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pH-dependent and carrier-mediated transport of salicylic acid across Caco-2 cells.

The transport of monocarboxylic acid drugs such as salicylic acid was examined in the human colon adenocarcinoma cell line, Caco-2 cells that possess intestinal epithelia-like properties. [14C]Salicylic acid transport was pH-dependent and appeared to follow the pH-partition hypothesis. However, 10 mM unlabelled salicylic acid significantly reduced the permeability coefficient of [14C]salicylic acid. Kinetic analysis of the concentration dependence of the permeation rate of salicylic acid across Caco-2 cells showed both saturable (Kt = 5.28 +/- 0.72 mM Jmax = 36.6 +/- 3.54 nmol min-1 (mg protein)-1) and nonsaturable (kd = 0.37 +/- 0.08 microL min-1 (mg protein)-1) processes. The permeation rate of [14C]salicylic acid was competitively inhibited by both acetic acid and benzoic acid, which were demonstrated in our previous studies to be transported in the carrier-mediated-transport mechanism which is responsible for monocarboxylic acids. Furthermore, certain monocarboxylic acids significantly inhibited [14C]salicylic acid transport, whereas salicylamide and dicarboxylic acids such as succinic acid did not. From these results, it was concluded that the transcellular transport of [14C]salicylic acid across Caco-2 cells is by the pH-dependent and carrier-mediated transport mechanism specific for monocarboxylic acids.

Acetates↗

Enzymes associated with reductive activation and action of nitazoxanide, nitrofurans, and metronidazole in Helicobacter pylori.

Nitazoxanide (NTZ) is a redox-active nitrothiazolyl-salicylamide prodrug that kills Helicobacter pylori and also many anaerobic bacterial, protozoan, and helminthic species. Here we describe development and use of a spectrophotometric assay, based on nitroreduction of NTZ at 412 nm, to identify H. pylori enzymes responsible for its activation and mode of action. Three enzymes that reduce NTZ were identified: two related NADPH nitroreductases, which also mediate susceptibility to metronidazole (MTZ) (RdxA and FrxA), and pyruvate oxidoreductase (POR). Recombinant His-tagged RdxA, FrxA, and POR, overexpressed in nitroreductase-deficient Escherichia coli, each rapidly reduced NTZ, whereas only FrxA and to a lesser extent POR reduced nitrofuran substrates (furazolidone, nitrofurantoin, and nitrofurazone). POR exhibited no MTZ reductase activity either in extracts of H. pylori or following overexpression in E. coli; RdxA exhibited no nitrofuran reductase activity, and FrxA exhibited no MTZ reductase activity. Analysis of mutation to rifampin resistance (Rif(r)) indicated that NTZ was not mutagenic and that nitrofurans were only weakly mutagenic. Alkaline gel DNA electrophoresis indicated that none of these prodrugs caused DNA breakage. In contrast, MTZ caused DNA damage and was strongly mutagenic. We conclude that POR, an essential enzyme, is responsible for most or all of the bactericidal effects of NTZ against H. pylori. While loss-of-function mutations in rdxA and frxA produce a Mtz(r) phenotype, they do not contribute much to the innate susceptibility of H. pylori to NTZ or nitrofurans.

Biotransformation↗

Inhibitory effects of lipophilic acids and related compounds on bacteria and mammalian cells.

