Allergic rhinitis: meaningful and less meaningful combination treatments including reminiscences.

Allergic rhinitis (AR) results from a complex allergen-driven mucosal inflammation in the nasal cavity. Current guideline-based therapy for allergic rhinitis include oral and nasal antihistamines, topical and systemic glucocorticoids, decongestants, antimuscarinic agents, mast cell stabilizing drugs, leukotriene-receptor antagonists, and others. In spite of guideline recommendations, most patients are using multiple therapies in an attempt to achieve symptom control. Therefore, more effective therapies for the management of AR are clearly required. Recently, a novel fixed dose combination containing azelastine and fluticasone propionate has successfully been introduced. At present, it represents the only meaningful topical drug combination. Perhaps, it will be followed by others.

Soft drugs for future treatment of chronic obstructive pulmonary disease (COPD).

COPD is a major cause of chronic morbidity and mortality worldwide. Current treatment is aimed at symptomatic relief. In contrast to bronchial asthma, glucocorticoid treatment strategies have proved disappointing. Consequently, there is a need to develop more effective therapeutic strategies to replace present treatment. Advances in understanding the pathogenesis of COPD have the potential for identifying new therapeutic targets. Additionally, forgotten old compounds might undergo a revival by means of novel pharmaceutical technology.

Can corticosteroids be beaten in future asthma therapy?

Despite the enormous therapeutic advance, there is a general trend towards increasing morbidity and mortality due to asthma, which suggests that there is a need for new and improved treatments. The past decade was determined by the so-called "new biology" that identified and cloned almost all receptors and ion channels. This scientific revolution should lead to a more rapid identification of novel targets for major diseases and processes like high throughput screening and combinatorial chemistry should have improved and fastened the development of new drugs. Interestingly, exactly the opposite has happened. With the exception of leukotriene receptor antagonists and some monoclonal antibodies, no new developments have been introduced into asthma therapy during the last decade. The most promising approach is still to find drugs like corticosteroids with multiple functions. However, there is no evidence at the very moment that corticosteroids can be beaten in the next ten years. Therefore, our task is to improve the corticosteroids and make therapy with them even safer. The so-called soft-steroids such as loteprednol and etiprednol belong to the future promising therapeutically effective and safe treatments of allergic disorders.

Evaluation of physical dependence liability of l-deprenyl (selegiline) in animals.

l-Deprenyl is a useful drug that has been successful in the clinical treatment of parkinsonism. However, l-deprenyl is a phenylalkylamine derivative that undergoes metabolic transformation to l-methamphetamine and l-amphetamine. Therefore, the question arises whether l-deprenyl possesses amphetamine-like abuse liability. This article reviews a series of different preclinical studies in rats that used experimental procedures to provide preclinical information predictive of human abuse liability. In one series we investigated whether repeated administration of l-deprenyl to rats resulted in observable signs of physical dependence. In a second series of studies, the effects of l-deprenyl on the cortical electrical activity of freely moving rats were investigated. Finally, the influence of l-deprenyl on behavior of the animals was studied. In all studies, different stereospecific configurations of amphetamine and deprenyl were compared. During and after 6 weeks of oral administration of l-deprenyl, no signs of physical dependence were observed in rats after withdrawal of the drug. In contrast, with d-deprenyl, d-amphetamine, and racemic d,l-amphetamine, signs indicative of physical dependence were observed after withdrawal of the drug. For example, the body weight of the rats was increased. In addition, changes in electroencephalograms and behavior of rats induced by l-deprenyl and l-amphetamine were different from those produced by the d-enantiomers. Thus preclinical results confirm the clinical experience that therapeutically relevant doses of l-deprenyl are without physical dependence liability.

Comparison of changes in the EEG of freely moving rats induced by enciprazine, buspirone and diazepam.

