bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectrophotometric and Spectrofluorimetric Determination of Fluorouracil in the Presence of its Degradation Products
Authors: Amer M M , Hassan S S M , El-Fatah S A Abd , El-Kosasy A M
Published: April 2011

Three reliable spectrophotometric and spectrofluorimetric procedures are described for the determination of fluorouracil in bulk powder and ampoules in the presence of its degradation products.

One spectrophotometric procedure, based on measurement at 555 nm of the violet-coloured complex formed by fluorouracil with cobalt(II), has a detection limit of 0.03 mg mL−1. Two sensitive spectrofluorimetric procedures are also proposed. One is based on measurement of the intrinsic fluorescence of the liberated fluorouracil at 375 nm, after precipitation as its cobalt(II) complex, decomposition of the precipitate with sulphuric acid and excitation at 295 nm. The second depends on excitation of the fluorouracil-cobalt(II) complex at 395 nm and measuring its fluorescence at 483 nm. The limits of detection of the two spectrofluorimetric procedures are 0.5 and 2 μg mL−1, respectively.

The three procedures have been used successfully for the determination of fluorouracil ampoules. The validity of the methods has been assessed by applying the standard addition technique.
Transdermal Delivery and Accumulation of Indomethacin in Subcutaneous Tissues in Rats
Authors: Mikulak Stephen A , Vangsness C Thomas , Nimni Marcel E
Published: April 2011

Oral non-steroidal anti-inflammatory drugs (NSAIDs) are effective pharmacotherapy for a wide variety of painful, inflammatory disorders. Development of an efficient means of topical administration of NSAIDs could increase local soft-tissue and joint concentrations while reducing systemic distribution of the drug, thereby reducing side-effects. With this in mind we studied the effects of a novel topical penetration enhancer for lipophilic compounds, a trans-phase delivery system (TPDS), a solution of benzyl alcohol, iso-propanol and acetone, on the distribution of indomethacin in various tissues locally and remote from the site of application. We compared the TPDS with a 50:50 (v/v) mixture of propylene glycol and ethanol, a commonly used penetration enhancer, and with oral administration.

We found that the TPDS was significantly superior to the other approaches at achieving high local-tissue concentrations in the vicinity of the site of application. In addition, comparison of these two carrier systems seems to clarify the different aqueous and hydrophobic pathways of drug penetration which emerge from various experimental findings and theoretical considerations.

Our results suggest that this non-aqueous solvent system, and benzyl alcohol in particular, because of its unique physicochemical and solvating characteristics, might be able to deliver therapeutic levels of indomethacin to tissues close to the site of application in a safer and more effective manner than presently accepted forms of delivery.
Evaluation of Oral Mucoadhesive Microspheres in Man on the Basis of the Pharmacokinetics of Furosemide and Riboflavin, Compounds with Limited Gastrointestinal Absorption Sites
Authors: Akiyama Yohko , Nagahara Naoki , Nara Eiji , Kitano Megumi , Iwasa SUSUMU , Yamamoto Isamu , Azuma Junichi , Ogawa Yasuaki
Published: April 2011

When sustained-release adhesive and non-adhesive microspheres which release the same drugs at similar rates are administered orally, drug absorption after administration of adhesive microspheres should, if the gastrointestinal residence of adhesive microspheres is prolonged as a result of mucoadhesion, be higher than that after administration of non-adhesive microspheres. The gastrointestinal transit of oral adhesive microspheres in man has been evaluated pharmacokinetically using furosemide and riboflavin, compounds with limited absorption sites in the upper small intestine.

In a preliminary experiment with fasted rats it was confirmed that a higher percentage of the drug remained in the stomach and that plasma drug levels were higher when furosemide was administered in the form of adhesive rather than non-adhesive microspheres. Two kinds of sustained-release microsphere, adhesive and non-adhesive, containing furosemide and riboflavin in hard gelatin capsules were prepared and orally administered to 10 healthy fasted volunteers in a cross-over design. Areas under the plasma concentration-time curves (AUC) were 1.8 times larger for furosemide and urinary recovery was 2.4 times higher for riboflavin when adhesive microspheres rather than when non-adhesive microspheres were used. When adhesive microspheres containing riboflavin were administered to fed volunteers, urinary recovery was 2.1 times higher and mean residence time (MRT) was more prolonged than when the microspheres were administered to fasted volunteers.

Adhesive microspheres were found to adhere to the gastric or intestinal mucosa with high affinity in man and rats, resulting in prolonged gastrointestinal residence.
Pharmacokinetics and Haemodynamic Effect of Diltiazem in Rats: Effect of Route of Administration
Authors: Tsui Ban C H , Feng Joe D Z , Yeung Pollen K F
Published: April 2011

Diltiazem is a calcium antagonist widely used for the treatment of angina and hypertension. Previous studies in patients have shown that the haemodynamic effects of diltiazem are greater after parenteral rather than oral administration. The rat has been used as an animal model to determine the effect of the route of administration on the pharmacokinetic and haemodynamic effects of diltiazem.

The results showed that plasma concentrations of diltiazem were more than 10 times higher after the intra-arterial dose. The plasma concentrations of the major metabolites were also higher after intra-arterial administration, although only for deacetyl diltiazem (M1) did the difference reach statistical significance (P < 0.05). The haemodynamic effects (on blood pressure and heart rate) of diltiazem were considerably greater after intra-arterial administration; this was attributed mainly to the much higher plasma concentrations of diltiazem. The hypotensive and chronotropic effects of diltiazem were similar; Emax and EC50 for diastolic blood pressure were 72 ± 19% and 4.4 ± 5.9 μg mL−1; for heart rate they were 77 ± 32% and 10.0 ± 11.7 μg mL−1, respectively.