The inhibitory effect of lipophilic acids, antimicrobial food additives, and analgesics-antipyretics was examined at concentrations from 0.1 to 100 mM in bacteria (Bacillus subtilis and Escherichia coli) and mammalian cells (HeLa, human fibroblasts, and mouse neuroblastoma cells). Most compounds inhibit the growth of HeLa cells about as efficiently as that of B. subtilis. However, butyrate and propionate, as well as acetaminophen, antipyrene, phenacetin, and salicylamide, inhibit HeLa at millimolar concentrations whereas, at least 10 times higher concentrations are needed to inhibit B. subtilis. The concentrations needed to inhibit growth by 50% decrease with increasing octanol-water partition coefficients of the compound. Growth of E. coli is inhibited similar to that of B. subtilis by all compounds except butylbenzoate, decanoate, and linoleate which cannot penetrate the lipopolysaccharide layer. All growth inhibitors inhibit amino acid uptake into bacteria and their vesicles, and oxygen consumption in bacteria. In HeLa cells or human fibroblasts, neither amino acid uptake nor adenine 5'-triphosphate synthesis are inhibited by fatty acids at concentrations that completely inhibit growth. Short chain fatty acids (propionate, butyrate, and pentanoate) induce in HeLa the formation of cell processes. In neuroblastoma cells, grown in the presence of 10% fetal calf serum, butyrate also induces such processes which slowly continue to grow in length for at least 7 days; these processes differ in speed of formation, width, and cycloheximide susceptibility from the thin processes produced by serum deprivation alone.

Bacteria↗

Relationship of inhibition of prostaglandin biosynthesis by analgesics to asthma attacks in aspirin-sensitive patients.

Eleven patients with asthma and aspirin hypersensitivity have been challenged with eight non-steroidal anti-inflammatory drugs. Each drug was given by mouth in at least three different doses and the patients' symptoms and peak expiratory flow (PEF) rates were observed over a three-hour period. Indomethacin 5 mg caused bronchoconstriction in all patients. Therapeutic doses of mefenamic or flufenamic acid caused bronchoconstriction in most patients. Phenylbutazone 200-400 mg induced a moderate fall in PEF. There were no reactions to therapeutic doses of salicylamide, paracetamol, benzydamine, and chloroquine. Microsomal prostaglandin synthetase, activity was inhibited by aspirin, indomethacin, mefenamic acid, flufenamic acid, and phenylbutazone. The other four drugs had no inhibitory effect. We suggest that precipitation of attacks in asthmatic patients hypersensitive to certain anti-inflammatory drugs is related to drug's ability to inhibit prostaglandin biosynthesis.

Adult↗

Effect of salicylates on histamine and L-histidine metabolism. Inhibition of imidazoleacetate phosphoribosyl transferase.

In man and other animals, urinary excretion of the histidine and histamine metabolite, imidazoleacetate, is increased and that of its conjugated metabolite, ribosylimidazoleacetate, decreased by salicylates. Imidazoleacetate has been reported to produce analgesia and narcosis. Its accumulation as a result of transferase inhibition could play a part in the therapeutic effects of salicylates. To determine the locus of salicylate action, we have investigated the effect of anti-inflammatory drugs on imidazoleacetate phosphoribosyl transferase, the enzyme that catalyzes the ATP-dependent conjugation of imidazoleacetate with phosphoribosylpyrophosphate. As little as 0.2 mM aspirin produced 50% inhibition of the rat liver transferase. In vivo, a 30% decrease in the urinary excretion of ribosylimidazoleacetate has been observed with plasma salicylate concentrations of 0.4 mM. The enzyme was also inhibited by sodium salicylate but not by salicylamide, sodium gentisate, aminopyrine, phenacetin, phenylbutazone, or indomethacin. The last four drugs have been shown previously not to alter the excretion of ribosylimidazoleacetate when administered in vivo. Since both the drug specificity and inhibitory concentrations are similar in vivo and in vitro, it seems probable that the effect of salicylates on imidazoleacetate conjugation results from inhibition of imidazoleacetate phosphoribosyl transferase.

Anti-Inflammatory Agents↗

Clinical consequences of nonnarcotic analgesic use.