The effect of enciprazine, buspirone and diazepam was investigated on the cortical electrical activity in freely-moving rats. Enciprazine (5 mg/kg, i.p.) and buspirone (5 mg/kg, i.p.) induced comparable changes, consisting in decreases of mean power values in delta and theta and increases in alpha and beta EEG frequency bands. Regarding only a particular area of the brain or particular frequency bands, these two compounds could not be clearly separated from each other. Changes in frequency bands induced by O-methoxy-phenyl-piperazine (5 mg/kg i.p.) (D 15157), the presumed main metabolite of enciprazine, were dose-related to that caused by the parent compound. The second metabolite (R,S)-1-4-(1-methoxy-4-hydroxy-phenyl)piperazin-1-yl-3-(3,4,5- trimethoxyphenoxy)propan-2-ol-dihydrochloride (D 20092) (5 mg/kg i.p.) evoked only minimal changes in the different frequency bands of the rats. The power spectra did not significantly differ from those seen in animals treated with saline. The action of diazepam (2 mg/kg i.p.) was characterized by decreases in alpha and delta frequency bands, accompanied by marked increases in fast beta waves. The marked frequency shifts caused by buspirone and enciprazine could clearly be differentiated from the EEG changes evoked by the minor tranquilizer, diazepam.

Effect of enantiomers of deprenyl (selegiline) and amphetamine on physical abuse liability and cortical electrical activity in rats.

In the present study, whether the repeated administration of (-)deprenyl to rats resulted in physical dependency was investigated. In a second experiment, the effect of (-)-deprenyl was investigated on the cortical electrical activity of freely moving rats and last, the influence of (-)-deprenyl on the behaviour of the animals was studied. In all experiments, different stereospecific configurations of amphetamine and deprenyl were also employed in order to establish differences and similarities. During and after the chronic oral administration of (-)-deprenyl (4 mg/kg) over 6 weeks, no signs of physical dependency were observed in rats after withdrawal of the drug. By contrast, (+)-deprenyl (5 mg/kg, p.o.) and (+)-amphetamine (5 mg/kg, p.o.) induced typical symptoms of amphetamine-dependency: during withdrawal of drug, the body weight of the rats was increased. A similar phenomenon was observed after oral administration of (+/-)-amphetamine (6 mg/kg, p.o.). After a single oral administration of (-)-deprenyl (1 and 5 mg/kg) and (-)-amphetamine (10 mg/kg, p.o.), decreases in delta and increases in theta frequency bands in the EEG were observed. In contrast, (+)-amphetamine (1 mg/kg, p.o.), (+/-)-amphetamine (5 mg/kg, p.o.) and (+)-deprenyl (1 and 5 mg/kg, p.o.) evoked increases in the mean power values in delta and decreases in theta frequency bands. In agreement with the EEG studies, the (-) and (+)-isomers of amphetamine and deprenyl caused differences in the behaviour of the animals. Based on these findings, it can be concluded that (-)-deprenyl undergoes a stereospecific metabolism in the organism and the amounts of its metabolites with (+) configuration might be negligible, even at the larger doses which are necessary to inhibit monoamine oxidase-B (MAOB) in brain.

2-[(3-Pyridinylmethyl)thio]pyrimidine derivatives: new bronchosecretolytic agents.

2-[(3-Pyridinylmethyl)thio]pyrimidine derivatives (1a-n) promote the excretion of phenol red into the mouse trachea, indicating an increased tracheobronchial secretion. Furthermore, 2-[(3-pyridinylmethyl)thio]pyrimidine (1a) (tasuldine) produces greater excretion of phenol red into the mouse trachea after systemic administration than the known bronchosecretolytic ambroxol. Compound 1a also reduces the viscosity of canine bronchial mucus. Compound 1a has been selected for clinical investigations.

New N-(pyridin-4-yl)-(indol-3-yl)acetamides and propanamides as antiallergic agents.

