Selim Kortunay

Penetration of topical and oral ciprofloxacin into the aqueous and vitreous humor in inflamed eyes.

PURPOSE To assess the aqueous and vitreous penetration of ciprofloxacin after topical and combined topical and oral administration and investigate the effects of inflammation on drug penetration. METHODS A standardized penetrating injury was made in the right eyes of 16 rabbits. Intraocular inflammation was induced by intravitreal injection of a suspension of Staphylococcus aureus in these eyes. The animals were divided into two groups according to treatment methodology: topical and topical-oral. The intact left eyes of the animals were maintained as controls. In the topical treatment group, two drops of ciprofloxacin 0.3% were instilled to both eyes every 30 minutes for 4 hours. In the topical-oral treatment group, animals were given two oral 40 mg/kg doses of ciprofloxacin at 12-hour intervals. After the last oral dose, the protocol of the topical group was applied to these eyes. Half an hour after the last drop, 100-microL samples were taken from aqueous and vitreous humor of all eyes. Drug concentrations were measured using high-pressure liquid chromatography. RESULTS Mean aqueous levels of ciprofloxacin in control eyes were 2.31 microg/mL (range, 1.02-6.27 microg/mL) in the topical group and 5.88 microg/mL (1.52-17.81) in the topical-oral group. Mean aqueous levels in inflamed eyes were 7.36 microg/mL (2.34-17.15) in the topical group and 14.43 microg/mL (2.18-18.66) in the topical-oral group. Mean vitreous levels in control eyes were 0.77 microg/mL (0.09-1.93) in the topical group and 1.01 microg/mL (0.49-1.57) in the topical-oral group. Mean vitreous levels in inflamed eyes were 0.95 microg/mL (0.18-1.27) in the topical group and 1.98 microg/mL (0.51-3.34) in the topical-oral group. There was no significant difference among the groups (P > 0.05). Mean aqueous levels in all eyes and mean vitreous levels in the combined topical and oral group of inflamed eyes were above the 90% minimum inhibitory concentration for most of the common microorganisms causing endophthalmitis. CONCLUSION There is an increase in both aqueous and vitreous humor concentrations with inflammation and with oral and topical administrations, as opposed to topical only, of ciprofloxacin. Using oral as well as topical treatment may be a beneficial method of antibiotic prophylaxis in ocular trauma once a patient has received intravenous or intravitreal therapy.

Penetration of topical and oral ofloxacin into the aqueous and vitreous humor of inflamed rabbit eyes.

PURPOSE This study aimed to investigate the penetration of topical and oral ofloxacin into aqueous humor and vitreous humor in post-traumatic endophthalmitis model in rabbits. METHODS A standardized intraocular infection after penetrating injury was made in the right eyes of 16 rabbits. Intraocular infection was induced by intravitreal injection of a suspension of Staphylococcus aureus. The intact left eyes were maintained as controls. The animals were divided randomly into two groups. (1) In the topical group, two drops of ofloxacin 0.3% eyedrops were instilled to both eyes every 30 min for 4 h. (2) In the topical-oral group, two doses of 25 mg/kg of ofloxacin at 12-h intervals were given orally, then the protocol of the first group was applied. Aqueous and vitreous humor samples were taken 30 min after the last drop. Ofloxacin concentrations were measured by using HPLC. RESULTS Mean aqueous levels of ofloxacin in control eyes were: 3.25 +/- 2.55 microg/ml in topical group. 4.58 +/- 5.39 microg/ml in topical-oral group. Mean aqueous levels in inflamed eyes were: 5.21 +/- 4.55 microg/ml in topical group, 10.34 +/- 8.88 microg/ml in topical-oral group. Mean vitreous levels of ofloxacin in control eyes were: 0.17 +/- 0.07 microg/ml in topical group, 1.30 +/- 1.23 microg/ml in topical-oral group. Mean vitreous levels in inflamed eyes were: 0.35 +/- 0.22 microg/ml in topical group, 3.48 +/- 2.69 microg/ml in topical-oral group. There was no significant difference among the groups (P > 0.05), however. CONCLUSIONS The result of this study suggests that oral supplementation of ofloxacin to topical instillation increased the ocular levels of ofloxacin in the post-traumatic endophthalmitis model. Mean drug concentrations in aqueous and vitreous humors were above the 90% minimum inhibitory concentrations (MIC90) for most of the common microorganisms causing endophthalmitis in all eyes, except in the vitreous humors of the intact eyes instilled topically.

Effects of trauma and infection on ciprofloxacin levels in the vitreous cavity.