The accuracy of the economic analysis of the selected adverse events evaluated by McGoldrick and Bailie is questionable. The quantitative perspective on the economics of the adverse events associated with nonnarcotic analgesic use proposed by these authors is limited by the fact that they have combined data on over 30 different NSAIDs into a single value for comparison with two single-entity agents: acetaminophen and aspirin. The relative prevalence of major organ system toxicities varies markedly among the NSAIDs, and this variance invalidates the use of a class conclusion approach. Their conservative incidence estimates, the lack of data in some areas (i.e., hepatic injury), and the exclusion of combination analgesics further limit the utility of their conclusions. However, it is difficult to argue authoritatively that the relative costs of toxicities associated with the three analgesic classes they reviewed are not representative. The ultimate question is, "What is the optimal analgesic for a given patient?" This question can be addressed only if one considers the underlying cause of pain, its chronicity/acuity, the patient's concurrent disease states, if any, and the potential for drug interactions with the patient's concomitant medications. McGoldrick and Bailie concluded on an economic basis that acetaminophen is the analgesic of choice for most patients, including those with impaired renal function. This recommendation is in agreement with those of the Analgesics and the Kidney Ad Hoc Committee of the National Kidney Foundation. It also would seem prudent to use acetaminophen as the first-line agent for those patients in whom aspirin and NSAID use should be avoided or used only with caution along with frequent monitoring of renal function, blood pressure, electrolytes, and/or coagulation status. Thus, there is little to no controversy in their recommendation to initiate treatment with acetaminophen. The authors, however, also suggested that switching patients from an NSAID to acetaminophen would result in significantly decreased costs and morbidity. These authors, however, did not address one key issue that impacts their economic analysis: the relative efficacy of acetaminophen and NSAIDs. If efficacy is similar, then the risk/benefit ratio and economic consequences would favor the use of acetaminophen. However, if many patients are receiving NSAIDs because they did not obtain pain relief with the use of acetaminophen, there would be neither rationale or likely benefit with a change in therapy to acetaminophen. Finally, McGoldrick and Bailie did not evaluate an issue that has perhaps the most far-reaching consequence. Many OTC analgesics are currently marketed as combinations of aspirin, acetaminophen, salicylamide, or caffeine (Table 2). Although the intent of these combinations was [Table: see text] to enhance efficacy while minimizing adverse events, it is now apparent that at least concerning adverse events, the goal was not achieved. Therefore, in light of the markedly higher risk for renal injury with combination analgesics, these agents should be withdrawn from the marketplace. While some might argue that patient education is the key and that addition of an explicit warning on the label of OTC combination products should be an adequate intervention, this agreement is not supported by the Belgium experience. The removal of combination analgesics from the OTC marketplace could be accomplished by governmental action, such as the ban on phenacetin over 10 years ago. Alternatively, pharmacists could no longer sell these products and counsel patients on the rational use of OTC analgesics. The choice among single-entity agents could then be individualized on the basis of patient's current medical status and the adverse event profile of the available agents.

Acetaminophen↗

A study of the 3,5,3'-triiodothyronine sulfation activity in the adult and the fetal rat.

We have employed a new in vitro assay for study of the T3 sulfation activity in rat tissues. The assay measures by RIA the generation of T3 sulfate (T3S) during incubation of T3 with cytosol of rat tissues as the source of phenol sulfotransferase(s) and 3-phosphoadenosine-5'-phosphosulfate as the sulfate donor. The conversion of T3 to T3S proceeded rapidly for 30 min at 37 C, and the optimal pH of the reaction was 8.0. Heating the cytosol at 44 C for 15 min decreased T3S production to 63% of its value at 37 C. T3 sulfation activity was plentiful in rat liver, brain, and kidney, but little activity was demonstrable in other tissues. The Km and maximum velocity of the hepatic conversion of T3 to T3S were 114 microM and 159 pmol/mg protein.h, respectively. There was a marked inhibition of the conversion of T3 to T3S with salicylamide, 3'-monoiodothyronine, thyronine, and rT3; the IC50 of these inhibitors approximated 15, less than 0.1, 9.5, and 43 microM, respectively. On day 17 of gestation, the T3 to T3S conversion activity was more abundant in fetal skin than in other fetal tissues. However, the activity decreased in fetal skin while it increased in fetal liver, kidney, and brain nearer to term on day 20. Placenta demonstrated lower T3 to T3S conversion activity than several fetal or maternal tissues. There was no effect of hypothyroidism or hyperthyroidism on T3 sulfation activity. We conclude that T3 sulfation activity in the rat is 1) most abundant in liver, kidney, and brain tissues of the adult; 2) inhibited more avidly by 3'-monoiodothyronine than other thyronines; 3) very abundant in fetal skin early in gestation; and 4) little affected by the thyroidal status of the animal.

