Pharmacodynamics of amoxicillin against Mannheimia haemolytica and Pasteurella multocida and pharmacokinetic/pharmacodynamic (PK/PD) correlation in sheep.

Silicone-made tissue cages were implanted in sheep. Blood serum (SBS) and tissue cage fluid (TCF) samples were collected after amoxicillin intravenous and intramuscular administrations, at the dose of 15 mg/kg. Amoxicillin pharmacodynamics were studied in an artificial culture medium, SBS and TCF with use of a Mannheimia haemolytica and a Pasteurella multocida strain.

Influence of the injection site on the pharmacokinetics of amoxicillin after intramuscular administration of a conventional and a long-acting formulation in sheep.

The pharmacokinetics of amoxicillin (AMX) were investigated in sheep following intravenous (i.v.) and intramuscular (i.

Peripheral distribution of amoxicillin in sheep and influence of local inflammation.

The pharmacokinetics of amoxicillin (AMX) in blood serum (SBS) and tissue cage fluid (TCF) was studied in sheep. Four tissue cages, prepared from silicone rubber tubing, were subcutaneously inserted in the neck area (two on each side) of the experimental animals and AMX was administered both intravenously (IV) and intramuscularly (IM) at the dose rate of 15mg/kg bodyweight. The impact of local inflammation on AMX distribution in TCF was studied after intra-cavity injection of a lambda carrageenan solution in one of the two tissue cages used after each administration.

Application and validation of a LC/fluorescence method for the determination of amoxicillin in sheep serum and tissue cage fluid.

A LC method with fluorescence detection after pre-column mercury dichloride derivation was developed and validated for the quantitative determination of amoxicillin in sheep blood serum and tissue cage fluid at levels down to 100 and 200ng/mL, respectively. Spiked blood serum and tissue cage fluid samples were deproteinized, derivatized with mercury dichloride and extracted prior to reversed phase LC analysis with fluorescence spectrophotometric detection at an excitation wavelength of 355nm and an emission wavelength of 435nm. Separation was carried out on a C(18) column with a mobile phase consisting of phosphate buffer, octanesulphonate sodium (OCT), and acetronitrile.

Enhancing and inhibitory effects of H2-receptor antagonists on the GABA and the GABAA-agonist muscimol responses of the isolated guinea pig ileum: a pharmacodynamic interaction.

This study investigates the effect of histamine H(2)-receptor antagonists on the GABA-responses of the intestine. GABA and the GABA(A)-agonist muscimol were applied to isolated ileal guinea pig preparations in the absence, and presence of two H(2)-receptor antagonists, famotidine and cimetidine. Both GABA and muscimol produced a concentration-dependent contractile effect on the guinea pig ileum.

Cisapride reverses the anticholinergic effect of disopyramide on the isolated guinea-pig urinary bladder.

The present investigation aims to examine whether the prokinetic agent cisapride is able to reverse disopyramide's anticholinergic effect on the isolated guinea-pig urinary bladder. Acetylcholine, at concentrations ranging from 10(-7) to 10(-3) M, produced a stimulatory effect on the urinary bladder (pEC(50) value=5.1).

New simple liquid chromatographic method for the determination of trimethoprim, sulfadiazine and N4-acetylsulfadiazine in plasma of broilers.

A new method for simultaneous quantification of trimethoprim, sulfadiazine and N4-acetylsulfadiazine in plasma of broilers at levels down to 13-16 ng/ml has been developed. Samples were deproteinized with acetonitrile, defatted with hexane, and extracted with dichloromethane. Chromatographic analysis was carried out on a C18 column in the presence of tetrabutylammonium hydrogen sulfate, a competing base, while detection was performed at 240 nm for trimethoprim, and 270 nm for both sulfadiazine and N4-acetylsulfadiazine.

Biphenylacetic acid enhances the antagonistic action of fluoroquinolones on the GABA(A)-mediated responses of the isolated guinea-pig ileum.

This paper examines the effect of biphenylacetic acid on the antagonistic action of norfloxacin and enoxacin on the GABA(A)-mediated responses of the isolated guinea-pig ileum. GABA produced transient contractions followed by relaxation. The contractile effect of exogenously applied GABA was concentration-dependent with EC(50)= 9.

Synergistic and antagonistic pharmacodynamic interaction between ranitidine and cisapride: a study on the isolated rabbit intestine.

The present study examines the pharmacodynamic interaction between the H(2)-receptor antagonist ranitidine and the prokinetic agent cisapride on the isolated rabbit intestine. Ranitidine produced a concentration-dependent contractile effect on the duodenal, ileal and ascending colon preparations, with EC(50)values of 1.35 x 10(-4)M for the duodenum, 1.

Propofol's biphasic effect on GABA(A)-receptor-mediated response of the isolated guinea pig ileum.

This study examines the effect of the anaesthetic agent propofol on the guinea pig ileum and whether this effect derives from an interaction of the drug with GABA receptors. Propofol produced a biphasic effect consisting of a dose-dependent contractile effect (EC(50)=2.2x10(-5)m) followed by an 'after relaxation'.

Cisapride counteracts the anticholinergic effect of disopyramide on the guinea pig isolated small but not large intestine.

This study examines the influence of the prokinetic agent cisapride on the disopyramide's effect on the isolated duodenum and ileum, as well as on the ascending colon of the guinea pig. Acetylcholine produced the well known stimulatory effect on the intestinal parts with EC50 values 9.6 x 10(-8), 7 x 10(-9) and 1.

Effect of combined fenthion and cimetidine use in rats on lethality, blood cholinesterase activities, and serum cholinesterase isoenzymes.

