Mordechai Muszkat

CYP2C9 Genotype-guided Warfarin Prescribing Enhances the Efficacy and Safety of Anticoagulation : A Prospective Randomized Controlled Study

Warfarin anticoagulation effect is characterized by marked variability, some of which has been attributed to CYP2C9 polymorphisms. This study prospectively examines whether a priori knowledge of CYP2C9 genotype may improve warfarin therapy. Patients were randomly assigned to receive warfarin by a validated algorithm (“control”, 96 patients) or CYP2C9 genotype‐adjusted algorithms (“study”, 95 patients). The first therapeutic international normalized ratio and stable anticoagulation were reached 2.73 and 18.1 days earlier in the study group, respectively (P<0.001). The faster rate of initial anticoagulation was driven by a 28% higher daily dose in the study group (P<0.001). Study group patients spent more time within the therapeutic range (80.4 vs 63.4%, respectively, P<0.001) and experienced less minor bleeding (3.2 vs 12.5%, P<0.02, respectively). In conclusion, CYP2C9 genotype‐guided warfarin therapy is more efficient and safer than the “average‐dose” protocol. Future research should focus on construction of algorithms that incorporate other polymorphisms (VKORC1), host factors, and environmental influences.

Population differences in S‐warfarin metabolism between CYP2C9 genotype‐matched Caucasian and Japanese patients

Our objective was to investigate population differences in the metabolic activity of cytochrome P450 (CYP) 2C9 between genotypically matched Caucasian and Japanese patients by using the unbound oral clearance of S‐warfarin as an in vivo phenotypic trait measure.

Local and systemic immune response in community-dwelling elderly after intranasal or intramuscular immunization with inactivated influenza vaccine.

Intramuscular (IM) influenza vaccines are about 50% effective in preventing clinical illness among the elderly and their effectiveness in eliciting mucosal response may be even lower. The aim of the present study was to evaluate the immunological effect of a novel inactivated intranasal (IN) trivalent whole influenza virus vaccine among community‐dwelling elderly. Sixty‐one subjects were vaccinated with two doses of an IN vaccine and a control group of 31 subjects was vaccinated with a commercial IM vaccine. Viral strains in the 1997/8 vaccine used were A/Nanchang/933/95(H3N2), A/Johannesburg/82/96(H1N1) and B/Harbin/7/94. Serum IgG and nasal IgA were determined by HI and ELISA, respectively. Only a few minor local adverse events were reported after vaccination. Seroconversion for the three antigens tested was higher after IM vaccination, although not statistically significant. Local antibody response to the three antigens tested was detected in 50–53% and 19–26% of IN and IM immunized subjects, respectively. The IN vaccine tested was significantly more effective than the IM vaccine in inducing mucosal IgA response. This may prevent influenza at its early stages and thus contribute to the reduction of complications in the elderly. J. Med. Virol. 61:100–106, 2000.

Warfarin metabolism and anticoagulant effect: a prospective, observational study of the impact of CYP2C9 genetic polymorphism in the presence of drug-disease and drug-drug interactions.

BACKGROUND Cytocbrome P450 (CYP) 2C9 polymorphism affects the warfarin dosage requirement in stable outpatients. However, it is not known whether the CYP2C9 genotype contributes to the variability in warfarin dosage in the presence of drug-disease and drug-drug interactions. OBJECTIVE The aim of this study was to examine the effects of CYP2C9 genetic polymorphism on warfarin dosage requirements in patients with severe comorbid conditions and those treated with medications that potentially interact with warfarin. METHODS This prospective, observational study was conducted at Hadassah University Hospital, Jerusalem, Israel. Data from consecutive patients treated with warfarin for at least 3 months and admitted to the internal medicine ward were eligible for inclusion. Clinical data, international normalized ratio (INR), and warfarin dosage were recorded from medical records. The CYP2C9 genotype was determined using polymerase chain reaction restriction fragment length polymorphism, and plasma concentrations of (S)- and (R)-warfarin were determined by high-performance liquid chromatography using chiral methods. RESULTS One hundred nineteen subjects (52% women) were studied. Mean age was 65.8 years (95% CI, 63.1-68.4), and weight was 74.9 kg (95% CI, 72.1-77.7). The mean warfarin dosage was 33% lower in patients with the CYP2C9-*1/*3 genotype (mean [SEM], 0.045 [0.006] mg/kg x d(-1)) compared with the CYP2C9-*1/*1 genotype (0.067 [0.004] mg/kg x d(-1)) (P=0.008); an intermediate value was found for the CYP2C9-*1/*2 genotype (0.062 [0.008] mg/kg x d(-1)). However, despite the lower dosage, INR was significantly higher in patients with the *1/*3 genotype (mean [95% CI], 3.29 [2.44-4.14]) (n=18) compared with the *1/*1 genotype (2.52 [2.34-2.71]) (n=64) (P=0.029). In addition to genotype, older age, congestive heart failure (CHF), and treatment with antibiotics were associated with lower warfarin dosages, whereas treatment with drug-metabolism inducers was associated with higher warfarin dosages. In addition, the ratios of (S)- to (R)-warfarin concentrations were significantly higher in patients with *1/*3 compared with those in patients with the *1/*1 genotype. CONCLUSIONS In this study population of patients with severe comorbid conditions and those treated with medications that potentially interact with warfarin, CYP2C9 *1/*3 genotype, older age, CHF, and the use of antibiotics were associated with lower warfarin dosage requirements. The CYP2C9*1/*3 genotype, compared with CYP2C9 *1/*1, was associated with 33% lower mean warfarin dosage requirements and higher INR values, which were higher than the upper therapeutic range of INR (ie, 3). Genetic CYP2C9 polymorphism contributed to the variability in warfarin dosage requirements in the presence of drug-disease and drug-drug interactions.