The haemodynamic effects of diltiazem are much greater after intra-arterial administration, mainly because of the much higher plasma concentrations of the drug. The contribution by the metabolites would be minimal after this route of administration.
Analgesic and Thermic Effects, and Cerebrospinal Fluid and Plasma Pharmacokinetics, of Intracerebroventricularly Administered Morphine in Normal and Sensitized Rats
Authors: Bhargava Hemendra N , Villar Vincent M , Cortijo Julio , Morcillo Esteban J
Published: April 2011

The relationship between asthma and opioids has barely been investigated. This study examines whether active sensitization of rats changes the analgesic and thermic effects of intracerebroventricular morphine or the pharmacokinetics of the drug.

Morphine (5, 10 and 20 μg) was given intracerebroventricularly to sensitized (active immunization to ovalbumin and Al(OH)3 then airway challenge with ovalbumin after 12 days) and normal (i.e. non-sensitized) male Sprague-Dawley rats. The tail-flick latencies and changes in colon temperature were determined before morphine injection and at 30 min intervals for a period of 300 min afterwards. Results were expressed as the area under the time-response curve. The analgesic and hyperthermic response to morphine for sensitized rats was less than that obtained for normal rats. Cerebrospinal fluid and blood samples were collected periodically for a period of 240 min and morphine levels were determined by a highly sensitive radioimmunoassay. The pharmacokinetic parameters half-life, terminal elimination rate constant and the mean residence time were determined in both cerebrospinal fluid and plasma by non-compartmental analysis. The area under the cerebrospinal fluid concentration-time curve from time zero to infinity was higher for sensitized rats than for normal rats for all three doses of morphine but these differences did not correspond with similar changes in pharmacological responses.

In conclusion, the attenuated analgesic and thermic responses to intracerebroventricular morphine in the sensitized rats might be a result of pharmacodynamic alterations rather than to pharmacokinetic changes.
Differential Effects of Nicorandil on the Vasodepressor Responses to Vasoactive Polypeptides Administered Intravenously to Rats
Authors: Sakai Kazushige , Akima Michitaka , Saito Keiji
Published: April 2011

The effects of nicorandil on vasodepressor responses to vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and substance P have been examined in anaesthetized rats.

Intravenous bolus injections of VIP (0.3 μg kg−1), CGRP (0.1 μg kg−1) and substance P (0.1 μg kg−1) induced reductions of blood pressure accompanied by slight increases (less than 5%) in heart rate. Nicorandil infused intravenously at 10 or 30 μg kg−1 min−1 significantly augmented the vasodepressor responses to VIP and CGRP but did not modify the responses to substance P and acetylcholine (0.1 μg kg−1). Intravenous treatment with glibenclamide (20 μg kg−1) significantly attenuated not only the vasodepression caused by VIP and CGRP, but also the enhancement of the effects of the agents by nicorandil.

These results indicate that nicorandil can enhance the action of VIP and CGRP, in rats, at least partly through ATP-sensitive K+-channel activation.
Effects of Sho-saiko-to on the Pharmacokinetics and Pharmacodynamics of Tolbutamide in Rats
Authors: Nishimura Nobuhiro , Naora Kohji , Hirano Hidenari , Iwamoto Kikuo
Published: April 2011

Although Sho-saiko-to (Xiao Chai Hu Tang), a major Chinese traditional medicine, is frequently prescribed with other synthetic or biotechnological drugs for the treatment of various chronic diseases, there is a dearth of information about interactions between sho-saiko-to and co-administered drugs. This paper reports the effects of Sho-saiko-to on the pharmacokinetics and glucose responses of a sulphonylurea hypoglycaemic agent, tolbutamide, after their oral administration in rats.

After oral administration of tolbutamide (50 mg kg−1) with or without Sho-saiko-to extract powder (300 mg kg−1) to male Sprague-Dawley rats cannulated in the jugular vein, plasma tolbutamide and glucose levels were periodically measured. Co-administration of Sho-saiko-to tended to elevate the plasma tolbutamide concentration in the absorption phase. A two-compartment lag-time model was found to describe the plasma tolbutamide concentration-time data. The maximum concentration of tolbutamide was significantly increased and time to reach the maximum concentration was reduced to about 70% by co-administration with Sho-saiko-to. There was no significant change in area under the curve or in the elimination half-life of tolbutamide. The extent of the lowering effect of tolbutamide on plasma glucose levels was increased up to 0.75 h and decreased after 5 h after co-administration of Sho-saiko-to.

In conclusion, these studies suggest that sho-saiko-to slightly hastens the gastrointestinal absorption of tolbutamide. Furthermore, it is considered that elevation of the gastrointestinal absorption rate by Sho-saiko-to might potentiate the hypoglycaemic effect of this sulphonylurea in the early period after oral administration.
Extensive Binding of the Bioflavonoid Quercetin to Human Plasma Proteins
Authors: Boulton David W , Walle U Kristina , Walle Thomas
Published: April 2011

Although the bioflavonoids, a large group of polyphenolic natural products, exert chemopreventive effects in cardiovascular disease and cancer, there is little information about the disposition of these dietary components in man. The objective of this study was to investigate the plasma-protein binding of the most abundant bioflavonoid, quercetin, using 14C-labelled quercetin.

