索他洛尔治疗剂量对华法令抗凝药效的相关性研究

目的：探讨索他洛尔治疗剂量和华法令药效的相关性,为临床安全规范地应用华法令抗凝治疗提供预测依据,以期能增强抗凝疗效并减少其不良反应。方法：年龄60-75岁门诊和住院心房颤动患者46例,均应用索他洛尔、华法令和单用华法令两阶段,采用自身对照研究治疗剂量索他洛尔对达到标准抗凝强度所需华法令剂量的影响。结果：治疗剂量索他洛尔不影响达标抗凝强度的华法令所需量,两者差异无统计学意义（P〉0.05）。结论：心房颤动患者加用或停用索他洛尔无需对凝血酶原时间的国际标准化率（INR）值重新评估监测。     

Patient-specific factors predictive of warfarin dosage requirements

OBJECTIVE: To identify patient-specific factors predictive of maintenance warfarin dosage requirements >5 mg/d. METHODS: One hundred forty-six adults taking warfarin were identified from a community hospital and an outpatient anticoagulation clinic. Patient demographics and data on warfarin doses, laboratory results, and medication use were obtained by abstracting patient records. Estimates of vitamin K intake were obtained using a questionnaire and structured interview. Multiple logistic regression was used to identify patient characteristics independently predictive of warfarin maintenance requirements >5 mg/d. An assessment tool for estimating an individual patient's likelihood of requiring warfarin maintenance doses >5 mg/d was derived from the logistic regression model and was assessed in both the study cohort and a separate historical validation cohort of 125 patients. RESULTS: Five factors were independently associated with warfarin requirements >5 mg/d: age <55 years, male gender, African American ethnicity, vitamin K intake >400 micro g/d, and body weight >or=91 kg. The assessment tool derived from these factors correctly classified semiquantitative warfarin requirements as non-high-dose in 84 of 93 study cohort patients and 71 of 78 validation cohort patients, and correctly classified requirements as high-dose in 10 of 13 study cohort patients and 11 of 15 validation cohort patients. CONCLUSIONS: African American ethnicity is a newly identified predictor of warfarin requirements >5 mg/d and is independent of dietary vitamin K intake. An assessment tool incorporating this and other predictors can estimate a patient's likelihood of requiring such dosages.     

The influence of treatment modality and ethnicity on attitudes in type 2 diabetes

OBJECTIVE: The study examines diabetes attitude differences by treatment modality (insulin vs. no insulin), race/ethnicity, and the interaction of these two variables for people with type 2 diabetes. RESEARCH DESIGN AND METHODS: Data were collected with the Diabetes Care Profile (DCP), an instrument that assesses psychosocial factors related to diabetes. Participants (n = 672) were recruited in the metropolitan Detroit, Michigan, area from 1993 to 1996. A total of 68% of these participants were African-Americans with type 2 diabetes, and 32% were Caucasians with type 2 diabetes. Analyses of covariance were performed to examine the effects of race/ethnicity, treatment, and their interaction for each DCP scale. RESULTS: The four patient categories (two ethnicities by two treatment modalities) differed by age, years with diabetes, education, and sex distribution. Treatment modality had a significant effect on 6 of the 16 DCP scales (Control, Social and Personal Factors, Positive Attitude, Negative Attitude, Self-Care Ability, and Exercise Barriers). Ethnicity was a significant effect for three scales (Control, Support, and Support Attitudes). The interaction of race/ethnicity and treatment modality was a significant effect for two related attitude scales (Positive Attitude and Negative Attitude). CONCLUSIONS: The results suggest that attitudes toward diabetes are similar for African-American and Caucasian patients with type 2 diabetes. The results also suggest that treatment modality has a greater effect on attitudes than either race/ethnicity or the interaction effect. However, Caucasian patients using insulin differed from the other patient groups by having the least positive and the most negative attitudes regarding diabetes.     

The influence of fasting and stress on the response of rats to warfarin.

A study was undertaken to investigate the influence of fasting (24 hours), epinephrine (four 0.25 mg/kg s.c. doses at hourly intervals), adrenocorticotropin (two 40 I.U. s.c. doses at 2-hour intervals) and immobilization stress (4 hours) on the response of rats to some coumarin or indanedione anticoagulants. The anticoagulants were always administered first and were followed immediately or within the next hour by the appropriate challenge. Fasting produced a significant enhancement of the antiprothrombin response to warfarin (0.5 mg/kg i.v. or 0.75-3.0 mg/kg s.c.), bishydroxycoumarin (7.5 mg/kg i.p. or 10 mg/kg s.c.) and phenindione (40 mg/kg p.o). Epinephrine and immobilization stress, but not adrenocorticotropin, similarly prolonged the prothrombin time after warfarin (0.75-3.0 mg/kg s.c.). When used in the absence of anticoagulants, all challenges had no effect on the prothrombin time. In addition, fasting did not affect the response of anticoagulated animals to vitamin K. Plasma free fatty acids were significantly increased by the various challenges. The binding constant of warfarin to undiluted plasma proteins were decreased from the control value by a factor of 1.7 and 2.0 as a result of immobilization stress and fasting, respectively. Fasting per se increased the amount of bound endogenous free fatty acids per mole of protein; the latter parameter was further increased in the presence of warfarin. The present data show that fasting and stress enhance the anticoagulant response to warfarin and suggest that this might be due to an interference of endogenous free fatty acids with binding of warfarin to plasma proteins.     