OBJECTIVE This study was designed to determine the effects of trauma and infection on vitreous ciprofloxacin levels after intravitreal injection of ciprofloxacin in rabbits. METHODS A penetrating injury was made in the right eyes of 24 rabbits. In the eyes of half of the traumatized animals, a standardized intraocular infection was induced by intravitreal injection of a suspension of Staphylococcus aureus. The intact left eyes of the traumatized group were maintained as controls. Ciprofloxacin (200 microg/0.1 mL) was injected into the midvitreous cavity of both eyes in all animals and samples were obtained at 2, 8, 24, and 48 hours after injection. Drug concentrations were measured using high-pressure liquid chromatography analysis. RESULTS At the second hour, the mean vitreous concentration of ciprofloxacin in the traumatized eyes was lower than that in control eyes (P<0.05). The mean ciprofloxacin concentrations were significantly higher (P<0.05) in the traumatized-infected eyes than were those in control or traumatized eyes at 24 and 48 hours. The elimination half-life of ciprofloxacin in control and traumatized eyes was 6.02 hours and 5.02 hours, respectively, and infection prolonged the half-life to 15.06 hours. Vitreous levels of ciprofloxacin were above the minimum inhibitory concentration (MIC90) for most of the common microorganisms causing endophthalmitis in all groups at 2 and 8 hours, but also at 24 and 48 hours in traumatized-infected eyes. CONCLUSION Infection appears to decrease the clearance of ciprofloxacin. Therapeutic drug levels in traumatized-infected eyes were maintained up to 48 hours. Assuming that the animal model used may have a predictive value for the drug elimination in traumatized-infected human eyes, we suggest that local administration of ciprofloxacin every 2 days may be relevant from the therapeutic perspective.

The effects of prolonged acute use and inflammation on the ocular penetration of topical ciprofloxacin

PURPOSE To study the aqueous and vitreous penetration of ciprofloxacin after prolonged acute topical administration and to investigate the effects of inflammation on drug penetration. METHODS A standardized model of intraocular infection after penetrating injury was made in the right eyes of eight rabbits. The intact left eyes were maintained as the control. Two drops of ciprofloxacin 0.3% eyedrops were instilled topically every 1 h for 7 h to all eyes of the rabbits. Aqueous and vitreous samples (100 microl) were obtained half an hour after the last drop. Instillation was continued for 7 h more and samples were obtained as before. Drug concentrations were measured using HPLC. RESULTS The mean aqueous humor levels of ciprofloxacin were: in control eyes 1.31 +/- 0.78 microg/ml after 7 h and 1.85 +/- 1.69 microg/ml after 14 h of instillation: in inflamed eyes 2.18 +/- 1.02 microg/ml after 7 h and 2.91 +/- 2.12 microg/ml after 14 h. The mean vitreous humor levels were: in control eyes 0.65 +/- 0.44 microg/ml after 7 h and 0.72 +/- 0.8 microg/ml after 14 h of instillation; in inflamed eyes 0.67 +/- 0.77 microg/ml after 7 h and 1.01 +/- 0.43 microg/ml after 14 h. However, the differences among the groups were not significant (P > 0.05). CONCLUSIONS Ciprofloxacin penetration into aqueous humor was higher in 14-h topical application than that for 7 h. Inflammation increased the penetration of topical ciprofloxacin into aqueous while administered for 7 h and into both aqueous and vitreous humor while administered for 14 h. c

Ofloxacin levels after intravitreal injection. Effects of trauma and inflammation.

Purpose: This study was carried out to get an insight into the ofloxacin elimination after intravitreal injection in rabbits. We also studied the effects of trauma and inflammation on the vitreous ofloxacin levels after intravitreal injection of ofloxacin. Methods: A penetrating eye injury in the right eye was inflicted on 24 rabbits and another 12 animals were used as control. A standardized intraocular inflammation was induced by intravitreal injection of a suspension of Staphylococcus aureus in half of the traumatized eyes. Ofloxacin (200 µg/0.1 ml) was injected into the midvitreous cavity of both traumatized and control right eyes, and samples were obtained at 2, 8, 24 and 48 h after injection. Drug concentrations were measured using high-pressure liquid chromatography analysis. Results: Vitreous levels of ofloxacin were above the MIC90 at 2 and 8 h in all groups for most of the common microorganisms causing endophthalmitis and also at 24 h in traumatized-infected eyes. At the second hour, the mean vitreous concentrations of ofloxacin both in traumatized and traumatized-infected eyes were lower than that in the control eyes (p < 0.05). At 8 h, the mean vitreous concentrations of ofloxacin in the traumatized and in the traumatized-infected eyes were higher than that in the control eyes (p < 0.05). At 24 h, the mean ofloxacin concentration was higher in the traumatized-infected eyes than that in control (p < 0.01) and traumatized eyes (p < 0.05), and also higher in the traumatized eyes than that in the control eyes (p < 0.05). The mean ofloxacin concentrations in the traumatized and traumatized-infected eyes were significantly higher (p < 0.01) than those in the controls at 48 h. The elimination half-life of ofloxacin in the control eyes was 5.65 h and trauma and inflammation prolonged the half-life to 9.47 and 9.72 h, respectively. Conclusion: Clearance of ofloxacin is fast and appears to be reduced by trauma and inflammation. Therapeutic drug levels in traumatized-infected eyes were maintained up to 24 h. This may be an important pharmacokinetic advantage in treating endophthalmitis unless the dose used has local toxicity and allows a longer dose interval when the dose is repeated.

