects. Injecting these drugs increases the risk for contracting an infectious disease like hepatitis and HIV/AIDS and for collapsed veins, scarring and track marks, and skin abscesses.

Since both fentanyl and heroin are both short-acting opioid drugs, they may be replaced with a longer-acting opioid during detox and addiction treatment. Neither heroin nor fentanyl should ever be stopped cold turkey. An opioid withdrawal medication is often given and then slowly tapered off to to minimize withdrawal symptoms and cravings. Treatment for opioid addiction is similar for addiction to either fentanyl and heroin, often beginning with medical detox and followed with a complete care plan that addresses both the emotional and physical aspects of the disease.

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