Flow-injection chemiluminescence determination of dihydralazine sulfate in serum using luminol and diperiodatocuprate (III) system.

A novel flow-injection chemiluminescence (CL) method for the determination of dihydralazine sulfate (DHZS) is described. The method is based on the reaction of luminol and diperiodatocuprate (K(2)[Cu(H(2)IO(6))(OH)(2)], DPC) in alkaline medium to emit CL, which is greatly enhanced by DHZS. The possible CL mechanism was first proposed based on the kinetic characteristic, CL spectrum and UV spectra. The optimum condition for the CL reaction was in detail studied using flow-injection system. The experiments indicated that under optimum condition, the CL intensity was linearly related to the concentration of DHZS in the range of 7.0x10(-9) to 8.6x10(-7) g mL(-1) with a detection limit (3sigma) of 2.1x10(-9) g mL(-1). The proposed method had good reproducibility with the relative standard deviation 3.1% (n=7) for 5.2x10(-8) g mL(-1) of DHZS. This method has the advantages of simple operation, fast response and high sensitivity. The special advantage of the system is that very low concentration of luminol can react with DPC catalyzed by DHZS to get excellent experiment results. And CL cannot be observed nearly when luminol with same concentration reacts with other oxidants, so luminol-DPC system has higher selectivity than other luminol CL systems. The method has been successfully applied to determine DHZS in serum.

Method development for dihydralazine with HPLC-MS/MS--an old but tricky substance in human plasma.

An HPLC-MS/MS method was developed and validated for the determination of dihydralazine in human plasma. HPLC-MS/MS has not been used before in a published paper and provides better sensitivity and selectivity. Therefore a much easier sample preparation than published before is feasible (protein precipitation). As this substance is rather reactive and sensitive some specific care has to be taken hindering the conversion of the substance in whole blood and following human plasma after blood withdrawal. Hydrazines often are used for derivatization of aldehydes and ketones. With specific care (using 1,4-dithiothreitol (DTT) and cooling) dihydralazine can be preserved and analysed without decomposition or conversion in the tested range of 0.500-302 ng/mL of human plasma. The following inter-batch precision and accuracy of the Quality Control Samples resulted: QC-A (1.34 ng/mL plasma) with a precision of coefficient of variation (CV) 7.66% and an accuracy of 103.2%; QC-B (18.2 ng/mL 7.86%, acc. 101.3%); QC-C (258 ng/mL, 9.73%, acc. 98.3%). The inter-batch values of the LLOQ samples at 0.500 ng/mL were 7.17% for CV and accuracy of 106.4%. Mean recovery tested at the QC levels was found to be 103.8%. Specificity in six different plasma samples was good (<10% of the area of the LLOQ). Stability in plasma was tested under different conditions and was sufficient.

[Effect of Urapidil in antihypertensive therapy of preeclampsia on newborns]. / Auswirkungen von Urapidil in der antihypertensiven Therapie bei Präeklampsie auf die Neugeborenen.

OBJECTIVE: For the therapy of preeclamptic patients is Urapidil besides Dihydralazine another possible option for iv-therapy with good results in first clinical studies. Effects of both drugs on the newborns were observed. - METHODS: The maternal and fetal Urapidil plasma-concentrations and cardiovascular parameters of the newborns were observed in a randomised comparative therapy-study. - RESULTS: We found low fetal Urapidil plasma-concentrations as well as a less influence on cardiovascular parameters compared to dihydralazine. - DISCUSSION: With Urapaidil we have another therapeutic option in preeclampsia where we could not show any negative side-effects on the newborns.

[The quantitative determination of dihydralazine and selected metabolites in man]. / Zur quantitativen Bestimmung von Dihydralazin und ausgewählter Metabolite beim Menschen.

Dihydralazine and its metabolites were estimated in the steady-state in 9 hypertonic patients by gas chromatography. Serum levels of both dihydralazine and metabolites were very low and particularly below the detection limit. In urine and faeces about half of the dose was found mainly as metabolites, 2/3 of this in faeces. Acid labile hydrazones of dihydralazine (about 6% of the dose), primary acetylated and primary oxidized metabolites (both about 20%) were identified as main metabolites. Secondary metabolites (hydrazones, acetylated and oxidized products) were measured, too.