A series of new N-(pyridin-4-yl)-(indol-3-yl)alkylamides 44-84 has been prepared in the search of novel antiallergic compounds. Synthesis of the desired ethyl (2-methyindol-3-yl)acetates 1-4 was achieved by indolization under Fischer conditions; Japp-Klingemann method followed by 2-decarboxylation afforded the ethyl (indol-3-yl)alkanoates 17-25. Amidification was successfully carried out by condensation of the corresponding acids or their N-aryl(methyl) derivatives with 4-aminopyridine promoted by 2-chloro-1-methylpyridinium iodide. Efforts to improve the antiallergic potency of the title series by variation of the indole substituents (R1, R2, R) and the length of the alkanoic chain (n = 1, 2, 3) led to the selection of N-(pyridin-4-yl)-[1-(4-fluorobenzyl)indol-3-yl]acetamide 45, out of 41 compounds. This amide was 406-fold more potent than astemizole in the ovalbumin-induced histamine release assay, using guinea pig peritoneal mast cells, with an IC50 = 0.016 microM. Its inhibitory activity in IL-4 production test from Th-2 cells was identical to that of the reference histamine antagonist (IC50 = 8.0 microM) and twice higher in IL-5 assay: IC50 = 1.5 and 3.3 microM, respectively. In vivo antiallergic activity evaluation confirmed efficiency of 45 in sensitized guinea pig late phase eosinophilia inhibition, after parenteral and oral administration at 5 and 30 mg/kg, respectively. Its efficiency in inhibition of microvascular permeability was assessed in two rhinitis models; ovalbumin and capsaicin-induced rhinorrhea could be prevented after topical application of submicromolar concentrations of 45 (IC50 = 0.25 and 0.30 microM); and it also exerted significant inhibitory effect in the first test after iv and oral administration, with ID50 = 0.005 and 0.46 mg/kg.

Chemistry and pharmacology of the non-benzodiazepine anxiolytic enciprazine and related compounds.

In the course of studies on tranquilizers, new non-benzodiazepine-like compounds were synthesized. These are 1-(3,4,5-trimethoxyphenoxy)-3-[4-(2-methoxyphenyl)piperazinyl]prop an-2-ol (INN: enciprazine) and derivatives thereof which were screened pharmacologically in order to evaluate their central nervous system activity. Compounds with marked antiaggressive and anxiolytic properties but without dependence potential could be detected. Enciprazine was selected for clinical investigations.

Does pirenzepine distinguish between 'subtypes' of muscarinic receptors?

Pharmacological studies with pirenzepine were carried out on the isolated ileum and atrium of the guinea-pig and on the acid secretion from the isolated stomach of the mouse. Pirenzepine inhibited the bethanechol-evoked changes in all three organs in a dose-dependent manner. The slopes of the Schild-plots confirmed the competitive nature of the antagonism by pirenzepine. The estimated pA2-values were very similar. Based on these data, it might be concluded that pirenzepine is an anticholinoceptor compound without specific affinity for gastric muscarinic receptors.

Prostaglandin formation by isolated gastric parietal and nonparietal cells of the rat.

Rat gastric cells isolated by pronase and subdivided by Percoll into 3 fractions (F1, F2, F3) were used to study prostaglandin E2 (PGE2) formation and, as an indirect measure of parietal cell H+ production, [14C]-aminopyrine uptake. Cells that had not been fractionated, with 20 to 25% parietal cells, contained at 0 degree C 1.7 +/- 0.35 (s.e.mean) ng PGE2 10(8) cells-1. During incubation at 37 degrees C these cells steadily synthesized up to 4.36 +/- 0.73 ng PGE2 10(8) cells-1 from endogenous substrate. Indomethacin in concentrations higher than 10(-6) mol 1(-1) inhibited this basal formation completely, but 10(-4) mol 1(-1) did not reduce the cellular PGE2 level below 1.4 +/- 0.2 ng 10(8) cells-1. Arachidonic acid in concentrations higher than 10(-5) mol 1(-1) evoked an abundant formation of PGE2, and 10(-4) mol 1(-1) built up a plateau of over 7.5 +/- 1.65 ng PGE2 10(8) cells-1 within 15 min. PGE2 formation in cell fractions increased significantly with the number of parietal cells per assay tube. Indomethacin (10(-8) to 10(-4) mol 1(-1] did not influence the histamine-stimulated uptake of [14C]-aminopyrine, while arachidonic acid (10(-5) to 10(-4) mol 1(-1] inhibited this process. PGE2 formation in response to arachidonic acid was prevented by indomethacin, but the inhibition of aminopyrine uptake by arachidonic acid could not be prevented by indomethacin. The data suggest that isolated gastric cells of the rat sustain constant PGE2 synthesis in vitro, which is more pronounced in parietal than in mucosal and chief cells. PGE2 may exert different effects within distinct gastric cell types.

Mode of antinociceptive action of flupirtine in the rat.

