Methylnaltrexone
Severe
Textbook
Increased rates of accidental overdose and death.
Caution is advised, especially for patients with a history of drug abuse.
Source: G&G 14e
Drug reference
Meprobamate
Anxiolytic / sedative-hypnotic (carbamate; largely withdrawn) · Sedative-Hypnotic
START
Use discouraged (largely withdrawn); 400 mg TID if essential
TYPICAL MAX
2400 mg/day (historical)
STOP IF
Any rash/hypersensitivity, sedation, or dependence signs
WATCH
Sedation, skin, dependence; safer alternatives preferred
CDSCO restrictedSchedule HATC N05BC01
KDIGO 2024 + manufacturer label
- ONSET
- 45min · absorption
- PEAK
- 2h · Tmax
- t½
- 10h · t½
- DURATION
- 7h · per dose
EXCRETION
Renal — ~10% unchanged + metabolites
route + CYP
INTERACTIONS
12 major
SEVERE in our sources
PREGNANCY
Avoid; cleft-palate signal in animal studies.
FDA category + note
Top interactionssee all 12 →
- MethylnaltrexoneSevereTextbookG&G 14e
- NalmefeneSevereTextbookG&G 14e
- NaloxoneSevereTextbookG&G 14e
- NaltrexoneSevereTextbookG&G 14e
Mechanism
Carbamate that enhances GABAergic neurotransmission (poorly defined site distinct from benzodiazepines/barbiturates), producing sedation and anxiolysis; high dependence/overdose potential.
Indications
Historical: short-term anxiety. Largely WITHDRAWN/restricted due to addiction/abuse, overdose toxicity, and severe skin reactions (SJS); EMA recommended withdrawal 2012.
Dosing
- Adult
- Historical: 400 mg PO 3–4 times daily; max 2400 mg/day. Use discouraged/withdrawn.
- Pediatric
- Not recommended.
- Renal adjustment
- Reduce / avoid in significant impairment.
- Hepatic adjustment
- Reduce / avoid in significant impairment.
- Geriatric
- Avoid (Beers criteria — falls, cognition, dependence).
- Max dose
- 2400 mg/day (historical ceiling)
Pharmacokinetics
Onset
~30–60 min
Peak effect
~1–3 h
Duration
~6–8 h
Half-life
~6–17 h
Bioavailability
Well absorbed orally
Protein binding
~20%
Metabolism
Hepatic CYP2C19 + glucuronidation
Excretion
Renal (~10% unchanged + metabolites)
Contraindications
- Acute intermittent porphyria
- History of drug/alcohol dependence
- Severe respiratory insufficiency
- Hypersensitivity
- Use generally not recommended (withdrawn)
Side effects
Common
DrowsinessDizzinessHeadacheSlurred speechNausea
Serious
- Severe skin reactions (SJS/TEN)
- Dependence / abuse
- Respiratory depression (overdose)
- Death in overdose (narrow therapeutic index)
Pregnancy & lactation
Pregnancy
Avoid; cleft-palate signal in animal studies.
Lactation
Avoid (excreted in milk; neonatal sedation/dependence).
Drug interactions
Nalmefene
Severe
Textbook
Increased rates of accidental overdose and death.
Caution is advised, especially for patients with a history of drug abuse.
Source: G&G 14e
Naloxone
Severe
Textbook
Increased rates of accidental overdose and death.
Caution is advised, especially for patients with a history of drug abuse.
Source: G&G 14e
Naltrexone
Severe
Textbook
Increased rates of accidental overdose and death.
Caution is advised, especially for patients with a history of drug abuse.
Source: G&G 14e
Other Cns Depressants
Severe
Textbook
Typically fatal if combined in overdose.
Use with extreme caution; avoid if possible.
Source: G&G 14e
Alfentanil
Severe
Database
Increased rates of accidental overdose and death.
Caution is advised, especially for patients with a history of drug abuse.
Source: DDInter
Benzhydrocodone
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Buprenorphine
Severe
Database
Increased rates of accidental overdose and death.
Caution is advised, especially for patients with a history of drug abuse.
Source: DDInter
Butorphanol
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Codeine
Severe
Database
Increased rates of accidental overdose and death.
Caution is advised, especially for patients with a history of drug abuse.
Source: DDInter
Dextropropoxyphene
Severe
Database
Clinical effect not specified
Source: DDInter
Dezocine
Severe
Database
Clinical effect not specified
Source: DDInter
Related guidelines
Ask House about Meprobamate
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: Goodman & Gilman 14e, BNF·Verified: 2026-05-20 · House clinical team·Cockpit curated: 2026-05-20