Pharmacology of H 394/84, a dihydropyridine neuropeptide Y Y(1) receptor antagonist, in vivo.

The object of the present paper was to investigate the in vivo pharmacological profile of the dihydropyridine neuropeptide Y Y(1) receptor antagonist 1,4-Dihydro-4-[3-[[[[3-[spiro(indene-4,1'-piperidin-1-yl)]propyl]amino]carbonyl]amino]phenyl]-2,6-dimethyl-3,5-pyridine dicarboxylic acid, dimethylester (H 394/84). The renal vasoconstrictor response to neuropeptide Y in anaesthetized rats was dose-dependently antagonized by H 394/84 (ID(50) value=41+/-4 nmol/kg/min), whereas the renal vascular responses to noradrenaline and angiotensin II were only slightly affected by H 394/84 (500 nmol/kg/min). In pigs pretreated with reserpine and transection of sympathetic nerves (depleted of noradrenaline), H 394/84 dose-dependently antagonized renal and femoral vasoconstrictor responses evoked by sympathetic nerve activation (neuronally released neuropeptide Y) and exogenous neuropeptide Y. Significant inhibition was seen already at 1.0 nmol/kg/min, when plasma levels of the antagonist reached 29+/-4 nM. Around 70% of the antagonism remained 90 min after H 394/84 was given. The disposition of H 394/84 fits a biexponential model with initial and terminal half-lives of 2.6 and 48 min, respectively. H 394/84 (100 nmol/kg/min) did not inhibit vascular responses to neuropeptide Y Y(2) receptor-, alpha-adrenoceptor- or purinoceptor-activation in the pig in vivo. It is concluded that H 394/84 is a potent neuropeptide Y Y(1) receptor antagonist with rather long duration of action in vivo. The selectivity and specificity in vivo is more than 100-fold, and H 394/84 antagonizes vascular responses to exogenous and endogenous, neuronally released, neuropeptide Y with similar potency.

In vivo characterization of the novel neuropeptide Y Y1 receptor antagonist H 409/22.

We studied the effects of the novel neuropeptide Y (NPY) Y1 receptor antagonist H 409/22, and its inactive enantiomer H 510/45, on vascular responses evoked by endogenous and exogenous NPY in the pig in vivo. H 409/22 and H 510/45 were given as 30-min infusions, and the antagonistic effects and circulating plasma concentrations were measured. The initial and terminal half-lives of H 409/22 in plasma were approximately 3 and 30 min, respectively. In pigs pretreated with reserpine and transection of sympathetic nerves (depletion of noradrenaline), sympathetic nerve stimulation evoked nonadrenergic vasoconstrictor responses in kidney and hindlimb, mediated by neuronally released NPY. Significant inhibition of these vasoconstrictor responses, as well as of vascular responses to injections of exogenous NPY, were seen during a low-dose infusion of H 409/22 (1.8 nmol/kg/min), when plasma levels of the antagonist reached 77 +/- 8 nM. Greatest inhibitory effects were seen at the highest dose of H 409/22 (180 nmol/kg/min, giving plasma levels of 7.4 +/- 0.6 microM) when all vascular responses evoked by NPY were strongly attenuated or largely abolished. H 510/45 did not affect any of the vascular responses studied. It is concluded that H 409/22 potently and dose-dependently antagonizes vascular responses to exogenous and endogenous NPY in the pig, and thus represents an interesting tool for studies on NPY Y1 receptor-mediated effects in vivo.

The neuropeptide Y (NPY) Y1 receptor antagonist BIBP 3226: equal effects on vascular responses to exogenous and endogenous NPY in the pig in vivo.

