Aqueous humour penetration of moxifloxocin and gatifloxacin eye drops in different dosing regimens before phacoemulsification surgery.

AIM: To compare the aqueous humour penetration of moxifloxacin 0.5% and gatifloxacin 0.3% eye drops administered in two different dosing regimens during phacoemulsification surgery. METHODS: This prospective, randomised study included 97 patients. The patients were randomly divided into two treatment groups to receive either moxifloxacin or gatifloxacin. All patients received the topical antibiotics four times per day for 2 days prior to surgery. Patients in each group were further subdivided to receive additional doses of antibiotic drops as two drops 30 min apart (subgroup 1) versus four drops 10 min apart (subgroup 2) 1 h prior to the surgery. At the beginning of surgery, 0.1 ml of aqueous humour was aspirated, and the concentrations of moxifloxacin and gatifloxacin were analysed by high-performance liquid chromatography. RESULTS: The mean concentrations of moxifloxacin and gatifloxacin in the aqueous humour were 0.72 ± 0.40 µg/ml and 0.47 ± 0.29 µg/ml, respectively, in the first subgroup, and 1.95 ± 1.05 µg/ml and 0.77 ± 0.52 µg/ml, respectively, in the second subgroup. Both the inter-group (p=0.006 and p=0.000, respectively) and the intra-group (p=0.000 and p=0.035, respectively) differences between the aqueous humour concentrations of moxifloxacin and gatifloxacin subgroups were statistically significant. CONCLUSION: Moxifloxacin, given in the same dosage, penetrated the aqueous humour better then gatifloxacin during cataract surgery. The penetration of both antibiotics increased significantly when the dosage of the agent was doubled.

Association between the Glu298Asp and T(-786)C polymorphisms of the endothelial nitric oxide synthase gene and respiratory distress in preterm neonates.

Genetic polymorphisms in the gene that codes for endothelial nitric oxide synthase (eNOS) have been associated with less nitric oxide availability and with various cardiovascular diseases in humans. The objective of this study was to analyze the genotype distributions and allele frequencies for the Glu298Asp (G894T) and T(-786)C polymorphisms of the eNOS gene among neonates with respiratory distress in comparison to healthy control subjects. Fifty premature neonates with respiratory distress and 55 neonates without any respiratory problem were included in the study. Genomic DNA from all the neonates was analyzed by polymerase chain reaction. A polymerase chain reaction-restriction fragment length polymorphism analysis of eNOS gene polymorphisms was performed, and the results were compared. There were no significant differences between the groups regarding either genotype distributions or the allele frequencies for the Glu298Asp and T(-786)C polymorphisms. These results suggest that eNOS Glu298Asp and T(-786)C polymorphisms are not associated with development of respiratory distress.

Disposition of a CYP2C9 phenotyping agent, losartan, is not influenced by the common 3435C > T variation of the drug transporter gene ABCB1 (MDR1).

Losartan is oxidized to E3174 by cytochrome P450 2C9 (CYP2C9); it has been suggested as a useful probe drug for CYP2C9 activity. It has also been shown to be a substrate for the drug-efflux transporter ATP-binding cassette sub-family B member 1 (ABCB1, MDR1). Both CYP2C9 and ABCB1 genes are polymorphic. The aim of the study was to determine if losartan disposition was influenced by the 3435C > T polymorphism of ABCB1 in healthy persons. These participants (n = 58) whose CYP2C9 genotypes and phenotypes were determined previously were genotyped for 3435C > T polymorphism in ABCB1. The concentrations of losartan and E3174 were compared across genotypes for ABCB1 3435C > T variation. For persons with the ABCB1 3435 CC, CT, TT genotypes, the concentrations (microM, means +/- S.D.) of neither losartan (1.76 +/- 0.87, 1.68 +/- 0.84 and 1.80 +/- 0.85, respectively, P = 0.70) nor E3174 (2.97 +/- 2.49, 2.53 +/- 2.09 and 3.18 +/- 2.75, respectively, P = 0.65) were significantly different. These results suggest that ABCB1 3435C > T polymorphism does not have any influence on losartan disposition. Therefore, ABCB1 3435C > T polymorphism is probably not a confounding factor in the prediction of CYP2C9 activity by using losartan as a probe agent.

Multidrug resistance in patients undergoing resective epilepsy surgery is not associated with C3435T polymorphism in the ABCB1 (MDR1) gene.

