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Methaqualone (Quaalude / Mandrax)

Depressantoral · inferred

Historically significant sedative-hypnotic from the 1960s-80s, infamously marketed as Quaalude in the US and Mandrax in South Africa. Positive allosteric modulator at GABA-A (barbiturate-like site, distinct from benzodiazepine site) with unique euphoric/sedative profile. Weak PCP-site NMDA antagonist contributing to dissociative-tinged sedation. Long and highly variable half-life (20-60h). Manufactured illicitly in South Africa as Mandrax (often smoked with cannabis as "white pipe") where it remains widely abused. The 1970s Quaalude epidemic in the US led to its Schedule I classification.

Projected serum levels — 150 mg, as needed (shown daily)

Methaqualone (Quaalude / Mandrax)
Methaqualone (Quaalude / Mandrax) modeled serum levels, 150 mg as needed (shown daily) over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 5 days. 0 125 250 375 500 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 5
Methaqualone (Quaalude / Mandrax) modeled serum levels with a loading dose of 437 mg, then 150 mg as needed (shown daily) The first dose is larger so levels approach steady state faster. 0 125 250 375 500 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 150 mg as needed (shown daily) (oral).

Loading schedule: 437 mg on day 1, then 150 mg as needed (shown daily) — reaching therapeutic levels sooner.

Modeled steady state after ~5 days: peak ≈ 373 mg, trough ≈ 256 mg body load. Population-based estimate over 15 days for a 150 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Depressant
Route modeled
Oral
Model confidence
inferred
Half-life
40 h
Common dose
150 mg
Suggested maximum
300 mg/day
Reference dose range
75–300 mg (single dose)
Suggested cadence
as needed (shown daily)

Documented interactions

  • contraindicated
    Carbamazepine (Tegretol) + Methaqualone (Quaalude / Mandrax) CYP induction

    Carbamazepine (Tegretol) inducer of CYP3A4 predicted to change Methaqualone (Quaalude / Mandrax) AUC by ~0.20x

  • contraindicated
    Clarithromycin (Biaxin) + Methaqualone (Quaalude / Mandrax) CYP inhibition

    Clarithromycin (Biaxin) mechanism_based of CYP3A4 predicted to change Methaqualone (Quaalude / Mandrax) AUC by ~10.00x

  • contraindicated
    Dasatinib (Sprycel) + Methaqualone (Quaalude / Mandrax) CYP inhibition

    Dasatinib (Sprycel) time_dependent_inhibitor of CYP3A4 predicted to change Methaqualone (Quaalude / Mandrax) AUC by ~5.00x

  • contraindicated
    Diltiazem + Methaqualone (Quaalude / Mandrax) CYP inhibition

    Diltiazem mechanism_based of CYP3A4 predicted to change Methaqualone (Quaalude / Mandrax) AUC by ~10.00x

  • contraindicated
    Efavirenz (Sustiva) + Methaqualone (Quaalude / Mandrax) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Methaqualone (Quaalude / Mandrax) AUC by ~0.12x

  • contraindicated
    Grapefruit (whole fruit) + Methaqualone (Quaalude / Mandrax) CYP inhibition

    Grapefruit (whole fruit) mechanism_based of CYP3A4 predicted to change Methaqualone (Quaalude / Mandrax) AUC by ~10.00x

Serum checks 77 modeled interaction pairings for methaqualone (quaalude / mandrax) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Therapeutic and toxic blood concentrations of more than 800 drugs and other xenobiotics Schulz M et al. · Pharmazie, 2012

    Reference compilation including methaqualone blood concentration data: therapeutic range 1-3 mg/L, toxic >8 mg/L, lethal >10 mg/L. Wide therapeutic index but fatal overdoses documented.

  2. Mandrax abuse in South Africa — a review of the problem Bhana A et al. · South African Medical Research Council, 2002

    Comprehensive review documenting the ongoing Mandrax (methaqualone) epidemic in South Africa, where it remains one of the most widely abused illicit drugs, typically smoked in combination with cannabis ("white pipe").

2 published studies referenced in the app, each with a plain-language summary.