1. Flupirtine is a novel, centrally acting, non-opioid analgesic agent. The present investigation was undertaken to ascertain which neuronal systems might be responsible for its antinociceptive effect in rodents. The antinociceptive responses to the test compounds were examined in the tail-flick test. 2. The selective destruction of noradrenergic pathways by 6-hydroxydopamine considerably reduced the flupirtine-induced inhibition of nociceptive responses but not the clonidine-induced antinociception which was significantly enhanced. Depletion of spinal 5-hydroxytryptaminergic pathways by pretreatment with 5,7-dihydroxytryptamine failed to affect the action of flupirtine and clonidine. 3. The depletion of neurotransmitters by reserpine totally abolished the antinociceptive action of flupirtine. By contrast, clonidine-induced inhibition of nociceptive responses remained unchanged. 4. Inhibition of the synthesis of noradrenaline by alpha-methyl-L-p-tyrosine attenuated the antinociception induced by flupirtine. In contrast, inhibition of the synthesis of 5-hydroxytryptamine by (+/-)-6-fluorotryptophan did not influence the antinociceptive activity of flupirtine. 5. Inhibition of noradrenaline uptake by imipramine led to a significant augmentation of flupirtine-induced antinociception. 6. Selective antagonists at alpha-adrenoceptors significantly decreased the antinociceptive action of flupirtine. Antinociception induced by clonidine was significantly diminished by idazoxan but not by prazosin. 7. The 5-hydroxytryptamine (5-HT) antagonist, ketanserin diminished the antinociceptive activity of flupirtine, probably due to its additional alpha 1-adrenoceptor antagonist activity. The antinociceptive effect of clonidine was not influenced by ketanserin. 8. Cholinoceptor antagonists such as mecamylamine and pirenzepine did not alter the antinociceptive action of flupirtine. Flupirtine-induced antinociception also remained unchanged after pretreatment with haloperidol. 9. Flupirtine has no pharmacologically relevant affinity for alpha 1-, alpha 2-adrenoceptors, 5-HT1- and 5-HT2-receptors as shown in direct binding studies. 10. The present results indicate that the antinociceptive action induced by flupirtine depends on the descending noradrenergic pain-modulating system.

Anpirtoline, a novel, highly potent 5-HT1B receptor agonist with antinociceptive/antidepressant-like actions in rodents.

1. The purpose of the present study was to relate the effects of the novel drug, anpirtoline, on 5-hydroxytryptamine (5-HT) receptor subtypes to its antinociceptive and antidepressant-like actions in rodents. 2. Binding assays with rat brain membranes have shown that anpirtoline bound with a much higher affinity to 5-HT1B receptor (Ki = 28 nM) than to 5-HT1A (Ki = 150 nM) and 5-HT2 (Ki = 1.49 microM) receptors. 3. Like 5-HT, anpirtoline concentration-dependently inhibited forskolin-stimulated adenylate cyclase activity in homogenates from the rat substantia nigra. Both effects were not additive, and could be prevented by 5-HT1B receptor antagonists such as propranolol and penbutolol. 4. In superfused rat and pig brain cortex slices preincubated with [3H]-5-HT, the electrically evoked tritium overflow was inhibited by anpirtoline and 5-HT. Whereas 5-HT was equipotent in both tissues (EC50 = 69 nM), anpirtoline was markedly less potent in pig brain cortex slices (EC50 = 1190 nM) than in rat brain cortex slices (EC50 = 55 nM). The concentration-response curve for anpirtoline was shifted to the right by metitepine in both preparations. 5. In the social behaviour deficit test, anpirtoline and trifluoromethylphenyl-piperazine were effective in reversing the isolation-induced impairments in mice, an effect shown only by compounds with agonist properties at the 5-HT1B receptor. 6. In the electrostimulated pain test using mice, anpirtoline dose-dependently increased the pain threshold with an ED50 of 0.52 mg kg-1, i.p. The antinociceptive activity of anpirtoline was abolished by pretreatment with cyproheptadine or propranolol.7. In the forced swimming test in rats, anpirtoline induced a dose-related increase in swimming activity. With an ED50 value of 4.6mgkg-1, i.p., anpirtoline was 4 times more potent than the two standard compounds imipramine and desipramine. The decrease of immobility time or the increase of active periods in this model of behavioural despair is suggested to be characteristic of antidepressant drugs.8. Anpirtoline exhibits both antinociceptive and antidepressant-like activities in animals. It is probable that anpirtoline elicits these pharmacological effects via its agonist effect on 5-HT1B and 5-HT1A receptors.