An ultracentrifugation assay (170 000 g for 16 h at 20°C) was shown to sediment plasma proteins. Binding of quercetin to normal plasma was extensive (99.1 ± 0.5%, mean ± s.d., n = 5). The unbound fraction varied as much as 6-fold, 0.3–1.8%, between subjects. This high binding was independent of quercetin concentration over the range 1.5–15 μM (0.5–5 μg mL−1). Human serum albumin was the primary protein responsible for the binding of quercetin in plasma (99.4 ± 0.1%). Binding by α1-acid glycoprotein (39.2 ± 0.5%) and very-low-density lipoproteins (< 0.5% of total quercetin) did not make substantial contributions to overall plasma binding. The equilibrium association constant for the binding of quercetin to serum albumin was 267 ± 33 times 103 M−1 (n=15). Thermodynamic data for the binding of quercetin to serum albumin indicated spontaneous, endothermic association. Displacement studies suggested that in man the ‘IIA’ subdomain binding site of human serum albumin was the primary binding site for quercetin. Association of quercetin with erythrocytes was significantly (P < 0.001) reduced by plasma protein binding.

These data indicate poor cellular availability of quercetin because of its extensive binding to plasma proteins.
N- Acetyl-L-γ-glutamyl Derivatives of p-Nitroaniline,
Sulphamethoxazole and Sulphamethizole for Kidney-specific
Drug Delivery in Rats
Authors: Murakami Teruo , Kohno Kumiko , Yumoto Ryoko , Higashi Yutaka , Yata Noboru
Published: April 2011

Kidney-specific delivery of p-nitroaniline, sulphamethoxazole and sulphamethizole after either intravenous administration of the L-γ-glutamyl or N-acetyl-L-γ-glutamyl derivatives or the parent drugs has been examined in a rat model.

All L-γ-glutamyl derivatives were converted to the corresponding parent drugs within 60 min whereas the N-acetyl-L-γ-glutamyl derivatives were fairly stable in the systemic circulation after parenteral administration. Concentrations of p-nitroaniline and sulphamethoxazole 20 min after administration of the parent drugs were somewhat higher in the kidney than in the liver and lung. The concentration of sulphamethizole in the kidney was dramatically higher than those in the hepatic and pulmonary tissue. Kidney-specific delivery of the drugs of interest was evaluated by determining the tissue concentrations of the released parent drug and the total drug levels (i.e. drug levels after hydrolysis of all conjugate to the parent drug). For L-γ-glutamyl-p-nitroaniline released renal levels of p-nitroaniline and total p-nitroaniline concentrations were both higher than those obtained after p-nitroaniline dosing. Use of L-γ-glutamylsulphamethoxazole resulted in higher total sulphamethoxazole concentrations in the kidney, but did not lead to an increase in released (unconjugated) sulphamethoxazole levels. In contrast, no kidney-selective distribution was observed for L-γ-glutamylsulphamethizole. Markedly increased kidney distribution was observed for both N-acetyl-L-γ-glutamyl-p-nitroaniline and N-acetyl-L-γ-glutamylsulpha-methoxazole and the liver and lung concentrations were correspondingly reduced in comparison with parent drug dosing. Use of the N-acetyl-L-γ-glutamyl-p-nitroaniline conjugate increased the concentration of p-nitroaniline in the kidney to the same extent as did L-γ-glutamyl-p-nitroaniline.

In conclusion, N-acetyl-L-γ-glutamyl derivatization of certain compounds seems to be useful for kidney-specific ***drug delivery and preliminary data suggests that lipophilic drugs are better substrates than hydrophilic compounds. Results related to the selectivity of tissue distribution of the derivatives and species differences are discussed.
The Effect of a Drug-delivery System Consisting of Soybean Phosphatidyl Choline and Medium-chain Monoacylglycerol on the Intestinal Permeability of Hexarelin in the Rat
Authors: Fagerholm Urban , Sjöström Brita , Sroka-Markovic Janina , Wijk Annika , Svensson Marianne , Lennernäs Hans
Published: April 2011

The aim of this study was to investigate if the effective in-situ permeability (Peff) of a new growth hormone-releasing peptide, hexarelin, along rat intestine was enhanced by a lipid matrix drug-delivery system comprising a mixture of soybean phosphatidyl choline and medium-chain monoacylglycerol (PC-MG). The study was performed with and without a protease inhibitor, Pefabloc SC. To enable better understanding of the mechanism of action of this delivery system we also studied the uptake of a small hydrophilic molecule, atenolol.

PC-MG at a concentration of 15 mmol L−1 increased the jejunal Peff of hexarelin approximately 20-fold, both in the presence and absence of Pefabloc SC, whereas Peff was not increased in the ileum and colon. PC-MG had no effect on the jejunal, ileal and colonic Peff of atenolol. Complete recovery of the non-absorbable molecule PEG 4000 showed that functional intestinal viability was maintained in all experiments.

Although the results obtained in this study are promising, pharmacokinetic and toxicological studies are required to investigate if this delivery system is a suitable and safe candidate for improving the oral bioavailability of hexarelin.
Novel 5,8-Diazabenzo[c]phenanthrenes: Synthesis and Mutagenicity
Authors: Upton Mathew , Jaeda Moussa I , Upton Christopher
Published: April 2011

The polycyclic aromatic hydrocarbons have been recognized as carcinogens and mutagens since the early part of this century. More recently their aza and polyaza derivatives have been shown to have the same biological activity. A major source of these compounds is the combustion of fresh or metamorphosed plant materials; this contributes to the environmental burden of, and exposure to, these carcinogens. We report the synthesis and characterization of a series of novel 5,8-diazabenzo[c]phenanthrenes which are isosteric with the known epidermal carcinogen benzo[c]phenanthrene but have not yet been reported as components of soot or diesel particulate matter.

