Comparison of subretinal fluid levels of two 0.3% ciprofloxacin-containing eye drops.

PURPOSE: Two ophthalmic solutions of 0.3% ciprofloxacin eye drops are available in Turkey: Ciloxan and Siprogut. A previous study by the same authors was the first to report vitreous penetration of ciprofloxacin-containing eye drops. The aim of the present study was to compare the levels of drug found in the subretinal fluid by the two products following local administration. METHODS: Forty-three patients undergoing conventional retinal detachment surgery received either Ciloxan (22 patients) or Siprogut (21 patients). Beginning 6 h before surgery, two drops of solution were instilled onto the operative eye every 30 min for the first 3 h and then hourly for the next 3 h. Subretinal fluid samples were collected 30 min after administration of the last dose and were assayed for ciprofloxacin levels using a method involving high-performance liquid chromatography with fluorometric detection. RESULTS: The minimum and maximum subretinal fluid concentrations measured were 0.11 microg/mL and 0.65 microg/mL, respectively, with Ciloxan, and 0.08 microg/mL and 0.62 microg/mL, respectively wth Siprogut. There was no statistical difference between the subretinal fluid ciprofloxacin levels of the two products. The subretinal fluid drug evels attained by both products were below the minimum inhibitory concentrations of common ocular pathogens. CONCLUSIONS: Ciloxan and Siprogut can penetrate subretinal fluid. The ocular bioavailability of ciprofloxacin after local administration is equivalent for both pharmaceutical products.

N-acetyltransferase polymorphism in patients with Behçet's disease.

OBJECTIVES: The objective of our study was to investigate the possible role of human arylamine N-acetyltransferase 2 (NAT2) polymorphism in susceptibility to Behçet's disease. METHODS: Eighty-five patients with Behçet's disease gave their written informed consent to participate in the study. Seven point mutations (G191A, C282T, T341C, C481T, A803G, G590A, G857A) in the NAT2 gene were analysed using polymerase chain reaction/restriction fragment length polymorphism techniques. In addition, each patient received 100 mg dapsone orally to determine their NAT2 phenotype. Dapsone and its metabolite monoacetyl-dapsone were measured in 3-h plasma samples using high-performance liquid chromatography. Subjects with an acetylation ratio (monoacetyl-dapsone/dapsone) less than 0.4 were defined as slow acetylators. RESULTS: Of 85 patients with Behçet's disease, 54 (63.5%) were identified as genotypically slow acetylators. However, 60% (51 of 85) of patients were diagnosed as slow acetylators according to monoacetyl-dapsone/dapsone ratio. Thus, a low incidence of genotype/phenotype discrepancy (3.5%) was observed in Turkish patients with Behcet's disease. When we compared our results with previous phenotyping and genotyping studies in the Turkish population, frequencies of slow and rapid acetylators were not statistically different in patients with Behçet's disease. The frequency of the *5B allele was found to be slightly higher in patients with Behçet's disease than historic controls (44.7 vs 35.6%, P = 0.039). However, there was no significant difference in the frequency of the overall genotypes and alleles of NAT2 between patients and controls. CONCLUSION: Although the frequency of the NAT2*5B allele, responsible for slow acetylation, was slightly higher in patients than historic controls, our results failed to show an association between NAT2-acetylator status and risk for developing Behçet's disease.

Penetration of topical, oral, and combined administered ofloxacin into the subretinal fluid.

AIMS: To assess the subretinal fluid (SRF) levels of ofloxacin following topical, oral or combined administration. METHODS: 31 patients undergoing conventional retinal reattachment surgery were randomly assigned to three groups. Nine patients received topical ofloxacin, 11 patients received oral ofloxacin, and the other 11 patients received combined administration. Collected SRF samples were analysed for drug level by using high performance liquid chromatography. RESULTS: SRF drug levels after oral and combined administration were significantly higher than that after topical administration (p=0.0002 and p=0.0002, respectively) while there was no significant difference between oral and combined administration (p=0.0844). CONCLUSIONS: Ocular bioavailability of ofloxacin in SRF after oral and combined administration is equivalent. The addition of oral ofloxacin to topical therapy increased drug SRF penetration sixfold.

