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This prospective, single-blind, randomized study was designed to evaluate the effect of genotype-based warfarin dosing compared with standard warfarin dosing in Korean patients with mechanical cardiac valves. Patients were assigned to either the genotype-based dosing group or the standard dosing group using stratified block randomization. The genotype-based dosing equation was adopted from a previous study which included VKORC1 rs9934438, CYP2C9 rs1057910, CYP4F2 rs2108622, and age. Primary outcomes included the percentage of time in the therapeutic range (pTTR): (i) during the first week following initiation of warfarin therapy, (ii) during hospitalization and (iii) until the first outpatient visit. A total of 91 patients were included in the analysis, 42 treated with genotype-based warfarin dosing and 49 treated with standard warfarin dosing. The genotype frequency differences of the three SNPs included in this study (ie, VKORC1, CYP2C9, CYP4F2), between the genotype-based dosing and standard dosing groups were not different. The genotype-based dosing group trended toward higher pTTR when compared with the standard dosing group, although this difference was not statistically significant. In patients with aortic valve replacement, TTRTraditional and TTRRosendaal were significantly higher in the genotype-based dosing group when compared with the standard dosing group during the first week following treatment initiation [ie, 58.5% vs. 38.1% (p = 0.009) and 64.0% vs. 44.6% (p = 0.012), respectively]. Based on the results, the genotype-guided dosing did not offer a significant clinical advantage, but a possible benefit in patients with aortic valve replacement has been suggested.

Objectives The aim of this study was to evaluate the associations between polymorphisms of VKORC1, CYP2C9, CYP4F2, NR3C1 and VDR genes and stable warfarin doses in Korean patients with mechanical heart valves. Methods Seventeen single-nucleotide polymorphisms (SNPs) in 204 patients with stable warfarin dose were analyzed: VKORC1 (rs9934438), CYP2C9 (rs1057910), CYP4F2 (rs2108622), NR3C1 (rs41423247, rs1800445, rs56149945, rs10052957, rs6198, rs33388, rs6196, and rs244465), and VDR (rs1544410, rs11568820, rs731236, rs757343, rs7975232, and rs2228570). Statistical analyses were conducted to evaluate the associations of gene variations with stable warfarin dose. Number needed to genotype was obtained by calculating the percentage of patients whose predicted dose was at least 20% higher or lower than the actual stable dose. Results The combined genotypes of rs7975232 and rs2228570 of the VDR gene revealed a significant association with stable warfarin dose, along with VKORC1 , CYP2C9 , and CYP4F2 polymorphisms. Patients with the genotype combination GT,TT/CT,CC of VDR rs7975232/rs2228570 required significantly higher stable warfarin dose (5.79±2.02mg) than those with the other genotypic combinations (5.19±1.78mg, p =0.034). Multivariate analysis showed that VDR rs7975232/rs2228570 explained 2.0% of the 47.5% variability in overall warfarin dose. Adding VDR SNP combinations to the base model including non-genetic variables (age, sex, and body weight) and genetic variables ( VKORC1 rs9934438, CYP2C9 rs1057910, and CYP4F2 rs2108622) gave a number needed to genotype of 41. Conclusions This study showed that stable warfarin dose is associated with VDR SNPs along with VKORC1 , CYP2C9 , and CYP4F2 SNPs.

As a tocolytic agent, ritodrine has been used in European and Asian countries but has lost popularity due to safety concerns. This study aimed to investigate the relationship between adverse drug events caused by ritodrine and the CACNA1C polymorphisms in preterm labor patients. Data were collected from medical records including maternal age, gestational age, body mass index, dilation score, effacement score, modified Bishop score, maximum infusion rate, and adverse drug events. Five single-nucleotide polymorphisms of the CACNA1C gene (rs10774053, rs215994, rs215976, rs2239128, and rs2041135) were analyzed. One hundred eighty-six patients were included, 33 of whom had adverse drug events. A allele carriers of rs10774053 showed about 0.293-fold lower adverse drug events than GG genotype carriers (p = 0.012, absolute risk reduction = 16.5%) after adjusting for other confounding variables; the number needed to genotype for preventing one patient with GG genotype from suffering higher incidence of adverse drug events was calculated to be 14.6. Increase in maximum infusion rate of 1 mL/h was associated with a 1.03-fold (95% CI 1.01~1.06, p = 0.005) increased risk of adverse drug events. None of the patients with a CC genotype of rs215994 had adverse drug events, whereas 22.1% of the T allele carriers had adverse drug events. This study showed that CACNA1C gene polymorphisms could alter the probability of adverse drug event risk when ritodrine is used in preterm labor.