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At least 649 records · Page 36Linked to original sources

PubMed1976

The effect of antihistamines on experimental posttraumatic edema of the spinal cord.

The present experiments were designed to test the effect of antihistamines on the formation of post-traumatic edema of the spinal cord. Ten rhesus monkeys received 600 gm cm injuries to the T10 level of the spinal cord. Five animals received antihistamine treatment and five animals acted as untreated controls. Posttraumatic edema was estimated using radio-active tagged serum albumin. A significant increase in radioactivity of the injured segment was demonstrated in both groups when compared to noninjured issue, but no difference was demonstrated in the radioactivity of the injured segment in the treated versus the nontreated group.

Animals↗

PubMed1982

Suppression of histamine-induced adrenocorticotropic hormone release by antihistamines and antidepressants.

The antihistaminic activity of many antidepressant drugs is well documented in vitro but has not been investigated as thoroughly in vivo. In the course of an investigation of the roles of H1 and H2 receptors in histamine-induced adrenocorticotropic hormone (ACTH) release in rats, it was observed that several antidepressants were potent inhibitors of this response. Male Sprague-Dawley rats were injected with test drugs and then with histamine or histamine agonists. Serum ACTH concentrations were determined by radioimmunoassay. ACTH secretion was induced by both H1 and H2 receptor stimulation. Histamine-induced ACTH release was markedly attenuated by several H1 antihistamines, whereas the H2 antagonists were not as effective. The antidepressants imipramine, doxepin, mianserin, desipramine and amitriptyline suppressed histamine-induced ACTH release. However, iprindole and the antianxiety agent diazepam were without effect. ACTH release induced by histamine agonists was also diminished by pretreatment with some of these blocking agents.

Adrenocorticotropic Hormone↗

PubMed1982

[The relationship of antihistaminics to cadmium necrosis in rat testes].

Selective necrosis of rat testicles is known to be produced by cadmium in subtoxic doses due to impairment of vessel structures. Classical antihistaminics in the same time in order to exclude that the lesion might have been produced by local release of histamine. Antihistaminics did not prevent necrosis. Instead, Clemastine stressed an interstitial testicular haemorrhage a bit. Methyldosulepine administered with calcium could decrease the vascular permeability because haemorrhage was almost lacking. The finding supports an idea of possible interaction between calcium and cadmium ions.

Animals↗

PubMed1983

[Antihistamines and reactivity].

In two consecutive partial studies conducted under double-blind conditions the potential effects of the antihistamine 1-(4-fluorophenylmethyl)-N-[1-[2-(4-methoxypenyl)ethyl]-4-piperidinyl]- 1H-benzimidazole-2-amine (astemizole) on the ability to drive and the safe operation of machinery was tested in a total of 85 volunteers. The test was performed with psychometrical methods and included the activation level (= objective tiredness), the subjective feeling of tiredness as well as their impact on concentration and reactivity. It was shown, that after a single administration (first partial study) there was no difference in performance between astemizole and placebo, whereas under the influence of the reference substance ketotifen concentration and reactivity were significantly impaired. It should be mentioned that the volunteers of the reference group did not yet experience a subjective feeling of tiredness, while their performance had already fallen off. Also after seven days of treatment (second partial study) with astemizole or placebo the active group did not exhibit any decline in performance. The authors advise against the generalized reference to a "possibly impaired reactivity" in the case of antihistamines.

Adolescent↗

PubMed1995

Three explorative studies on the efficacy of the antihistamine mebhydroline (Omeril).

The efficacy of a multiple oral dose treatment with mebhydroline (Omeril coated tablets, 100 mg t.i.d.) was examined in 3 studies which were performed in a randomized, double-blind and placebo-controlled 2-way cross-over design. A second target was to investigate the suitability of different pharmacodynamic models for testing the efficacy of antihistamines. Study A involved a nasal provocation with a specific allergen in 11 symptom-free patients suffering from seasonal allergic rhinitis. In study B, a nasal provocation with histamine was investigated in 11 healthy volunteers. Study C involved a cutaneous provocation with a specific allergen in 12 symptom-free patients suffering from seasonal allergic rhinitis/atopy. The mebhydroline treatment's superiority over placebo was shown statistically at the 95% confidence level for the symptoms itchy nose in study A and for nasal congestion in study B. In study C, allergen-induced weals (planimetric measurement) and itching (visual analog scale) were significantly changed by mebhydroline. A qualitative evaluation revealed a reaction intensity that differed between the 2 treatments to a clinically relevant degree, however, without reaching significance. On the basis of the data it is expected that the clinical efficacy of mebhydroline may be further substantiated in confirmatory clinical trials which should include placebo and positive controls. The test methods used differed in their suitability for measuring the pharmacodynamic effects of antihistamines. Overall, the most clear-cut results were seen in hay fever patients using a specific allergen for provocation. The planimetric assessment of weal response should be preferred as a cutaneous model. Both AR and AARM have their clinical relevance. Based on highly significant results of a subgroup analysis there are indications in favor to AR, but momentary there is no definite conclusion in favor of or against either of the 2 methods.