Low frequency of defective alleles of cytochrome P450 enzymes 2C19 and 2D6 in the Turkish population.

BACKGROUND AND OBJECTIVES: The genetically polymorphic cytochrome P450 enzymes 2Cl9 (CYP2Cl9) and 2D6 (CYP2D6) contribute to the metabolism of about 30% of all drugs. For analysis of the ethnic-related differences in drug disposition and as a preparation for routine genotyping, we examined CYP2C19 and CYP2D6 mutations in a large Turkish population. METHODS: CYP2C19 and CYP2D6 alleles were determined with use of genomic deoxyribonucleic acid from 404 unrelated Turkish individuals. CYP2C19 alleles *1 to *5 and CYP2D6 alleles *1 to *12, and *14, *15, and *17 were measured by polymerase chain reaction-restriction fragment length polymorphism assays. RESULTS: From 404 subjects genotyped for CYP2C19, allele frequencies of CYP2C19*1 (wt), CYP2C19*2 (ml), and CYP2C19*3 (m2) were 0.88, 0.12, and 0.004, respectively; mutations m3 and m4 were not found. Four individuals (1.0%) were predicted to be poor metabolizers (CYP2C19*2/*2), a significantly lower frequency compared to Middle European populations. Among 404 subjects genotyped for CYP2D6, most frequent alleles were CYP2D6*1 (allele frequency 0.37), *2 (0.35), *4 (0.11), *10 (0.06), duplications *1x2, *2x2, or *4x2 (0.06), *5 (0.01), and *17(0.01). Overall, six subjects (1.49%) were predicted to be CYP2D6 poor metabolizers, and 35 subjects (8.66%) were predicted to be ultrarapid metabolizers as a result of CYP2D6 gene duplications. CONCLUSION: Obviously, within Europe there is a north-south gradient, with decreasing frequency of poor metabolizers of CYP2C19 and CYP2D6 to the south and a corresponding increase of ultrarapid metabolizers of CYP2D6. As in other white groups, only CYP2C19*2 plays a relevant role for the CYP2C19 poor metabolizer phenotype. The mutational spectrum of CYP2D6 indicated partial ethnic relationships to Asian and African populations.

Penetration of ofloxacin and ciprofloxacin in aqueous humor after topical administration.

BACKGROUND AND OBJECTIVE: To compare the aqueous humor levels of 0.3% ofloxacin and 0.3% ciprofloxacin containing eyedrops in patients with healthy cornea. PATIENTS AND METHODS: Fifty patients with cataract were randomly assigned to have 0.3% ofloxacin containing eyedrop (25 patients) or 0.3% ciprofloxacin containing eyedrop (25 patients). Both drugs were repetitively instilled to each patient for 6 hours before the surgery. Aqueous samples were collected after penetrating the anterior chamber during cataract extraction and assayed by high-performance liquid chromatography method. RESULTS: The aqueous humor level of ofloxacin (1.43 +/- 0.26 microg/ml, mean +/- SEM) was significantly higher than that of ciprofloxacin (0.35 +/- 0.07 microg/ml) following the topical application (P < .0002). CONCLUSION: Aqueous humor penetration of topical ofloxacin is about 4 times higher than that of topical ciprofloxacin when the drugs are applied as described above.

CYP2C19 genotype does not represent a genetic predisposition in idiopathic systemic lupus erythematosus.