Local and systemic immune response in nursing-home elderly following intranasal or intramuscular immunization with inactivated influenza vaccine.

Intramuscular (IM) influenza vaccines are only 30-40% effective in preventing clinical illness among the elderly, and their effectiveness in eliciting mucosal response may be even lower. The aim of the present study was to evaluate the immunological effect of a novel inactivated intranasal (IN) trivalent whole influenza virus vaccine among nursing-home elderly. Twenty-one institutionalized elderly subjects were vaccinated IN with an inactivated novel vaccine, twice, 21 days apart, and with no adverse effects. Twenty-two subjects were vaccinated once with a commercial IM vaccine. Viral strains used in the 1998/9 vaccine (20 microg of each per dose) were A/Beijing/262/95, A/Sydney/5/97 and B/Harbin/7/94. Serum antibodies (IgG and IgM) and nasal IgA were determined by the hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA), respectively. Mucosal antibody response to the three vaccine strains was detected in 47.6-71.4% and 18.1-31.8% of IN and IM immunized subjects, respectively. Serum antibody response to the three antigens tested was detected in 20.0-61.9% and 18.2-72.7% of IN and IM immunized subjects, respectively. Seroconversion was not significantly different after IN or IM vaccination for both A/Sydney and B/Harbin, but higher for A/Beijing following IM vaccination. On study completion, 57.1, 65.0 and 50.0% of IN vaccinees were seroprotected to A/Beijing, A/Sydney and B/Harbin, respectively. Similarly, 68.1, 77.2 and 54.5% were immune after IM vaccination. The IN vaccine tested was significantly more effective than the IM vaccine in inducing mucosal IgA response. This may prevent influenza at its early stages and thus contribute to the reduction of morbidity and complications in nursing-home elderly.

Ethnic and Genetic Determinants of Cardiovascular Response to the Selective α2-Adrenoceptor Agonist Dexmedetomidine

The &agr;2-adrenoceptor agonist clonidine reduces blood pressure more effectively in White than Black Americans despite similar degrees of sympatholysis. Functional genetic variation in receptor signaling mechanisms, for example in the &bgr;3 G-protein subunit (GNB3 C825T) and in the &agr;2C-adrenoceptor subtype (ADRA2C del322–325), may affect drug responses. We examined the hypothesis that there are ethnic differences in the responses to the highly selective &agr;2-agonist, dexmedetomidine, and that these genetic variants contribute to interindividual variability in drug responses. In a placebo-controlled, single-masked study, 73 healthy subjects (37 whites and 36 blacks) received 3 placebo infusions and then 3 incremental doses of dexmedetomidine (cumulative dose, 0.4 &mgr;g/kg), each separated by 30 minutes. Blood pressure, heart rate, and plasma catecholamine concentrations were determined after each infusion. We measured dexmedetomidine concentrations after the last infusion and determined ADRA2C del322–325 and GNB3 C825T genotypes. Dexmedetomidine lowered blood pressure and plasma catecholamine concentrations significantly (all P<0.001). There was substantial interindividual variability in the reduction of systolic blood pressure (range, 1 to 34 mm Hg) and plasma norepinephrine concentrations (range, 24 to 424 pg/mL). However, there were no differences between black and white subjects in dexmedetomidine responses (P>0.16 for all outcomes) before or after adjustment for covariates. Neither ADRA2C del322–325 nor GNB3 C825T genotypes affected the responses to dexmedetomidine (all P>0.66). There is large interindividual variability in response to the selective &agr;2-AR agonist dexmedetomidine, and neither ethnicity nor ADRA2C and GNB3 genotypes contribute to it. Further studies to identify determinants of &agr;2-AR–mediated responses will be of interest.

