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Carisoprodol Facts

Depressant; Sedative; 1,3-Propanediol dicarbamate; GABA-A receptor positive allosteric modulator

Description

Carisoprodol — Soma — is a synthetic depressant of the propanediol dicarbamate class. It is a structural relative of meprobamate, modified to deliver muscle relaxation with reduced abuse liability. It amplifies inhibitory GABA signaling in the brain — and can open GABA receptors directly without GABA present — producing sedation, anxiety relief, and muscle relaxation.[1]

Subjective effects include sedation, anxiolysis, muscle relaxation, dizziness, and psychomotor impairment. The experience is defined by a heavy, body-dominant calm that blankets motor control and thought simultaneously — more physically engulfing than benzodiazepine sedation.[2]

Carisoprodol produces rapid physical dependence, and the gap between a therapeutic and fatal blood concentration is narrow.[3] Its active metabolite meprobamate accumulates with repeated dosing and compounds both dependence and overdose risk; combining carisoprodol with opioids increases overdose risk by 84%.[4]

Dose and durationby route · individual sensitivity varies

Oral(mg)
Threshold< 50 mgLight100 – 325 mgCommon325 – 500 mgStrong500 – 750 mgHeavy750+ mg

Starts in 15 – 60 minLasts 4 – 8 hoursAfter-effects 1 – 12 hours

Body and dependence

Acute toxicity
High
Chronic toxicity
High
Physical dependence
High
Psychological dependence
High
Withdrawal
Life-threatening · fatal · medical supervision
Compulsive redosing
Moderate

Tolerance

Builds
Moderate
Fully resets after
30 days
Carries over to
benzodiazepines; barbiturates; alcohol

Effectslikely at a common dose

Perception
none likely · 5 possible, including Spatial disorientation, Visual acuity suppression, Vestibular distortion
Body
Sedation; Motor control impairment; Muscle relaxation; Physical fatigue; +10 possible, including Dizziness, Nausea, Headache
Thinking
Cognitive impairment; +18 possible, including Analysis suppression, Decision impairment, Information processing suppression
Feeling
none likely · 3 possible
Self
none likely · 4 possible, including Communication suppression
Time
none likely · 2 possible, including Temporal disorientation

Who shouldn't take it

Absolute
Concurrent opioid use; CYP2C19 poor metabolizer status; Meprobamate or carisoprodol hypersensitivity
Relative
Concurrent benzodiazepine use; Respiratory compromise; Myasthenia gravis; Concurrent serotonergic agents; Severe hepatic impairment; CYP2C19 inhibitor co-administration; Pregnancy; Elderly patients (>65 years); Pediatric patients (<16 years); Concurrent alcohol use; Treatment duration exceeding 2-3 weeks

Combinations60 recorded

Lethal (1)
Opioids
Dangerous (21)
Alpha-2 adrenergic receptor antagonist; Antipsychotics; Atypical antipsychotics; Benzodiazepines; Buprenorphine, Kratom; Cannabis, THC; Clonidine, Guanfacine; Gabapentin, Pregabalin; GHB, Baclofen; GHB, GBL; Local anesthetics; Naltrexone; SNRIs; Stimulants; Synthetic cannabinoids; Ibogaine; Ketamine, DXM, PCP; MAOIs; NSAIDs; Poppers (Alkyl nitrites); Poppers, Nitrates
Caution (26)
See full page: psychedex.org/substances/carisoprodol
Not graded (12)
Not listed never means safe.

Seek help immediately if

  • Extreme drowsiness — can't stay awake or be roused
  • Confusion, slurred speech, severe loss of coordination
  • Slow, shallow, or irregular breathing
  • Unconsciousness / unresponsive; limp, floppy body
  • Blue lips or fingertips
  • Vomiting while sedated (choking / aspiration risk)
  • Cold, clammy skin; weak pulse

What to do

  1. Try to wake them — shout, firm sternal rub
  2. If unresponsive or breathing is impaired, call emergency services
  3. Place them in the recovery position — critical, they can choke on vomit
  4. Monitor breathing continuously; be ready to give rescue breaths / CPR
  5. Never leave them alone to "sleep it off"
  6. Do not give other drugs, stimulants, or more depressants

Most depressant overdoses resolve with airway protection, breathing support, and monitoring. The danger is respiratory depression and choking on vomit — sharply worse when combined with opioids or alcohol. GHB/GBL overdoses often involve sudden deep unconsciousness and may self-resolve, but airway protection is essential.

988 Suicide & Crisis LifelineFireside Project: 62-FIRESIDE

Version r1 · Not medical advice

References

  1. [1]
    ^Kumar M, Gonzalez LA, Dillon GH (2015) Assessment of subunit-dependent direct gating and allosteric modulatory effects of carisoprodol at GABA(A) receptors — Neuropharmacology doi:10.1016/j.neuropharm.2015.04.007
  2. [2]
    ^Zacny JP, Paice JA, Coalson DW (2011) Characterizing the subjective and psychomotor effects of carisoprodol in healthy volunteers — Pharmacology Biochemistry and Behavior doi:10.1016/j.pbb.2011.08.011
  3. [3]
    ^McIntyre IM, Sherrard J, Lucas J (2012) Postmortem carisoprodol and meprobamate concentrations in blood and liver: lack of significant redistribution — Journal of Analytical Toxicology doi:10.1093/jat/bks011
  4. [4]
    ^Li Y, Delcher C, Wei YJ, Reisfield GM, Brown JD, Tighe P, Winterstein AG (2020) Risk of Opioid Overdose Associated With Concomitant Use of Opioids and Skeletal Muscle Relaxants: A Population-Based Cohort Study — Clinical Pharmacology and Therapeutics doi:10.1002/cpt.1807
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