BACKGROUND: The aetiology of systemic lupus erythematosus (SLE) is still unknown. In several cases, however, chemicals or drugs were identified as aetiological agents and associations with certain phenotypes of drug metabolising enzymes have been reported. The purpose of this study was to discover if there is an association between CYP2C19 polymorphism and susceptibility to SLE. METHODS: Racemic mephenytoin (100 mg orally) was given to healthy volunteers (n = 161) and SLE patients (n = 37) and then S-mephenytoin and R-mephenytoin were determined in eight hour urine samples. A 10 ml blood sample was obtained from healthy volunteers (n = 80) and SLE patients (n = 69) for genotypic assay. Each blood sample was tested for the detection of CYP2C19*1 and CYP2C19*2 (formerly wt and m1 respectively) by oligonucleotide ligation assay. RESULTS: The ratio of S/R-mephenytoin ranged from < 0.1 to 1.293 in healthy subjects and from < 0.1 to 1.067 in SLE patients. PM phenotype was observed in 2 of 37 patients with idiopathic SLE (5.4%) and 6 of 161 healthy subjects (3.7%). There were no significant differences in the frequency of PM phenotypes between the groups (Fisher's exact test, p = 0.64) or in the frequency distribution profiles of ratios of S-mephenytoin to R-mephenytoin. No significant differences in distribution of overall genotypes and in allele frequencies were observed between the two groups. No significant relation was found between clinical features and the overall genotype. CONCLUSION: The results of this study indicate that CYP2C19 genotype does not represent a genetic predisposition in idiopathic SLE patients.

CYP2D6 polymorphism in systemic lupus erythematosus patients.

OBJECTIVES: 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 (Fisher's 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.

Aqueous humour levels of topically applied ciprofloxacin and ofloxacin in the same subjects.

PURPOSE: To evaluate aqueous humour levels of topical 0.3% ciprofloxacin and 0.3% ofloxacin in the same subjects. METHODS: Thirty-two bilateral cataractous patients received topical 0.3% ciprofloxacin in one eye and 0.3% ofloxacin in the other eye before each cataract extraction. Eyedrops were repetitively instilled for 6 h. Aqueous humour samples were collected and assayed for drug concentrations by a method described originally by us using high-performance liquid chromatography. RESULTS: Mean aqueous ciprofloxacin and ofloxacin levels were 0.33 +/- 0.04 microgram/ml (mean +/- SEM) and 1.34 +/- 0.14 micrograms/ml respectively (p < 0.0001). CONCLUSION: Ofloxacin level in the aqueous humour is 4 times higher than that of ciprofloxacin in the same subjects.

Human aqueous and vitreous humour levels of ciprofloxacin following oral and topical administration.

PURPOSE: To assess aqueous and vitreous humour ciprofloxacin concentrations following oral and topical administration of ciprofloxacin in patients with non-inflamed cornea and an intact crystalline lens, and to compare the concentrations of the drug given by either route. METHODS: In this prospective study, 34 patients undergoing pars plana vitrectomy for various ocular pathologies were divided into two groups. Eighteen patients received 2 drops of 0.3% ophthalmic solution of ciprofloxacin every 30 min for 3 h and then every 60 min for the next 3 h, and 16 patients received a single oral dose of 1000 mg ciprofloxacin 6 h before surgery. The aqueous and vitreous humour samples were simultaneously harvested after oral or topical administration during pars plana vitrectomy to assess penetration of the drug. These samples were assayed for ciprofloxacin concentrations by a method described previously by us using high-performance liquid chromatography. RESULTS: The aqueous and vitreous humour levels of ciprofloxacin were 0.59 +/- 0.06 microgram/ml (mean +/- SEM) and 0.64 +/- 0.06 microgram/ml after oral and 0.44 +/- 0.07 microgram/ml and 0.22 +/- 0.04 microgram/ml after topical ciprofloxacin administration, respectively. Aqueous humour levels were not statistically significantly different following oral and topical administration (p = 0.069). However, the vitreous level of the drug after oral administration was significantly higher than that after topical administration (p < 0.001). CONCLUSION: Ocular bioavailability of ciprofloxacin in aqueous humour following oral and topical administration is found to be similar when the drug was applied as described above. Penetration of ciprofloxacin into vitreous humour is less than that into aqueous humour after topical administration.

Penetration of ofloxacin in human aqueous and vitreous humors following oral and topical administration.

