Experimental studies on acute and chronic action of azelastine on nasal mucosa in guinea pigs, rats and dogs.

Azelastine (CAS 37932-96-0) nasal spray (Allergodil, Rhinolast, Astelin) was investigated in acute experiments in guinea pigs and after a 26-week local application period with daily repeated administration for effects on ciliary beat activity (acute experiments) and morphology of nasal mucosa. The commercially available spray did not inhibit ciliary beat activity in guinea pigs nor did it cause any inflammatory or atrophic changes after 26-week daily local application on nasal mucosa in rats and dogs.

Synergistic protective effects with azelastine and salbutamol in a guinea pig asthma model.

Azelastine prevents down-regulation of beta 2-receptors and adenylate cyclase and upregulation of alpha 1-adrenoceptors induced by repeated allergen challenge in the guinea pig lung. In the present study the protective effects of azelastine and salbutamol and a combination of both drugs was investigated using aeroallergen-induced acute allergic bronchoconstrictor responses in conscious, actively sensitized guinea pig. The drugs were given orally 1 h prior to challenge. The oral PD50 was 230 micrograms/kg for azelastine and 1200 micrograms/kg for salbutamol. Both drugs showed a synergistic protective effect with a PD50 of 60 micrograms/kg of azelastine plus 120 micrograms/kg of salbutamol indicating a reduction in the PD50 of azelastine by a factor of 4 and of salbutamol by a factor of 10. These findings may explain the reduction in the use of salbutamol and theophylline with azelastine by chronic asthmatics.

Influence of azelastine and some selected drugs on mucociliary clearance.

The effect of azelastine and some selected compounds on ciliary beating frequency (CBF) was investigated in vitro using human mucosal samples and in vivo using anesthetized guinea pigs. Further influence of azelastine on mucus secretion was evaluated in mice and on mucociliary clearance in anesthetized rabbits. Azelastine influenced the ciliary beating frequency neither in vitro nor in vivo. Azelastine, similarly to salbutamol, ambroxol, and bromhexine, increased mucus secretion measured by the tracheal output of phenol red. Azelastine dose-dependently enhanced mucociliary clearance measured by elimination of 99mTc-labeled erythrocytes in rabbits. The activity of azelastine proved to be about 10 times stronger than that of bromhexine. Since the ciliary activity remained unchanged under the influence of azelastine, it is likely that azelastine increases the mucociliary clearance by enhancing bronchial secretion. It is possible that the observed increase in mucociliary clearance may contribute to the beneficial effect of azelastine in the treatment of respiratory diseases.

Azelastine: a multifaceted drug for asthma therapy.

Azelastine (4-(p-chlorobenzyl)-2-(hexahydro-1-methyl-1H-azepin-4-yl)-1-(2H)-p hthalazinone hydrochloride), a novel long-acting antiasthmatic/antiallergic drug has been demonstrated to be effective in the treatment both of asthma and of allergic rhinitis. In this paper some selected properties of azelastine are presented which might contribute to its antiasthmatic and antiallergic effect. Azelastine causes a marked inhibition of generation of oxygen radicals in alveolar macrophages. A bronchosecretolytic activity of azelastine is observed which is based on the secretion of a more liquid mucus. Furthermore, the mucociliary clearance is enhanced as demonstrated in a rabbit model. Also IL-1 generation is inhibited in vitro and in vivo. Finally, the possible tissue and cellular accumulation of azelastine in lung and alveolar macrophages resp. is discussed.

Effect of azelastine on microviscosity of bronchial lavage fluid obtained from actively sensitized and challenged guinea pigs.

Fluorescence polarisation technique was adapted to measure microviscosity in the bronchoalveolar lavage fluid (BAL) of guinea pigs. In sensitized guinea pigs, 20 hours after antigen challenge, the microviscosity of BAL was increased by 86%, suggesting that antigen-induced bronchospasm is followed by inflammatory events. Pretreatment with azelastine (3 mg/kg, p.o., 2 hours prior to antigen challenge) tended to normalize microviscosity in the bronchoalveolar lavage fluid obtained from challenged guinea pigs. The present results suggest that azelastine inhibits the increase of microviscosity of BAL, a symptom of the late phase reactions.

Azelastine inhibits bronchial hyperreactivity to acetylcholine in guinea pigs.

Contractile responses to acetylcholine were measured using isolated tracheae obtained from actively sensitized guinea pigs 0.5, 1, 5, 20, 24, 48 and 72 h after antigen challenge. Tracheal contractions to acetylcholine and to histamine were significantly increased 20 h but not 0.5, 1, 5, 24, 48 and 72 h after antigen challenge indicating bronchial hyperreactivity. When animals were pretreated with azelastine and then exposed to antigen challenge, concentration-response curve to acetylcholine did not differ from that obtained in control (non-challenged) tracheae. It is likely that azelastine is able to inhibit bronchial hyperresponsiveness to chemical mediators of bronchial asthma.