The synthesis of the compounds exploits a versatile, double Friedlander reaction between the appropriately substituted 2,2′-diaminobenzophenone and β-diketones, with yields of purified product ranging from 30–90%. The nucleophilic substitution of these diazabenzophenanthrenes with ethanolamine is also described. This strategy will enable further elaboration of these heterocyclic nuclei at a later date.

Mutagenicity testing of these agents was performed using spot tests and in Ames plate-incorporation assays using Escherichia coli WP2 and WP2uvrA as test organisms. The plate-incorporation assays were performed in the presence or absence of metabolic enzymes contained in the S9 liver fraction from Aroclor 1254-induced rats, to investigate whether bioactivation of the diazabenzophenanthrenes contributed to their toxicity. No differences between these two protocols were observed, with neither test showing reversion to prototrophic behaviour. Furthermore, the compounds were not toxic to the test organism.

These initial results suggest that these compounds are not mutagenic in the Ames tests employed.
Investigation into the Presence of Insulin-degrading Enzyme in Cultured Type I1 Alveolar Cells and the Effects of Enzyme Inhibitors on Pulmonary Bioavailability of Insulin in Rats
Authors: Hsu Matt Cheng-Pang , Bai Jane P F
Published: April 2011

The purpose of this study was to investigate the role of insulin-degrading enzyme (IDE, EC 3.4.22.11) in insulin degradation in alveolar epithelium. The primary culture of isolated rat type-II pneumocytes was used for the in-vitro characterization of IDE. Insulin was then administered intratracheally with various inhibitors to assess the improvement in its pulmonary bioavailability.

In cultured type-II pneumocytes, the cytosolic insulin-degrading activity contributed 81% of total insulin degradation, reached a maximum at pH 7-5 and had an apparent Michaelis-Menten constant (Km) of 135 nM. N-Ethylmaleimide, p-chloromercuribenzoic acid and 1,10-phenanthroline inhibited insulin-degrading activity almost completely in both crude homogenate and cytosol. An immunoprecipitation study showed that IDE contributed 74% of cytosolic insulin-degrading activity. Western blot analysis showing a single band of 110 kDa on reduced SDS (sodium dodecylsulphate) gels confirmed the presence of IDE in cultured type-II cells. When given intratracheally with insulin, inhibitors including N-ethylmaleimide, p-chloromercuribenzoic acid, and 1,10-phenanthroline significantly enhanced the absolute bioavailability of insulin and the compound’s hypoglycaemic effects.

These results suggest that IDE is present in alveolar epithelium and might be involved in limiting insulin absorption in the lung.
Effects of 17β-Oestradiol on Rat Isolated Coronary and Mesenteric Artery Tone: Involvement of Nitric Oxide
Authors: Otter Donna , Austin Clare
Published: April 2011

Pre- and post-menopausal women receiving oestrogen replacement therapy have a significantly reduced risk of cardiovascular disorders. It has been suggested that this protection might be partly a result of a direct relaxant effect of oestrogens on coronary arteries. This study examines and directly compares the effects of 17β-oestradiol on rat isolated coronary and mesenteric vessels. The influence of nitric oxide on these responses was also investigated.

17β-Oestradiol caused similar concentration-dependent relaxation of isolated coronary and mesenteric resistance arteries pre-contracted with either KCl (60 mM) or 9,11-dideoxy-11α,9α-epoxymethanoprostaglandin (U46619; 1 μM). The relaxation responses to 17β-oestradiol were significantly reduced, but not totally inhibited, in the presence of Nω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase; they were not altered by indomethacin, an inhibitor of prostaglandin synthesis. The responses to 17β-oestradiol in the presence of L-NAME were not dependent on the vessel studied or the precontracting agent used.

These results suggest that nitric oxide might contribute to the vasodilatory effects of 17β-oestradiol in rat isolated coronary and mesenteric resistance arteries.
5-Hvdroxvtrvotamine-induced Secretion bv Rat Jeiunum In-vitro Involves Several 5-Hydroxytryptamine Receptor Subtypes
Authors: Hardcastle J , Hardcastle P T
Published: April 2011

The receptors contributing to 5-hydroxytryptamine (5-HT)-induced anion secretion by rat jejunum have been investigated by testing the effects of selective agonists and antagonists in-vitro using both intact and stripped intestinal sheets.

In both intact and stripped jejunum 5-HT and 5-methoxytryptamine, an agonist that lacks affinity for 5-HT3 receptors, induced concentration-dependent increases in the short-circuit current (SCC), although 5-methoxytryptamine induced a smaller maximum response. In intact sheets 1-phenylbiguanide, a selective 5-HT3 agonist, induced a response that was similar in magnitude to that of 5-methoxytryptamine, but in stripped preparations it had little effect. Tetrodotoxin inhibited the response of intact jejunum to 5-HT (by 86%) and 5-methoxytryptamine (by 85%) and abolished the response to 1-phenylbiguanide. In stripped sheets inhibition of the 5-HT response by tetrodotoxin was reduced to 27%. Desensitization to 1-phenylbiguanide reduced the response to 5-HT in intact but not stripped sheets whereas, in contrast, desensitization to 5-methoxytryptamine inhibited the 5-HT response in stripped sheets but was without effect in intact sheets. Mianserin, a 5-HT1, 5-HT2 and 5-HT3 antagonist, and renzapride, a 5-HT1 and 5-HT3 antagonist, both reduced the maximum response to 5-HT, but 5-HTP-DP, a 5-HT1 antagonist, was without effect. The 5-HT3 antagonist granisetron reduced the response to 5-HT in intact, but not in stripped sheets. Tropisetron, a 5-HT3 and 5-HT4 antagonist, inhibited the response to 5-methoxytryptamine in both preparations, but did not alter the response to 5-HT.