5-HT3 receptor antagonism by anpirtoline, a mixed 5-HT1 receptor agonist/5-HT3 receptor antagonist.

1. The aim of this study was to provide evidence that anpirtoline, which is an agonist at 5-HT1B and 5-HT1D receptors and also displays submicromolar affinity for 5-HT1A recognition sites, in addition, acts as an antagonist at 5-HT3 receptors. 2. In radioligand binding studies on rat brain cortical membranes, anpirtoline inhibited specific binding of [3H]-(S)-zacopride to 5-HT3 receptor recognition sites (pKi: 7.53). 3. In N1E-115 neuroblastoma cells in which [14C]-guanidinium was used as a tool to measure cation influx through the 5-HT3 receptor channel, the 5-HT-induced influx was concentration-dependently inhibited by anpirtoline. In this respect, anpirtoline mimicked other 5-HT3 receptor antagonists; the rank order of potency was ondansetron > anpirtoline > metoclopramide. 4. The concentration-response curve for 5-HT as a stimulator of [14C]-guanidinium influx was shifted to the right by anpirtoline (apparent pA2: 7.78). 5. In urethane-anaesthetized rats, anpirtoline inhibited (at lower potency than zacopride and tropisetron) the 5-HT- or phenylbiguanide-induced bradycardia (Bezold-Jarisch reflex), but did not induce this reflex by itself. 6. Intravenous infusion of cisplatin in the domestic pig caused a consistent emetic response which was antagonized by anpirtoline. 7. It is concluded that anpirtoline, which was previously characterized as a 5-HT1 receptor agonist also proved to be a 5-HT3 receptor antagonist in several experimental models and, hence, exhibits a unique pattern of properties at different 5-HT receptors.

Therapy of bronchial asthma with adenosine receptor agonists or antagonists.

Adenosine is an endogenous nucleoside that is released under pathological conditions and interacts with four G-protein-coupled receptor subtypes. These receptors are widely distributed throughout the body. They are involved in many central and peripheral processes, including immunological and inflammatory responses. In inflammatory and asthmatic conditions, the extracellular concentration of adenosine increases in the airway tissue. It enhances mast cell degranulation and bronchoconstriction, but may also inhibit eosinophil or lymphocyte function or modulate reactive oxygen species generation in neutrophils. Despite a large number of studies clearly indicating the effects of adenosine in vitro, many aspects of the mechanisms involved in the adenosine-mediated responses are still unclear, and our knowledge is limited in understanding the complex multifactorial interactions occurring in the whole body. The discovery of adenosine receptor compounds acting with increasing selectivity will bring new approaches to the use of adenosine receptor agonists and antagonists and may clarify some of the current uncertainties. On the basis of our present knowledge, the development of adenosine A(2A)- or (A3)-receptor agonists as antiinflammatory agents or A(2B)-receptor antagonists as inhibitors of mast cell degranulation for the treatment of asthma holds promise.

The real gordian knot: racemic mixtures versus pure enantiomers.

Many drugs exist as asymmetric three-dimensional (chiral) molecules and will therefore have several stereoisomers. There are often pharmacodynamic, pharmacokinetic and/or toxicological differences between enantiomers. The choice between developing a racemate or single enantiomers depends on therapeutic advances and developmental costs involved. Regarding the target environment for drug intervention, even if natural physiological mediators are achiral, their receptors may demonstrate a preference for the (-)- or (+)-enantiomer of agonists or antagonists. It is also obvious that the majority of enzymes and channels are stereospecific, at least to a variable extent. From a pharmacokinetics point of view, chirality can have an influence on drug absorption, distribution, metabolism and elimination. With a few exceptions, toxicological differences between isomers of known drugs are less dramatic than thought to be and only seldom substantiate the necessity of a racemic switch. The pharmaceutical industry is currently very interested in the so-called "racemic switch." Before proceeding to a racemic switch it is necessary to determine if 1) it is chemically feasible to produce a single enantiomer; 2) a clinical advantage is obtainable through a racemic switch; and 3) a marketing advantage is obtainable. The real goal of a racemic switch should be the rational development of compounds that are profitable for the company and--first of all--beneficial for the patient.

Evidence for a functional cytoprotective effect produced by antacids in the rat stomach.

