Serum Rifampicin Research Articles

Fluorometric and microbiological assays for rifampicin and the determination of serum levels in the dog.

Rifampicin is oxidized with hydrogen peroxide to a product that is fluorescent in alkaline solutions. Maximum fluorescence is measured at 480 nm with an excitation wavelength of 370 nm. The lower limit of detection of rifampicin in water is 0.1 μg/ml. A microbiological assay with Staphylococcus aureus 560 as the assay organism verified the reliability of the fluorometric assay. The fluorametric and microbiological assays were applied to the estimation of rifampicin in serum and were used to obtain concentration-time data for dogs that had been treated orally with 10 mg/kg rifampicin. Half-life of rifampicin in the dog was 8 h.

Kinetic studies on rifampicin. I. Serum concentration analysis in subjects treated with different oral doses over a period of two weeks.

A study aimed at contributing to the elucidation of the decrease in serum rifampicin concentrations observed during repeated administration of the antibiotic was carried out in a group of 18 healthy subjects. Three dose levels were investigated: 900 mg once daily, 600 mg once daily and 300 mg 12-hourly, and the behaviour over a period of 14 days of the peak and 12-hour serum concentrations and of the biological half-life was evaluated. The study demonstrates that during treatment with repeated doses of rifampicin the kinetics of the antibiotic undergo definite changes. While the peak serum concentrations do not appear to be affected in a consistent way by the duration of treatment, the 12-hour serum concentrations show a definite decrease, which takes place mainly during the first 6 days of treatment; a further decrease between 6 and 14 days was seen but was found not to be significant. A definite decrease in biological half-life is also observed during the first 6 days of treatment; such a decrease is directly correlated with the dose given on each administration. As a consequence, the half-life values, which are correlated with the doses on the first day of treatment, are no longer different for the different doses on the sixth day. The hypothesis that the increase in rate of disappearance of rifampicin from blood, which takes place mainly during the first 6 days of treatment, is due to an increased rate of biliary excretion is discussed.

Pharmacological Study of Rifampicin after Repeated High Dosage during Intermittent Combined Therapy. I. Variation of the Rifampicin Serum Levels (947 Determinations)

A study, carried out in 100 African patients on intermittent therapy with RMP in high dosage (30 mg/kg) combined with INH or EMB, has shown that high and long-lasting RMP serum levels could be obtained, covering a 24-hour period. The mean RMP peak levels reached 17.7 µg/ml, the mean serum levels after 12 h still 6.4 µg/ml and after 24 h 1.3 µg/ml. No signs of accumulation have been observed after administration of three such high doses on alternate days. On the contrary the 12- and 24-hour serum levels were significantly lower after the second and third drug administration. Patients treated with RMP-INH had somewhat higher RMP serum levels than patients with RMP-EMB.