It is concluded that 5-HT-induced jejunal secretion involves more than one 5-HT receptor subtype, with both neural and non-neural mechanisms contributing to the response.
Flavonoids Reduce Morphine Withdrawal In-vitro
Authors: Capasso A , Piacente S , Pizza C , Sorrentino L
Published: April 2011

The effects of quercetin, flavone, catechin and chrysin on the naloxone-precipitated withdrawal contracture of the acute morphine-dependent guinea-pig ileum have been investigated in-vitro.

After 4 min in-vitro exposure to morphine a strong contracture of guinea-pig isolated ileum was observed after the addition of naloxone. All the flavonoids, injected 10 min before morphine at concentrations between 10−7 and 10−5 M, were capable of blocking naloxone-induced contracture after exposure to morphine in a concentration-dependent fashion. IC50 values calculated for quercetin, flavone, catechin and chrysin were 2.7 times 10−6, 7.3 times 10−7, 8.5 times 10−7 and 5.3 times 10−6 M, respectively.

These results suggest that flavonoids might play an important role in the control of morphine withdrawal.
Study of the Interaction of Dithranol with Heptakis( 2,3,6-tri-O-methyl)-β-cyclodextrin in Solution and in the Solid State
Authors: Cafaggi Sergio , Vallarino Marisa , Caviglioli Gabriele , Parodi Brunella , Bignardi Gaetano
Published: April 2011

The interaction between dithranol and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TMBCyD) has been investigated in aqueous solution containing isoascorbic acid (0·2% w/v) as antioxidant and in the solid state. The interaction in the solid state was studied by differential scanning calorimetry (DSC), infrared spectroscopy (IR), X-ray powder diffractometry (XPD) and a dissolution-rate method.

The extent of complexation between the two substances was poor, as indicated by the low value of the slope of the linear part of the solubility curve. A phase diagram was constructed by measuring the thermal behaviour of various re-solidified physical mixtures of dithranol and of TMBCyD previously subjected to heating until melting of the TMBCyD. The loss of dithranol, owing to sublimation and degradation caused by the thermal treatment used, was less than 10%. In keeping with XPD and IR data, the phase diagram indicated that a complex was formed containing 13·7% dithranol (molar ratio 1:1) which had a congruent melting point at 164°C. The drug dissolution rate from the 1:1 complex was measurable, unlike that of the corresponding physical mixture, and was significantly increased when the complex was dispersed in the glassy matrix of TMBCyD, as it was in re-solidified mixtures containing 2–7% dithranol.

The results show that the solubility of dithranol is increased significantly as a consequence of its interaction with TMBCyD, despite the low extent of complexation between the two substances.
Kinetic Characterization and Identification of the Enzymes Responsible for the Hepatic Biotransformation of Adinazolam and N-Desmethyladinazolam in Man
Authors: Venkatakrishnan Karthik , Von Moltke Lisa L , Duan Su Xiang , Fleishaker Joseph C , Shader Richard I , Greenblatt David J
Published: April 2011

The kinetics of the N-demethylation of adinazolam to N-desmethyladinazolam (NDMAD), and of NDMAD to didesmethyladinazolam (DDMAD), were studied with human liver microsomes using substrate concentrations in the range 10–1000 μm. The specific cytochrome P450 (CYP) isoforms mediating the biotransformations were identified using microsomes containing specific recombinant CYP isozymes expressed in human lympho-blastoid cells, and by the use of CYP isoform-selective chemical inhibitors.

Adinazolam was demethylated by human liver microsomes to NDMAD, and NDMAD was demethylated to DDMAD; the substrate concentrations, Km, at which the reaction velocities were 50% of the maximum were 92 and 259 μm, respectively. Another metabolite of yet undetermined identity (U) was also formed from NDMAD (Km 498 μm). Adinazolam was demethylated by cDNA-expressed CYP 2C19 (Km 39 μm) and CYP 3A4 (Km 83 μm); no detectable activity was observed for CYPs 1A2, 2C9, 2D6 and 2E1. Ketoconazole, a relatively specific CYP 3A4 inhibitor, inhibited the reaction; the concentration resulting in 50% of maximum inhibition, IC50, was 0·15 μm and the inhibition constant, Ki, was < 0·04 μm in five of six livers tested. Troleandomycin, a specific inhibitor of CYP 3A4, inhibited adinazolam N-demethylation with an IC50 of 1·96 μm. The CYP 2C19-inhibitor omeprazole resulted in only partial inhibition (IC50 21 μm) and sulphaphenazole, α-naphthoflavone, quinidine and diethyldithiocarbamate did not inhibit the reaction. NDMAD was demethylated by cDNA-expressed CYP 3A4 (Km 220 μm, Hill number A 1·21), CYP 2C19 (Km 187 μm, Hill number A 1·29) and CYP 2C9 (Km 1068 μm). Formation of U was catalysed by CYP 3A4 alone. Ketoconazole strongly inhibited NDMAD demethylation (IC50 0·14 μm) and formation of U (IC50 < 0·1 μm) whereas omeprazole and sulphaphenazole had no effect on reaction rates.