PURPOSE: The C3435T polymorphism in the gene coding for P-glycoprotein (ABCB1) has been correlated with drug resistance in patients with epilepsy. However, replication studies have revealed conflicting results and the reason for this is not clear. We investigated the frequency of C3435T polymorphism in epileptic Turkish patients who underwent resective epilepsy surgery and compared our results with healthy controls. METHODS: DNA samples were obtained from 100 healthy controls and 89 consecutive adult patients who underwent resective brain surgery due to refractory seizures at our epilepsy center. Genotypes for the C3435T polymorphism were determined by PCR and restriction analysis. RESULTS: Comparison of drug-resistant patients and healthy controls revealed no significant difference in allele frequency (C vs. T; chi(2)=0.015, p=0.90) and genotype frequency (chi(2)=2.05, p=0.36). The findings in the pure hippocampal sclerosis (HS) group (n=73) were not significantly different from control subjects, either (allele frequency: chi(2)=0.29, p=0.59; genotype frequency: chi(2)=2.14, p=0.34). CONCLUSIONS: Our findings failed to prove an association between C3435T polymorphism and drug resistance in a sample of Turkish patients with refractory epilepsy who underwent resective brain surgery.

Association of drug transporter gene ABCB1 (MDR1) 3435C to T polymorphism with colchicine response in familial Mediterranean fever.

OBJECTIVE: Colchicine is a mainstay of treatment in familial Mediterranean fever (FMF); however, 5%-10% of patients do not respond to colchicine. Adenosine triphosphate-binding cassette subfamily B member 1 (ABCB1 or MDR1) is a drug transporter that extrudes colchicine out of cells. ABCB1 gene 3435C to T polymorphism has been demonstrated to alter MDR1 expression in mononuclear cells. Thus, the amount of MDR1 in mononuclear cells may alter response to colchicine. We investigated the association between MDR1 3435C to T polymorphism and colchicine response in patients with FMF. METHODS: Patients (n = 120) were examined for colchicine responses. ABCB1 gene 3435C to T genotypes were determined to analyze associations with colchicine resistance. RESULTS: Ninety-eight patients were evaluated as responders and 22 as nonresponders. The distributions of ABCB1 CC, CT, and TT genotypes were significantly different between responsive and nonresponsive groups (chi-square = 6.86, p = 0.032). Colchicine resistance was significantly higher in patients harboring the C allele than in patients with TT genotype (odds ratio 9.71, 95% CI 1.58-58.76). Similarly, the mean colchicine dose to prevent remission was significantly lower in the TT group compared with subjects with the C allele (p = 0.014). CONCLUSION: Our study revealed an association between 3435C to T polymorphism and colchicine response in patients with FMF. Patients with the TT genotype for the ABCB1 3435C to T variant responded better to colchicine in terms of treatment efficacy and colchicine dose requirements.

Inhibitory effect of valproic acid on cytochrome P450 2C9 activity in epilepsy patients.

Drug interactions constitute a major problem in the treatment of epilepsy because drug combinations are so common. Valproic acid is a widely used anticonvulsant drug with a broad therapeutic spectrum. Case reports suggest interaction between valproic acid and other drugs metabolized mainly by cytochrome P450 isoforms. The aim of this study was to evaluate the inhibitory effect of valproic acid on cytochrome P450 2C9 (CYP2C9) activity by using losartan oxidation as a probe in epilepsy patients. Patients were prescribed sodium valproate (mean 200 mg/day for the first week and 400 mg/day in the following period) according to their clinical need. A single oral dose of 25 mg losartan was given to patients before and after the first dose, first week and 4 weeks of valproic acid treatment. Losartan and E3174, the CYP2C9-derived carboxylic acid metabolite of losartan in 8 hr urine were assayed by using high pressure liquid chromatography. Urinary losartan/E3174 ratio did not change significantly on the first day (0.9, 0.3-3.5; median, range), and first week (0.6, 0.2-3.8; median, range), while a significant increase was observed after 4 weeks of valproic acid treatment (1.1, 0.3-5.7; median, range) as compared to that of measured before valproic acid administration (0.6, 0.1-2.1; median, range) (P = 0.039). The degree of inhibition was correlated with the steady-state plasma concentrations of valproic acid (r(2) = 0.70, P = 0.04). The results suggest an inhibitory effect of valproic acid on CYP2C9 enzyme activity in epilepsy patients at steady state. The risk of pharmacokinetic drug-drug interactions should be taken into account during concomitant use of valproic acid and CYP2C9 substrates.

Neonatal jaundice and bilirubin UDP-glucuronosyl transferase 1A1 gene polymorphism in Turkish patients.