H2-receptor antagonists inhibit cholinesterase (ChE) activity. We examined perturbations in ChE isoenzyme patterns and ChE activities of rats from the combined effects of fenthion (FEN) and cimetidine (CIM). Sixty-four female Sprague-Dawley rats were divided into 8 groups.

Effect of cisapride on the isolated guinea pig gall bladder and common bile duct.

1. In this study, the effect of cisapride on the isolated guinea pig gall bladder (GB) and common bile duct (CBD) motility was investigated. 2.

Inhibitory effect of flumequine, enoxacin and norfloxacin on the GABA-induced contractile effect on the guinea pig ileum.

1. In the present study the effect of flumequine, enoxacin and norfloxacin on the GABA-elicited contractions (EC50 1.10 x 10(-5) M) on the isolated guinea pig ileum was investigated, in a comparative manner.

Ketamine may modify intestinal motility by acting at GABAA-receptor complex; an in vitro study on the guinea pig intestine.

In the present study the effect of ketamine, a dissociative anaesthetic, on the GABA- and on the specific GABAA-agonist muscimol-induced responses of the isolated guinea pig ileum was investigated. GABA as well as muscimol produce a concentration-dependent contractile effect on the duodenum, jejunum and ileum. The sensitivity of the intestinal parts to both the above substances increases from the duodenum to the ileum.

The effect of xylazine on the isolated sheep trachea.

The effect of xylazine on the isolated sheep trachea and its possible interactions with the alpha 2-adrenergic antagonist, atipamezole, and the anticholinergic agent, atropine, was studied. The mechanical responses of the tracheal preparations were recorded after exposing each one to cumulatively increasing concentrations of xylazine alone or in the presence of atipamezole or atropine. Xylazine exerted a concentration-dependent contractile effect, with a threshold concentration of 10(-7) M while the maximum activity was produced at a concentration of 10(-5) M (EC50 = 2.

Ketamine protects acetylcholinesterase against inhibition by propoxur and phoxim.

In the present study the effect of ketamine on the contractions caused by propoxur and phoxim on the isolated guinea pig ileum was investigated. Ketamine was found able to inhibit in a concentration-dependent manner the contractile responses of the ileum to propoxur and phoxim, while it did not significantly modify the contractions induced by acetylcholine. Propoxur and phoxim augmented the contractile responses induced by acetylcholine in the presence of acetylcholinesterase.

Ketamine inhibits the anticholinesterase activity of ranitidine and physostigmine.

1. The present study was performed to investigate the effect of ketamine on the contractile responses induced by the H2-receptor antagonist ranitidine and the anticholinesterase agent physostigmine on the isolated guinea pig ileum. 2.

Effect of nizatidine and ranitidine on the D-tubocurarine neuromuscular blockade in the toad rectus abdominis muscle.

The influence of varying concentrations of the H2-receptor antagonists nizatidine and ranitidine on the acetylcholine- and carbachol-induced contractures on the toad rectus abdominis muscle, as well as the possible interaction between the above H2-receptor antagonists and D-tubocurarine were studied. Nizatidine and ranitidine at a concentration of 3.2 x 10(-4) mol l-1 augmented, and at 3.

Effect of erythromycin on different parts of the rabbit intestine: comparison with motilin.

1. The effect of erythromycin on the rabbit intestinal smooth muscle was investigated and was compared to that of motilin. 2.

Comparative study of erythromycin, troleandomycin and tylosin on the rabbit intestine.

The macrolide antimicrobial agents, erythromycin, troleandomycin and tylosin were tested for their effect on isolated whole segments of the rabbit duodenum, jejunum, ileum and ascending colon, as well as on strips of the circular and longitudinal smooth muscle of the ascending colon. The 14-membered macrolides erythromycin and troleandomycin were found to possess a concentration-dependent contractile effect on the intestinal smooth muscle. The order of potency was: erythromycin > troleandomycin.

Effect of cimetidine on the histamine and dimaprit induced responses on the guinea pig ileum during development.

1. In ileal segments obtained from 1, 15, 30, 45 and 60-day-old guinea pigs, histamine produced a dose-dependent significant contractile response from a threshold concentration of 3.2 x 10(-8) M.

Comparative study of the H2-receptor antagonists cimetidine, ranitidine, famotidine and nizatidine on the rabbit stomach fundus and sigmoid colon.

The H2-receptor antagonists, cimetidine, ranitidine, famotidine and nizatidine, were tested for their effect on the isolated smooth muscle strips from the rabbit stomach fundus and sigmoid colon. These H2-receptor antagonists were found to possess a concentration-dependent contractile effect on the above smooth muscle preparations and the order of potency was: ranitidine = nizatidine > famotidine > cimetidine. In addition, the smooth muscle preparations from the sigmoid colon were significantly more sensitive to the above compounds than the smooth muscle preparations from the stomach fundus.

Inhibition of acetylcholinesterase by the H2-receptor antagonist nizatidine.

The purpose of the present investigation was to study if the stimulating effect of nizatidine on the intestinal smooth muscle is related to the acetylcholinesterase activity. Isolated segments of guinea pig ileum were used in Tyrode solution at 37 degrees C. Nizatidine (from 3.

The excitatory effect of the new histamine H2-receptor antagonist nizatidine (LY 139037) on the guinea pig ileum.

The histamine H2-receptor antagonist, nizatidine (LY 139037), was tested for its effect on the intestinal smooth muscle. Isolated segments of guinea pig ileum were used in Tyrode solution at 37 degrees C. Nizatidine (from 3.