Acetylator phenotype and genotype in patients infected with HIV: discordance between methods for phenotype determination and genotype

The acetylator phenotype and genotype of AIDS patients, with and without an acute illness, was compared with that of healthy control subjects (30 per group). Two probe drugs, caffeine and dapsone, were used to determine the phenotype in the acutely ill cohort. Polymerase chain reaction amplification and restriction fragment length polymorphism analysis served to distinguish between the 26 known NAT2 alleles and the 21 most common NAT1 alleles. The distribution (%) of slow:rapid acetylator phenotype seen among acutely ill AIDS patients differed with the probe substrate used: 70:30 with caffeine versus 53:47 with dapsone. Phenotype assignment differed considerably between the two methods and there were numerous discrepancies between phenotype and genotype. The NAT2 genotype distribution was 45:55 slow:rapid. Control subjects, phenotyped only with caffeine, were 67:33 slow:rapid versus 60:40 genotypically. Stable AIDS patients, phenotyped only with dapsone, were 55:45 slow:rapid versus 46:54 genotypically. Following resolution of their acute infections, 12 of the acutely ill subjects were rephenotyped with dapsone. Phenotype assignment remained unchanged in all cases. The distribution of NAT1 alleles was similar in all three groups. It is evident from the amount of discordance between caffeine phenotype and dapsone phenotype or genotype that caution should be exercised in the use of caffeine as a probe for NAT2 in acutely ill patients. It is also clear that meaningful study of the acetylation polymorphism requires both phenotypic and genotypic data.     

Slow acetylator phenotype and genotype in HIV-positive patients with sulphamethoxazole hypersensitivity

AIMS: To test the role of acetylator status, and to investigate the reported discrepancy between acetylator phenotype and genotype in HIV-positive patients with sulphamethoxazole (SMX) hypersensitivity. METHODS: Forty HIV-positive patients (32 of whom were SMX-hypersensitive), and 26 healthy volunteers, were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis, and phenotyped using dapsone (50 mg) as a probe, for acetylator status. Sequencing of the NAT2 exon was performed where discrepancy between phenotyping and genotyping was detected. Our results were also pooled with published studies addressing slow acetylator status in HIV-positive SMX-hypersensitive patients. RESULTS: Slow acetylator genotype and phenotype frequencies did not differ between HIV-positive SMX-hypersensitive and nonhypersensitive patients, and healthy controls, which was further confirmed in a meta-analysis of published studies (pooled odds ratio 2.25, 95% confidence interval 0.45, 11.17). Discordance between phenotype and genotype was resolved in four of the subjects by sequencing of the whole NAT2 exon, which revealed rare mutations, leaving three (9%) HIV-positive SMX-hypersensitive patients and one (4%) healthy volunteer who continued to demonstrate the discordance. CONCLUSIONS: Slow acetylator phenotype or genotype is unlikely to predispose to SMX hypersensitivity in HIV-positive patients, although a minor role cannot be excluded. Phenotype-genotype discrepancies are partly due to nondetection of all rare alleles by PCR methodology, and can be circumvented by sequencing of the gene in patients showing a discrepancy.     

Acetylator phenotype and congenital malformations

Summary The hypothesis has been tested that an unusual maternal acetylator phenotype can predispose to congenital malformations in the fetus. The acetylator phenotype of normal caucasian control women and of mothers of malformed children was established by measuring urinary sulphadimidine and its acetylated metabolite. A further control group was the fathers of the malformed newborn. The malformations studied were facial cleft, spina-bifida and congenital heart disease. The acetylator phenotype was shown not be modified by pregnancy. 49 of 100 (49%) control women were rapid acetylators. Amongst the 108 mothers of malformed babies, 56 (52.8%) were slow acetylators and 52 (47.2%) were fast acetylators, 42 out of 83 (50.5%) of the fathers of malformed were slow acetylators and 41 (49.5%) were fast acetylators. Thus, the acetylator phenotype of the mothers of malformed children is no different from the acetylator phenotype of controls.     