Determination of dosage requirements of warfarin in Iranian patients using HPLC technique

In this study the warfarin level in the plasma of 60 patients receiving different dosage regimens of warfarin were determined by HPLC. The corresponding prothrombin times (PT) were also measured. The steady state plasma level of warfarin in 10 healthy volunteers was 900·7±158·21 ng/ml. A mean dose of 3·79±1·02 mg of warfarin corresponded to a therapeutic level of 1193·81±300·35 ng/ml with a mean PT of 20·13±0·69 s. The results of this study suggest that Iranian subjects are more sensitive to warfarin than North American and European subjects, but have responses very similar to those of Asians. Dietary, ethnic and geographical factors as well as differences in drug dispensition may be the cause of the observed dosage variability of warfarin.     

Prospective study of warfarin dosage requirements based on CYP2C9 and VKORC1 genotypes

Polymorphisms in CYP2C9 and VKORC1 have been shown to be associated with warfarin dose requirements and could be used to predict warfarin dose. We conducted a prospective study in which warfarin dose was prescribed based on CYP2C9 and VKORC1 polymorphisms in 108 Han-Chinese patients without prior warfarin treatments. Using the genotype-based dosing, 83% of patients reached stable, therapeutic international normalized ratio (INR) within 2 weeks of treatment initiation and none of the patients developed clinical bleeding or thromboembolic event. Ten percent (11) of patients with INR > 4 and no clinical bleeding were detected during this study. At 12 weeks, 69% of the patients' maintenance doses matched the prediction. Dosing algorithms incorporating genetic factors, age, and body surface area were developed, which could explain up to 62% of the total variation (R(2) of 0.62). This study demonstrated that pharmacogenetics-based dosing could improve time to stable, therapeutic INR, reduce adverse events, and achieve high sensitivity.     

CALU(rs2307040)基因多态性与华法林稳定剂量的关系研究

目的:探讨CALU(rs2307040)基因型在中国汉族人群中的分布情况及其基因多态性与瓣膜置换术后华法林稳定剂量的相关性。方法:采用Snapshot技术检测226例研究对象CALU(rs2307040)位点基因型,研究其基因型及等位基因频率;比较其中176例瓣膜置换术患者基因多态性与华法林稳定剂量的相关性。结果:226例研究对象,CALU(rs2307040)位点基因型AA、AG和GG分别有0、40和186例,各占0%、17.7%和82.3%,A和G等位基因的频率分别为8.8%和91.2%;176例瓣膜置换术后患者服用华法林达稳定状态,AA型未检出,AG组与GG组比较,华法林日维持剂量、INR值和PT值均无显著统计学差异。结论:中国汉族人群CALU(rs2307040)基因多态性可能不是瓣膜置换术后华法林个体剂量差异的影响因素。     

The influence of dosage time of midazolam on its pharmacokinetics and effects in humans.

The influence of dosage time of midazolam on its pharmacokinetics and effects on the central nervous system were investigated in six healthy volunteers, with pharmacokinetic-pharmacodynamic modeling. Each volunteer received single oral doses of 15 mg midazolam on four separate occasions: 8 AM, 2 PM, 8 PM, and 2 AM. An almost significant circadian variation was found in elimination half-life, shortest at 2 PM (1.26 +/- 0.47 hours, mean +/- SD) and longest at 2 AM (1.57 +/- 0.44 hours) (p = 0.05). Drug effects measured were alpha activity of the electroencepalograph and P100 latency of the visual-evoked response. The maximum drug effect (Emax) model described the concentration-effect relationship, extended with either a threshold drug concentration or a sigmoidicity parameter. A significant circadian variation was found in baseline alpha activity: highest at 8 AM (109% +/- 19% of the 24-hour mean) and lowest at 2 AM (80% +/- 12%). For alpha activity the drug concentration at half-maximum effect of both threshold Emax model and sigmoid Emax model showed lower values at 8 AM and 2 AM and higher values at 2 PM and 8 PM. However, these differences were either not significant (p = 0.10, threshold model) or on the verge of statistical significance (p = 0.05, sigmoid model). No circadian variation was found in the parameters describing the effect on the visual-evoked response. We conclude that the sensitivity of the central nervous system to midazolam, as reflected in alpha activity, possibly shows a circadian variation.     

Initiation of oral anticoagulant treatment: comparison between different dosage regimens of warfarin and phenprocoumon

A high "loading dosage" is often given during initiation of oral anticoagulant treatment in order to reach sufficient anticoagulation within short time. Increased bleeding risk as well as a transient prothrombotic tendency are complications of this treatment schedule. The aim of our study was to find proper dosage regimens of phenprocoumon and warfarin allowing initiation of oral anticoagulant treatment in a short time. For 50% of the patients 7.5 mg warfarin daily resulted in stable INR values within 4 days. Patients receiving higher (10 mg) or lower (5 mg) daily dosages of warfarin or 6 or 9 mg phenprocoumon daily during the first days of therapy reached the therapeutic range significantly later. Furthermore, no significant differences of prothrombin fragment F 1+2 were observed, indicating that no enhanced thrombin formation occurred. Thus, initiation of oral anticoagulant treatment using 7.5 mg warfarin daily is a simple and safe dosage regimen.     

