Updated on April 3, 2024
6 min read

What Is Phenazepam?

Key Takeaways

What Is Phenazepam?

Phenazepam (fenazepam) is a long-acting benzodiazepine and psychoactive drug originally developed in the Soviet Union. 

Benzodiazepines have anxiolytic and sedative effects on the body, including the central nervous system (CNS). These effects lead to feelings of relaxation and calm. 

In the U.K., phenazepam is a prescription drug labeled as a Class C drug. These drugs are considered to be the least harmful of the controlled drugs. 

In the U.S., it is not classified as a controlled substance. However, it's still illegal to sell for human consumption.


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Why Is Phenazepam Abused?

Phenazepam is sometimes used as a recreational drug for its euphoric effects. It's also used for its ability to enhance the effects of opioids, which can be extremely dangerous.

Some people use depressant drugs like phenazepam to reduce the 'come down' of other substances like:

  • Acid
  • Speed
  • Ecstasy

Using the drug in this way can lead to overdose or death, especially in high doses. 

Phenazepam can also be used to make fake Valium (diazepam). In some cases, people have taken what they thought was a typical dose of Valium but was actually a high dose of phenazepam.

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What Are the Side Effects of Phenazepam?

There's a range of possible side effects, from minor to extremely serious, which require emergency help. The more common side effects of phenazepam include:

  • Drowsiness
  • Confusion
  • Headaches
  • Retrograde amnesia

These side effects may stop naturally or when your dosage is adjusted.

Severe Side Effects of Phenazepam Use

The more severe side effects of phenazepam occur when you take it in large doses, including:

  • Suicidal thoughts
  • Loss of coordination
  • Severely depressed heart rate
  • Liver damage
  • Significantly lowered white blood count
  • Accidental overdose
  • Respiratory depression
  • Coma

Phenazepam Risks

Phenazepam carries the same risks linked to benzodiazepines, including:

  • Drug addiction
  • Benzodiazepine dependence
  • Overdose
  • Benzodiazepine withdrawal symptoms

From 2008 to 2018, the United States Drug Enforcement Administration produced 562 reports that included illegal human consumption of phenazepam. The highest rates of illicit use were in 2013.

Symptoms of Phenazepam Overdose

When overdosed, phenazepam is extremely dangerous and potentially fatal. The dosage of phenazepam required to cause an overdose differs depending on a person’s tolerance to the drug. The maximum safe dosage of phenazepam is 10 mg per day.7

Illegal users often take benzodiazepines with other intoxicants and CNS depressants. This greatly leads to the increased risk of experiencing overdose symptoms and severe intoxication, which include:

  • Respiratory depression
  • Loss of consciousness
  • Inability to move or stand
  • Unresponsiveness
  • Slurred speaking
  • Delirium
  • Death

What Substances Does Phenazepam Interact With?

Phenazepam can be extremely dangerous or deadly when misused or combined with alcohol and other depressants. These substances include:8

  • Barbiturates
  • Other benzodiazepines
  • Sedatives
  • Opioids
  • Gamma-hydroxybutyric acid (commonly called GHB)
  • Tricyclic antidepressants
  • First-generation antihistamines

When illegally obtained, it's often combined with other drugs, like synthetic cannabinoid products. Phenazepam can also have a more neutralizing effect with stimulants such as cocaine.

Other Names for Phenazepam

Phenazepam is also known under the following street names:

  • Bonsai
  • Bonsai Supersleep
  • Soviet Benzo
  • Fenaz
  • Panda

How Is Phenazepam Used?

Although benzodiazepines are widely used prescription drugs, phenazepam doesn't have an accepted medical use in the U.S. However, the drug is still used in European countries like Russia and the Commonwealth of Independent States (CIS) to treat the following:

  • Alcohol withdrawal syndrome
  • Insomnia
  • Panic disorders and anxiety
  • Epilepsy

It also works as an anticonvulsant. However, the drug's powerful anti-anxiety and muscle relaxant properties make it twice as likely to be abused.

Phenazepam Dosage

The recommended dose generally comes in 0.5 mg to 1 mg tablets. They also come as transdermal patches or injectable solutions. Illegally, phenazepam is sold as a fine white powder or liquid. 

Higher doses may be associated with more significant toxic effects. The upper dosage limit for phenazepam is 10 mg.

The drug is ten times stronger than diazepam, with higher doses sometimes prescribed for severe anxiety or epileptic seizures.

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How Long Does Phenazepam Stay in Your Body?