Acetylator phenotype and serum levels of sulfapyridine in patients with inflammatory bowel disease

Summary Twenty-eight outpatients receiving sulfasalazine for inflammatory bowel disease were monitored. Assessment of acetylator phenotype according to the percentage of acetylated sulfapyridine in serum provided a clear distinction between rapid and slow acetylators. In comparison, the percentage of acetylated sulfapyridine in saliva or urine was a less precise index of phenotype. Determination of saliva concentrations of sulfapyridine and N⁴-acetylsulfapyridine did not provide a reliable estimate of serum levels. Slow acetylators had significantly higher serum concentrations of sulfapyridine (21.9±14.0 [SD] µg/ml) than rapid acetylators (8.8±4.3 µg/ml) and had a higher incidence of toxicity (not statistically significant,p>0.05). Serum concentrations of sulfapyridine were significantly higher in patients with symptoms of toxicity (23.2±15.9 µg/ml) than those without (13.9±9.5 µg/ml) (p<0.05). However, serum concentrations of total sulfapyridine (sulfapyridine plus N⁴-acetylsulfapyridine) were not significantly different in patients with (32.9±21.2 µg/ml) or without (22.8±12.0 µg/ml) toxicity (p>0.05). For all patients serum concentrations of sulfapyridine (total sulfapyridine) ranged from 3.5 to 73.1 (5.7 to 95.1) µg/ml in patients with controlled disease and 6.3 to 38.0 (14.0 to 54.7) µg/ml in patients with active disease. A significant correlation between clinical status of disease and serum drug concentrations was only apparent for rapid acetylators (p<0.05). The daily sulfasalazine dosage (mg/kg of body weight, log value) and serum drug concentrations (log values) were highly correlated (p<0.05). For clinical evaluation of inflammatory bowel disease patients determination of serum sulfapyridine concentrations appears to be more important for monitoring toxicity than therapeutic efficacy of sulfasalazine. Assessment of acetylator status appears to be useful for predicting serum sulfapyridine levels in patients receiving sulfasalazine therapy.     

磺胺类药物过敏和交叉过敏的研究进展

磺胺类药物是指含有-SO2NH2结构的药物。磺胺类药物的交叉过敏仍是困扰临床的一个用药难题。有磺胺类抗菌药过敏史的患者在临床上并不罕见,这些患者是否可以使用其他磺胺类药物,相关药品说明书的描述并不一致,也无标准的操作流程或指南。本文回顾了磺胺类抗菌药发生超敏反应的机制,发现其发生主要与磺胺类抗菌药N4位的芳香胺取代基和N1位的杂环取代基有关,而多数磺胺类非抗菌药(如呋塞米、噻嗪类利尿剂、塞来昔布等)并不含有这两个取代基,因此磺胺类抗菌药和非抗菌药之间发生交叉过敏的可能性较低。此外,本文也对磺胺类药物交叉过敏的相关临床研究进行了回顾。一个大规模的回顾性研究提示,有磺胺类抗菌药过敏史者使用磺胺类非抗菌药过敏反应的发生率较无磺胺过敏史者高,但并非与磺胺基团有关,而是和患者本身过敏反应易感性高有关。磺胺类抗菌药和非抗菌药之间发生交叉过敏的理论和循证依据尚不充分,但鉴于有磺胺类抗菌药过敏史的患者对药物过敏的易感性较高,这些患者是否可使用其他磺胺类药物,取决于相关药品说明书的规定、既往发生过敏反应的严重程度以及是否有其他替代药物。     

Acetylation genotype and phenotype in patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease affecting various tissues and organs. In the studies on SLE etiopathogenesis, a potential role of genetically determined impairment of xenobiotic metabolism has been emphasized. N-acetyltransferase 2 enzyme (NAT2) exhibits gene polymorphism and the acetylation rate with NAT2 involvement varies from person to person. The study on acetylation phenotype was carried out using isonicotinic acid hydrazide (isoniazid) as a model drug, while NAT2 alleles were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assays. Among patients with SLE, NAT2*4/NAT2*6 and NAT2*5/NAT2*5 genotypes occurred most frequently, while NAT2*4/NAT2*6 and NAT2*5/NAT2*6 prevailed in the control group. The concordance of 96.8% was achieved between acetylation phenotype and NAT2 genotype in the group of SLE patients studied. Conclusion: Acetylation polymorphism appears not to be an important risk factor in SLE.     