These results show that CYP 3A4 is the primary hepatic CYP isoform mediating the N-demethylation of adinazolam and NDMAD. Co-administration of adinazolam with CYP 3A4 inhibitors such as ketoconazole or erythromycin might lead to reduced efficacy, since adinazolam by itself has relatively weak benzodiazepine agonist activity, with much of the pharmacological activity of adinazolam being attributable to its active metabolite NDMAD.
Distribution of Bismuth in the Rat after Oral Dosing with Ranitidine Bismuth Citrate and Bismuth Subcitrate
Authors: Canena J , Reis J , Pinto A S , Santos A M , Leitão J , Pinheiro T , Quina M G
Published: April 2011

Bismuth preparations are used world-wide for the management of peptic ulcer disease, for eradication of Helicobacter pylori, and in the prevention and treatment of diarrhoea. However neurological toxicity of bismuth has always been a major concern and evidence has been found of the absorption of bismuth. Recent studies have suggested that the absorption of bismuth increases when bismuth salts are used with ranitidine hydrochloride. The absorption and deposition of bismuth as a result of the use of the new drug ranitidine bismuth citrate have not been yet clarified.

After 15 days of twice daily oral gavage with bismuth subcitrate, 13·7 mg kg−1 day−1 to eight rats, deposition of bismuth was found in all the tissues studied, especially the kidney (30·81 ± 8·59 μg g−1 dry weight). A similar pattern of distribution and tissue concentrations was found when bismuth subcitrate was given with ranitidine hydrochloride 8·6 mg kg−1 day−1 to another eight rats, although this combination resulted in lower brain levels (3·12 + 1·31 μg g−1 dry weight) than after administration of bismuth subcitrate alone (4·77 ± 0·97 μg g−1 dry weight). When six rats were given ranitidine bismuth citrate by gavage at 22·8 mg kg−1 day−1 for 15 days, kidney levels were lower (4·24 ± 1·75 μg g−1 dry weight) and brain levels were below detection limits; the bismuth concentrations in the faeces from this group were also significantly lower (1603 ± 104·0 μg g−1 dry weight) than for the two other groups. After dosing with bismuth alone or in association with ranitidine hydrochloride, bismuth was detected in several organs and deposition was not influenced by gastric pH. Blood levels correlate poorly with organ deposition and brain deposition was not always associated with encephalopathy. After administration of ranitidine bismuth citrate, significantly lower concentrations of bismuth were found in the kidney and bismuth was not detectable in the brain, suggesting lower bismuth absorption. This was confirmed by higher levels in the faeces after dosing with ranitidine bismuth citrate. Thirty days after dosing with ranitidine bismuth citrate or bismuth subcitrate, bismuth could not be detected in any of the organs examined but could be found in the urine.

In conclusion, bismuth was deposited in the kidney, brain, lung and liver of rats after oral dosing with bismuth subcitrate. After oral dosing with an equivalent amount of bismuth in the form of ranitidine bismuth citrate, significantly lower concentrations of bismuth were deposited in the kidney; in the brain bismuth was not detectable.
Influence of New Fenpropimorph Fungicides on the Growth and Sterol Composition in Saccharomyces cerevisiae: Relationship Between Structure and Activity
Authors: Šajbidor Jan , Lamačka Martin , Baláž Štefan , Huong Lai Mai , Ciesarová Zuzana
Published: April 2011

The toxicity of fenpropimorph and seven newly synthesized analogues against Saccharomyces cerevisiae has been determined in liquid media.

The inhibitory effect of the most efficient derivative is 120 times more than that of standard fenpropimorph. The non-linear relationship between hydrophobicity and toxicity indicates that the binding of the compounds to the receptors does not differ and so the differences in toxicity reflect changes in the rate of metabolism. The presence of inhibitors in the fermentation medium resulted in a reduction in harvested biomass and lipid yield, and changes in sterol composition - the amount of ergosterol decreased whereas the amounts of lanosterol, dihydroergosterol and squalene increased.

The toxicity of the compounds was most influenced by their lipophilicity. Use of this information could lead to development of more potent ergosterol inhibitors.
In-vitro Negative Chronotropic and Inotropic Effects of a Novel Dihydropyridine Derivative, CD-832, in the Guinea-pig: - - Comparison with Calcium-channel Antagonists
Authors: Noguchi Kazuo , Takahashi Kenzo , Higuchi Shohei
Published: April 2011

The effects of CD-832 (4R-(-)-2-(nicotinoylamino)ethyl-3-nitroxypropyl-1,4-dihydro-2,6-dimethyl-4,3-nitrophenyl, 3,5-pyridine dicarboxylate), a novel dihydropyridine derivative, on guinea-pig isolated myocardial preparations have been compared with those of Ca2+-channel antagonists.

All ten compounds induced concentration-dependent negative chronotropic effects on preparations of isolated right atria and negative inotropic effects on isolated right ventricular papillary muscles. The order of potency for the negative chronotropic effect was CD-832 > nicardipine = gallopamil > clentiazem > nifedipine = efonidipine > amlodipine = semotiadil > verapamil > diltiazem; that for the negative inotropic effect was nicardipine = gallopamil > nifedipine > verapamil > CD-832 > diltiazem > clentiazem > efonidipine = semotiadil > amlodipine. The ratio of the EC50 (the concentration of Ca2+ antagonist having 50% of the maximum effect) for the negative inotropic effect divided by the EC50 for the negative chronotropic effect, considered to be an index of selectivity for negative chronotropic effect, was higher for CD-832, amlodipine, efonidipine and semotiadil than for the other Ca2+ antagonists. The ratio for CD-832, nifedipine, nicardipine, efonidipine, amlodipine, verapamil, gallopamil, diltiazem, clentiazem and semotiadil was 11·4, 0·29, 0·87, 35·4, 37·1, 0·65, 0·87, 0·92, 7·11 and 30·0, respectively.

