Updated on February 3, 2023
6 min read

Phenazepam Dosage, Risks, and Treatment

What is Phenazepam?

Phenazepam (fenazepam) is a long-acting benzodiazepine and psychoactive drug.

Benzodiazepines have anxiolytic and sedative effects on the body and central nervous system (CNS). This leads to feelings of calm and relaxation. Phenazepam is sold illegally as a fine white powder or liquid.

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

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

Phenazepam is sometimes sold online and in retail stores as an entirely different product, including:

  • Incense
  • Air fresheners
  • A “research chemical”

Street names for phenazepam include:

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

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How is Phenazepam Used?

Phenazepam was developed in the Soviet Union for the treatment of anxiety and other psychiatric disorders. It was first prescribed in 1978. The drug is still used in Russia and the Commonwealth of Independent States (CIS) countries.

Phenazepam is also 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.

Additionally, phenazepam is used to treat a range of problems, including:

  • Alcohol withdrawal: Symptoms that occur when someone who is alcohol-dependent stops or drastically reduces their intake.
  • Insomnia: A habitual difficulty falling and/or staying asleep.
  • Panic disorders: Anxiety disorders that bring about frightening and recurring panic attacks. Symptoms may include increased heart rate, shortness of breath, and overwhelming fear.

Phenazepam can treat certain neurological disorders and 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.

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

  • Acid
  • Speed
  • Ecstasy

Taking any drug in this way is extremely dangerous. It can lead to an overdose or death, especially in high doses.

Phenazepam Cost

The price of phenazepam at Russian pharmacies ranges from $1.55 to $2.54 for tablets. It costs between $2.25 to $3 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, buying prescription drugs illegally is extremely dangerous and never recommended.

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Phenazepam Dosage

In countries where doctors prescribe phenazepam, doses generally come in tablets of 0.5 to 1 mg. They also come as transdermal patches or an injectable solution.

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

However, it still carries the following risks linked with benzodiazepines:

  • Addiction
  • Overdose
  • Withdrawal symptoms

Additionally, the drug is ten times more potent than diazepam. Higher doses are sometimes prescribed for severe anxiety or epileptic seizures.

Side Effects of Phenazepam

There's a range of possible side effects from minor to extremely serious and warranting emergency help.

More general side effects that may stop naturally or with adjusted dosages include:

  • Drowsiness
  • Confusion
  • Headaches
  • Retrograde amnesia

More severe side effects can arise. This is especially true if you take phenazepam in large doses:

  • Suicidal thoughts
  • Loss of coordination
  • Severely depressed heart rate
  • Liver damage
  • Potentially severe lowered white blood count
  • Accidental overdose
  • Respiratory depression and coma

How Long Does Phenazepam Stay in Your System?

Phenazepam has a half-life of up to 60 hours.7 This is because phenazepam is a long-acting benzodiazepine. 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.

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Phenazepam Interactions, Risks & Addiction Symptoms

Phenazepam can be extremely dangerous or deadly when misused or in combination with alcohol and other CNS depressants.

CNS depressants include:8

  • Barbiturates
  • Benzodiazepines
  • Sedatives
  • Alcohol
  • Opioids
  • Gamma-Hydroxybutyric Acid (commonly called GHB)
  • Tricyclic antidepressants
  • First-generation antihistamines

In the U.S., the U.K., and other countries where phenazepam is illegal, people who obtain it risk ingesting unknown and harmful additives.

When illegally obtained, it is often already combined with other intoxicants. For example, synthetic cannabinoid products. Phenazepam can have a more neutralizing effect with stimulants such as cocaine.

Even when prescribed, the drug requires particular caution for:

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

Phenazepam Withdrawal

Discontinuing even a short-term dose of phenazepam can potentially cause many difficult withdrawals. This is especially true if discontinuation is improperly tapered.

These symptoms include:

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

Phenazepam Abuse & Physical Addiction

Phenazepam has a high potential for dependency and abuse. As such, phenazepam is generally prescribed short-term.