The pharmacokinetics of fluconazole in healthy Chinese adult volunteers: influence of ethnicity and gender

Objective: The purpose of the present study was to investigate and compare the influence of ethnicity (including Han, Mongolian, Korean, Hui and Uygur) and gender on the pharmacokinetics of fluconazole in healthy adult volunteers after administration of 200‐mg fluconazole tablet. Methods: Ten healthy subjects (five males and five females) of each ethnicity were recruited and given a single 200‐mg dose of fluconazole in tablet form. Blood samples were obtained before dosing and at various predetermined time points after administration up to 96 h. Drug levels were measured by high‐performance liquid chromatography. The blood concentration–time profiles were analyzed using a non‐compartmental approach to estimate the absorption parameters (AUC_(0–96), C_max and t_max), the distribution parameter (V_d) and the disposition parameters (t_1/2 and CL). Results: Ethnicity did not affect the parameter estimates, but gender did. However, the gender differences in pharmacokinetic parameter could be accounted for by differences in weight. There was a high linear correlation between weight and ln C_max, ln AUC (ln means natural logarithmic transformation), V_d and CL. Conclusions: Ethnicity (Chinese Han, Mongolian, Korean, Hui and Uygur) influences the pharmacokinetics of fluconazole tablet. However, there were statistically significant gender differences in AUC, C_max, V_d and CL. But these could be accounted for by weight differences. If fluconazole dose‐adjustment is deemed necessary, this can be done on a weight basis rather than gender basis.     

VKORC1-1639G／A基因多态性与华法林应用剂量关系的研究

目的探讨维生素K环氧化物还原酶复合物1基因（VKORC1）-1639G／A多态性对中国汉族人华法林应用剂量的影响。方法应用PCR—RFLP法检测129例长期口服华法林的患者和198例健康对照者VKORC1-1639G／A多态性，比较VKORC1不同基因型间平均华法林剂量。结果病例组VKORC1-1639AA、AG、GG基因型频率分别为74．4％（96／129）、23．3％（30／129）、2．3％（3／129），等位基因A和G频率分别为86％和14％。病例组与健康对照者VKORC1-1639G／A多态性分布差异无统计学意义（P〉0．05）。VKORC1-1639不同基因型患者所需华法林平均剂量差异有显著统计学意义（P〈0．（301），AA型剂量[（1．444±0．282）mg／INR]显著低于AG型[（1．629±0．258）mg／INR，P=0．002]和GG型患者[（2．031±0．087）mg／INR，P=0．017]。结论中国人华法林应用剂量偏低可能与VKORC1-1639AA型占多数有关。     

Interethnic variability of warfarin maintenance requirement is explained by VKORC1 genotype in an Asian population

BACKGROUND: Chinese and Malay subjects have been reported to require less maintenance warfarin than Indians that could not be accounted for by cytochrome P450 (CYP) 2C9 variants. Vitamin K epoxide reductase complex 1 (VKORC1) is the target enzyme of warfarin, and VKORC1 intronic variants and haplotypes have recently been shown to influence VKORC1 activity and warfarin requirements. METHODS: We sequenced the coding regions of CYP2C9 and VKORC1 and inferred VKORC1 haplotype from 10 intronic variants in 147 Chinese, 85 Malay, and 43 Indian patients receiving maintenance warfarin. RESULTS: The mean weight-normalized warfarin dose was lower for Chinese and Malays than for Indians (0.058 +/- 0.025 mg/kg, 0.059 +/- 0.023 mg/kg, and 0.089 +/- 0.036 mg/kg, respectively; P < .001 for comparisons between Chinese and Malays with Indians). CYP2C9*2 and VKORC1 coding region variants were rare (<2%), whereas CYP2C9*3 associated with lower warfarin requirements was less common in Chinese and Malays (7% and 9%, respectively) than in Indians (18%) and could not account for their lower warfarin requirements. VKORC1 H1 and H7/H8/H9 haplotypes were associated with lower and higher warfarin requirements, respectively (0.050 +/- 0.019 mg/kg and 0.092 +/- 0.057 mg/kg, respectively; P < .001). VKORC1 H1 haplotype (requiring low warfarin doses) was common in Chinese (87%) and Malays (65%) but uncommon in Indians (12%), whereas H7, H8, and H9 haplotypes (requiring high warfarin doses) were rare in Chinese (9%), intermediate in Malays (30%), and common in Indians (82%). The interethnic difference in warfarin requirements became nonsignificant when adjusted for VKORC1 haplotype. CONCLUSIONS: Interethnic difference in VKORC1 haplotypes accounts for the difference in warfarin requirements between Chinese, Malays, and Indians, providing interesting insights into genetic variation between ethnogeographically distinct Asian groups.