Gamma hydroxybutyrate toxicity

Background
  • Abbreviation: GHB
  • Central nervous system depressant
  • Abused for:
    • Body building or sleep enhancement
    • euphoric, sexual, stimulant, and relaxant effects
    • Surreptitious drugging to facilitate sexual assault

Pharmacokinetics
  • effect starts 15*20min, peaks in 30*60 min,
  • lipid soluble, no protein binding so crosses BBB readily
  • elimination is dose dependant with half life of 20*50 min
  • The duration of GHB's clinical effects depends upon the dose, and ranges from 2.5 to 4 hours

Pharmacology
  • Is a metabolite and precursor of GABA
  • Interacts with GHB-specific receptors and also acts as a direct agonist of GABA-B receptors
  • Affects multiple neurotransmitter systems, including those of opioids, dopamine, serotonin, glutamate, and acetylcholine
  • Gamma butyrolactone (GBL) and 1,4 butanediol (BD) are GHB analogs that are rapidly metabolized to GHB after ingestion, with the same toxic and recreational effects

Clinical Features
  • cns and respiratory depression
  • also cardioa and gi symptoms
  • many times have cointoxicants
  • usually young white male from nightclub
  • can have nausea and vomiting, respiratory deprsn, bradycardia, seizure
  • get euphoria s hang over
  • can also get ataxia, nystagmus, somnolence and aggression
  • resp/ cns deprrsion resolves abruptly
  • resp depression worse with other cns depressants-alcohol
  • periods of apnea and hyperventilation-is periodic breathing
  • decreases respiratory rate but tidal vol increases so minute vol stable
  • can also have seizure but eeg shows no epileptiform changes
  • bradycardia, hypotension*ekg change occasionally but rare
  • also get vomitting, hypothermia

Clinical Course
  • recover 2-6 hrs
  • may be extubated and sent home
  • if longer than 6hr, look for other cause
  • can have cross tolerance with other drugs-alcohol and others that effect liver p450 cytochome oxidase system

Differential Diagnosis

Sedative/hypnotic toxicity

Drugs of abuse

Evaluation
  • Not detectable on routine toxicology screens

Management
  • supportive
  • look for coingestants and occult trauma
  • charcoal not helpful since rapidly absorbed and since can vomit and aspirate
  • protein bound so can use dialysis*but so short course usually do not need.

Antidotes

Disposition

See Also

References
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