Concentration-Time Profiles of Gamma-Hydroxybutyrate in Blood After Recreational Doses are Best Described by Zero-Order Rather Than First-Order Kinetics
2009 (English)In: Journal of Analytical Toxicology, ISSN 0146-4760, Vol. 33, no 6, 332-335 p.Article in journal (Refereed) Published
The recreational drug gamma-hydroxybutyrate (GHB) has a short plasma elimination half-life (t(1/2)) reported to be about 30-50 min. However, this represents a terminal half-life and therefore might not necessarily apply after large (abuse) doses are taken. Clinical studies with sodium oxybate (sodium salt of GHB) suggest that zero-order rather than first-order kinetics are more appropriate to describe post-peak concentration-time (C-T) profiles. We report the case of a 23-year-old male found unconscious by the police and a blood sample contained 100 mg/L GHB and 0.14 g% ethanol. On regaining consciousness the man admitted drinking alcohol about 6 h earlier but claimed that his drink must have been spiked with GHB. The police wanted to know how much GHB had been administered to account for the man's clinical condition. A back-calculation for 6 h, assuming a GHB half-life of 40 min, gives a very high concentration in blood of approximately 900 mg/L, which would probably have proven fatal. Back-calculating using zero-order kinetics and a proposed elimination rate of 18 mg/L per hour leads to a GHB concentration of 208 mg/L, which is much more realistic. Toxicologists should not arbitrarily apply the principles of first-order kinetics after abuse doses of drugs, when zero-order or saturation kinetics (Michaelis-Menten) are more appropriate.
Place, publisher, year, edition, pages
2009. Vol. 33, no 6, 332-335 p.
National CategoryEngineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-53855ISI: 000268152800007PubMedID: 19653937OAI: oai:DiVA.org:liu-53855DiVA: diva2:292422