摘要:

Warfarin is clinically the most widely used oral anticoagulant and its properties have been extensively studied. Assay methods for these compounds have until recently been relatively non-specific. The advent of chromatographically based techniques has enabled a re-evaluation of the pharmacokinetics of oral anticoagulants, but most work continues to involve warfarin. The most important recent work has concerned the different anticoagulant potencies and metabolic pathways of the optical isomers of some of these drugs.The effects of age and some diseases on pharmacokinetics of warfarin have been examined but much remains to be done, especially with oral anticoagulants other than warfarin.There are several well established pharmacokinetic drug interactions with warfarin. There is a wide awareness of the drugs most likely to reduce anticoagulant effects by enzyme induction and alternative drugs can be used. Mechanisms of some interactions have been re-investigated.In vivodrug displacement interactions are complicated by the correlation between hepatic clearance of these drugs and the size of the unbound fraction in plasma. The interactions between phenylbutazone and warfarin and metronidazole and warfarin, resulting in potentiation of anticoagulant effect have been suggested to be due mainly to an inhibition of the metabolism of the more potent S isomer of warfarin.

ISSN:0312-5963    

出版商:ADIS    

年代:1979

数据来源: ADIS

摘要:

Marked changes in physiological function and in the metabolism of endogenous substances take place after trauma and operation, and these may influence the pharmacokinetics of drugs. Increased secretion of hormones, such as hydrocortisone and glucagon occurs. The liver blood flow increases, whereas gastrointestinal motility decreases. There is a tendency to hyperglycaemia, and fat is mobilised from the body stores. During the first few days after operation there is increased protein breakdown, and the plasma concentration of albumin is reduced for 10 to 14 days.To date, few investigations have been performed to elucidate the pharmacokinetic consequences of these physiological changes, but it is apparent that altered disposition of drugs can occur. The absorption of some orally administered drugs may well be altered during the early postoperative period owing to decreased gastrointestinal motility. The degree of plasma protein binding of phenytoin and quinidine has been found to be modified after surgery, mostly due to altered concentration of plasma proteins. Although this is probably compensated by changes in distribution and elimination of the drug. it is conceivable that high unbound drug concentrations may be achieved temporarily. Many factors apparently accelerate the elimination of drugs after operation. Liver blood flow increases, plasma protein binding of acidic drugs diminishes, and further, the drug metabolising enzyme activity of the liver has been found to increase. The elimination rate of antipyrine is increased after surgery, and is thought to be due to acceleration of the metabolism of the drug. The increase in enzyme activity may be explained by the altered secretion of hormones, but may also be due to the concomitant use of other drugs.The use of drugs in relation to surgery is important. Further investigation to elucidate their pharmacokinetics in the postoperative period is clearly necessary in order to establish safe and effective therapy.

ISSN:0312-5963    

出版商:ADIS    

年代:1979

数据来源: ADIS

ISSN:0312-5963    

出版商:ADIS    

年代:1979

数据来源: ADIS

摘要:

The relation between steady-state plasma ethosuximide level and drug dose was studied in 46 patients. In this population, plasma drug levels were proportional to drug dose, expressed on a body weight basis. Age did not alter this relationship, but plasma levels increased more rapidly, relative to dose, in females than in males. Intake of methylphenobarbitone, but not intake of certain other anticonvulsants (phenytoin, phenobarbitone, primidone and carbamazepine) altered the relationship between plasma ethosuximide level and ethosuximide dose. In individual patients, successive dose increments of equal size produced progressively greater increases in steady-state plasma ethosuximide levels. This phenomenon has obvious therapeutic implications.

ISSN:0312-5963    

出版商:ADIS    

年代:1979

数据来源: ADIS

摘要:

In an open prospective clinical study, plasma clearance of phenytoin, phenobarbitone and carbamazepine was assessed in 14 epileptic patients during and after pregnancy. Plasma clearance showed a marked increase during pregnancy, reached a maximum just before or after delivery, and then decreased to early pregnancy values. The relative plasma concentration of carbamazepine-10,11-epoxide to that of carbamazepine increased similarly during pregnancy. The protein binding of carbamazepine and the epoxide was not influenced by pregnancy.A higher rate of hepatic drug metabolism, due to alteration of the physiological state in pregnancy is suggested as the most reasonable explanation.No change in seizure frequency was seen, probably because of frequent dose adjustments in order to keep plasma levels within the optimum range.

ISSN:0312-5963    

出版商:ADIS    

年代:1979

数据来源: ADIS

摘要:

Hydrochlorothiazide 775mg was administered orally to 5 patients who had undergone intestinal shunt operations for obesity 1.5 to 6 years previously. Postoperative weight loss averaged 53.4kg. The concentrations of hydrochlorothiazide in plasma and urine were determined with gas/liquid chromatography. The mean area under the plasma concentration time curve during 9h in 4 of the patients was 889ng/ml · h. Mean total urinary recovery of hydrochlorothiazide amounted to 23.0mg in the 5 patients, which corresponds to approximately half that seen in healthy volunteers. The gastrointestinal hydrochlorothiazide appears to be substantially reduced after intestinal shunt surgery.

ISSN:0312-5963    

出版商:ADIS    

年代:1979

数据来源: ADIS

ISSN:0312-5963    

出版商:ADIS    

年代:1979

数据来源: ADIS