These findings indicate that CD-832 and the newly developed Ca2+ antagonists including amlodipine, efonidipine, semotiadil and clentiazem were selective for a negative chronotropic effect rather than for a negative inotropic effect. This ‘chrono-selective’ effect of these drugs might be of benefit in the treatment of cardiovascular disorders.
Why Do We Need New Treatments for Rheumatoid Arthritis?
Authors: Chikanza I C , Jawed S , Naughton D , Blake D R
Published: April 2011

Rheumatoid arthritis is a chronic systemic autoimmune inflammatory disease characterized by progressive joint damage. The classical treatments of the disease such as myocrisin and sulphasalazine, are not always effective at controlling the disease. This has necessitated the development of novel agents for treating rheumatoid arthritis. Most of these drugs are biological in nature and are targeted at specific sites of the inflammatory cascade of reactions. A number of clinical trials have been conducted.

The clinical effects that have been observed are transient, necessitating repeated treatments and the risk of vaccination effects. Many of these agents have to be administered parenterally, production costs are very high. Consequently, chemical entities which can be taken orally need to be developed. Since the immune system is very complex with pleiotropic cytokines and redundancy in some of the regulatory networks, it may therefore be necessary to use multiple agents targeted at different specific sites of the inflammatory cascade or that different agents could be given at different stages of the disease, to induce disease remission and maintain the response to therapy. Cytokines such as tumour necrosis factor (TNF) and interleukin 1 (IL-1) play important physiological roles in the host’s defence systems against infections and malignancy. The chronic inhibition of these cytokines by targeted therapies may therefore lead to the development of side effects. Thus, carefully controlled long-term studies will be required to assess the safety of selective targeting of processes involved in inflammation.

A more recent novel approach is to target hypoxic tissues with bioreductive agents. Thus, some of the established rheumatoid arthritis treatments could be linked to bioreductive agents and released in hypoxic tissues where inflammation is occurring. This review summarizes the important developments in the therapy of rheumatoid arthritis. There is no doubt that despite these developments we need to develop new and advanced treatment modalities for rheumatoid arthritis.
In-vivo Monitoring of Dosage Forms
Authors: Wilson Clive G
Published: April 2011

The use of imaging techniques including gamma scintigraphy to follow the behaviour of drug formulations has revolutionized our knowledge of absorption and distribution in drug delivery. The development of gamma camera techniques as physiological tools to explore organ function became routine by the mid-seventies. Several research groups started to explore the applications of technique in drug delivery. Within 5 years, the utility of the technique became obvious and scintigraphy is now widely accepted as an important investigation tool in formulation research.

Gamma scintigraphy is especially useful in exploring sources of inter-subject variation, especially in examining food effects in pharmacokinetic estimations and establishing windows of absorption for oral delivery. As a tool to examine drug delivery to the lung and to the eye, scintigraphy is the method of choice.

Magnetic Resonance Imaging (MRI) became more generally employed in medicine two decades after the gamma camera. The superior soft-tissue contrast and resolution compared to computed X-ray tomography rapidly established MRI in clinical investigation. Recent applications in oral drug research has allowed the pharmaceutical scientist to explore new facets of delivery and ultimately combine MRI and scintigraphy in human clinical trials.
The Design of Selectively-activated Anti-cancer Prodrugs for use in Antibody-directed and Gene-directed Enzyme-Prodrug Therapies
Authors: Denny William A , Wilson William R
Published: April 2011

Systemic anti-proliferative agents (cytotoxins) have been the most successful single design concept for anti-cancer drugs. However, they have inherent limitations (they target dividing cells rather than cancer cells) which limit their clinical efficacy, especially toward the more slowly-growing solid tumours. New concepts are required to improve the selectivity of their killing of tumour cells.

One possibility is the use of prodrugs which can be activated selectively in tumour tissue. Several potential mechanisms for this are being explored, including tumour hypoxia, low extracellular pH, therapeutic radiation and tumour-specific endogenous or exogenous enzymes. In the last approach the exogenous enzyme can be delivered by attachment to monoclonal antibodies (ADEPT) or as DNA constructs containing the corresponding gene (GDEPT). A limitation of both approaches is that only a small proportion of the tumour cells become activation-competent, but this can be substantially overcome by the design of appropriate prodrugs capable of killing activation-incompetent cells via a bystander effect.

We have proposed a modular approach to prodrug design in which a trigger unit determines tumour selectivity and an effector unit achieves the desired level of killing of cells when the trigger is activated. For ADEPT and GDEPT prodrugs the primary requirement of the trigger is efficient and selective activation by the appropriate enzyme; the released effector must be a potent, diffusible cytotoxin which fully exploits the small proportion of cells capable of activating the prodrug. A wide variety of chemistries has been used, but many of the existing effectors do not have all of these properties. We report work on two types of cytotoxin derived from very potent anti-tumour antibiotics (enediynes and amino-seco-cyclopropylindolines) as effectors in prodrugs for ADEPT and GDEPT applications.
Genetic Toxicology
Authors: Kramer P J
Published: April 2011

Systems for testing genetic toxicology are components of carcinogenic and genetic risk assessment. Present routine genotoxicity-testing is based on at least 20 years of development during which many different test systems have been introduced and used. Today, it is clear that no single test is capable of detecting all genotoxic agents. Therefore, the usual approach is to perform a standard battery of in-vitro and in-vivo tests for genotoxicity. Work-groups of the European Union (EU), the Organization for Economic Co-operation and Development (OECD), and, very recently, the work-group of the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) have defined such standard battery tests. These and some currently used supplementary or confirmatory tests are briefly discussed here.