Inhibition of cysteinyl-leukotriene production by azelastine and its biological significance.

Azelastine is a phthalazinone derivative with a wide spectrum of pharmacological activities. Actively sensitized guinea pigs were used to examine the broncholytic effect of azelastine in vivo. Furthermore, the influence of azelastine on the production of arachidonic acid (AA) metabolites was investigated in vitro and compared to the effects of nordihydroguaiaretic acid (NDGA), indomethacin and ketotifen. In vivo, azelastine protected actively sensitized guinea-pigs against ovalbumin-induced bronchospasm with an ID50 of 0.08 mg/kg orally. Ketotifen was similarly active (ID50 = 0.05 mg/kg). Antigen-induced contraction of isolated tracheal rings of sensitized guinea-pigs was concentration-dependently inhibited by azelastine and NDGA with IC50-values of 94.1 and 34.2 mumol/l, respectively. Ketotifen exerted only weak inhibitory activity (18% at 100 mumol/l). The arachidonic acid-induced contraction of isolated guinea-pig tracheal rings was also inhibited both by azelastine (IC50 = 92.6 mumol/l) and NDGA (IC50 = 20.4 mumol/l). Ketotifen was inactive on this model. Antigen challenge of chopped lung tissue from sensitized guinea-pigs resulted in the release of cysteinyl-leukotrienes (LT) which were identified by reversed phase high pressure liquid chromatography (HPLC) as LTD4 and LTE4. The release of cysteinyl-LT from sensitized guinea-pig lung tissue induced by antigen challenge was concentration-dependently inhibited by azelastine (IC50 = 35.2 mumol/l) and NDGA (IC50 = 8.4 mumol/l) but not by ketotifen and indomethacin. By contrast, indomethacin caused a pronounced augmentation of cysteinyl-LT release. The concentration of indomethacin, which augmented cysteinyl-LT release by 50% was 0.19 mumol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of azelastine with adenosine receptors in guinea pig trachea.

The effects of azelastine, 8-phenyltheophylline, NDGA, atropine and mepyramine on PIA-induced contraction and relaxation of isolated guinea pig tracheal chains were investigated. Atropine (1 nM) and mepyramine (1 microM) had no effect on PIA-induced relaxation whereas 8-phenyltheophylline (5 microM) caused strong inhibition of PIA-induced relaxation, indicating that the latter effect is mediated by stimulation of extracellular adenosine receptors. NDGA (0.5 microM) caused potentiation of PIA-induced relaxation. Azelastine (10 nM-1 microM) caused dose-dependent potentiation of PIA-induced relaxation. In another model for investigation of extracellular adenosine receptors, namely the negative inotropic effect in the electrically driven isolated guinea pig atrium, the action of PIA was fully reversed by the addition of 8-phenyltheophylline. In contrast, the negative inotropic effect of azelastine was not reversed by 8-phenyltheophylline, indicating that azelastine does not act on extracellular adenosine receptors. The negative inotropic effect of azelastine can be reversed by addition of calcium as for verapamil. It is concluded that the calcium-antagonistic and perhaps antiallergic properties of azelastine are responsible for the potentiation of extracellular adenosine receptor mediated relaxation by azelastine. Since asthmatics show increased hyperreagibility (bronchospasm) to inhalation of adenosine, the inhibition of PIA-induced contraction by azelastine indicates that the drug may be worthwhile in the treatment bronchial hyperreactivity in asthmatic patients.

Azelastine, a new antiallergic/antiasthmatic agent, inhibits PAF-acether-induced platelet aggregation, paw edema and bronchoconstriction.

Azelastine is a phthalazinone derivative with a wide spectrum of pharmacologically relevant activities. Since PAF-acether has been considered to be a potent mediator of asthma, azelastine was assayed for its ability to counteract PAF-acether-induced platelet aggregation, paw edema development and bronchoconstriction. Azelastine exerted a concentration-dependent inhibition of PAF-acether-induced platelet aggregation in human platelet rich plasma with an IC50 of 87 mumol/l and was as effective as ketotifen. PAF-acether-induced paw edema was reduced by intraperitoneal administration of azelastine resulting in an ID50 of 14.4 mg/kg after 2 h. By contrast, ketotifen was not able to inhibit edema development up to a dose of 32 mg/kg i.p. Azelastine and ketotifen, administered intravenously, dose-dependently inhibited PAF-acether-induced bronchoconstriction, starting from the dose of 0.01 mg/kg and resulting in ID50s of 0.03 and 0.02 mg/kg, respectively. These results show that azelastine is endowed with a peculiar anti-PAF-acether action, which may be advantageous in its therapeutic use, in the treatment of asthma.