The evaluation of pleural effusions in patients with heart failure

PURPOSE To determine the causes of pleural effusions in patients with heart failure, and the association of the characteristics of these statistics with the use of diuretics. SUBJECTS AND METHODS Eighty-one patients with a definite diagnosis of heart failure who underwent thoracentesis were evaluated. Fluids were classified as transudates or exudates using Lights criteria. RESULTS Forty-one effusions (in 34 patients) were transudates, and 54 (in 47 patients) were exudates. A specific cause was found for 32 of the exudates (27 patients); except for heart failure, no obvious cause was found for the remaining 22 fluids (20 patients). Exudates with a specific cause for an exudate were more likely to have at least two of Lights criteria (18 of 27 [67%]) than did exudates without a known cause (2 of 21 [10%]). Intravenous diuretic therapy in the 24 hours before thoracentesis was significantly more common among patients with exudates without a specific cause. CONCLUSIONS Patients with heart failure may have exudative pleural effusions without an obvious cause except heart failure.

Tariquidar, a selective P-glycoprotein inhibitor, does not potentiate loperamide's opioid brain effects in humans despite full inhibition of lymphocyte P-glycoprotein.

Background:Loperamide, a potent opioid, has been used as an in vivo probe to assess P-glycoprotein activity at the blood–brain barrier, because P-glycoprotein inhibition allows loperamide to cross the blood–brain barrier and exert its central opioid effects. In humans, studies with nonselective and moderately potent inhibitors resulted in mild opioid effects but were confounded by the concurrent inhibition of loperamide’s metabolism. The authors studied the effect of the highly selective, potent P-glycoprotein inhibitor tariquidar on loperamide’s central opioid effects. Methods:In a randomized, double-blind, crossover study, nine healthy subjects received on 2 study days oral loperamide (32 mg) followed by an intravenous infusion of either tariquidar (150 mg) or placebo. Central opioid effects (pupil diameter, sedation) were measured for 12 h, and blood samples were drawn up to 48 h after drug administration to determine plasma loperamide concentrations and ex vivo P-glycoprotein activity in T lymphocytes. Values for pupil diameter and loperamide concentrations were plotted over time, and the areas under the curves on the tariquidar and placebo study day were compared within each subject. Results:Tariquidar did not significantly affect loperamide’s central effects (median reduction in pupil diameter area under the curve, 6.9% [interquartile range, −1.4 to 12.1%]; P = 0.11) or plasma loperamide concentrations (P = 0.12) but profoundly inhibited P-glycoprotein in lymphocytes by 93.7% (95% confidence interval, 92.0–95.3%). Conclusion:These results suggest that despite full inhibition of lymphocyte P-glycoprotein, the selective P-glycoprotein inhibitor tariquidar does not potentiate loperamide’s opioid brain effects in humans.

Genetic variants in the α2C-adrenoceptor and G-protein contribute to ethnic differences in cardiovascular stress responses

Objectives Cardiovascular responses to stressors are regulated by sympathetic activity, increased in black Americans, and associated with future cardiovascular morbidity. Our aim was to determine whether two functional variants in genes regulating sympathetic activity, a deletion in the &agr;2C-adrenergic receptor (ADRA2C del322–325) and a G-protein &bgr;3-subunit variant (GNB3 G825T), affect cardiovascular responses to physiologic stressors and contribute to their ethnic differences. Methods We measured heart rate and blood pressure responses to a cold pressor test (CPT) in 79 healthy participants (40 blacks, 39 whites), aged 25.7±5.3 years, and determined genotypes for the ADRA2C and GNB3 variants. We examined the response variables (increase in heart rate and blood pressure) in multiple linear regression analyses adjusting first for baseline measures, ethnicity, and other covariates, and then additionally for genotypes. Results Black participants had a greater heart rate response to CPT than whites [mean difference, 9.9 bpm; 95% confidence interval (CI), 4.1 to 15.6; P=0.001]. Both the ADRA2C del/del (15.8 bpm; 95% CI, 8.0–23.7; P<0.001) and GNB3 T/T genotypes (6.8 bpm; 95% CI, 0.9–12.7; P=0.026) were associated with greater heart rate response. After adjusting for genotypes, the ethnic difference was abrogated (1.3 bpm; 95% CI, −5.4–8.0; P=0.70), suggesting that the genetic variants contributed substantially to ethnic differences. Conclusion Variation in genes that regulate sympathetic activity affects hemodynamic stress responses and contributes to their ethnic differences. This study elucidates how genetic factors may in part explain ethnic differences in cardiovascular regulation.

Local SIgA response following administration of a novel intranasal inactivated influenza virus vaccine in community residing elderly

Community-residing elderly were immunized twice intranasally three weeks apart with a new inactivated whole influenza vaccine. A control group was immunized intramuscularly with conventional influenza vaccine. Local antibody response was detected in about 50% of intranasally immunized subjects compared to about 20% of intramuscularly immunized subjects, to the three viral strains. Increasing the incidence of elevated IgA response may prevent influenza at its early stages thus reducing complications in the elderly.