Bilirubin uridine diphosphate-glucuronosyltransferase (B-UGT) is the rate-limiting enzyme for the conjugation of bilirubin with glucuronic acid in its excretion process into the bile. Variations in B-UGT gene (UGT-1A1) have been related to disorders characterised by hyperbilirubinaemia. The aim of this study was to investigate whether the number of thymine-adenine repeats in the promoter region of UGT-1A1 was related to non-physiologic hyperbilirubinemia of unexplained aetiology in Turkish newborns. These patients (n=106) were genotyped for their thymine-adenine repeat number in the promoter region of UGT-1A1, and were divided into two groups according to their bilirubin level. Forty-nine newborns with bilirubin levels higher than 17 mg/dl within the first ten days of life comprised the hyperbilirubinaemia group and 25 newborns with bilirubin levels higher than 10 mg/dl after fifteen days of life formed the prolonged jaundice group. Thirty-two newborns were included as healthy controls. The observed frequencies for the wild-type six repeat allele thymine-adenine (TA(6)) within each subject group were similar (P>0.05; 75.5%, 78.0% and 73.4%, respectively). Likewise, the distribution of TA(6/6), TA(6/7) and TA(7/7) genotypes among three groups were similar. These results imply that the TA(7) repeat allele of UGT1A1 (UGT1A1*28) is a common variant in the Turkish population. Our results do not suggest an association between thymine-adenine repeat polymorphism of UGT1A1 and hyperbilirubinaemia of unexplained aetiology or prolonged jaundice in Turkish neonates.

Inhibitory effect of 5-fluorouracil on cytochrome P450 2C9 activity in cancer patients.

Drug interactions have been reported between 5-fluorouracil and cytochrome P450 2C9 (CYP2C9) substrates, S-warfarin and phenytoin. This study was performed to determine the influence of 5-fluorouracil on cytochrome P450 2C9 (CYP2C9) activity in colorectal cancer patients (n=17) receiving 5-fluorouracil. Losartan was used as a marker to assess CYP2C9 activity. Losartan and its CYP2C9 dependent metabolite, E-3174, were determined in urine. The ratios of urinary losartan/E-3174 before and after the 5-fluorouracil treatment were compared for each patient. Genotyping was performed to detect the CYP2C9*2 and CYP2C9*3. At the end of the first cycle of 5-fluorouracil, losartan/E-3174 ratio was increased by 28.0% compared to the pre-treatment values (P=0.15). In five patients recruited for phenotyping after three 5-fluorouracil cycles, the metabolic ratio was increased significantly by 5.3 times (P=0.03). The results suggest that in most patients 5-fluorouracil inhibited CYP2C9 activity. This inhibition was more pronounced when the total administered dose increased. This finding may help explain the mechanism of interaction between 5-fluorouracil and CYP2C9 substrates.

Association of the ABCB1 3435C>T polymorphism with antiemetic efficacy of 5-hydroxytryptamine type 3 antagonists.

BACKGROUND: Resistance to antiemetic treatment with 5-hydroxytryptamine type 3 (5-HT(3)) receptor antagonists is still a major problem resulting in patient discomfort and poor compliance to chemotherapy. We hypothesized that clinical resistance to 5-HT(3) antagonists is associated with the single-nucleotide polymorphism (3435C>T) in the gene that codes for the drug efflux transporter adenosine triphosphate-binding cassette subfamily B member 1 (ABCB1). METHODS: Patients with cancer (N = 216) treated with chemotherapeutic regimens composed of highly or moderately emetogenic agents were examined for their antiemetic responses to tropisetron, ondansetron, or granisetron. The efficacy of antiemetic treatment was documented by self-report charts for 5 days after chemotherapy. ABCB1 3435C>T genotype was determined to analyze its association with the antiemetic efficacy of 5-HT(3) antagonists. RESULTS: Within the first 24 hours of chemotherapy, the complete control rate of nausea and vomiting was higher in subjects with the ABCB1 TT genotype (n = 49) as compared with those with the CC (n = 60) or CT (n = 107) genotype (P = .044). The type of 5-HT(3) antagonists influenced the effect of genotype on antiemetic responses. The complete control rates were 92.9% in TT subjects (n = 14) in comparison to homozygote (47.6%, n = 21, P = .009) or heterozygote (56.1%, n = 41, P = .02) carriers of the 3435 C allele in granisetron-treated patients. However, during the delayed phase of chemotherapy, the complete control rates did not differ across genotypes. CONCLUSION: These results suggest that ABCB1 3435C>T polymorphism is associated with antiemetic treatment efficacy in patients with cancer treated with 5-HT(3) antagonists, particularly in granisetron-treated patients, during the short-term phase of chemotherapy.