Phenazepam has a half-life of up to 60 hours because it's a long-acting benzodiazepine.7 The drug can potentially delay the onset of withdrawal symptoms for up to five days.

The effects of phenazepam can take several hours to develop, so it's essential not to re-dose. People taking long-lasting benzodiazepines generally have greater success tapering off.

Who Is at Risk When Taking Phenazepam?

Some people may experience adverse effects when using the drug, even if it's legally prescribed. The following should avoid taking phenazepam:

  • Those with existing drug dependencies
  • Children
  • Older people
  • Pregnant women

What Are the Phenazepam Withdrawal Symptoms?

Discontinuing even a short-term dose of phenazepam can potentially cause difficult withdrawal symptoms, especially if you suddenly stop using it without tapering.

Phenazepam withdrawal symptoms include:

  • Depression
  • Anxiety
  • Insomnia
  • Irritability
  • Restlessness, tremors, and muscle twitching/spasms
  • Hallucinations
  • Cognitive and memory impairment
  • Panic attacks

What Are the Signs of Phenazepam Abuse & Addiction?

Phenazepam has a high potential for dependency and abuse. Because of this, it's generally prescribed short-term.

The early signs of addiction can be difficult to distinguish from general side effects. Because of this, talking to your doctor when you experience side effects is important.

Signs of phenazepam addiction include:

  • Headaches
  • Confusion
  • Fatigue
  • Depression
  • Anxiety
  • Brain damage
  • Suicidal behaviors
  • Risky behavior
  • Legal or financial troubles
  • Problems at work or school
  • Neglecting familial or social obligations

How Can You Taper Off Phenazepam?

If phenazepam use is discontinued abruptly, you may experience withdrawal symptoms. Because of this, you'll need structures tapering to stop using the drug. This is especially necessary for people who've become addicted to the drug.

The most basic way of managing a dependency is usually staged dispensing. Medical providers would give out small prescriptions to someone frequently through staged dispensing. A tapering method like this prevents them from taking large doses.

What Are the Treatment Options for Phenazepam Drug Addiction?

Treatment approaches and their effectiveness vary with different people. A treatment program that works for you may not work for someone else.  

You should talk to a doctor or an addiction specialist when getting treatment for phenazepam addiction. They can provide recommendations for programs that cater to your needs.

Available addiction treatment options include:

How Much Does Phenazepam Cost?

Phenazepam prices at Russian pharmacies range from $1.55 to $2.54 for tablets. It costs between $2.25 to $3.00 for the intramuscular injection solution.

You can't buy phenazepam in the U.S. because it's an unapproved medicine. All phenazepam suppliers are illegal.

Others decide to buy phenazepam legally online using Google and other search engines. However, illegally purchasing prescription drugs is extremely dangerous and never recommended.


Phenazepam (fenazepam) is a powerful, long-acting benzodiazepine. It has a sedative effect on the central nervous system (CNS), leading to feelings of relaxation and euphoria.

Phenazepam treats alcohol withdrawal, anxiety, and panic disorders in Russia and other CIS countries. However, it has no accepted use in the U.S. and is considered an illegal drug there. 

It's occasionally used as a recreational drug in the U.S. for its euphoric effects. However, abusing phenazepam can lead to severe adverse effects and be fatal.

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Updated on April 3, 2024
8 sources cited
Updated on April 3, 2024
  1. Votaw et al. “The epidemiology of benzodiazepine misuse: A systematic review.” Drug and Alcohol Dependence, 2019.
  2. Brett, J., and Bridin, M. "Management of benzodiazepine misuse and dependence." Australian Prescriber, 2015.
  3. U.S. Department of Justice. “Depressants.” United States Drug Enforcement Administration, 2023.
  4. Drug and Chemical Evaluation Section. “Phenazepam (Street Names: Bonsai, Soviet Benzo, Fenaz, Panda).” Diversion Control Division, Drug Enforcement Administration, 2023.
  5. Lann, M., and Molina, K. "A fatal case of benzodiazepine withdrawal." The American Journal of Forensic Medicine and Pathology, 2009.
  6. Maskell et al. “Phenazepam: the drug that came in from the cold.” Journal of Forensic and Legal Medicine, 2012.
  7. Phenazepam.” Release Legal Emergency & Drugs Service Ltd. 
  8. U.S. Department of Health and Human Services. “Prescription CNS Depressants DrugFacts .” National Institute on Drug Abuse, 2018.

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