Warfarin determination

Before administering the first dose of warfarin, die nurse questions the patient about all drags taken during the previous 2 to 3 weeks (if the patient was recendy admitted to the hospital). If the patient took any drug before admission, the nurse notifies the primary healdi care provider before the first dose is administered. Usually, the prothrombin time (PT) is ordered and die international normalized ratio (INR) determined before tiierapy is started. The first dose of warfarin is not given until blood for a baseline PT/ INR is drawn. The dosage is individualized based on die results of the PT or die INR. 

Promoting an Optimal Response to Therapy Before administering each dose of warfarin, the nurse checks the prothrombin flow sheet or the laboratory report to determine the current PT or INR (PT/INR) results (see Nursing Alerts below). The patient also is checked for any evidence of bleeding. 

Mr. Harris, age 72 years, is a widower who has lived alone since his wife died 5 years ago. He has been prescribed warfarin to take at home after his dismissal from the hospital. Determine which questions concerning the home environment would be important to ask Mr. Harris to prepare him to care for himself and prevent any complications associated with the warfarin. 

The distribution of the ionic species is determined by the molecular properties of the compound, but also by the nature and the concentration of the counterions present in the media [78]. For example, the influence of [Na ] on the transport kinehcs of warfarin through an octanol membrane has been reported [79]. 

In those receiving warfarin for AF, determine whether the patient s INR is therapeutic. 

Evaluate patient comorbidities and medications to determine if additional work-up is necessary prior to tumor debulking surgery. Do any medications need to be stopped or changed prior to surgery (e.g., aspirin, warfarin, or non-steroidal anti-inflammatory agents) ... 

Figure 5.7 shows lipophilicity profiles (log D vs. pH) for an acid (warfarin), a base (tetracaine), and an ampholyte (morphine). The dashed curves correspond to the values determined in octanol-water and the solid curves, to values in liposome-water. As is readily apparent, the major differences between octanol and liposomes... 

Brush-type, proteins, CDs, natural molecular imprint-based polymers (MIP), and macrocyclic antibiotics have been immobilized as chiral selectors on packed-CEC columns. Zheng and Shamsi demonstrated the possibility of using chiral CEC—ESI/MS with a commercially packed column for the determination of warfarin enantiomers in human plasma using coumachlor as an internal standard (IS). Robustness of this chiral CEC capillary was recently improved by a novel procedure and applied for the simultaneous enantiosepara-tion of height /1-blockers with multimodal CSP using different combinations of vancomycin and teicoplanin, as presented in Figure 5. ... 

Two representative examples of single-column SMGPC separations are presented in Figures 2 and 3. The sample for Figure 2 was a rodent bait from which the active ingredient warfarin was to be determined. Quantitation of this component by SMGPC was shown to be as reliable as for the reversed-phase method which is commonly used (35), with the advantage of a several-fold faster sample clean-up U2). 

Figure 2. Determination of warfarin from grain bait by SMGPC.

It was also essential to determine how effective bromethalin was against warfarin-resistant rats and mice. Such animals, whose resistance to anticoagulants had been determined by World Health Organization tests,(17) were subjected to a standard EPA choice feeding efficacy test with bromethalin at 0.005% in the treated diet. The results indicate (Appendix 6) that 90% of the animals were killed and that consumption patterns were similar to those observed in other choice tests. 

As tinzaparin may theoretically affect the prothrombin time (PT)/INR, draw blood for PT/INR determination just prior to the next scheduled dose of tinzaparin for patients receiving tinzaparin and warfarin. 

Conversion from heparin therapy Because the anticoagulant effect of warfarin is delayed, heparin is preferred initially for rapid anticoagulation. Conversion to warfarin therapy may begin concomitantly with heparin therapy or may be delayed 3 to 6 days. To ensure continuous anticoagulation, it is advisable to continue full dose heparin therapy and that warfarin therapy be overlapped with heparin for 4 to 5 days, until warfarin therapy has produced the desired therapeutic response as determined by PT/INR. When warfarin has produced the desired PT/INR or prothrombin activity, heparin may be discontinued. 

Conversion from heparin therapy - As heparin may affect the PT/INR, patients receiving both heparin and warfarin should have blood for PT/INR determination drawn at least ... 

Warfarin has hccn drlcrmiiicd from plasma 3f>7). Siinlics of iis metabolic fate due to the action of hepatic mixed function oxidases have profited from the use of reversed-phase columns for the determination of metabolites (368). Related studies on warfarin resistance have utilized vitamin Kt 2,3-epoxide to examine the rate of its reduction in rats to form X ilamin h the rraxMion was follitwcil x liromalxtitrapliii allv... 

The pesticide rotenone and five other rotenoids were determined in formulations by using RPC (597, 598). The assay of warfarin in rodenti-cide preparations has been reported by Billings et al. (599). Methiocarb (3,5-dimethyl-4-(methylthio)phenylmethylcarbamate) has been determined in commercial preparations (666). The diaistereomers of sumicidin. 

Haining, R. L., Jones, J. R, Henne, K. R., et al. (1999) Enzymatic determinants of the substrate specificity of CYP2C9 role of B -C loop residues in providing the pi-stacking anchor site for warfarin binding. Biochemistry 38, 3285-3292. 

The frontal analysis technique has been used for the determination of enantioselective binding constants of chiral drugs such as warfarin, verapamil, nilvadipine, and semotidil with proteins such as bovine serum albumin (BSA), human serum albumin (HSA), and plasma lipoproteins (45-51). 

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