The influence of drug interaction and protein variants on the binding disposition of ropivacaine to alpha1-acid glycoprotein (AGP) was examined. The subjects were five patients who received epidural infusion of ropivacaine for 24-54 h in off-pump coronary artery bypass grafting followed by drug combination therapy, and 10 healthy volunteers. The post-operation plasma albumin concentration showed little overall change, while the AGP concentration in the five patients decreased for 6 h, then increased gradually to about 3-times the initial value by 54 h. The unbound fraction in plasma (fu) of ropivacaine gradually decreased as the AGP concentration increased, but there was large inter-individual variation among the five patients. In contrast, there was a good correlation between the fu value and AGP concentration when ropivacaine was added to blood samples from the 10 healthy volunteers. Among the volunteers, eight showed F1S variants and two showed F1 variant without S variant of AGP. The fu value of ropivacaine did not differ between these two groups. However, when ropivacaine was added in combination with dipyridamole, the fu values of ropivacaine in blood from volunteers with F1S variants were greater than those in blood from volunteers without S variant. In the case of co-administration of disopyramide or lidocaine, there was no such difference. Among the patients, one showed F1S variants and four showed F1 variant without S variant. The results indicate that variability in the side-effects of therapy with ropivacaine alone is caused by the change of the unbound concentration upon changes in the AGP concentration. However, in combination therapy, it is also important to consider the AGP variant-dependence of the inhibitory effect of concomitantly administered drugs.

The binding of drugs to proteins is an important determinant of their efficacy and/or side-effects in clinical use. Many basic drugs bind mainly to a 1 -acid glycoprotein (AGP), an acute phase reactant, in plasma, but the plasma level of AGP varies greatly in various diseases. It is increased by inflammatory reaction, injury, and surgery, [1][2][3] but decreased by liver cancer, hepatitis and nephritic syndrome. [4][5][6] We have shown that there is a good correlation between the unbound fraction (f u ) of ropivacaine and AGP concentration after surgery. 3)Recently, it has been reported that human AGP exists as a heterogeneous population of three genetic variants of ORM1 F 1 and ORM1 S derived from the AGP-A gene and ORM2 A derived from the AGP-B/BЈ genes in the plasma of most individuals. 7,8) The variants can be identified by isoelectric focusing assay 9) and separated by chromatography on an immobilized copper(II) affinity adsorbent. 10,11) Fitos et al. demonstrated that the two main forms (the F 1 S and A variants) have different drug binding properties by means of circular dichroism (CD) spectroscopy using dicumarol and acridine orange as probes.12) It has been clarified that some drugs bind selectively to different AGP variants: for example, dipyridamole binds selectively to the F 1 S variant, and disopyramide to the A variant, whereas lidocaine binds to both the F 1 S and A variants. [13][14][15][16] However, there are few reports regarding the effects of drug-drug interaction arising from selective binding to AGP variants on the f u values of basic drugs. In this study, we evaluated the selective competitive binding of basic drugs to the F 1 S and A variants isolated from native human AGP. MATERIALS AND METHODS Materials Anapeine injection® (ropivacaine hydrochloride) and Xylocaine injection ® (lidocaine hydrochloride) were purchased from AstraZeneca Co., Ltd. (Osaka, Japan). Persantin injection ® (dipyridamole) was purchased from Boehringer Ingelheim Co., Ltd. (Tokyo, Japan). Vasolan injection ® (verapamil hydrochloride) was purchased from Eisai Co., Ltd. (Tokyo, Japan). Rythmodan P injection ® (disopyramide phosphate) was purchased from Chugai Pharmaceutical Co., Ltd. (Tokyo, Japan). Nifejipine and amlodipine besilate were purchased from Wako Pure Chemicals Co., Ltd. (Osaka, Japan). Herbesser injection ® (diltiazem hydrochloride) was purchased from Tanabe Co., Ltd. (Tokyo, Japan). Carvedilol was purchased from LKT Laboratories, Inc. (MN, U.S.A.). Native human a 1 -acid glycoprotein (total AGP) was purchased from Sigma-Aldrich Co., Ltd. (MO, U.S.A.). 3,3Ј-Methylene-bis(4-hydroxycoumarin)(dicumarol), acridine orange hemi(zinc chloride) salt and mepivacaine were purchased from Sigma-Aldrich Co., Ltd. Other chemicals were of reagent grade.Drug Assays Concentrations of ropivacaine, lidocaine and disopyramide were determined by GC-MS (Model GC-17 system Class 5000, Shimadzu, Kyoto, Japan). The assay for these drugs was carried out by using the procedure described for ropivacaine by Yokogawa et al. 3)Aliquots...

Conscious young adult male rats were given total parenteral nutrition (TPN) with or without soybean fat for 4 days. Those given fat-free TPN developed severe fatty liver, with hyperglycaemia, hyperinsulinaemia, and hypotriglyceridaemia. These disorders were clearly improved by supplementing TPN with soybean fat, in an amount equivalent to 20% of total calories, and correspondingly reducing glucose. Insulin resistance also developed over a 4-day infusion of fat-free TPN in mature rats. Even after over-night fasting after stopping the TPN infusion, the levels of serum glucose and insulin were higher in the fat-free TPN group than in the control group, and intravenous glucose tolerance test results indicated insulin resistance in the fat-free TPN group. The HOMA-IR index of insulin resistance was significantly improved by supplementation with soybean fat. In conclusion, fat-free TPN infusion induced hyperglycaemia and hyperinsulinaemia, leading to fatty liver and insulin resistance. TPN with glucose should be supplemented with soybean fat emulsion as replacement for part of the glucose calories.

No abstract