[The pharmacologic effect of flupirtine, a structurally new analgesic]. / Untersuchungen zur pharmakologischen Wirkung von Flupirtin, einem strukturell neuartigen Analgetikum.

The analgesic potency of ethyl-N-[2-amino-6-(4-fluorophenylmethylamino)pyridin-3-yl]carb ama te (flupirtine, D 9998) in mice and rats in Haffner's test, electro-pain test and Randall-Selitto test (inflammation induced pain) lies between the more potent dextromoramide and methadone and the more weakly active pethidine, dextropropoxyphene, codeine, phenacetin and paracetamol. In comparison to codeine flupirtine is up to 4 times more potent, up to 2 times more active than pethidine and 4 times more potent than dextropropoxyphene in the above-mentioned methods. With one exception of inflammation induced pain, where flupirtine shows an activity of about 1 1/2 times that of phenacetin and paracetamol, both analgesics are about 10 to nearly 30 times less active than flupirtine in other above-mentioned tests. In the hot plate test flupirtine is twice as active as codeine and approximately 10 times more active than phenacetin and paracetamol. The weakest analgesic activity of flupirtine is seen in acetic acid test where it is about half as active as codein and approximately as active as dextropropoxyphene. Nevertheless, flupirtine is up to 10 times more potent than phenacetin and paracetamol. The acetic acid test is claimed to be non-specific according to our own experience and to other authors. Flupirtine is enterally absorbed at a higher degree than the other tested centrally acting analgesics. In regard to the results of various analgesic investigations in mice and rats flupirtine can be classified as a medium to strong acting analgesic. The duration of action of flupirtine is comparable to that of codeine. Experiments with flupirtine suggest that there are some convincing criteria for a pronounced central acting component of its analgesic activity. These criteria are the strong efficacy in the hot-plate and Haffner's test, in which only centrally acting analgesics show distinct effects, and the finding that flupirtine increases the pain threshold for vocalisation in rats and mice excluding a pure reflex of the spinal cord. In current experiments concerning the mode of action flupirtine exhibits a distinct central analgesic component of action. In spite of its relatively high analgesic potency which corresponds to that of opiates flupirtine does not show any other signs of opiate properties and other potent analgesics. Thus, flupirtine does not develop tolerance in mice and rats after 19 or 17 days of daily administration.(ABSTRACT TRUNCATED AT 400 WORDS)

[General pharmacologic studies on the analgesic flupirtine]. / Allgemeine pharmakologische Untersuchungen mit dem Analgetikum Flupirtin.

In the present study the general pharmacological properties of ethyl-N-[2-amino-6-(4-fluor-phenylmethylamino)pyridin-3-yl]carbama te (flupirtine, D 9998), a structural new analgesic, are described. In several tests with mice flupirtine shows a centrally depressant component of action. However, regarding undesirable side effects as ataxia, inhibition of motor activity etc. this action is, with respect to the analgesic effective doses less pronounced than those of comparable analgesics, for instance phenacetin. In relatively low doses flupirtine antagonizes tremor induced by oxotremorine in mice. This activity is probably not caused by a central anticholinergic action, because other anticholinergic effects have not been observed. It should be pointed out that flupirtine antagonizes the morphine-induced tail phenomenon in mice in relatively low doses. This action obviously differentiates flupirtine from opiates. Up to high doses flupirtine does not cause catalepsia in mice, consequently its centrally depressant activity does not resemble that of reserpine and also is not comparable with those of neuroleptic agents. The corneal and pinnal reflexes are not influenced by flupirtine and the righting reflex is slightly delayed in high doses. The anticonvulsive activity of flupirtine observed in the pentetrazol shock test (mouse) after high doses probably cannot be considered to occur within the analgesic dose range. Inhibition of amphetamine toxicity in mice observed in doses near the hypnotic doses may be caused by non-specific effects. In vitro tests with isolated trachea or ileum of guinea pigs show that flupirtine possesses no or very weak antagonism against histamine-induced spasms. In spasms caused by barium chloride flupirtine shows a weak musculotropic-spasmolytic activity. Investigations on the circulatory system of dogs do not indicate any incompatibilities with flupirtine. No evidence of antiarrhythmic activity was found in rats. Flupirtine has no local anesthetic activity in mice but some weak effects on the cornea of rabbits. Like several other analgesics flupirtine shows in rats a reversible antidiuretic action including sodium and chloride retention which is of relatively short duration and is not observed in long-term studies in rats and dogs. In contrast to many stronger antiinflammatory compounds, flupirtine does not possess ulcerogenic activity in rats up to high doses. A minimal inhibition of intestinal motility (mouse) is observed only in doses higher than the analgesic effective doses.