Adult↗

PubMed1995

Antihistamines reduce blood-retinal barrier permeability in type I (insulin-dependent) diabetic patients with nonproliferative retinopathy. A pilot study.

PURPOSE: To determine if histamine receptor stimulation mediates increased blood-retinal barrier (BRB) permeability in patients with diabetic retinopathy, as it does in experimental diabetes. METHODS: Fourteen patients with type I (insulin-dependent) diabetes and mild nonproliferative diabetic retinopathy were treated with combined astemizole, 20 mg, and ranitidine, 600 mg, or an identical placebo for 6 months in a double-masked fashion. Blood-retinal barrier permeability was measured by vitreous fluorometry at baseline and at 3 and 6 months. RESULTS: Permeability was significantly reduced in the group treated with antihistamines (P < 0.05) compared with the placebo group. There were no concomitant significant changes in systemic arterial blood pressure or HbA1c values. CONCLUSION: These pilot data suggest that histamine receptors influence permeability of the BRB in human diabetes. Further studies of the effects of antihistamines on diabetic retinopathy are warranted.

Adult↗

PubMed1994

Effects of two antihistamines on chloroquine and histamine induced weal and flare in healthy African volunteers.

This study investigated the effects of single doses of clemastine (2mg orally), mepyramine (2 micrograms intradermally) and placebo on weal and flare caused by intradermal chloroquine 2.5mg and histamine 2 micrograms in 11 healthy black subjects who experienced generalised pruritus with oral chloroquine. Compared with placebo, both antihistamines caused significant reductions in histamine-induced weal and flare. By contrast, chloroquine-induced weal and flare were not significantly altered by clemastine or mepyramine when compared with placebo. It is concluded that histamine is unlikely to be the main mediator of chloroquine-induced weal and flare. These findings are in consonance with the lack of significant effect of antihistamines on chloroquine-induced generalised pruritus.

Administration, Oral↗

PubMed1993

Effects of antihistamines on inflammatory mediators.

The nasal antigen challenge model has proved useful in assessing the roles of inflammatory mediators in the clinical allergic response. Studies using this model have revealed that the acute allergic response is associated with increased concentrations of histamine, prostaglandin D2 (PGD2), leukotrienes, tryptase, and kinins, and with increased TAME-esterase activity. The effects of antihistamines on the clinical response and inhibition of mediator release have also been examined with this model. Premedication with terfenadine caused a marked reduction in sneezing as well as decreased histamine release, kinin levels, and TAME-esterase activity. Levels of PGD2 also decreased, although not significantly. Release of leukotriene C4 (LTC4) was not affected by this agent. Terfenadine also reduced vascular permeability as reflected in decreased albumin levels. In this model, cetirizine reduced sneezing, TAME-esterase activity, and albumin levels, whereas histamine release and PGD2 levels remained unaffected. Pretreatment with cetirizine resulted in significantly reduced levels of LTC4. Loratadine markedly, but not significantly, inhibited the sneezing response and reduced release of histamine, PGD2, and LTC4. Albumin and kinin levels were significantly diminished. The clinical significance of the inhibitory effects of antihistamines on mediator release has yet to be determined.

Cetirizine↗

PubMed1995

[The effect of antihistamines on stimulated blood platelet functions].

