Simple and rapid high-performance liquid chromatography method for the determination of ofloxacin concentrations in plasma and urine

A high-performance liquid chromatographic method for the determination of ofloxacin in human plasma and urine was developed. The method involved deproteinisation of the sample with perchloric acid and analysis of the supernatant using a reversed-phase C column and fluorescence detection at an excitation wavelength of 290 nm and an emission wavelength of 18 460 nm. The assay was linear from 0.5 to 10.0 mg/ ml. The relative standard deviation of intra- and inter-day assays was lower than 5%. The average recovery of ofloxacin from plasma was 93%. The method was evaluated in samples from healthy subjects whose drug levels were already measured by microbiological assay. Ó 2001 Elsevier Science B.V. All rights reserved

Dose related pharmacokinetics of ofloxacin in healthy volunteers

OBJECTIVE: To evaluate the pharmacokinetic profile of ofloxacin in healthy volunteers after single oral doses of 600 and 800 mg. DESIGN: Seven healthy volunteers were administered 600 and 800 mg of ofloxacin on two occasions with an interval of one week. Paired samples of blood and saliva were collected after 1, 2, 3, 6, 9, 12, 24, 32 and 48 hours post-dose. Urine samples were collected over a period of 0–6, 6–12 and 12–24 hours. Concentrations of ofloxacin in plasma, saliva and urine were assayed by high performance liquid chromatography. RESULTS: Increases of 22% in peak plasma concentration (Cmax) and 40% in area under the concentrationtime curve (AUC0–24) were observed with the 800 mg dose. The other parameters, namely time to attain Cmax, half-life, the apparent volume of distribution, plasma and renal clearance and percentage of dose excreted in urine over 24 hours were independent of doses. The mean ratios of the concentration in saliva to the concentration in plasma ranged from 0.4–0.6, and the correlation coefficient was 0.94. CONCLUSIONS: Dose proportionality was observed in Cmax and AUC0–24 when 600 and 800 mg doses of ofloxacin were given. Ofloxacin determined in saliva seems to be suitable for therapeutic drug monitoring

Self-induction of rifampicin metabolism in man

Self-induction of rifampicin metabolism caused by daily administration of the drug was studied in 7 healthy subjects. Rifampicin 600 mg was administered daily for 10 days and additional doses were administered on the 4th and 8th days after drug administration ceased. The mean serum half-life of rifampicin decreased from 4.9 h on the 1st day to 3.5 h on the 4th day (P<0.01), to 2.7 h on the 7th day (P<0.001), and 2.5 h on the 10th day (P<0.001). The difference between the mean values on the 7th and the 10th days was not significant. The mean value on the 8th day after stopping drag administration (3.8 h), was significantly higher than that on the last day of daily administration (P=0.02), but was still lower than that on the 1st day (P=0.05). There was a decrease in the excretion of both rifampicin and desacetylrifampicin in urine on induction, followed by a gradual return to normal when drug administration was stopped

Salivary cortisol in the assessment of adrenocortical function in patients with pulmonary tuberculosis

Adrenocortical function was assessed on the basis of changes in salivary cortisol in patients with pulmonary tuberculosis and the findings compared with those in healthy subjects. A method of direct radioimmunoassay of salivary cortisol was standardized and the sensitivity was 0.8 nmol/l. Cortisol levels in saliva were significantly higher in the patients than in the healthy subjects (P < 0.001). The diurnal rhythm of cortisol secretion was disturbed in the patients with a significant increase in salivary cortisol beyond 1800 h. While dexamethasone caused an appreciable suppression (87%), stimulation with ACTH (tetracosactrin) resulted in a marked increase in salivary cortisol, the increase being significantly higher in the healthy subjects than in the patients (P < 0.001). Attempts to classify subjects as positive or negative responders to tetracosactrin based on increases in salivary cortisol in relation to ‘plasma cortisol changes were however not successful, as the agreement between the two methods ranged from 73 to 80 per cent with various criteria used

Acute phase proteins in tuberculous patients

The serum concentrations of some acute phase proteins were determined on admission, during treatment, at the end of treatment and at 12 months after stopping treatment in 20 patients with pulmonary tuberculosis. Measurements were also made, on admission and at the end of treatment, in 19 patients with abdominal tuberculosis, and 11 children with tuberculous meningitis. All 20 patients with pulmonary TB had quiescent disease by the end of treatment and none had a bacteriological relapse during the followup period of 12 months. The response to treatment was considered favorable in 18 of the 19 patients with abdominal TB, and the CSF findings had returned to normal in 9 of 11 patients with TB meningitis. There was a significant decrease with treatment in the concentrations of C-reactive protein, ceruloplasmin, haptoglobin and a1 -acid glycoprotein in all 3 groups of patients. While there was an increase in the concentrations of transferrin in patients with pulmonary and abdominal TB, there was a significant decrease in those with TB meningitis, a2- macroglobulin did not appear to function as an acute phase reactant in any of the 3 groups. Amalgamating the findings in all 3 groups of tuberculous patients, the proportions of patients with abnormal values on admission and at the end of treatment were 62% and 14% for C-reactive protein, 78% and 50% for ceruloplasmin, 86% and 26% for haptoglobin and 92% and 6% for a1- acid glycoprotein, respectively