Acetylator phenotype among individuals with glucose 6-phosphate dehydrogenase variants

The acetylator phenotype was determined for 142 Nigerian adults by administering sulphamethazine (40 mg/kg body wt) and analysing six hour urines for free and acetylated drug. Of these 142 subjects, 21 (14.8%) had no red cell glucose 6-phosphate dehydrogenase activity, 35 (24.6%) had partial activity and 86 (60.56%) had normal activity. The percentage of slow acetylators among the three groups was 38.1%, 40% and 40.7% respectively. The differences between the three groups were not statistically significant. However, individuals with no red cell glucose 6-phosphate dehydrogenase activity and who are also slow acetylators may be more sensitive to the effects of drugs like sulphamethazine, dapsone and isoniazid.     

Efavirenz concentrations in HIV-infected patients with and without viral hepatitis

AIMS

Data on efavirenz in HIV/viral hepatitis co-infected patients is non-consensual, probably due to liver function heterogeneity in the patients included.

METHODS

A case control study was performed on 27 HIV-infected patients, with controlled and homogenous markers of hepatic function, either mono-infected or co-infected with HBV/HCV, to ascertain the influence of viral hepatitis on efavirenz concentrations over a 2-year follow-up period.

RESULTS

No differences were found in efavirenz concentrations between groups both during and at the end of the follow-up period: control (2.43 ± 1.91 mg l^–1) vs. co-infected individuals (2.37 ± 0.37 mg l^–1).

CONCLUSION

It was concluded that HBV/HCV infections in themselves do not predispose to an overexposure to efavirenz.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• HIV-1 co-infection with HBV/HCV is the most important factor determining efavirenz-induced liver toxicity. Higher efavirenz plasma concentrations have been reported in these patients facilitating concentration drug-related adverse effects.
• It is not known whether changes in efavirenz disposition are due to the hepatitis infection/inflammation or to liver failure. As a consequence, the guidelines for the application of therapeutic drug monitoring of efavirenz in HBV/HCV co-infected patients have not been established.

WHAT THIS STUDY ADDS

• The present study has shown that HBV/HCV infection in itself does not predispose to higher efavirenz plasma concentrations. In the absence of hepatic failure, the risk of efavirenz concentration-dependent toxicity is not increased.
• Thus, therapeutic drug monitoring indications in co-infected patients with hepatic function within the normal range should be the same as in HIV-1 mono-infected patients.

     

Acetylator phenotype and the clinical pharmacology of slow-release procainamide

Slow-release procainamide given 8-hourly is shown to produce plasma levels generally accepted as giving effective prophylaxis against ventricular dysrhythmias occurring after recent myocardial infarction. Patients can be classified into 'slow' and 'fast' acetylators of procainamide. Knowledge of acetylator status is helpful in determining the dose of procainamide necessary to attain effective steady-state plasma levels while avoiding toxic ones. Acetylator status cannot be assessed accurately using sulphadimidine when the patients are also taking procainamide.     

Acetylator phenotyping with sulphadimidine in patients receiving isoniazid

The possible competition of isoniazid for the acetylation of sulphadimidine was studied by comparing the degree of acetylation of urine sulphadimidine (1 g orally) in isoniazid-treated and in isoniazid-untreated patients. The former group (isoniazid 300 mg once daily) consisted of 5 slow and 5 rapid acetylators and the latter group of 5 and 6 respective acetylator phenotypes. In all of the 4-8, 8-12 and 12-24 h urine fractions, the acetylation percentage of sulphadimidine and its distribution pattern were practically unaffected by the isoniazid. This suggests that isoniazid therapy does not interfere significantly with the routine acetylator phenotyping by means of sulphadimidine.     

Thiopurine methyltransferase genotype and phenotype status in Japanese patients with systemic lupus erythematosus

We investigated the genotypic status of thiopurine methyltransferase (TPMT) polymorphism to evaluate the possible risk of the toxicity of azathioprine (AZA) in 68 patients with systemic lupus erythematosus (SLE). The allele frequency of TPMT mutation in the SLE group (2.9%) was higher than that in 174 Japanese healthy volunteers (1.1%), although it did not reach statistically significant difference (p=0.23). The mean value of TPMT activities in 51 subjects with TPMT*1/*1 was 40% higher than that of 4 subjects with TPMT*1/*3C in SLE group (18.1+/-6.1 nmol/h/ml packed red blood cells (pRBC) versus 13.2+/-3.2 nmol/h/ml pRBC; p=0.11). Two out of 4 SLE patients with TPMT*1/*3C had been treated with AZA, and one patient showed a leucopenia. The TPMT genotyping before AZA treatment is recommended for Japanese SLE patient group to avoid the AZA-induced adverse events, although detection of the patient with low TPMT activity by genotyping is still imperfect.     

