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Pharmacokinetics of intravenous, intrathecal and epidural morphine and fentanyl in the goat
Author(s) -
Andersen H. B.,
Christensen B.,
Findlay J. W. A.,
Jansen J. A.
Publication year - 1986
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1986.tb02437.x
Subject(s) - fentanyl , medicine , morphine , epidural administration , anesthesia , pharmacokinetics , intrathecal , radioimmunoassay , sufentanil , cannula , pharmacology , surgery
Intrathecal and epidural catheters and an intravenous cannula were inserted in 10 goats. After administration of either morphine 4 mg, intravenously, 1 mg intrathecally or 4 and 8 mg epidurally. or fentanyl 0.1 mg intravenously, 0.05 mg intrathecally or 0.1 and 0.2 mg epidurally, venous blood and CSP were sampled at 2, 5, 10. 15, 30 min and 1, 2, 4, 6, 8 and 24 h. The concentrations of the drugs were measured by radioimmunoassay. After administration of intravenous morphine the plasma concentrarion‐time curve fitted a 3‐compartment model (body clearance = 84 ±23 ml/min/kg, mean ± s.d., N = 5), while after fentanyl the plasma concentration‐time curve was best described by a 2‐compartment model (body clearance = 3.9–5.8 ml/min/kg, N = 3)). After intrathecal injection the elimination rates of the opioids from CSF were 0.3 to 2.0 and 0.6 to 2.4 ml/h/kg for morphine and fentanyl, respectively (N = 3). The time to reach maximum CSF concentration after epidural administration was 0.22 ±0.14 h for morphine (N = 6) and 0.22 ±0.13 11 for fentanyl (N = 8). In the same goat the CSF availability was 2.3 and 11.3% for morphine and 0.8 and 3.3%, for fentanyl following epidural administration of the low and high doses, respectively. After cpidural administration, morphine and fentanyl are absorbed into CSF at the same rate but the relative amount of drug absorbed may be higher for morphine than fentanyl. Bulk flow is supposed to be the principal mechanism of opioid elimination from CSF.