The hydroxylation of omeprazole correlates with S-mephenytoin and proguanil metabolism

AbstractObjectives: This pharmacogenetic study was aimed at studying the pattern of oxidation of omeprazole in a Turkish population and testing whether omeprazole metabolism cosegregates with the genetically determined metabolism of mephenytoin and proguanil in Turkish subjects. Methods: The hydroxylation of omeprazole was measured in 116 unrelated healthy Turkish subjects after administration of a single oral dose of omeprazole (20 mg), using the ratio of omeprazole to 5-hydroxyomeprazole in plasma 3 h after dosing. To 31 subjects, who were phenotyped with omeprazole, mephenytoin (100 mg, p.o.) or proguanil (200 mg, p.o.) were administered at least 1 week apart. The S/R ratio of mephenytoin and the ratio of proguanil to cycloguanil were determined from an 8-h urine collection. Results: Based on the distribution of the log (omeprazole/hydroxyomeprazole) values and using the antimode value of 0.8, the frequency of poor metabolizers of omeprazole was estimated to be 7.7% (95% confidence interval 3–18%) which was similar to that in the other Caucasian populations (P = 0.54, Fishers exact test). Three poor metabolizers of omeprazole were also classified as poor metabolizers of both mephenytoin and proguanil and no misclassification occurred with three phenotyping methods. All three methods separated poor or extensive metabolizer phenotypes with complete concordance. The ratio of omeprazole to hydroxyomeprazole correlated with the S/R ratio of mephenytoin and the ratio of proguanil to cycloguanil. Conclusion: These results support the hypothesis that the oxidative metabolism of three different drugs may be catalyzed by the same cytochrome P450 enzyme.

CYP2D6 polymorphism in systemic lupus erythematosus patients

AbstractObjectives: To determine whether patients with idiopathic systemic lupus erythematosus (SLE) are associated with impaired CYP2D6 activity and to gain insight into whether there is an association between particular CYP2D6 genotypes and susceptibility to SLE, and whether CYP2D6 polymorphism is linked to any specific clinical features of SLE. Methods: Debrisoquine sulfate (10 mg p.o.) was given to 159 healthy volunteers and 39 idiopathic SLE patients. Genotypic assay was carried out in 80 healthy volunteers and 32 patients. A 10-ml blood sample was drawn for genotypic assay. Debrisoquine and 4-hydroxydebrisoquine were determined in 8-h urine samples. Blood samples were analysed for the presence of mutations in the CYP2D6 gene, by using polymerase chain reaction (PCR) specific for CYP2D6*3 and CYP2D6*4 alleles. Results: The metabolic ratio of debrisoquine to 4-hydroxydebrisoquine ranged from 0.01 to 86.98 in healthy subjects and from 0.02 to 96 in SLE patients. We observed the poor metabolizer(PM) debrisoquine phenotype in three of 39 patients with idiopathic SLE (7.6%) and five of 159 healthy subjects (3.1%). There was no significant difference in the frequency of PM phenotypes between idiopathic SLE and healthy subjects (Fishers exact test, P = 0.19). No significant difference in the distribution of overall genotypes and allele frequencies were observed between the two groups. No significant relationships were found between specific clinical features and the overall genotype. Conclusion: The results of this study confirm that CYP2D6 activity is not impaired in SLE and that there is no association between SLE and phenotypic CYP2D6 status. The results also showed that there was no difference in the frequency of CYP2D6A and CYP2D6B alleles between controls and patients with SLE.

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

SummaryThe 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 metabolisers. The volunteers took increasing single oral doses of one of the two antihistaminic drugs in randomized order, at weeklyy intervals, followed 1 h later by debrisoquine test. Terfenadine and diphhenhydramine 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.