1. The antagonistic effects of the neuropeptide Y (NPY) Y1 receptor antagonist BIBP 3226 on equally prominent vascular responses evoked by sympathetic nerve stimulation and exogenous NPY were compared during different intravenous (i.v.) infusions of the antagonist (0.19-190 nmol kg-1 min-1 for 30 min). 2. High frequency sympathetic nerve stimulation in reserpine-treated pigs in vivo evoked non-adrenergic vasoconstrictor responses in kidney and hind limb, in the latter followed by a long-lasting phase of decreased blood flow. The vascular response in the kidney and the long-lasting phase in hind limb resembled the effects of exogenous NPY administered i.v. (kidney) and intraarterially (i.a.) (in the hind limb, which only responded to higher NPY doses). 3. Plasma levels of BIBP 3226 reached a plateau within 20 min and the inhibitory effects on vascular responses were studied during the last ten minutes of infusion. The elimination of BIBP 3226 from plasma was found to fit a two-compartment model with an alpha-phase of 2.0 +/- 0.2 min and a beta-phase of 20.1 +/- 0.9 min. 4. Significant inhibition of presumably Y1 receptor-mediated vascular responses evoked by both endogenous and exogenous NPY in kidney and hind limb was seen even during low-dose infusion of BIBP 3226 (1.9 nmol kg-1 min-1), when plasma levels of the antagonist reached 59 +/- 8 nM. The maximum inhibitory effects of BIBP 3226 were seen during the highest-dose infusion (190 nmol kg-1 min-1), when the long-lasting vasoconstrictor responses in hind limb to sympathetic nerve stimulation and exogenous NPY administration (i.a.) were abolished. Simultaneously, the vascular responses in kidney to exogenous NPY were inhibited by 89% and to sympathetic nerve stimulation by 60%. 5. It is concluded that BIBP 3226 has a short half-life in plasma and should preferably be given by i.v. infusions to maintain blockade and avoid non-specific effects. Furthermore, BIBP 3226 dose-dependently and with similar potency antagonizes vascular responses to exogenous and endogenous NPY both in the kidney and hind limb of the reserpine-treated pig in vivo. Thus, inhibition of vascular responses to exogenous NPY may be a good indicator of the dose of this antagonist needed to inhibit sympathetic Y1 receptor-transmission.

Enantioselective assay of warfarin in blood plasma by liquid chromatography on Chiralcel OC.

A stereoselective method for the two enantiomers of warfarin has been developed. Warfarin is extracted into dichloromethane-hexane from blood plasma. After concentration by evaporation, the enantiomers are resolved by liquid chromatography on Chiralcel OC employing a non-polar mobile phase. By fluorometric detection, concentrations in plasma down to 80 nmol/l (25 ng/ml) can be determined with a coefficient of variation of less than 15%. At the 200 nmol/l level, a coefficient of variation of ca. 4% was found.

Direct chiral separation of almokalant on Chiralcel OD and Chiralpak AD for liquid chromatographic assay of biological samples.

The four isomers of almokalant, a new antiarrhythmic substance under investigation, were separated by liquid chromatography on a Chiralcel OD and a Chiralpak AD column containing cellulose and amylose tris(3,5-dimethylphenylcarbamate), respectively. Both chiral stationary phases separate almokalant into the four isomers, but the retention orders are different if the carbamate is derivatized on cellulose or amylose. The Chiralcel OD column was used for the separation and determination of the isomers in urine at levels down to 100 nmol/l for the first three eluted and 200 nmol/l for the last with a relative standard deviation of less than 15%. The fluorescence response was increased by post-column ionization after stereoselective separation on the Chiralpak AD column. The isomers of almokalant could be determined at levels down to 10 nmol/l in plasma with a relative standard deviation of less than 15%.

Liquid chromatographic separation of the enantiomers of metoprolol and its alpha-hydroxy metabolite on Chiralcel OD for determination in plasma and urine.

The two enantiomers of metoprolol and the four enantiomeric forms of alpha-hydroxymetoprolol were separated by liquid chromatography on a Chiralcel OD column containing a cellulose tris(3,5-dimethyl-phenylcarbamate) chiral stationary phase. The column efficiency was strongly dependent on the flow-rate and the enantioselectivity was influenced by temperature. Of utmost importance for the chiral separation was the water content of the mobile organic phase. The separation system was used for the separation and determination of the enantiomers in plasma and urine samples. The metoprolol enantiomers could be determined by fluorescence down to 10 nmol/l of each in plasma with a relative standard deviation of less than 15%.

Enantioselective determination of metoprolol in plasma by liquid chromatography on a silica-bonded alpha 1-acid glycoprotein column.

The enantiomers of metoprolol were determined in plasma samples after direct resolution on a silica bonded alpha 1-acid glycoprotein column. Metoprolol was extracted from plasma into a diethyl ether-dichloromethane mixture and after back extraction to dilute phosphoric acid and adjustment of pH the sample was injected on a Chiral-AGP column for separation of R- and S-metoprolol. It was possible to measure down to 2 nmol per litre plasma with a relative standard deviation of less than 15% by use of gradient elution and fluorescence detection. The analytical method was employed to study the pharmacokinetics of the metoprolol enantiomers after administration of the racemate to humans.