Pharmacokinetics of rifabutin in HIV-infected patients with or without wasting syndrome

AIMS: The purpose of the study was to compare the pharmacokinetic parameters of rifabutin obtained in a group of patients without wasting syndrome (NWS) with those obtained in a group with wasting syndrome (WS). METHODS: A single dose of 300 mg rifabutin was administered in the fasting state to the patients in both study groups and blood samples were scheduled to be collected at the following times: 0 (predose), 0.5, 1, 2, 3, 4, 6, 8, 24, 48, 72 and 96 h following administration. Data were analysed using noncompartmental methods. The pharmacokinetic parameters of rifabutin in patients with and without wasting syndrome were compared using the Mann-Whitney U-test. RESULTS: Cmax was 0.34+/-0. 14 mg l-1 in NWS patients and 0.55+/-0.16 mg l-1 (P=0.01) in patients with WS. tmax was 4.2+/-1.5 and 3.3+/-2.3 h (P=0.17) in NWS and WS patients, respectively. The AUCs were similar in the two study groups. V/F was 2905+/-1646 l in NWS patients and 1701+/-492 l (P=0.07) for the WS group. These differences are less pronounced following normalization of V/F to patients body weight (43.7+/-20.1 vs 35.4+/-10.3 l kg-1 ). t1/2,lambdaz tended to be shorter in patients with WS (31.4+/-12.9 vs 46.0+/-23.5 h, P=0.12). CONCLUSIONS: Our study suggests that the pharmacokinetics of rifabutin in patients with wasting syndrome are not altered to a degree that is clinically important.     

难治性肾病综合征患者谷胱甘肽硫转移酶活性和基因多态性研究

目的:研究谷胱甘肽硫转移酶(GSTs)活性与基因多态性在难治性肾病综合征(RNS)患者中的分布特征。方法:运用等位基因特异性PCR(ASPCR)和PCR-限制性片段长度多态性(PCR-RFLP)的方法分析健康人和难治性肾病综合征患者谷胱甘肽硫转移酶基因型;用紫外分光光度法分别测定两者红细胞GSTs活性。结果:RNS患者的GSTs基因型分布与健康者差异无显著性;难治性肾病综合征患者GSTs活性与健康人存在差异,难治性肾病综合征患者平均GSTs活性(5.9±2.0)U/gHb高于健康人(4.3±2.6)U/gHb,杂合子I/V基因型组的平均GSTs活性比野生I/I基因型的GST活性低,比突变v/v基因型的GSTs活性高。在RNS患者中,GSTM1基因型之间GSTs活性差异不大。结论:借鉴健康人的基因型研究结果,综合分析RNS患者GST的活性和基因多态性特征,为疾病个体化治疗提供研究基础。     

A discordance of the cytochrome P450 2C19 genotype and phenotype in patients with advanced cancer

AIMS: To examine the relationship between cytochrome P450 2C19 (CYP2C19) genotype and expressed metabolic activity in 16 patients with advanced metastatic cancer. METHODS: Individual CYP2C19 genotypes were determined by PCR-based amplification, followed by restriction fragment length analysis, and compared with observed CYP2C19 metabolic activity, as determined using the log hydroxylation index of omeprazole. RESULTS: All 16 patients had an extensive metabolizer genotype. However, based on the antimode in a distribution of log omeprazole hydroxylation indices from healthy volunteers, four of the patients had a poor metabolizer phenotype and there was a general shift of the remaining 12 patients towards a slower metabolic phenotype. This suggests a reduction in metabolic activity for all patients relative to healthy volunteers. A careful analysis of patient medical records failed to reveal any drug interactions or other source for the observed discordance between genotype and phenotype. CONCLUSIONS: There are no previous reports of a 'discordance' between genotype and expressed enzyme activity in cancer patients. Such a decrease in enzyme activity could have an impact on the efficacy and toxicity of chemotherapeutic agents and other drugs, used in standard oncology practice.     