Animals↗

Effect of taurine on drug absorption from the rat gastrointestinal tract.

Effect of taurine on drug absorption from the rat gastrointestinal tract was investigated by using in situ loop method for the stomach and in situ recirculation method for the small or large intestine. Aspirin absorption from the stomach or the small intestine was enhanced by the presence of taurine, but not from the large intestine. The absorption enhancement effect of taurine was not only site-specific, but also substrate-specific. Taurine increased the absorption of aminopyrine from the small intestine, but not from the stomach. On the other hand, the absorption of salicylamide, o-methoxybenzoic acid and o-ethoxybenzoic acid was enhanced in the stomach, although they were not influenced in the small intestine. Furthermore, among the taurine analogues investigated only homotaurine showed the taurine-like action in the small intestine. Glycine also increased the gastric absorption of aspirin. These effects were observed neither by the pretreatment of the intestine with taurine, nor by i.v. administered taurine. Taurine at the site of drug absorption, even at a low concentration, seems to influence the drug absorption due to its effect on the permeability characteristics of the mucosal membrane.

Animals↗

Preparation of a photoaffinity probe for the Man6P/IGF-II receptor.

A photoaffinity probe, 2-(4-phosphopentamanniminophenyl)ethyl-(4-azido) salicylamide, was prepared for photolabelling of the mannose 6-phosphate/insulin-like growth factor II receptor. The probe was synthesized from phosphopentamannan and 2-(4-aminophenyl)ethylamine followed by coupling with photosensitive 4-azidosalicylic acid. The 125I-labelled probe was reacted with receptor purified from rat liver under irradiation with ultraviolet light. Fluorography of the reaction product on a polyacrylamide gel effectively detected the receptor coupled to the photoprobe as a molecular mass of 250 kDa. Specific binding of the probe or of radiolabelled insulin-like growth factor II was not inhibited by the growth factor or by mannose 6-phosphate, confirming different binding sites to the receptor between the ligands.

Affinity Labels↗

Interference with fluorimetric assay of catecholamine by labetalol.

Influence of labetalol and 5-(1-hydroxy-2-aminoethyl)salicylamide (SA), a part of the chemical structure of labetalol, on the fluorimetric assay of catecholamine (CA) was studied. Both labetalol and SA have a weak but significant fluorescence which is indistinguishable from that of CA with peaks of excitation/emission wavelengths at 410/490. It is thus concluded that an apparent increase in urinary CA observed in patients receiving labetalol is caused by the contamination of labetalol and/or its metabolite, and that the evaluation of urinary CA in hypertensive patients must be done prior to the use of labetalol to avoid any confusion in diagnosis of pheochromocytoma.

Drug Interactions↗

Pharmacology of combined alpha-beta-blockade. I.

