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Two healthy male volunteers received 10 mg carbamazepine (CBZ) as a 2-h constant-rate intravenous (i.v.) infusion and 100 mg 15N-labeled CBZ as a 2% oral suspension, concomitantly. The two compounds have identical pharmacokinetics. Their respective concentrations in plasma were determined by gas chromatography-mass spectrometry (GC-MS) for 168 h. The comparison of the areas under the plasma curves (AUC) obtained by the two routes of administration, showed the systemic availability of CBZ given as an oral suspension to be equal to its availability when given intravenously. A two-compartment model was estimated: The apparent volume of distribution of CBZ at the steady-state (Vss) was approximately 1 L/kg.

By means of transumbilical portal catheterization immunoreactive insulin (IRI) concentrations in portal vein (POV) and in peripheral vein (PEV) were compared after administration of glucose, galactose, xylitol and tolbutamide. Fasting portal IRI concentration was about twice that found in PEV. After ß.cell-stimulation the maximal IRI rise in POV was several times greater compared to PEV. Xylitol produced a significant IRI rise in POV but non in PEV. Thus, absence of IRI elevation in PEV does not exc1ude stimulation of IRI secretion. Factors affecting the difference between portal and peripheral venous IRI concentrations are discussed.

1 A mathematical model describing the relationship between plasma concentrations of oxprenolol and submaximal-exercise heart rates has been developed on the basis of data available from 34 healthy volunteers. 2 This relationship, which is exponential in type, is consistent with the 'law of diminishing returns', and is independent of the pharmaceutical formulations used; it appears to be established instantaneously, and is not modified by repeated drug administration over 8 days.3 At oxprenolol concentrations of 190-250 ng/ml, between half and three-quarters of the subjects investigated reached 90% of their estimated maximum levels ofadrenoceptor blockade.