Early signs of addiction can be hard to distinguish from general side effects, including:

  • Headaches
  • Confusion
  • Fatigue

More severe signs of abuse include:

  • Depression
  • Anxiety
  • Brain damage
  • Suicidal behaviors

Often, phenazepam addiction comes with other problems like:

  • Withdrawal symptoms when unable to obtain the drug
  • Uncharacteristic, dangerous, and illegal behaviors undertaken to obtain or use the substance
  • Adverse effects in their financial, social, professional, and other components of life

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

— Drug Enforcement Administration, Diversion Control Division Drug & Chemical Evaluation Section

Symptoms of Phenazepam Overdose

When overdosed, phenazepam is extremely dangerous and potentially fatal.

The dose of phenazepam required to cause an overdose differs depending on a person’s tolerance to the drug. The maximum safe dosage of phenazepam is 10mg per day.7

Illegal users often take benzodiazepines with other intoxicants and CNS depressants.

This greatly increases the risk of experiencing overdose symptoms, which include:

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

Addiction Treatment Options

Abrupt discontinuation of phenazepam leads to a withdrawal syndrome. However, structured tapering may be necessary for those addicted to the drug.

The most basic way of managing a dependency is usually staged dispensing. This is when a medical provider provides small prescriptions to someone frequently. A tapering method like this prevents them from taking large doses.

In many countries, phenazepam is illegal, and addiction to the drug often requires serious treatment.

Treatment approaches vary, as does their success with different people. Any treatment programs or routines should be evidence-based with a proven history of success.

Treatment plans for phenazepam include:

  1. The slow taper of safer, replacement substances
  2. Addiction recovery services matched to the severity of addiction
  3. Resources available to help patients

The range of addiction recovery settings and services include:

Partial Hospitalization Programs

This treatment option is for high-risk situations of detoxification that require constant monitoring and access to medical services.

Inpatient Treatment

Short-term detox and longer-term treatment programs may help those who need significant daily lifestyle changes and support.

These programs can range from one week to several months. Most long-term treatments last from one to three months.

Outpatient Treatment

People who can continue their daily lives while tapering and recovering from phenazepam addiction may be best served in outpatient programs. These programs offer a range of treatment and support programs with less disruption to the person's life.


Addiction and its linked behaviors affect a person's psychological state. Regardless of the treatment method one uses, therapy is helpful in the recovery process. It's a central part of comprehensive treatment programs.

Peer Support and Mentorship

Peer support is often a positive and powerful addition to addiction treatment. Mentorship from peers can also help.

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Updated on February 3, 2023
8 sources cited
Updated on February 3, 2023
  1. Authier, N., et al. "Benzodiazepine dependence: focus on withdrawal syndrome." Annales pharmaceutiques francaises. Vol. 67. No. 6. Elsevier Masson, 2009
  2. Brett, Jonathan, and Bridin Murnion. "Management of benzodiazepine misuse and dependence." Australian prescriber 38.5 : 152
  3. “Depressant.” Taxonomy, United States Drug Enforcement Administration
  4. Drug and Chemical Evaluation Section. “Phenazepam (Street Names: Bonsai, Soviet Benzo, Fenaz, Panda).” Diversion Control Division. Drug Enforcement Administration, July, 2019
  5. Lann, Meredith A., and D. Kimberley Molina. "A fatal case of benzodiazepine withdrawal." The American journal of forensic medicine and pathology 30.2 : 177-179
  6. Maskell, Peter D et al. “Phenazepam: the drug that came in from the cold.” Journal of forensic and legal medicine vol. 19,3 : 122-5
  7. Phenazepam (Street Names: Bonsai, Soviet Benzo, Fenaz, Panda), World Health Organization (WHO), November 2015
  8. Prescription CNS Depressants, National Institute on Drug Abuse (NIH), March 2018

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