Studies on the kinetics and distribution of dihydralazine in pregnancy.

Plasma kinetics of dihydralazine (50 mg p.o.) was studied in 11 women in late pregnancy. The distribution pattern between maternal and umbilical plasma was investigated in 12 patients who received 75-100 mg dihydralazine per day. In one patient amniotic fluid concentration and in another breast milk levels could be evaluated twice. Plasma concentrations of dihydralazine were very low. Continuous plasma level curves could be estimated in only four of the examined patients. In every case dihydralazine concentrations were higher in umbilical blood than in maternal plasma. Concentrations found in breast milk were clinically negligible.

Liquid chromatographic determination of dihydralazine and hydralazine in human plasma and its application to pharmacokinetic studies of dihydralazine.

An analytical method is described for the concurrent determination of dihydralazine (1) and hydralazine (2) in human plasma as unchanged or apparent compounds. For the assay of the unchanged compounds, plasma samples were acidified with 0.02 M HCI and derivatized first with nitrous acid, and afterwards with sodium methylate. For the assay of the apparent compounds, plasma samples were acidified with 3 M HCI, incubated at 90 degrees C for 30 min and derivatized as above. The derivatives were extracted and chromatographed by reversed-phase mode on a C18 mu Bondapak column. The fluorescence of the compounds was measured (excitation wavelength = 230 nm, emission wavelength = 430 nm). The limits of quantitation were 0.5 ng/mL for the unchanged compounds and 1 ng/ml for the apparent compounds. After oral administration of 25 mg of 1 to 2 healthy volunteers, the mean areas under the plasma concentration-time curves were respectively 43.7 and 590 ng X h/mL for unchanged and apparent 1. The corresponding mean elimination half-lives were 1.03 and 3.9 h. The mean area under the curve measured for 2 amounted to 6.3% of that obtained for 1 for the unchanged compounds and to 10.3% for the apparent compounds.

Plasma concentrations and pharmacokinetics of dihydralazine after single oral doses to human subjects.

After single oral doses of 20 mg of a suspension of dihydralazine sulphate to human subjects, the peak of mean plasma concentrations of dihydralazine of 47.0 ng ml-1 +/- 11.0 standard deviation (S.D.) (n = 7) was reached at 1 h. Mean concentrations declined biphasically with apparent half-lives of 0.57 and 4.96 h respectively. Dihydralazine was partly converted to hydralazine. The peak of mean plasma concentrations of the latter drug of 3.9 ng ml-1 +/- 1.7 S.D. (n = 7) occurred at 1-2 h after dosing with dihydralazine sulphate and declined to 1.5 ng ml-1 +/- 1.5 S.D. at 6 h. Of the seven subjects studied, three were classified as fast and four as slow acetylators. Mean clearances appeared to be slightly more rapid in fast acetylators (1.63 l min-1 +/- 0.32 S.D.) when compared to slow acetylators (1.31 l min-1 +/- 0.31 S.D.) but this difference and differences in plasma concentrations and in areas under the plasma drug concentration-time curves were not significant (p > 0.1).

Effect of hydralazine and dihydralazine on connective tissue and binding to serum protein.

Hydralazine and dihydralazine, chelators of Fe2+, Fe3+ and Mn2+ ions, inhibited collagen biosynthesis in organ culture of chicken embryo tibiae. Both substances inhibited the in vitro hydroxylation of [14C]Pro-labelled protocollagen by protocollagen proline hydroxylase. A decreased incorporation of [14C]-D-glucosamine into glyco- and/or muco-proteins was found under the effect of the two drugs. Dihydralazine, a cationic compound, was bound to DNA and acid mucopolysaccharides (glycosaminoglycans), forming an insoluble complex. Both substances were bound to serum alpha 2-globulin. Subcutaneous injections of dihydralazine in rats produced a local as well as a general toxic effect.