We studied the effect of diabetes on the pharmacokinetics of cyclosporin A (CyA) after intravenous and oral administration of CyA using the plasma and lymph of streptozotocin (STZ)-induced diabetic rat. There were no significant differences in the systemic and lymphatic availabilities after intravenous administration of CyA in diabetic rats compared with those of the controls. On the other hand, systemic and lymphatic availabilities after oral administration of CyA were significantly different in diabetic rats compared to those in the controls. These results suggest that the pharmacokinetics of CyA, particularly absorption, were altered in diabetic rats. Gastrointestinal transit in diabetic rats was also studied. The gastric emptying rate in diabetic rats was enhanced compared with that of the controls, but small intestinal transit was reduced in diabetic rats, suggesting that a change in gastrointestinal transit in diabetic rats may influence the absorption of CyA. The increased absorption of CyA from the digestive tract of diabetic rats altered not only the systemic availability but also the lymphatic availability, suggesting that altered systemic availability may cause adverse effects and that altered lymphatic availability may influence the immunosuppressive effects.
An ovomucoid-conjugated column has been developed for the chiral stationary-phase liquid chromatographic resolution of racemic chlorpheniramine with a quantitation limit of 0.05 microgram mL-1. The assay was used to study the stereoselective kinetics of chlorpheniramine enantiomers in rats. After bolus intravenous administration of racemic chlorpheniramine maleate (20 mg kg-1), plasma concentration of the (-)-form was higher than that of the (+)-form. In the elimination phase, the concentrations of (+)- and (-)-chlorpheniramine in the plasma declined biexponentially with half-lives of 18.2 and 50.0 min, respectively. Although there was no significant difference in blood-to-plasma concentration ratio of both enantiomers, the apparent total blood clearance of (+)-chlorpheniramine was twice as large as that of the (-)-isomer. Binding of (-)-chlorpheniramine to rat plasma protein was stronger than that of (+)-chlorpheniramine suggesting stereoselective pharmacokinetics may be due to a difference in the plasma protein binding.
An HPLC method using an ovomucoid-conjugated column has been developed for measurement of thioperamide, a histamine H3 antagonist, with a minimum quantitation limit of 0.05 micrograms mL-1. The assay was used to study the disposition of thioperamide in rats. After bolus intravenous administration of thioperamide (10 mg kg-1), the plasma concentration decreased monoexponentially with a half-life of 26.9 min. The apparent total body clearance of thioperamide from rat plasma was 74.6 mL min-1 kg-1. Although thioperamide was quickly transferred to various tissues, its concentrations in peripheral tissues were higher than that in the brain. However, the brain regional tissue/plasma ratios of thioperamide increased continuously after its injection.
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