PURPOSE: To determine aqueous and vitreous humor ofloxacin levels following oral and topical application of ofloxacin in patients with noninflamed cornea and intact crystalline lens, and to compare the drug levels provided by each route. MATERIALS AND METHODS: Twenty-six patients undergoing pars plana vitrectomy for various ocular pathologies were divided into two groups. Fourteen patients received two drops of 0.3% ophthalmic solution of ofloxacin every 30 minutes for 3 hours and every 60 minutes for the next 3 hours, and 12 patients received a single oral dose of 400 mg ofloxacin 8 hours before surgery. The aqueous and vitreous humor samples were simultaneously collected after oral or topical administration during pars plana vitrectomy to assess penetration of the drug. Samples were assayed for ofloxacin concentrations by a previously described method using high-performance liquid chromatography. RESULTS: The aqueous and vitreous humor levels of ofloxacin were 1.54 +/- 0.27 microg/mL (mean +/- standard error) and 1.77 +/- 0.24 microg/mL after oral and 1.44 +/- 0.24 microg/mL and 0.37 +/- 0.05 microg/mL after topical ofloxacin administration, respectively. Aqueous humor levels were not statistically different following oral or topical administration (P > 0.8). However, vitreous level of the drug after oral administration was significantly higher than that after topical administration (P < 0.001). CONCLUSION: Ocular bioavailability of ofloxacin in aqueous humor after oral and topical administration is similar when the drug is applied as described. Penetration of ofloxacin into vitreous humor is less than that into aqueous humor following topical application. The aqueous humor levels of ofloxacin via both routes and the vitreous level of the drug after oral route exceed the minimum inhibitory concentrations for certain bacterial species that frequently cause intraocular infection.

Omission of the deconjugation step in urine analysis and the unaltered outcome of CYP2D6 phenotyping with dextromethorphan.

The present study was aimed at determining whether the deconjugation step in chemical analysis could be omitted without altering the outcome of phenotyping CYP2D6 with dextromethorphan. This drug and its metabolite, dextrorphan, were assayed by high-performance liquid chromatography (HPLC) in urine. Urinary levels of dextromethorphan and dextrorphan with and without enzymatic (beta-glucuronidase) treatment of urine and the metabolic ratios for dextromethorphan were determined in 45 subjects. Although the enzymatic treatment did not alter the urinary concentration of dextromethorphan in both phenotypes, it increased the urinary concentration of dextrorphan in both poor and extensive metabolizers by 3.7- and 12.8-fold, respectively. A urinary unconjugated dextromethorphan/unconjugated dextrorphan metabolic ratio of 2.00 and a total dextromethorphan/total dextrorphan metabolic ratio of 0.30, respectively, identified three poor metabolizers. Enzymatic treatment decreased the urinary antimode value. Moreover, the urinary metabolic ratio based on unconjugated dextrorphan and dextromethorphan correlated well with that based on assay of total dextrorphan and dextromethorphan (rs = 0.9458, P < 0.001). The results show that urinary analysis of dextrorphan and dextromethorphan omitting the enzymatic deconjugation step is a fast, reliable and sensitive method and could be used for studying CYP2D6 type genetic polymorphism in man.

Comparison of aqueous humour and vitreous humour levels of two 0.3% ciprofloxacin eyedrops.

BACKGROUND: Two ophthalmic solutions of 0.3% ciprofloxacin eyedrops are available in Turkey: Ciloxan and Siprogut. The objective of this study was to compare the concentrations of drug produced by the two products in the aqueous humour and vitreous humour after local administration. METHODS: Twenty-one patients undergoing primary vitreoretinal surgery received either Ciloxan (10 patients) or Siprogut (11 patients). Six hours before surgery, two drops of solution were instilled onto the operative eye. Drops were then instilled every 30 minutes for the first 3 hours and then hourly for the next 3 hours. Aqueous and vitreous samples were collected 30 minutes after administration of the last dose and were assayed for ciprofloxacin concentration by means of high-performance liquid chromatography with fluorometric detection. RESULTS: The mean aqueous humour concentrations of Ciloxan and Siprogut were 0.36 (standard error of the mean [SEM] 0.09) microgram/mL and 0.44 (SEM 0.17) microgram/mL respectively. The corresponding vitreous humour concentrations were 0.21 (SEM 0.05) microgram/mL and 0.22 (SEM 0.06) microgram/mL. Neither of these differences was statistically significant. The aqueous and vitreous levels of both products exceeded the minimum inhibitory concentrations for certain bacterial species that frequently cause intraocular infections. INTERPRETATION: Our results show that the ocular bioavailability of Ciloxan and Siprogut after local administration is equivalent. Penetration of ciprofloxacin into the vitreous humour seems to be poorer than that into the aqueous humour.

