Immunoassays for the detection of nicergoline and its metabolites in human plasma

In order to determine nicergoline pharmacokinetics after oral administration to humans, we have developed two radioimmunoassays, one directed against nicergoline and the other directed against known nicergoline metabolites. The assays were validated according to the recommendations of international regulatory agencies and their limits of quantification were 40 and 10 pg/ml, respectively. In order to further validate the methods, a chromatographic separation of immunoreactive entities was performed with samples from healthy volunteers who were given 15 mg of Sermion (nicergoline orally administered). Chromatographic determination of assay specificity showed that the metabolite radioimmunoassay recognised known nicergoline metabolites but also a new metabolite. Using the antibodies directed against nicergoline, we were unable to detect nicergoline in the human plasma. This suggests that nicergoline is absent in the circulation because of complete metabolism through its first-pass effect.

[Pharmacokinetics in healthy subjects of althiazide and spironolactone in a fixed combination for 2 doses]

Pharmacokinetic plasma curves of altizide (ALT), spironolactone (SPI) and two of the main metabolites of spironolactone, 7 alpha-thiomethyl-spirolactone (7TM) and canrenone (CAN) have been established in 12 healthy human volunteers (6 men and 6 women) after unique oral administration of 1 or 2 tablets of a combination of the two diuretic compounds: altizide (15 mg per tablet) and spironolactone (25 mg per tablets). Main pharmacokinetic parameters have been calculated using a biexponential (ALT and SPI) or a triexponential model (7TM and CAN). Spironolactone is rapidly absorbed. Plasma curves show Tmax respectively equal to 1.19 +/- 0.47 hours (1 tablet) or 1.21 +/- 0.46 (2 tablets). Spironolactone is rapidly metabolized as it is shown by the mean Tmax of metabolites: 7TM and CAN Tmax are respectively 1.56 +/- 0.45 hours and 2.54 +/- 1.06 hours after administration of 1 tablet, or 1.58 +/- 0.42 hours and 2.67 +/- 1.13 hours after administration of 2 tablets. The mean residence time (MRT) of ALT [4.94 +/- 1.14 hours (1 tablet) or 5.31 +/- 1.06 hours (2 tablets)] and SPI [1.81 +/- 0.45 hours (1 tablet) or 1.88 +/- 0.50 hours (2 tablets)] shows a rapid elimination of both drugs. SPI metabolites present higher MRT than the unchanged drug. 7TM MRT after administration of 1 or 2 tablets, are 24.51 +/- 15.35 hours and 18.11 +/- 11.87 hours, respectively. CAN MRT are 39.65 +/- 23.58 hours (1 tablet) and 38.93 +/- 24.58 (2 tablets). Statistical analysis shows no significant administration order effect on the different parametres. Student' t test shows a significant sex effect on CAN AUC, for both formulations.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of dihydroergotamine by a cytochrome P-450 similar to that involved in the metabolism of macrolide antibiotics

1. Previous studies have shown that the macrolide antibiotics, such as oleandomycin and erythromycin, enhance their own transformation into a stable metabolite-cytochrome P-450 complex, thus impairing monooxygenase activity. This cytochrome P-450 induced by macrolides is similar to the major form induced in rats by pregnenolone-16 alpha-carbonitrile (PCN) (III A1 isozyme). 2. The cytochrome P-450 isozyme induced in rats by PCN or macrolide antibiotics bound dihydroergotamine (DHE) with high affinity and was also capable of metabolizing the drug. However, phenobarbital administration enhanced the metabolism of DHE to a greater extent than would be expected from the levels of the PB-PCNE isoenzyme, indicating that other cytochrome P-450 proteins may also be involved in DHE metabolism. 3. DHE metabolism was inhibited by macrolide antibiotics both ex vivo and in vitro. The metabolite-cytochrome P-450 complex formed by the antibiotics impairs the metabolism of DHE, so that when the complex is dissociated the metabolic activity is restored. These findings explain the observed clinical interactions between macrolides and other drugs, and such an approach may prove useful in their prediction.