Clinical trials for pharmacogenomics testing for warfarin dosing: Relevance to general community practices

Association between Patients' Knowledge and Adherence to Anticoagulants, and Its Effect on Coagulation Control

BACKGROUND

Warfarin requires strict monitoring by measuring prothrombin time (PT), international normalized ratio (INR), and time in therapeutic range (TTR). Several factors can lead to poor PT/INR control including vitamin K status, medication adherence, knowledge, and quality of life. The present study aims to assess patient adherence to warfarin treatment and its correlation with INR control.

METHODS

A cross-sectional study was conducted between October 2017 and January 2018 at Tripoli University Hospital. Data were collected by structured questionnaires which included; demographic and clinical characteristics, the Oral Anticoagulation Knowledge (OAK) test, and the Morisky Medication Adherence Scale (MMAS-8).

RESULTS

The final analysis included 88 out of 140 patients (73.33%). There were significant differences in age range, gender, marital status, and education level between the 2 groups (poor knowledge and adequate knowledge) (p < 0.05). There was a significant positive correlation between OAK test score and TTR. Overall, 76.2% of patients were adherent to warfarin (MMAS score ≥6) and 20.45% of patients were of high adherence (MMAS score of 8). The median score was 6 (IQR 6-7). A statistically significant, strong positive correlation between adherence to medication and TTR as an indicator of INR control was found (rs[86] = 0.472, p < 0.0001).

CONCLUSION

The study addressed and identified several areas for future improvement of patient outcomes. The implementation of new approaches to enhance patient knowledge and adherence is warranted, and measures to provide treatment for all patients that require it are needed, to improve outcomes and decrease adverse drug effects.

Evaluation of the anticoagulant effect and timing of the concomitant use of S-1 and warfarin

Objectives

To evaluate the effects of the timing of warfarin (WF) administration in patients with gastric cancer who received S-1 oral chemotherapy.

Methods

This retrospective chart review collected patient data including the prothrombin time international normalized ratio (PT-INR). Patients were categorized into three groups based on the timing of WF administration in relation to S-1 oral chemotherapy: group A patients received WF before S-1 chemotherapy; group B patients started WF during S-1 chemotherapy; and group C patients started WF after completing S-1 chemotherapy.

Results

A total of 21 patients with gastric cancer were included in the study; group A ( n = 8), group B ( n = 10) and group C ( n = 3). Seven patients (88%) in group A, seven (70%) in group B and all of the patients (100%) in group C had >2.5 PT-INR. There was no significant difference in the time-to-exceed 2.5 PT-INR between groups A and B.

Conclusions

These findings suggest that the timing of WF use in relation to S-1 chemotherapy might not be an important factor for PT-INR, although the low patient numbers included in the study should be taken into consideration.

Variability of warfarin dose response associated with CYP2C9 and VKORC1 gene polymorphisms in Chinese patients

OBJECTIVE

To investigate the prevalence and implication of cytochrome P450, family 2, subfamily C, polypeptide 9 (CYP2C9) variants and vitamin K epoxide reductase complex, subunit 1 (VKORC1)-1639 G > A polymorphisms in Chinese patients receiving warfarin therapy.

METHODS

Chinese Han patients requiring oral warfarin therapy were consecutively enrolled. Correlations between CYP2C9*1, *2, *3, *4, *5 variants and VKORC1-1639 G > A polymorphisms, fourth-day international normalized ratios (INRs) and warfarin maintenance dose were investigated.

RESULTS

Out of 101 patients, there were no significant differences in fourth-day INR or warfarin daily maintenance doses between patients with CYP2C9*1*1 and CYP2C9*1*3 genotypes. Patients with the VKORC1-1639 AA genotype had a higher fourth-day INR (1.87 ± 0.14) than those with the VKORC1-1639 AG genotype (1.32 ± 0.15). Warfarin maintenance dose for patients with the VKORC1-1639 AA genotype (2.40 ± 0.70 mg/day) was significantly lower than for patients with the VKORC1-1639 AG genotype (4.83 ± 0.70 mg/day).

CONCLUSIONS

Unlike Caucasian populations, VKORC1-1639 G > A polymorphisms in the Chinese population may be the dominant genetic factors associated with warfarin response variability.