Determination of ofloxacin in human aqueous humour by high-performance liquid chromatography with fluorescence detection.

A reversed-phase high-performance liquid chromatographic method is described for the determination of ofloxacin in human aqueous humour; the method involves fluorescence detection (excitation at 290 nm; emission at 500 nm) after direct injection of samples. The method utilized a 100 mm x 8 mm i.d. cartridge column packed with 4 microns Novapak C18 with a mobile phase methanol-acetonitrile-0.4 M citric acid (3:1:10, v/v/v) and a flow rate of 1 ml min-1 at ambient temperature. The retention times for the internal standard pipemidic acid and for ofloxacin were 4.82 and 7.32 min respectively. The mean recovery (+/- ISD) from human aqueous humour was 103.24 +/- 4.45% for ofloxacin at 1 microgram ml-1 (n = 6). The within-day and day-to-day RSDs at 0.1 microgram ml-1 and 1 microgram ml-1 were less than 6.71% (n = 6) and the lower limit of reliable determination corresponding to a signal-to-noise ratio of 2.5:1 was 20 ng ml-1. The assay was shown to be suitable for measuring ofloxacin levels in human aqueous humour samples after topical, oral and intravenous administration.

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

OBJECTIVES: 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, Fisher's 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.

Nitric oxide synthase inhibition attenuates signs of ethanol withdrawal in rats.

The effects of N(G)-nitro arginine methyl ester (L-NAME) and 7-nitroindazole (7-NI), nitric oxide synthase inhibitors, and L-arginine, a nitric oxide precursor, on ethanol withdrawal signs were investigated in rats. Ethanol (7.2% v/v) was given to rats by a liquid diet for 16 days. L-NAME (30 and 60 mg/kg), 7-NI (40 and 80 mg/kg), L-arginine (100 mg/kg), a combination of L-arginine (100 mg/kg) and 7-NI (40 mg/kg), and saline or vehicle were injected to rats intraperitoneally 30 min before ethanol withdrawal. A second series of injections was given at 6 hour after the first one, and subjects were then tested for audiogenic seizures. 7-NI (40 mg/kg), vehicle and saline were also administered to naive rats. 7-NI (40 mg/kg) did not produce any significant change in locomotor activity in naive rats. Both L-NAME and 7-NI significantly inhibited locomotor hyperactivity from the 2nd to the 6th hour of the withdrawal period. They also reduced the total ethanol withdrawal score from the 30th min to the 6th hour, and they significantly decreased audiogenic seizures. Neither drug increased locomotor activity nor total ethanol withdrawal score, which were increased significantly by L-arginine (100 mg/kg); however, L-arginine (100 mg/kg) prevented the inhibitory effects of 7-NI (40 mg/kg) on increased locomotor activity, total ethanol withdrawal score, and audiogenic seizure. Our results suggest that nitric oxide synthase inhibition by L-NAME and 7-NI alleviates the signs of ethanol withdrawal. The data also support the hypothesis that nitric oxide may take part in the neuroadaptation that develops during chronic ethanol ingestion in rats.

Proguanil metabolism in relation to S-mephenytoin oxidation in a Turkish population.

The oxidation of proguanil was studied in 89 unrelated healthy Turkish volunteers after administration of proguanil (single dose, 200 mg, orally). Based on the distribution of the ratio of proguanil to cycloguanil excreted in urine, and using an antimode value of 15, the prevalence of poor metabolizers in a Turkish population was estimated to be 5.6% (95% confidence interval 2.0%-17.3%) which was similar to that in the other Caucasian populations. The relationship between the oxidative capacities of CYP2C19 for the two substrates, proguanil and mephenytoin, was studied in 39 subjects (two poor and 37 extensive metabolizers of proguanil). The two poor metabolizers of proguanil were also identified as poor metabolizers of S-mephenytoin and no misclassification by the two phenotyping methods was observed. The correlation between the metabolic ratio of proguanil to cycloguanil and the S/R-mephenytoin ratio as assessed by Spearman's rank test, was statistically significant (rs = 0.50, P < 0.001).