Additional test systems for the assessment of genotoxic and carcinogenic hazard and risk are seriously needed. These tests must be more relevant to man than are current assays and less demanding in respect of cost, time and number of animals. Another aspect for reassessment derives from the actual situation in the pharmaceutical industry. Companies have to prepare for the world economy of the 21st century. Therefore, pharmaceutical research is speeding up tremendously by use of tools such as genomics, combinatorial chemistry, high throughput screening and proteomics. Toxicology and genotoxicology need to re-evaluate their changing environment and must find ways to respond to these needs.

In conclusion, genetic toxicology needs to answer questions coming from two major directions: hazard and risk identification and high throughput testing.
A Study on the In-vitro Percutaneous Absorption of Propranolol from Disperse Systems
Authors: Ktistis G , Niopas I
Published: April 2011

Transdermal administration of propranolol can be used to avoid hepatic first-pass metabolism of the drug. The effect of polysorbate 80 concentration on the permeation of propranolol incorporated into micelles of polysorbate 80 in water, oil-in-water microemulsions of isopropyl myristate-polysorbate 80-sorbitol-water and oil-in-water emulsions of isopropyl myristate-polysorbate 80-sorbitan monooleate-water has been investigated by use of an artificial double-layer membrane, composed of a barrier foil and a lipid barrier, in Franz-type diffusion cells. Reversed-phase high-performance liquid chromatography, with celiprolol as internal standard, was used to determine the concentration of propranolol in the receptor compartment and a logarithmic equation was used to estimate the apparent permeability coefficient of propranolol from disperse systems.

For each disperse system the apparent permeability coefficient of propranolol decreased with increasing polysorbate 80 concentration. Moreover, for a given polysorbate 80 concentration the apparent permeability coefficient of propranolol increased when the disperse system was changed from emulsion to microemulsion and then to solubilized system, because of the increasing interfacial area of total disperse phase.

The results show that transdermal permeation of propranolol is greater when it is diffused from solubilized systems rather than from microemulsions or emulsions.
Hepatic Clearance of ONO-5046, a Novel Neutrophil Elastase Inhibitor, in Rats and in the Rat Perfused Liver
Authors: Murakami Teruo , Sato Masahiko , Higashikawa Fumiko , Okochi Atsuko , Higashi Yutaka , Yata Noboru , Takano Mikihisa
Published: April 2011

The hepatic clearance of ONO-5046 (N-[2-[4-(2,2-dimethylpropionyloxy)phenylsulphonyl-amino]benzoyl]aminoacetic acid), a low-molecular-weight neutrophil elastase inhibitor, has been investigated in rats and in the rat perfused liver.

This ester was easily hydrolysed to its inactive metabolite EI-601 (N-[2-[(4-hydroxy-phenyl)sulphonylamino]benzoyl]aminoacetic acid) in liver homogenate and in erythrocytes suspension in-vitro. On the other hand, it was stable in biological media such as plasma and whole blood, which contain plasma proteins. Scatchard plot analysis of ONO-5046 binding to bovine serum albumin (BSA) in-vitro indicated that the association constant (K) and number of binding sites (n) were 6.91 times 104 (M−1) and 4.33, respectively. Thus, ONO-5046 (100 μM) would bind to plasma proteins to an extent >99% at physiological plasma-protein concentrations. The total plasma clearance of ONO-5046 in rats was constant (approximately 9 mL min−1 kg−1) under different steady-state plasma concentrations (5–50 μM) a value equivalent to the hepatic clearance. In the rat perfused liver, the hepatic extraction ratio of ONO-5046 was significantly reduced by adding BSA to the dosing solution. Thus, the relatively low hepatic clearance of ONO-5046, which has an ester linkage in its structure and is naturally susceptible to enzymatic hydrolysis, was found to be because of the extremely high protein-binding of the compound.
Effect of Thioridazine or Chlorpromazine on Increased Hepatic NAD+ Level in Rats Fed Clofibrate, a Hypolipidaemic Drug
Authors: Shin Mariko , Asada Sumiyo , Mizumori Nanae , Sano Keiji , Umezawa Chisae
Published: April 2011

The effect of the phenothiazines, thioridazine and chlorpromazine, on the increased hepatic NAD+ level of rats fed clofibrate, a hypolipidaemic drug, has been investigated.

Short-term (6 days) addition of phenothiazines to the diet negatively affected diet intake and body-weight gain, but increased liver weight and hepatic NAD+ levels, which was synergistic to clofibrate. The phenothiazines were shown to inhibit hepatic peroxisomal fatty acid oxidation in-vivo, as determined by the increased residual catalase activity. In hepatocytes prepared from clofibrate-fed rats, phenothiazines inhibited not only peroxisomal but also mitochondrial fatty acid oxidation to the same extent. In the hepatocytes, NAD+ was maintained at the high level until the phenothiazine concentration was increased to 0–2 mM.

The result suggests that the increase of hepatic NAD+ in rats fed Clofibrate is not related to peroxisomal fatty acid oxidation.