Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/14748
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Type: Journal article
Title: In vivo cerebral pharmacokinetics and pharmacodynamics of diazepam and midazolam after short intravenous infusion administration in sheep
Author: Upton, R.
Ludbrook, G.
Grant, C.
Martinez, A.
Citation: Journal of Pharmacokinetics and Pharmacodynamics, 2001; 28(2):129-153
Publisher: Kluwer Academic/Plenum Publ
Issue Date: 2001
ISSN: 1567-567X
1573-8744
Statement of
Responsibility: 
Upton R.N., Ludbrook G.L., Grant C. and Martinez A.
Abstract: The cerebral pharmacokinetics and pharmacodynamics of midazolam and diazepam were examined in chronically instrumented sheep via measurements of their arterio-venous concentration difference across the brain during and after 2-min iv infusions. Diazepam (30 mg) or midazolam (10 mg) were administered on 5 separate occasions to 4 sheep. For both drugs, rapid cerebral uptake occurred during the infusion, which quickly turned to elution in the postinfusion period. However, this process was more rapid for midazolam than diazepam. The cerebral pharmacokinetics of both was better described by a kinetic model with slight membrane limitation rather than flow limitation. For diazepam, the estimated brain:plasma partition coefficient was 2.67, and the first and second compartments filled with half-lives of 2.2 and 0.5 min, respectively. For midazolam, these values were 0.27, 0.26 and 1.34 min, respectively. In a subset of sheep, pulmonary arterial–arterial gradients were too small to measure suggesting limited metabolism and small distribution volumes for both drugs in the lungs. Simultaneous dynamic measurements of cerebral blood flow and algesimetry lagged behind both the arterial and sagittal sinus blood concentrations. The changes in cerebral blood flow were best described by a previously published a dynamic model that incorporated long half-lives for drug dissociation from the benzodiazepine receptor (13.3 and 5.5 min for midazolam and diazepam, respectively). Effect compartment modeling of the cerebral blood flow data showed apparent effect compartment half-lives (t_1/2,keo) that were longer than the half-lives of cerebral equilibration.
Keywords: midazolam; diazepam; cerebral blood flow; cerebral pharmacokinetics; lung pharmacokinetics; pharmacodynamics
RMID: 0020010730
DOI: 10.1023/A:1011550915515
Description (link): http://adelaideaus.library.ingentaconnect.com/content/klu/jopa/2001/00000028/00000002/00299111?format=print
Appears in Collections:Anaesthesia and Intensive Care publications

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