May 17, 2025, 9:32 am | Read time: 6 minutes
Originally developed as a medication for severe pain, fentanyl now has a dark side: The highly potent substance is increasingly being abused as a recreational drug—sometimes with deadly consequences. What makes this opioid so dangerous? It acts faster and more powerfully than heroin, carries an extreme risk of addiction, and is difficult to dose accurately. FITBOOK writer Julia Freiberger explains the effects and dangers of the substance.
In the U.S., fentanyl has caused a severe health crisis. Reports of dangerous misuse are also increasing in Germany–for example, in Halle or Dresden. Could fentanyl trigger a crisis in Germany as well?
Overview
What is Fentanyl?
Fentanyl is a synthetically produced opioid originally used to treat chronic and severe pain. It was developed in 1959 by Belgian chemist Paul Janssen and his team. Fentanyl belongs to the group of anilinopiperidines. In medical practice, it is commonly used for cancer patients or anesthesia–such as injections, nasal sprays, lozenges, or transdermal patches.1
Additionally, the World Health Organization (WHO) lists fentanyl as an essential medicine. Notably, the substance is about 100 times stronger than morphine and has an extremely narrow therapeutic range. Simply put, even slight deviations in dosage can be toxic. Two milligrams of intravenously administered fentanyl can potentially cause fatal respiratory paralysis.2
What are Opioids?
Opioids are prescription pain relievers that primarily act on the central nervous system—specifically in certain brain and spinal cord cells with opioid receptors. They block the transmission of pain signals. There are weaker substances like codeine or tramadol and stronger ones like morphine or fentanyl. Opioids can not only relieve severe pain but also have a calming effect. Stronger opioids often cause unpleasant side effects, such as constipation, nausea, dizziness, and fatigue.3
Where Does the Name “Zombie Drug” Come From?
The term “zombie drug” has become established mainly in the U.S. and describes the physical decay and movement disorders that occur with long-term use. Since fentanyl can cause muscle stiffness, affected individuals may only be able to move in a jerky, swaying, or uncoordinated manner. This is accompanied by mental lapses reminiscent of the behavior of the undead—hence the term “zombie drug.”
How is the Active Ingredient Administered?
Fentanyl can be administered in various ways, depending on how quickly the substance should take effect and how long its effects should last. Even small amounts are sufficient to relieve severe pain.
Intravenous Administration
When fentanyl is injected directly into a vein, it acts particularly quickly—often within five minutes. This method is frequently used during surgeries, such as to induce anesthesia or treat severe acute pain. It is often combined with sedatives or muscle relaxants.
Tablets and Sprays
Fentanyl is also available as lozenges, sublingual tablets (to dissolve under the tongue), buccal tablets (for use in the cheek pouch), or nasal sprays. These forms act particularly quickly—often within minutes—and are usually used for sudden, very severe pain, such as in cancer patients.
Transdermal Patches
The use of fentanyl via so-called transdermal patches is particularly widespread. These are patches applied to the skin that continuously release the substance over several days. The effect begins after about 12 to 24 hours and lasts up to 72 hours. This method is mainly suitable for people with persistent severe pain—but not for acute complaints.
What Effects Does Fentanyl Have?
Fentanyl enters the brain through the bloodstream and acts on opioid receptors. It blocks pain signals, calms, and induces a strong feeling of euphoria. The effect occurs very quickly, depending on the form of application.4 Typical physical effects include:
- Slowed breathing
- Calmness and drowsiness
- Slowed pulse
- Euphoria
- Gastrointestinal issues like constipation
- Dizziness, headaches
- Nausea, vomiting
- Heart rhythm disturbances
Psychological Effects
Fentanyl acts directly on the central nervous system and affects the brain’s reward system. It can trigger a strong sense of well-being that people want to experience repeatedly. The risk of psychological dependence is high, especially with abusive use.
What Are the Risks of Misuse?
Fentanyl carries a very high risk of physical and psychological dependence—even with medically prescribed use. Particularly dangerous is the combination with alcohol, sleeping pills, or other drugs—this can quickly lead to respiratory arrest.
Short-term Side Effects
- Nausea, vomiting, diarrhea, or constipation
- Drowsiness, dizziness
- Sleep disturbances, nervousness
- Heart rhythm disturbances
Medium-term Consequences
- Tolerance development: Increasing doses are needed
- Withdrawal symptoms when stopping use
- Anxiety, chills, restlessness
Long-term Effects:
- Social isolation
- Loss of job, family, stability
- Criminal activity to obtain drugs
- Life-threatening overdose5
Who Is Particularly at Risk?
Two groups are considered particularly at risk:
- Chronic pain patients who regularly take fentanyl over a long period. Even with correct medical use, tolerance and addiction can develop. Therefore, treatment should be as short as possible.
- Drug users who use fentanyl as a recreational drug. Often, used or illegally obtained patches are misused by being boiled and injected—with unpredictable risks. Since the exact dosage is not controlled, the risk of overdose is extremely high.
Symptoms of Fentanyl Addiction
Signs of a developing or existing addiction often include:
- Constant craving for the drug, even without pain
- Disregard for side effects
- Obsessive thoughts about the next dose
- Withdrawal symptoms when a dose is missed or stopped
(e.g., nausea, diarrhea, dizziness, insomnia)
The Opioid Crisis in the U.S.
In the United States, fentanyl has triggered an unprecedented health crisis since the mid-2010s. The substance is often mixed into illegal drugs like heroin, cocaine, or methamphetamine—often without the users’ knowledge. The result is a high number of overdoses. In 2023 alone, about 75,000 people in the U.S. died from fentanyl—accounting for three-quarters of all drug-related deaths. Fentanyl has thus become the leading cause of death among young adults aged 18 to 45.6
The crisis is not only due to misuse but also the extreme potency of the substance and illegal production—mainly in Asia. Large quantities reach North America via smuggling routes.
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Possible Consequences for Germany
In Germany, fentanyl is a prescription-controlled narcotic and is strictly regulated. Nevertheless, reports of misuse are increasing, especially in eastern Germany. In cities like Halle and Dresden, fentanyl has already been seized in illegal contexts—often in the form of active ingredient solutions extracted from patches.
It also happens that fentanyl is unknowingly consumed, such as when heroin or other substances are cut with the drug. The danger: An overdose in such cases is hardly predictable and can be fatal even in minimal amounts.
Although the number of cases in Germany is still significantly lower than in North America, experts warn of a possible increase. The rising number of medical prescriptions is seen as particularly critical—they indirectly increase availability in circulation. However, reliable figures on illegal consumption, deaths, or seizures are still lacking in Germany.7