Functional impact of CYP2C95, CYP2C96, CYP2C98, and CYP2C911 in vivo among black Africans.

UNLABELLED: Background and aim Previous data indicate that the urinary losartan/E-3174 ratio is a marker for cytochrome P450 (CYP) 2C9 activity in vivo. The functional impact of CYP2C9*5, *6, *8, and *11 polymorphisms in vivo has not been investigated previously in humans. METHODS: A single oral dose of losartan (25 mg) was given to 19 Beninese subjects with CYP2C9*1/*1 (n = 9), *1/*5 (n = 1), *1/*6 (n = 1), *1/*8 (n = 2), *1/*11 (n = 3), *5/*6 (n = 1), *5/*8 (n = 1), and *8/*11 (n = 1) genotypes. Concentrations of losartan and its active metabolite E-3174 were determined in urine from 0 to 8 hours by HPLC. The losartan/E-3174 metabolic ratio was used as a measure of losartan oxidation in vivo. RESULTS: The urinary losartan/E-3174 ratio in the various genotypes was as follows: 1.85 +/- 2.4 (mean +/- SD) for CYP2C9*1/*1, 14.6 for CYP2C9*1/*5, 4.2 for CYP2C9*1/*6, 188 for CYP2C9*5/*6, 11.6 for CYP2C9*5/*8, 0.44 +/- 0.13 (mean +/- SD) for CYP2C9*1/*8, 2.2 for CYP2C9*8/*11, and 5.72 +/- 4.5 (mean +/- SD) for CYP2C9*1/*11. Compared with the CYP2C9*1/*1 genotypes, the losartan/E-3174 ratio was significantly different in the CYP2C9*5 allele carriers (CYP2C9*1/*5, CYP2C9*5/*8, and CYP2C9*5/*6 genotypes) (P =.01, Mann-Whitney) but was not different in CYP2C9*1/*8 (P =.16) and CYP2C9*1/*11 (P =.11) carriers. The urinary losartan/E-3174 ratio of the single CYP2C9*1/*6 subject was higher than the 95% confidence interval of the mean of the CYP2C9*1/*1 group (0.0-3.7), whereas the metabolic ratio of the CYP2C9*8/*11 carrier was inside the 95% confidence interval of the means of the CYP2C9*1/*1 and CYP2C9*1/*11 groups (0.0-18). CONCLUSIONS: The CYP2C9*5 and *6 alleles are associated with decreased enzyme activity in vivo compared with the wild-type variant, whereas the CYP2C9*8 and *11 variants did not appear to have large in vivo effects.

CYP2C9 genetic variants and losartan oxidation in a Turkish population.

OBJECTIVE: Cytochrome P(450) 2C9 (CYP2C9) is a polymorphic enzyme catalysing the metabolism of several important drugs. Losartan has recently been suggested as a selective probe for CYP2C9 metabolic activity. The aim of the study was to determine the activity of CYP2C9, using losartan as a probe drug, in relation to CYP2C9 genotype in healthy Turkish subjects. METHODS: A single oral dose of 25 mg losartan was given to 85 Turkish unrelated subjects. Concentrations of losartan and its carboxylic acid metabolite, E3174, were analysed by means of high-performance liquid chromatography in urine collected for 8 h. The CYP2C9 genotypes were determined in 85 subjects using polymerase chain reaction-based endonuclease digestion methods specific for CYP2C9*2 and *3. Losartan oxidation was also studied in vitro, using human CYP2C8 and CYP2C9 enzymes expressed in yeast. RESULTS: The frequencies of the allelic variants CYP2C9*2 and CYP2C9*3 were 0.100 and 0.088, respectively. The urinary losartan/E3174 ratio was significantly higher in subjects with CYP2C9*1/*3 genotype (median 2.35, n=12) than in subjects with CYP2C9*1/*1 (0.71, n=58) and *1/*2 (0.85, n=10) genotypes ( P<0.05). In contrast to CYP2C9, no E3174 was formed by CYP2C8 in vitro. CONCLUSION: The urinary losartan to E3174 metabolic ratio after a 25-mg losartan dose was found to be a safe and useful phenotyping assay for CYP2C9 activity in vivo. CYP2C9*3 variant allele is a major determinant of the enzyme activity, and it decreases losartan metabolism significantly, while CYP2C9*2 allele has less impact on enzyme function.

Frequency and enzyme activity of the butyrylcholinesterase K-variant in a Turkish population.