Metabolic ratios of four probes of CYP2D6 in Turkish subjects: a cross-over study.

The relationships among the metabolic ratios for the standard probe drugs of CYP2D6 activity, such as debrisoquine, sparteine, metoprolol and dextromethorphan, were studied in 32 Turkish subjects. All subjects were randomly selected according to their phenotypes from a group of 111 Turkish subjects whose oxidation status had been tested for debrisoquine previously. All subjects were given a 10 mg debrisoquine tablet, a 100 mg sparteine tablet, a 100 mg. metoprolol tablet and a 20 mg dextromethorphan capsule orally with a wash-out period of at least 1 week between each probe administration. Metabolic ratios were calculated as percentage of dose excreted as parent drug/percentage of dose excreted as its hydroxymetabolite of parent drug in 0-8 h urine. Three poor metabolisers (PM) of debrisoquine were identified. They were also PMs of the other test probes and no misclassification by the 4 phenotyping methods was observed. All six correlations among the metabolic ratios of the 4 probe drugs assessed by Spearman's rank test were highly significant (P < 0.001). The present findings indicate that the oxidative metabolism of debrisoquine, sparteine, metoprolol and dextromethorphan is catalysed by the same cytochrome P450 in the Turkish subjects.

A study on the mediators of antidromic vasodilatation elicited by sciatic nerve stimulation in cats.

This study was undertaken to ascertain whether a purinergic substance, histamine, dopamine or prostaglandins are mediators involved in antidromic vasodilatation. This type of vasodilatation was elicited by stimulation of the distal end of sectioned sciatic nerve at 40 V with 2 msec pulses for 30 sec in autoperfused hindlimb of reserpine-pretreated and anesthetized cats. Artificial respiration was applied because of curarization that was done to abolish the vascular responses due to contractions of striated muscle. Stimulation of sciatic nerve caused a sustained vasodilatation which was more marked at a frequency of 30 pps. The responsiveness of the perfused vessels to vasodilator stimuli tended to increase by increasing the duration of perfusion as controlled by papaverine administration at certain intervals. Both mepyramine and subsequent administration of metiamide did not produce any change in the vasodilator response to nerve stimulation though they blocked the vasodilator response to histamine. Dopamine injected intra-arterially elicited a pressor response which was reversed into a vasodilator one by phentolamine. This vasodilator response to dopamine tended to be reduced by haloperidol which produced either no change or a slight increase in antidromic vasodilatation. Pretreatment with theophylline to antagonize the likely purinergic mediators or with indomethacin to inhibit the synthesis of prostaglandins had no effect on antidromic vasodilatation elicited by sciatic nerve stimulation. These results suggest that the above-mentioned compounds might not be involved in antidromic vasodilatation.

Rapid liquid chromatographic assay of ciprofloxacin in human aqueous humor.

A simple, selective and sensitive method has been developed to determine ciprofloxacin in human aqueous humor. Separation of ciprofloxacin was carried out with pipemidic acid as internal standard using a Novapak C18 reversed-phase cartridge column (100 x 8 mm i.d., particle size 4 microns) and a mobile phase consisting of methanol-acetonitrile-citric acid (0.4 M) (3:1:10, v/v/v) at a flow rate of 1 ml min-1. The column effluent was monitored with fluorescence detection at 278 nm (excitation) and 450 nm (emission) after direct injection. The retention times were 4.88 min for pipemidic acid and 7.52 min for ciprofloxacin. The within-day and day-to-day reproducibilities were less than 7% for ciprofloxacin at 0.1 and 1 microgram ml-1 (n = 6). The mean recovery from aqueous humor was found to be 101.37 +/- 6.7% for ciprofloxacin at 0.1 micrograms ml-1 (n = 6 and the detection limit corresponding to a signal-to-noise ratio of 2.5:1 was 250 pg ml-1. The method was shown to be suitable for determining ciprofloxacin levels in human aqueous humor samples.