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Updated on August 12, 2021

Phenazepam Dosage, Risks, and Treatment

What is Phenazepam?

Phenazepam (fenazepam) is a long-acting benzodiazepine and psychoactive drug. Benzodiazepines produce anxiolytic and sedative effects on the body and central nervous system (CNS), resulting in feelings of calm and relaxation. Phenazepam is sold as a fine white powder or liquid.

In the U.S., phenazepam is not classified as a controlled substance but is nonetheless illegal to sell for human consumption. This drug is considered a class C drug in the U.K., which means it has the least risk for harm.

This legal gray area has allowed it to gain popularity as an illicit drug that is sometimes sold online and in retail stores as entirely different products, such as incense, air fresheners, or a “research chemical.”

Street names for phenazepam include:

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

What is Phenazepam used for?

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

The drug is also used to make fake Valium (diazepam). In many cases, people have taken what they thought was a usual Valium dose but is a high dose of phenazepam.

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

  • Alcohol withdrawal syndrome — the range of physical and emotional challenges 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 debilitating and recurring panic attacks, which may include increased heart rate, shortness of breath, and overwhelming fear

Phenazepam can also treat certain neurological disorders, epilepsy, and also works as an anticonvulsant. However, the powerful anti-anxiety and muscle relaxant properties of the drug make it twice as likely to be abused.

Some people may use depressant drugs like phenazepam to help them to come down off other drugs like acid, speed, or ecstasy after a big night.

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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.

In the United States, it is not possible to purchase phenazepam because it is not an approved medicine. Some people look for an illegal phenazepam supplier in the United States. Others decide to buy phenazepam legally online using Google and other search engines. However, buying prescription drugs illegally is extremely dangerous and never recommended.

Phenazepam Dosage

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

While the toxicity of phenazepam is relatively low in relation to dosage, it still carries the addiction, overdose, and withdrawal risks associated with benzodiazepines. Additionally, the drug is potent at one-tenth of the normal dose of diazepam.

Higher doses of phenazepam are sometimes prescribed for severe anxiety or epileptic seizures.

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Side Effects of Phenazepam

There are a range of possible side effects from minor to extremely serious and warranting emergency help. More general side effects that may subside naturally or with adjusted dosages include:

  • Drowsiness
  • Confusion
  • Headaches
  • Retrograde amnesia

More severe side effects can appear, especially if a user takes phenazepam in big doses or without a prescription:

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

Some people use phenazepam as a "chill out drug" when they are coming down from speed, ecstasy, or acid. Taking the drug in this way is extremely dangerous and can lead to an overdose or death, especially when taken in high doses.

How Long Does Phenazepam Stay in Your System?

Phenazepam has a half-life of up to 60 hours, making it among longer-lasting benzodiazepines and potentially delaying the onset of withdrawal symptoms for up to five days. The effects of Phenazepam can take several hours to develop so it is important not to re-dose.

People taking long-lasting benzodiazepines generally have greater success tapering off their usage.

Phenazepam Interactions, Risks & Addiction Symptoms

As with other benzodiazepines, phenazepam can be extremely dangerous or deadly when misused or in combination with alcohol and other Central Nervous System (CNS) depressants. In the U.S., the U.K., and other countries where phenazepam is illegal or not approved for humans, consumers who obtain it are at risk of ingesting unknown and harmful additives.

Even when prescribed, it requires special caution for those with existing drug dependencies, as well as children, the elderly, and pregnant women.

Drug Interactions

As with all benzodiazepines, the use of phenazepam in combination with other drugs and tranquillisers that are central nervous system (CNS) depressants is especially dangerous and is the primary cause of death associated with phenazepam use.

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

CNS depressants include barbiturates, benzodiazepines, sedatives, alcohol, opioids, and Gamma-Hydroxybutyric Acid (commonly called GHB).

Phenazepam Withdrawal

Discontinuing even a short-term, therapeutic dose of phenazepam can potentially cause many difficult withdrawal symptoms if discontinuation is improperly tapered. These symptoms include:

  • Depression
  • Anxiety
  • Insomnia
  • Irritability
  • Restlessness, tremors, and muscle spasms
  • Visual, auditory, and tactile hallucinations
  • Cognitive and memory impairment
  • Panic attacks

Phenazepam Abuse & Physical Addiction

Due to its high potential for dependency and abuse, phenazepam is generally prescribed short-term. Early signs of addiction can be hard to distinguish from general side effects, including such things as headaches, confusion, and fatigue. More severe signs of abuse include depression, anxiety, brain damage, and suicidal behaviors.

Often, phenazepam addiction accompanies other difficulties, such as:

  • Withdrawal symptoms when unable to obtain the drug
  • Uncharacteristic, dangerous, and illegal behaviors undertaken to obtain or use the substance
  • Rippling 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, with the highest rates in 2013.

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

Symptoms of Phenazepam Overdose

When overdosed, benzodiazepines such as phenazepam are extremely dangerous and potentially fatal. This is in part because the threshold for overdose is dependent on a person’s existing tolerance.

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.

Illegal users often take benzodiazepines with other intoxicants and CNS depressants, greatly increasing 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

The proper tapering of a prescribed schedule of phenazepam will mitigate many effects of withdrawal; however, where addiction has developed by illicit use or long-term treatment, more structured treatment options become necessary.

For those who are prescribed phenazepam or other benzodiazepines, the most basic way of managing a dependency might be the implementation of staged dispensing. This is a practice where a medical provider issues small prescriptions to a patient on a frequent basis, preventing them from taking large doses and forcing them to taper.

In the U.S., U.K., China, and elsewhere, any use of phenazepam is illegal and likely in the context of benzodiazepine addiction needing serious treatment. Treatment approaches vary as does their success with different individuals, but any treatment programs or routines should be evidence-based and have a demonstrated history of success.

Treatment plans for phenazepam will include two broad components:

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

The range of addiction recovery settings and services include:

Partial Hospitalization Programs

This treatment option is appropriate in 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 be appropriate for those who need significant daily lifestyle changes and support. These programs can range from one week to several months, with most long-term treatments lasting one to three months.

Outpatient Treatment

Patients who are able to continue their daily lives while tapering and recovering from phenazepam addiction may be best served in outpatient programs that offer a range of intensities and support programs with less disruption to the patient’s life.


Addiction and its associated behaviors are impacted by, and have an impact on, one’s psychological state. Regardless of the treatment method one uses, therapy is a helpful tool in the recovery process and a central part of comprehensive treatment programs.

Peer Support and Mentorship

While not necessarily direct treatment, peer support in group settings or informally, as well as peer mentorship, are often positive and powerful additions to a treatment protocol.

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Authier, N., et al. "Benzodiazepine dependence: focus on withdrawal syndrome." Annales pharmaceutiques francaises. Vol. 67. No. 6. Elsevier Masson, 2009,

Brett, Jonathan, and Bridin Murnion. "Management of benzodiazepine misuse and dependence." Australian prescriber 38.5 (2015): 152,

“Depressant.” Taxonomy, United States Drug Enforcement Administration,

Drug and Chemical Evaluation Section. “Phenazepam (Street Names: Bonsai, Soviet Benzo, Fenaz, Panda).” Diversion Control Division. Drug Enforcement Administration, July, 2019.

Lann, Meredith A., and D. Kimberley Molina. "A fatal case of benzodiazepine withdrawal." The American journal of forensic medicine and pathology 30.2 (2009): 177-179,

Maskell, Peter D et al. “Phenazepam: the drug that came in from the cold.” Journal of forensic and legal medicine vol. 19,3 (2012): 122-5,

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