Correlation between acetylation phenotype and genotype in Chinese women

OBJECTIVE: The acetylation polymorphism is a common inherited variation in human drug and carcinogen metabolism. Because N-acetyltransferase (NAT2) is important for the detoxification and/or bioactivation of drugs and carcinogens, this polymorphism has important implications in therapeutics and cancer susceptibility. A high correlation between acetylation phenotype and genotype has been demonstrated in several studies. However, no such data exist for Chinese females. The aim of the present study was to compare acetylation phenotype with NAT2 genotype in a population of primarily non-smoking Chinese females. METHODS: In the present study, the correlation between N-acetyltransferase activity and NAT2 genotype was evaluated in 103 unrelated Chinese female controls derived from a hospital-based case-control study of lung cancer in Singapore. Acetylation phenotype and genotype were respectively determined using caffeine and an allele-specific polymerase chain reaction (PCR). RESULTS: The proportions of rapid and slow phenotypes were 78% and 22%, respectively, while the distribution of rapid (heterozygotes and homozygotes combined) and slow acetylator genotypes was 76% and 24%, respectively. The distribution of the various NAT2 genotypes did not differ significantly (chi2 = 1.45, P > 0.05) from that predicted by the Hardy-Weinberg Law. All slow acetylators were accurately predicted (100%), whereas 2 of 80 rapid acetylators were erroneously predicted as slow (2.5%). The overall prediction rate of the PCR-based test for the acetylation phenotype was at 98.1% in our Chinese population. CONCLUSION: Our results suggest that genotyping with PCR may well become the preferred method for the determination of acetylation polymorphism in epidemiological studies in this Asian population.     

Quinidine disposition in relation to antipyrine elimination and debrisoquine phenotype in alcoholic patients with and without cirrhosis

Single dose disposition of oral quinidine (400 mg sulfate) was studied in a control group of subjects (No. = 6) and in hospitalized alcoholic patients involving one group with (No. = 6) and one group without (No. = 11) hepatic cirrhosis. All subjects also underwent an antipyrine and a debrisoquine test. Patients with cirrhosis had a prolonged elimination half-life (29.5 +/- 5.9 h) and low clearance (24 +/- 7 ml.kg-1.h-1) of antipyrine and also a considerably higher debrisoquine metabolic ratio (18.8 +/- 3.3) than the controls, whereas the alcoholics without cirrhosis had metabolic patterns for these two test compounds comparable to those seen in the controls (antipyrine half-life: 8.8 +/- 1.1 h and 9.8 +/- 2.0 h; debrisoquine metabolic ratio: 3.6 +/- 0.7 and 3.8 +/- 1.2 for alcoholics and controls respectively). In patients with cirrhosis the apparent elimination half-life of quinidine was longer (12.8 +/- 1.8 h) whereas after oral administration clearance of quinidine (15.6 +/- 3.5 l.h-1) and quinidine/3-hydroxyquinidine ratio (9.9 +/- 2.1) were not different from controls (quinidine clearance: 13.45 +/- 1.9 l.h-1; quinidine/3-hydroxyquinidine: 10.3 +/- 2.7). A possible change in distribution patterns of quinidine in cirrhotics may explain these findings.     

酿脓链球菌对大环内酯类抗菌药物耐药表型与基因型研究

目的 研究酿脓链球菌对大环内酯类抗菌药物的耐药表型与基因型。方法 采用琼脂平板稀释法测定97株酿脓链球菌对红霉素、克林霉素、麦迪霉素、阿奇霉素、克拉霉素和青霉素的敏感性；用双纸片法检测酿脓链球菌耐药表型；用PCR方法检测耐大环内酯的酿脓链球菌携带的耐药基因。结果 97株酿脓链球菌中82株表现为对大环内酯类抗菌药物不敏感，其中42株表现为eMLS型耐药，37株为iMLS型耐药，3株细菌为主动外排M型耐药；82株对大环内酯不敏感的酿脓链球菌中77株检测到耐药基因，其中12株具有ermB基因，25株具有ermTR基因，2株具有mefA基因，21株同时具有ermB／ermTR基因，5株同时具有ermB／mefA基因，3株同时具有ermTR／mefA基因，9株同时具有ermB／ermTR／mefA基因，5株未能检测到三种耐药基因。结论 酿脓链球菌对大环内酯类抗菌药物的耐药率较高，耐药表型以cMLS和iMLS为主，耐药基因以ermB和ermTR多见。