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ghb

gamma hydroxybutyrate (GHB)

introduction

  • a naturally occurring substance similar in structure to GABA, the neurotransmitter.
  • GHB is found in the brain, particularly in the basal ganglia, and readily crosses the blood brain barrier and placenta.
  • 1st synthesised in 1960 and was initially investigated as a potential anaesthetic agent as it could rapidly induce a deep coma with minimal cardiovascular or respiratory depressant effects but lacked analgesic properties and also caused seizure-like activity which limited its clinical usage.
  • In Europe, it is still used as an anesthetic, for alcohol and opiate addiction therapy, and for narcolepsy therapy.
  • body builders started using GHB as a food supplement in the 1980's as a fat burner and growth hormone promoter when L-tryptophan was withdrawn from the market.
  • FDA prohibited the sale and manufacture of GHB in 1990 but it was still available on the internet at least until 1999 when the FDA took further actions.
  • GHB is readily made using sodium hydroxide to saponify the floor cleaning solvent, gamma butyrolactone, but runs the risk of caustic burns when ingested.
  • GHB is sold illicitly as a clear colorless liquid - powder dissolved in water and sold in plastic bottles (often small soy sauce squeeze bottles) usually holding about 10 hits and known on the street as juice, G, Liquid G, fantasy, grievous bodily harm, scoop, liquid ecstasy, cherry meth, growth hormone booster, liquid x, and Georgia homeboy.
  • often taken using a small syringe or eye dropper to measure dose
  • single doses are usually 1-3mL and doses are often taken every 1-2 hours
  • use of more than 10mL/day is significant use and use as high as 80mL/day is extremely high use

pharmacology

  • rapidly absorbed after ingestion
  • peak plasma concentration occur at about 20-30min following the ingestion of a 12.5 mg/kg dose and 30-60 minutes with a dose of 50 mg/kg.
  • the elimination half-life is 27 minutes and proceeds in a dose-dependent saturable manner.
  • there may be some cross tolerance with ethanol (alcohol and alcohol withdrawal)
  • it binds to GABA-B receptors in the brain, inhibits noradrenaline release in the hypothalamus, and mediates the release of an opiate-like substance in the striatum.
  • it produces a biphasic dopamine response, increasing release at high doses and inhibiting release at lower doses.
  • chronic use may result in a withdrawal state starting 1-6 hours after last use and characterised by psychosis, severe agitation, anxiety, tremor, tachycardia, hypertension, perspiration, delirium and hallucinations which may last 5-15 days.

clinical effects

  • oral dose of 10 mg/kg produces short-term amnesia and hypotonia
  • 20-30 mg/kg produces drowsiness and sleep
  • 50-70 mg/kg results in profound hypnosis and rapid onset of deep coma with GCS of 3.
  • quickly initiates delta wave and rapid eye movement (REM) sleep
  • myoclonic jerks, seizure-like activity and respiratory depression accompany the descent into anesthesia.
  • a peculiar characteristic of GHB toxicity is that patients often demonstrate extreme combativeness and agitation despite profound CNS and respiratory depression.
  • coma usually lasts from 3-6 hours and spontaneously resolves, with usually rapid resolution often accompanied by agitation and seizure-like activity and nausea/vomiting.
  • may cause bradycardia
  • lip burns may be evidence of home-made GHB contaminated with sodium hydroxide.
  • has a very short half life but a very narrow dosing window, placing the patient at high risk of overdose
    • risk is increased if concurrent other substance use such as alcohol
  • It is important to note that there is no reversal agent for GHB

intoxication symptoms

  • fluctuating conscious state
  • euphoria
  • disinhibition
  • hallucinations
  • agitation
  • confusion
  • and in overdose, coma

Mx of GHB overdose

  • respiratory compromise from hypoventilation, airway obstruction and aspiration are common and therefore require high acuity monitoring and supportive care in the resuscitation area.
  • Often patients may require intubation and observation in ICU for 24 hours.

GHB withdrawal

  • The severity will depend on their frequency of use and the amount they use
  • Those at risk are:
    • daily use
    • around the clock dosing every 1-4 hours
    • those displaying signs of withdrawal already

features of GHB withdrawal

  • Insomnia
  • Anxiety
  • Restlessness
  • Tremor
  • Sweating
  • Tachycardia
  • Nausea / Vomiting
  • Confusion/disorientation
    • delirium with hallucinations, delusions and paranoia and can be very distressing to the patient and can last up to 14 days, often requires inpatient admission and 1:1 nursing special.

Mx of GHB withdrawal

  • The aim is to provide best care to the patient by keeping them safe from withdrawal harms and getting them comfortable to alleviate physical discomfort of withdrawal.
  • Where practical, they should be nursed in a low stimulus single room.
  • early oral diazepam 5-20mg hourly prn (may need 20mg load dose)
  • oral baclofen 10mg tds for 3 days then bd for 2 days then nightly for 2 nights
  • those with severe withdrawal with delirium/psychosis:
    • add lorazepam s/lingual 2.5mg 2hrly max 20mg/24hrs, OR,
    • IM midazolam 0.1-0.2mg/kg (max 20mg/24hrs)
  • discharge education for harm reduction strategies
ghb.txt · Last modified: 2022/06/16 03:37 by wh

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