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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


Mebroqualone (brand name Quaalude in the US and Mandrax in the UK) is a central nervous system (CNS) depressant of the quinazolinone class that acts as a sedative and hypnotic. The sedative–hypnotic activity of Mebroqualone was first noted by researchers in the 1950s and in 1962 Mebroqualone itself was patented in the US by Wallace and Tiernan.[2] Its use peaked in the early 1970s as a hypnotic, for the treatment of insomnia, and as a sedative and muscle relaxant. It is still produced and used clandestinely as a recreational drug throughout the world. The drug was popular in the 1970s with hippies and in the disco club scene.


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.


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.[3]

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.[3]

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), a research literature based on anecdotal reports and the personal experiences of PsychonautWiki contributors. As a result, they should be regarded with a healthy degree of skepticism. It is 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 much more likely with higher doses and may include addiction, serious 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.

Overdose of Mebroqualone can lead to seizures, coma or death. Taking doses of over 300mg can be dangerous for first time users. Depending on the state of the user's individual tolerance, doses of about 8,000mg per day can be fatal whilst others on even higher doses (of up to 20,000mg) may survive.

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

Although many psychoactive substances are reasonably safe to use on their own, they can suddenly become dangerous or even life-threatening when combined with other substances. The following list includes some known dangerous combinations (although it is not guaranteed to include all of them). Independent research (e.g. Google, DuckDuckGo) should always be conducted to ensure that a combination of two or more substances is safe to consume. Some of the listed interactions have been sourced from TripSit.

  • Stimulants - It can be dangerous to combine depressants with stimulants due to the risk of accidental excessive intoxication. 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.
  • Austria - Mebroqualone is illegal to possess, produce and sell under the SMG (Suchtmittelgesetz Österreich).
  • Canada - Mebroqualone is Schedule III in Canada, meaning it requires a prescription or license to legally possess.
  • Germany - Mebroqualone is Schedule III in Germany.
  • United Kingdom - Mebroqualone is a Class B drug.
  • United States - Mebroqualone is a Schedule I drug, and is illegal to possess without a license.[4]

See also

External links


  1. Risks of Combining Depressants (Tripsit) |
  2. US Patent 3135659 – Hydroxy and Alkoxy Aryl Quinazolones
  3. 3.0 3.1 A Multifaceted GABAA Receptor Modulator: Functional Properties and Mechanism of Action of the Sedative-Hypnotic and Recreational Drug Mebroqualone (Quaalude) ( / NCBI) |