Bioavailability of rifampicin following concomitant administration of ethambutol or isoniazid or pyrazinamide or a combination of the three drugs

Background & Objectives: Poor bioavailability of rifampicin (R) in combination with other anti-tuberculosis drugs such as isoniazid (H), pyrazinamide (Z), and ethambutol (E) is a subject of much concern for the last few decades. This could be due to an interaction between R and other drugs. An investigation was therefore undertaken to examine the bioavailability of R in the presence of H, Z and E or a combination of the three drugs. Methods: The study included eight healthy volunteers, each being investigated on four occasions at weekly intervals once with R alone and with three of the four combinations on the three remaining occasions. A partially balanced incomplete block design was employed and the allocation of R or the drug combinations was random. Plasma concentrations of R at intervals upto 12 h were determined by microbiological assay using Staphylococcus aureus as the test organism. The proportion (%) dose of R as R plus desacetyl R (DR) in urine excreted over the periods 0-8 and 8-12 h was also determined. Bioavailability was expressed as an index (BI) of area under time concentration curve (AUC) calculated from the plasma concentrations or proportion of dose of R excreted as R plus DR in urine with the combinations to that with R alone. Results: The bioavailability indices based on AUC were 0.96 with RE, 0.76 with RH, 1.08 with RZ and 0.65 with REHZ. The indices based on urine estimations (0-8 h) were similar, the values being 0.94, 0.84, 0.94 and 0.75, respectively. A second investigation revealed that the decrease of bioavailability of R with H was not due to the excipients present in H tablets. Interpretation & conclusion: Isoniazid alone or in combination with E and Z reduces the bioavailability of R. Urinary excretion data offer a simple and non invasive method for the assessment of bioavailability of R

Identification of a group of nontuberculous mycobacteria isolated from the South Indian BCG trial area by HPLC

Twenty-five isolates of nontuberculous mycobacteria isolated from the South Indian BCG trial area were analysed by high performance liquid chromatography (HPLC) for mycolic acid pattern. The chromatograms differentiated the isolates into four species, namely M. terrae complex, M. intracellulare, M. parafortuitum and M. fortuitum. Three strains were unidentified, one of which did not show any mycolic acid peaks. All isolates had been identified as M. diernhoferi by biochemical methods in a previous study. Nineteen of the isolates were analysed by gas chromatography-mass spectrometry (GC-MS) for the presence of tuberculostearic acid, 2-eicosanol and mycolic acid cleavage products, and were classified as nonchromogens or rapidly growing mycobacteria. The results show that HPLC can discriminate the described mycobacterial species better than biochemical methods and GC-MS

Classification of Subjects as Slow or Rapid Inactivators of Isoniazid Oral Administration of a Slow-release. Preparation of Isoniazid and Determination of the Ratio of Acetyisoniazid to Isoniazid in Urine

A simple method for classifying subjects as slow or rapid inactivators of isoniazid has beenevaluated on large numbers of patients. The method consists of determining the ratio of acetylisoniazid to isoniazid in a 24-26 h. urine collection following the oral administration of a slow-release preparation of isoniazid 30 mg./kg. body-weight. In a group of 101 patients, there was 100 per cent agreement between the classification based on this method and that based on a standard method, consisting of estimation of the serum isoniazid concentration, 4½ h. after an intramuscular dose of ordinary isoniazid 3 mg./kg. body-weight. Subsequent studies in other patients have confirmed that the method is efficient, and demonstrated that the classification is highly reproducible

Effect of administration of rifampicin on the adrenocortical function in patients with pulmonary tuberculosis

Adrenocortical function was studied on admission and during treatment in 57 newlydiagnosed patients with pulmonary tuberculosis, 16 of whom were treated with a daily regimen containing Rifampicin (R-7), 22 with a twiceweekly regimen containing the same drug (R-Z) and 19 with a daily regimen that did not contain Rifampicin (NR-7). In patients on daily treatment (R-7 and NR-7), there was a slight increase in plasma cortisol at 1 week followed by a decline; while the mean level at 4 weeks was similar to that on admission in the R-7 patients, that in the NR-7 patients was significantly lower (P < 0.01). No change was observed in the R-2 patients. A positive response to tetracosactrin was observed in the 7 R-7, 14 R-Z and 7 NR-7 patients on admission and in 6, 14 and 14, respectively at 4 weeks. The increase in the proportion of positive responders in the NH-7 patients was significant (P = 0.05). On admission, the diurnal rhythm of the release of cortisol, as assessed by changes in salivary cortisol, was disturbed in the patients with an evening rise in the cortisol levels; it had, however, reverted to a near-normal pattern after 2 months of treatment in all 3 groups of patients

A Modified Method for the Estimation of Acetylisoniazid in Urine

The method of Venkataraman et al. (1968) for the direct estimation of acetylisoniazid in urine has been modified to make it suitable for application to urine specimens containing sugar. The urine is first extracted with a mixture of chloroform and n-butanol, the organic phase re-extracted with dilute sulphuric acid, and the original method then applied to the acid extract. With the modified method, recoveries of acetylisoniazid were quantitative, both in the presence and the absence of glucose. Interference due to hydrazones and isonicotinyl glycine was substantially reduced by the modification, while that due to isoniazid remained the same. There was little or no interference from isonicotinic acid, with either the original or the modified method