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Fatal overdose may occur when GABAergic substances are combined with other depressants such as opiates, benzodiazepines, barbiturates, gabapentinoids, thienodiazepines or alcohol.[1]

It is strongly discouraged to combine these substances, particularly in common to heavy doses.

Summary sheet: Mebroqualone
Chemical Nomenclature
Common names Mebroqualone
Substitutive name Mebroqualone
Systematic name 3-(2-bromophenyl)-2-methylquinazolin-4(3H)-one
Class Membership
Psychoactive class Depressant
Chemical class Quinazolinone
Routes of Administration

WARNING: Always start with lower doses due to differences between individual body weight, tolerance, metabolism, and personal sensitivity. See responsible use section.

Threshold 2 mg
Light 2 - 4 mg
Common 4 - 8 mg
Strong 8 - 12 mg
Heavy 12mg +
Total 1 - 2 hours
Onset 10 - 20 seconds
Threshold 3 mg
Light 3 - 5 mg
Common 5 - 10 mg
Strong 10 - 15 mg
Heavy 15 mg +
Total 1 - 2 hours
Onset 20 - 30 minutes

DISCLAIMER: PW's dosage information is gathered from users and resources for educational purposes only. It is not a recommendation and should be verified with other sources for accuracy.


Mebroqualone is a central nervous system (CNS) depressant of the quinazolinone class that acts as a sedative and hypnotic.

Not much is known about this substance besides it being significantly more potent than methaqualone and shorter-lasting. It should be noted that mehaqualone and its derivatives are prone to dangerous side effects such as respiratory depression and convulsions.[citation needed] It is therefore highly suggested to use harm rediction practises if using this substance.


Mebroqualone, or 2-methyl-3-(2-methylphenyl)-4(3H)-quinazolinone, is a compound of the quinazolinone class. Quinazolinone is a bicyclic structure containing a phenyl ring bound to another six-membered ring with two nitrogen members and a ketone group bound to R4. In Mebroqualone, this structure is substituted at R2 with a methyl group. Additionally, Mebroqualone contains a phenyl ring with a methyl group bound to R2 which is attached to the quinazolinone structure at R3.


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Despite prior speculation, a 2015 study demonstrates that Mebroqualone exhibits distinct functional properties at the GABA receptor sites compared with other allosteric modulators, and it mediates these through a different mechanism than the barbiturates and benzodiazepines that it historically has been lumped together with.[2]

These distinctions could contribute to the reported differences in the in vivo effects induced by Mebroqualone and classic CNS depressants. In any case, the multifaceted functionality of Mebroqualone at GABA A receptors seems to be at the root of its clinical efficacy, as well as the addiction liability and recreational use associated with the drug.[2]

It could be speculated that despite differences in targeted receptors, Mebroqualone essentially produces a variety of effects by binding to its receptor sites and magnifying the efficiency and effects of the neurotransmitter gamma aminobutyric acid (GABA) by acting on its receptors. As this site is the most prolific inhibitory receptor set within the brain, its modulation would explain the resulting sedating or calming effects which ensue.

Subjective effects

Disclaimer: The effects listed below cite the Subjective Effect Index (SEI), an open research literature based on anecdotal user reports and the personal analyses of PsychonautWiki contributors. As a result, they should be viewed with a healthy degree of skepticism.

It is also worth noting that these effects will not necessarily occur in a predictable or reliable manner, although higher doses are more liable to induce the full spectrum of effects. Likewise, adverse effects become increasingly likely with higher doses and may include addiction, severe injury, or death ☠.

Physical effects

Visual effects

Experience reports

There are currently no anecdotal reports which describe the effects of this compound within our experience index.

Toxicity and harm potential

Independent research should always be done to ensure that a combination of two or more substances is safe before consumption.

Although the exact lethal dosage of Mebroqualone has not been formally established, like many depressants, it is safe at appropriate dosages. Complications may arise when administered in excess or in combination with other depressants.

It is strongly recommended that one use harm reduction practices when using this substance.

Tolerance and addiction potential

Mebroqualone is extremely addictive. Tolerance to the sedative-hypnotic effects develops within a couple of days of repeated administration. After that, it takes about 3 - 7 days for the tolerance to be reduced to half and 1 - 2 weeks to be back at baseline (in the absence of further consumption). Mebroqualone presents cross-tolerance with all gabaergic depressants, meaning that after the consumption of Mebroqualone all compounds of the same class will have a reduced effect.

Abrupt discontinuation of Mebroqualone following regular dosing over several days can result in a withdrawal phase which includes rebound symptoms such as increased anxiety and insomnia. It is possible to gradually reduce the dose over the course of several days, which will lengthen the duration of the withdrawal period but reduce the perceived intensity.

Dangerous interactions

Warning: Many psychoactive substances that are reasonably safe to use on their own can suddenly become dangerous and even life-threatening when combined with certain other substances. The following list provides some known dangerous interactions (although it is not guaranteed to include all of them).

Always conduct independent research (e.g. Google, DuckDuckGo, PubMed) to ensure that a combination of two or more substances is safe to consume. Some of the listed interactions have been sourced from TripSit.

  • Depressants (1,4-Butanediol, 2M2B, alcohol, benzodiazepines, barbiturates, GHB/GBL, methaqualone, opioids) - This combination potentiates the muscle relaxation, amnesia, sedation, and respiratory depression caused by one another. At higher doses, it can lead to a sudden, unexpected loss of consciousness along with a dangerous amount of depressed respiration. There is also an increased risk of suffocating on one's vomit while unconscious. If nausea or vomiting occurs before a loss of consciousness, users should attempt to fall asleep in the recovery position or have a friend move them into it.
  • Dissociatives - This combination can unpredictably potentiate the amnesia, sedation, motor control loss and delusions that can be caused by each other. It may also result in a sudden loss of consciousness accompanied by a dangerous degree of respiratory depression. If nausea or vomiting occurs before consciousness is lost, users should attempt to fall asleep in the recovery position or have a friend move them into it.
  • Stimulants - Stimulants mask the sedative effect of depressants, which is the main factor most people use to gauge their level of intoxication. Once the stimulant effects wear off, the effects of the depressant will significantly increase, leading to intensified disinhibition, motor control loss, and dangerous black-out states. This combination can also potentially result in severe dehydration if one's fluid intake is not closely monitored. If choosing to combine these substances, one should strictly limit themselves to a pre-set schedule of dosing only a certain amount per hour until a maximum threshold has been reached.

Legal status

  • Australia - Mebroqualone is Schedule 9 in Australia, meaning it is illegal without a license and deemed to have no medical value.[citation needed]
  • Austria - Mebroqualone is illegal to possess, produce and sell under the SMG (Suchtmittelgesetz Österreich).[citation needed]
  • Canada - Mebroqualone is Schedule III in Canada, meaning it requires a prescription or license to legally possess.[citation needed]
  • Germany - Mebroqualone is Schedule III in Germany.[citation needed]
  • United Kingdom - Mebroqualone is a Class B drug.[citation needed]
  • United States - Mebroqualone is unscheduled in the United States. It may be considered an analogue of Mecloqualone, a Schedule I drug under the Controlled Substances Act. As such, the sale for human consumption or the use for illicit non-medical or industrial intents and purposes could be prosecuted as crimes under the Federal Analogue Act.[3]

See also

External links


  1. Risks of Combining Depressants - TripSit 
  2. 2.0 2.1 A Multifaceted GABAA Receptor Modulator: Functional Properties and Mechanism of Action of the Sedative-Hypnotic and Recreational Drug Mebroqualone (Quaalude) ( / NCBI) |