The fall in potential difference evoked by taurocholate was diminished after exposure of the gastric mucosa of rats to aluminium-containing antacids. Other parameters of barrier disruption (H+ back diffusion, Na+ influx) exhibited the same pattern and correlated with the change in potential difference. This cytoprotective-like effect was abolished in animals pretreated with indomethacin. Taurocholate significantly diminished the PGE2 content in the gastric mucosa and its release into the instillate. The PGE2 content of gastric mucosa and instillate of animals pretreated with an aluminium-containing antacid was not decreased after exposure to taurocholate.

5-HT1A-agonistic properties of naftopidil, a novel antihypertensive drug.

Naftopidil, a novel antihypertensive compound, possesses 5-HT1A agonistic properties in addition to being an alpha 1-adrenoceptor antagonist. The IC50 values for alpha 1-adrenoceptors (235 nmol/l) and for 5-HT1A receptors (108 nmol/l) lie in the same concentration range. The reduction in blood pressure of anesthetized cats by 8-OH-DPAT and urapidil was completely abolished by spiroxatrine, a 5-HT1A antagonist. However, the decreases in blood pressure induced by naftopidil were only partly antagonized by spiroxatrine.

The effect of different corticosteroids and cyclosporin A on interleukin-4 and interleukin-5 release from murine TH2-type T cells.

By secretion of interleukin-4 and interleukin-5, TH2-type T cells are thought to play an important role in the pathogenesis of asthma. Corticosteroids are currently the most effective therapy available for asthma, but recently it has been demonstrated that cyclosporin A improves lung function in patients with severe corticosteroid-dependent asthma. In order to examine the effects of corticosteroids and cyclosporin A on anti-CD3-induced production of interleukin-4 and interleukin-5 we used the murine TH2-type cell clone D10.G4.1. Interleukin-4/interleukin-5 release was inhibited by all drugs tested with the following IC50 values (nmol/l) for interleukin-4 and interleukin-5, respectively: budesonide (0.32/0.22), beclomethasone (0.65/0.33), dexamethasone (4.70/3.52), 6 alpha-methyl-prednisolone (24.04/17.02), hydrocortisone (34.27/22.55), and cyclosporin A (72.59/242.21). In conclusion, corticosteroids exert strong inhibitory effects on cytokine production by TH2-cells, which may explain, at least partly, its clinical efficacy in asthma. Cyclosporin A also showed a concentration-dependent inhibition; however, in relation to corticosteroids the inhibitory activity of cyclosporin A was found to be weaker.

Emesis induced in domestic pigs: a new experimental tool for detection of antiemetic drugs and for evaluation of emetogenic potential of new anticancer agents.

The domestic pig was used to develop a new model for evaluating the emetogenic potential of anticancer drugs and determining the antiemetic activity of drugs. Emesis was characterized by expulsion of solid or liquid material. In each animal, the number of vomits after infusion of the emetogenic drug (infusion in ketamine and xylazine anesthesia) was recorded in 1-hr periods during the first 4 hr and then in a 4- and a 16-hr period. Intravenous infusion of cisplatin caused a concentration-dependent emetic response. Anti-cancer drugs other than cisplatin such as carboplatin, dactinomycin, cyclophosphamide, and ifosfamide, also induced emesis, indicating that the domestic pig is suitable to detect the emetogenic potential of chemotherapeutic agents. A cisplatin dose of 2 mg/kg i.v. proved to be most suitable for studying the effect of potential antiemetic drugs (applied as i.v. injection), because this cisplatin dose caused consistent emetic responses without other toxic signs in the 24 hr following its infusion. Emesis induced by cisplatin was reduced by high doses of metoclopramide (25 mg/pig; approximately 0.8 mg/kg). The more selective dopamine D2 receptor antagonists, alizapride and domperidone, even at high doses (25-50 mg/pig; approximately 0.8-1.6 mg/kg), did not inhibit cisplatin-induced emesis, nor did haloperidol up to 20 mg/pig (approximately 0.6 mg/kg). Sulpride (50 mg/pig; approximately 1.6 mg/kg) halved the occurrence of vomits in the first 4 hr after cisplatin, but this effect was followed by an increase in the frequency of vomits; thus, no change in the total number of vomits was observed in the 24-hr observation period.(ABSTRACT TRUNCATED AT 250 WORDS)