Several compounds of the chemical class arylethanolamines have been shown to possess combined alpha- or vasodilator and beta-adrenoceptor blocking properties. The first drug was labetalol (AH5158)[5-(1-hydroxy-2)1-methyl-3-phenylpropyl(amino)-ethyl (salicylamide)]. Others include medroxalol, bucindolol and YM-09538, which differ from labetalol either by the nature of the substitution on the primary benzene ring and/or on the terminal nitrogen. All of these drugs are non-selective beta-blockers, except for bucindolol whose selectivity has not been carefully defined. The rationale for the development of this group of drugs was the knowledge that blockade of one adrenoceptor subtype causes reflex stimulation of the other, i.e. vasoconstriction after nonspecific beta-blockade and tachycardia after alpha-blockade. Since both of these compensatory responses act to prevent a fall in blood pressure, a relatively weak blockade of both receptor types should act synergistically to produce a lowering of blood pressure with minimal physiological disturbance. Haemodynamic studies have confirmed that the additional alpha-blocking properties of labetalol produce a pattern of haemodynamic changes unlike that of propranolol and other simple beta-adrenoceptor blocking agents. Peripheral vascular resistance, which falls acutely during the initial administration of the drug, tends to fall further during prolonged administration and the pulse rate tends to remain only slightly lower than pretreatment levels. In addition, at normal dose levels cardiac output is maintained by a compensatory increase in stroke volume. Thus, blood pressure is lowered largely by a reduction in vascular resistance, and although the heart rate falls significantly during exercise, the cardiac output is maintained by an increase in stroke volume. This pattern of events is different to that seen with beta-blocking agents which consistently reduce cardiac output during exercise. Currently labetalol is the only member of this group of drugs which is in established clinical use. Its antihypertensive efficacy has been confirmed in many studies and it has been shown to be effective in the management of both hypertensive emergencies and in the long term management of severe hypertension. It is particularly valuable in allowing a reduction in the number of drugs required for adequate blood pressure control. The early theoretical prediction that postural hypotension would occur with high doses is now acknowledged to be labetalol's major dose-limiting side effect. Most of the available pharmacokinetic data on labetalol were derived from studies which utilised a fluorimetric assay.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic alpha-Antagonists↗

Sulfation in dog.

Sulfation has been thoroughly studied in several species including e.g. man and rat. However, one important species often used for pharmacological drug studies is the dog. Here we describe recent advances as well as older data in the field of dog sulfation. Species differences in sulfation have been reported. Stereoselectivity, inhibition by pentachlorophenol, bioactivation of DNA binding species, and gender differences have also been observed for canine sulfotransferases (SULTs). Several drugs are being sulfated in vivo in dog, e.g. xamoterol, 4'-hydroxypropanolol, paracetamol and salicylamide. However, studies have shown that also e.g. canine hepatocytes and liverslices will sulfate substrates e.g. paracetamol and 7-hydroxycoumarin in in vitro experiments. Recently, three different enzymes have been cloned and characterized from canine liver, cSULT1A1, cSULT1B1 and cSULT1D1. cSULT1A1 being very similar to the human ortholog in terms of substrate specificity and is also ubiquitously expressed in canine tissues. The cSULT1B1 enzyme is also very similar in both distribution pattern as well as substrate preference compared to the human ortholog. The third enzyme, cSULT1D1, sulfates dopamine with high efficiency and it has no counterpart in man since it is found as a pseudogene. The importance of amino acid residue 247 in cSULT1D1 will be discussed since it can alter the ratio of sulfation of dopamine versus para-nitrophenol. In addition, the phenomenon of the high expression of the canine enzymes in colon is discussed.

Animals↗

Methapyrilene toxicity.

Seven cases of drug overdosage involving methapyrilene have been presented, five of which resulted in death. Methapyrilene blood levels ranged fron 1.2 to 3.0 mg% (Table 2). Five of the seven cases involved multiple drug dosage with ethanol, salicylamide, amobarbital, secobarbital, and/or scopolamine. Of the remaining cases, involving only methapyrilene, ome fatality occurred at a blood level of 2.7 mg%. The surviving case involved the reported ingestion of 100 tablets of Sleep-eze (2.5 gm methapyrilene), wherein serial lavage removed 1.1 gm of methapyrilene. Urinalysis revealed 2.52 mg% of methapyrilene in 1300 ml of urine. The methapyrilene blood level was too low to quantitate.