Stereoselective interaction of omeprazole with warfarin in healthy men.

The effect of concomitant treatment with omeprazole (20 mg/day) on the plasma concentration and anticoagulation effect of warfarin was studied in 21 young healthy men. An initial three weeks' treatment with warfarin alone was administered to determine the doses required for the subjects' vitamin K-dependent coagulation factors to fall within 10-20% of the normal range, as determined by the Trombotest. Omeprazole and placebo were then administered concomitantly with warfarin for 2 weeks each in a double-blind, randomized, crossover fashion. Plasma concentrations of (R)- and (S)-warfarin, and Trombotest values were measured daily on weekdays throughout the crossover period. Omeprazole had no apparent effect on the mean (S)-warfarin plasma concentration (379 ng/ml with, versus 387 ng/ml without, omeprazole), but caused a slight (12%) although statistically significant increase in the mean (R)-warfarin concentration from 490 to 548 ng/ml (95% confidence interval for difference of means: 28-88). The Trombotest values exhibited large inter- and intrasubject variability during both omeprazole and placebo treatment; however, there was a small, although statistically significant decrease in the mean value from 21.1% without to 18.7% with omeprazole treatment (95% CI for difference of means: -4.6- -0.1). Those subjects with Trombotest values nearest the therapeutic range (5-15%) exhibited less change during omeprazole treatment, and no changes occurred that required a change in warfarin dosing. The interaction of omeprazole with warfarin was attributed to a stereoselective inhibition of the hepatic metabolism of the less potent (R)-warfarin enantiomer. The small effect of omeprazole on the anticoagulation activity of warfarin is not likely to be of clinical importance.

Determination of metoprolol and two major metabolites in plasma and urine by column liquid chromatography and fluorometric detection.

Metoprolol and its alpha-hydroxy metabolite were determined in plasma down to 2 nmol/l (S.D. 10-15%) after solvent extraction and bonded-phase liquid chromatography with fluorometric detection. The major metabolite with a carboxylic function was also measured in plasma when liquid-solid extraction on a column activated with dodecyl sulphate was applied. In urine the three components were assayed by direct injection of a diluted sample.

Fully automated gradient elution liquid chromatographic assay of omeprazole and two metabolites.

An automated liquid chromatographic method for the determination of omeprazole and two metabolites in plasma and urine is described. It utilizes the Technicon Fully-Automated-Sample-Treatment-LC system (FAST(R)-LC). Sample preparation is achieved by air-segmented continuous-flow providing solvent extraction, evaporation to dryness and reconstitution before injection onto a reversed-phase column. The compounds are separated by isocratic or gradient elution with acetonitrile-phosphate buffer mobile phases and quantified by UV-measurements at 302 nm. The limit of determination (relative standard deviation 10-15%) is 50 nmol l(-1) in plasma (800 microl) and 200 nmol l(-1) in urine (200 microl). The sample capacity is six or three samples per hour, depending on the elution mode.

[Aorto-enteral fistula--pathogenesis, clinical aspects and therapy]. / Aorto-enterische Fisteln--Pathogenese, Klinik und Therapie.

This report is based on 14 own observations and 166 patients collected from the literature. The most frequent location both of primary and secondary aortic-enteric fistulas (AEF) is the end part of the duodenum (60-70%). In the group of secondary AEF the paraprothetic type represents the most frequent morphological finding. The best diagnostic approach should be seen in a gastroduodenoscopy. The choice of surgical repair is still controversal. Most of the surgeons insist on a radical repair (Type A: restoration of the intestinal tract, complete removal of the vascular prosthesis, blind closure of the infrarenal aortic stump, axillo-bifemoral bypass). Type A repair is loaded with a high operative mortality (52%) and a number of secondary complications (e.g. recurrent AEF; bleeding from the aortic stump). As an alternative surgical approach the authors present an in-situ-repair (Type B: closing of the intestinal defect, partial exchange of inserted vascular prosthesis, a circular omentum sleeve covering the prosthesis and anastomosis). The Type B repair offers a time saving procedure with a reduced operative mortality (29%) and a better outcome for the patients. This method is only contraindicated in the presence of a spread infection of the retroperitoneal space including the vascular prosthesis.