OBJECTIVE: Among variants of the butyrylcholinesterase gene ( BChE), the K-variant causing Ala539Thr substitution is the most common one associated with about one-third reduction in the enzyme activity. This study aimed to detect the frequency of the K-variant allele in a Turkish population sample and also to evaluate how the plasma BChE activity was influenced by this variant. METHODS: Patients administered for elective surgery ( n=77) were examined for the presence of the K allele. The enzyme activity was determined in plasma. RESULTS: The K-variant of BChE is a common allele with a frequency of 0.266 (CI(95%) 0.196-0.336) in our sample from a Turkish population. Mean enzyme activity in subjects homozygous for the K-variant was about 40% lower than other subjects. CONCLUSION: The frequency of the BChE K-variant was significantly higher in a Turkish population than those reported for other populations and it is associated with a diminished enzyme activity.

Penetration of topically applied ciprofloxacin and ofloxacin into the aqueous humor and vitreous.

PURPOSE: To determine the intraocular penetration of topical drops of 2 antibiotics, ciprofloxacin 0.3% and ofloxacin 0.3%, into the aqueous humor and vitreous and to relate these levels to the miminum inhibitory concentration (MIC(90)) for organisms associated with ocular bacterial infections. SETTING: Department of Ophthalmology, Ankara Hospital, and Department of Pharmacology, Faculty of Medicine, Hacettepe University, Ankara, Turkey. METHODS: This prospective randomized clinical trial comprised 18 patients having cataract surgery, all with an intact corneal epithelium. The patients were randomly assigned to receive topical ciprofloxacin 0.3% (n = 10) or topical ofloxacin 0.3% (n = 8) 1 drop every 15 minutes 5 times and every 30 minutes 3 times before surgery. Aqueous and vitreous samples (if vitreous loss occurred during the cataract surgery) were collected 30 minutes after the administration of the last dose. Drug concentrations were determined by high-performance liquid chromatography (HPLC) fluorescence. RESULTS: All patients had detectable drug concentrations in the aqueous humor and vitreous measurable by HPLC. The mean aqueous humor concentration of ciprofloxacin was 1.13 microg/mL +/- 1.90 (SD) and the mean vitreous concentration, 0.23 +/- 0.06 microg/mL. Topical administration of ciprofloxacin yielded 4.9 times more drug concentration in the anterior chamber than in the vitreous. The mean aqueous concentration of ofloxacin was 2.06 +/- 1.06 microg/mL and the mean vitreous concentration, 0.46 +/- 0.10 microg/mL. Topical administration of ofloxacin yielded 4.7 times more drug concentration in the anterior chamber than in the vitreous. Aqueous humor concentrations of ofloxacin and ciprofloxacin were not statistically significantly different (P =.353). Intravitreal concentrations of ofloxacin were statistically significantly higher than those of ciprofloxacin (P =.001). CONCLUSIONS: Topical ofloxacin 0.3% penetrated better than topical ciprofloxacin 0.3% into the anterior chamber and vitreous in noninflamed eyes. Both drugs were above the MIC(90) for most ocular pathogens in the anterior chamber. The mean concentration in the vitreous of topically applied ofloxacin 0.3% was statistically significantly higher than that of ciprofloxacin 0.3%, but it was not sufficiently above the MIC(90) for most ocular pathogens in terms of empirical endopthalmitis therapy.

Effects of terfenadine and diphenhydramine on the CYP2D6 activity in healthy volunteers.

The aim of this study was to investigate the effects of two antihistaminic drugs, terfenadine and diphenhydramine on CYP2D6 activity by using debrisoquine as a model substrate. The study was carried out as an in vivo single-dose study in 12 young, healthy men. All volunteers had previously been identified as debrisoquine-extensive metabolizers. The volunteers took increasing single oral doses of one of the two antihistaminic drugs in randomized order, at weekly intervals, followed 1 h later by debrisoquine test. Terfenadine and diphenhydramine were given in the doses of 60 and 120 mg; 100 and 150 mg, respectively. The 8-hr urinary concentrations of debrisoquine and 4-hydroxydebrisoquine were determined by high-performance liquid chromatography (HPLC). With increasing doses of terfenadine and diphenhydramine, there was no statistically significant increase in the debrisoquine metabolic ratios (P > 0.05, Page's test for trend). The difference between the median debrisoquine metabolic ratios before and after treatments with terfenadine or diphenhydramine were not statistically significant (Wilcoxon's test). This investigation indicates that single-dose administration of diphenhydramine or terfenadine has no effect on the CYP2D6-mediated hydroxylation of debrisoquine in healthy volunteers.