Adult↗

[Niclosamide In The Treatment Of Tetagonimiasis]

Anthelmintic effect of niclosamide [N-(2-chloro-4-nitrophenyl)-5-chloro-salicylamide)] on Metagonimus infection was carried out to the cases in area of Seomjin-river. The drug, one tablet contains 0.5 g of niclosamide was supplied from Bu-gwang pharmaceutical company in Seoul. Sixty five cases were divided into three groups by the regimen: Group l given 2 g(4 tablets) for one day, Group II for two successive days and Group III for three successive days. Stool examination was done before and 2-3 weeks after the drug administration by formalin-ether concentration and Stoll's dilution egg counting techniques. The results were as follows: Egg negative conversion (cured) and egg reduction (more than 80% decrease) rates were 28.6%, 10.7% in group I, and 31.8%, 27.3% in group II. But of those in group III treated for three successive days, 73.3% was cured and 26.7% showed egg reduction, and the general egg reduction rate was 95.1%. The results in the present trial suggested that the niclosamide has anthelmintic efficacy when it is used in 2g for more than three successive days.

Journal Article↗

PLS-based quantitative structure-activity relationship for substituted benzamides of clebopride type. Application of experimental design in drug design.

The advantageous approach of using an experimentally designed training set as the basis for establishing a quantitative structure-activity relationship with good predictive capability is described. The training set was selected from a fractional factorial design scheme based on a principal component description of physico-chemical parameters of aromatic substituents. The derived model successfully predicts the activities of additional substituted benzamides of 6-methoxy-N-(4-piperidyl)salicylamide type. The major influence on activity of the 3-substituent is demonstrated.

Benzamides↗

Analgesic sensitivity in children with asthma.

First described as a component of a triad seen among adults with nonallergic asthma and nasal polyps, aspirin sensitivity has subsequently been documented as a frequent concomitant of a wide range of patients with chronic asthma. Recent reports suggest that its incidence among children with asthma is higher than previously suspected. Among aspirin-sensitive asthmatics, indomethacin and newer, nonsteroid anti-inflammatory agents precipitate airway obstruction with a high frequency while phenylbutazone has a lesser effect. Reports related to acetaminophen among these patients have been inconsistent. Salicylic acid and salicylamide appear to be tolerated. A correlation between the potential for causing airway obstruction among asthmatic patients and the drug's in vitro prostaglandin synthetase activity has been suggested, and elevation of plasma histamine level at the time of the pulmonary reaction has been described. Aspirin and other analgesics may therefore mediate bronchospasm by means of their effects on prostaglandin production and the resultant effects on intracellular cyclic nucleotide activity, which modulates histamine release from mast cells in lung tissue.

Acetaminophen↗

[Cardiovascular and hemodynamic effects of derivatives of metoclopramide].

Two salicylamides, thiapride and sultopride, were found to provoke a dose-related depressor effect in the anesthetized dog. This effect was qualitatively similar to that of procaïnamide and metoclopramide. The hypotensive and negative inotropic effects were not related to the parasympathic system. In fact these compounds are weak autonomic antagonists. They do not exert any anticholinesterase activity. Intra-arterial administration provoked vasodilation.

Animals↗

[Animal experiment studies on the effect of intra-articular injections of antiphlogistic-antirheumatic agents on articular cartilage in vivo].

Animal experiments have shown that weekly intraarticular injections of various antiphlogistic/antirheumatic drugs into the knee joint induce progressive degenerative alterations in joint cartilage. The observed degenerations and destructions are most similar to the pathophysiology of osteoarthrosis in humans. By X-ray and macroscopic techniques the degenerative processes can be studied qualitatively and quantitatively. A decrease of joint space is a sensitive and early indicator of osteoarthrosis and showed that 10 weeks after intraarticular application of Ibuprofen, Phenylbutazone, Oxyphenbutazone, Flufenamic acid, Niflumic acid, Na-salicylate, Clofezone, Bumadizone and Dexamethasone the degenerative alterations in the injected knee joints were more severe than by applications of Chloroquine,D-penicillamine, Salicylamide and Indometacin. The degenerative effect on articular cartilage by the investigated drugs can be explained by their inhibitory potency on anabolic metabolism of connective tissue. The results of our animal experiments lead to the conclusion, that antiinflammatory drugs may also in man induce or accelerate degenerative joint diseases especially after long term treatment with high doses of these drugs.

Animals↗