The histamine receptor H1-antagonists of cationic amphiphilic drug (CAD) structure BromadrylR (BRO) and DithiadenR (DIT) were investigated on stimulated functions of blood platelets in vitro. Both drugs dose-dependently decreased platelet aggregation. BRO significantly decreased aggregation in concentrations of 20 and 200 mumol/l in thrombin and ADP stimulated platelets, respectively. DIT was 10 times less active as compared with BRO. A dose-dependent inhibitory effect of BRO and DIT was demonstrated on thrombin stimulated production of malondialdehyde (MDA) and thromboxane (TXB2) generation in platelets. A significant decrease in MDA production and TXB2 generation was measured with BRO and DIT in 10 mumol/l concentration. Results showed that the antihistaminic drugs BRO and DIT inhibited stimulated aggregation in relation to membrane phospholipid peroxidation and arachidonic cascade activation in platelets. These data, along with results from studies on the effect of other CAD on platelets, revealed that antihistaminic drugs interfere with stimulated aggregation by inhibiting phospholipase A2 rather than the intraplatelet histamine receptor.

Adenosine Diphosphate↗

PubMed1993

Anticholinergic, antihistaminic and cardiovascular effects of two new congeners of quipazine and trazodone.

Two recently reported analogues of quipazine (CAS 4774-24-7) and trazodone (CAS 19794-93-5) were found to be selective inhibitors of 5-hydroxytryptamine (5-HT) uptake, with an antidepressant profile similar to the atypical antidepressants. In the present work the anticholinergic, antihistamine and cardiovascular effects of the compounds were investigated in experimental animals and compared with imipramine and trazodone. Both compounds have demonstrated weak anticholinergic and antihistamine activities on the guinea-pig ileum and showed weak negative inotropic effects on the isolated rabbit heart as compared to imipramine. The marked bradycardia produced by imipramine and trazodone, and the extrasystoles produced by imipramine were not produced by either compound. Binding studies at 5-HT receptors indicated that the quipazine analogue, compound I, has moderate affinity for the selective 5-HT1D ligand while the trazodone analogue, compound II, binds to 5-HT2 receptors. Structural modifications of these compounds may offer new potent analogues with selective affinity at 5-HT receptor-subtypes.

Animals↗

PubMed1993

New esters of heteryl acetic and mercaptoacetic acids. Synthesis and H1-antihistaminic evaluation.

Synthesis of esters containing 2 (N,N-dialkylamino) ethanolic and 2-alkoxyethanolic groups with heteroaryl acids was carried out. Three series of such esters: (2-substituted-3,4-dihydro-4-oxo-quniazolin-3-yl) acetates, S-(3-aryl-3,4-dihydro-4-oxo-quinazolin-2-yl) mercaptoacates and S-(1H-benzimidazol-2-yl) mercaptoacetates were synthesized from their respective acids/acid chlorides using appropriate alcohols. Their in vivo H1-antihistaminic potencies were evaluated using isolated guinea pig ileum method. The IC50 values indicate higher potencies of quinazolinonyl mercaptoacetates than the other two series, in general. Presence of an aryl group at position 3, with an electron-releasing substituent appears to enhance the antihistaminic activity. Similarly 2 (N,N-diethylamino) ethyl esters were found to be more active than the other type of esters tested.

Acetates↗

PubMed1993

Effects of sedating and nonsedating antihistamines on flying performance.

The purpose of this double-blind study was to compare the effects on flying performance of a nonsedating antihistamine, (terfenadine), two sedating antihistamines, (chlorpheniramine and diphenhydramine), and a placebo. Twelve USAF pilots were tested at 1-month intervals with the above medications, administered during separate testing periods. Medication was given twice daily for 3 days. On the third day, each pilot performed three landing approaches in a C5-B flight simulator, followed by assessment with psychological and neuropsychological tests. Evaluation of the flight data showed no significant differences in flight performance among any of the pilots while on four different medications. Psychological and neuropsychological testing demonstrated no significant differences in performance with the exception of the SCL-90-R, where pilots reported psychological and physiological subjective symptoms with diphenhydramine and chlorpheniramine, but not with terfenadine. While pilots were on each medication, open-ended questionnaires corroborated the results of the SCL-90-R. Both the flight and neuropsychological testing data suggest that terfenadine has no detectable effects on overall flying performance.

Aerospace Medicine↗

PubMed1993

[Clinical indications of an auxiliary effect of antihistamines (parenteral benadryl) in the treatment of RSV infections of cattle].

The BRSV-infection belongs to the Bovine Respiratory Disease (BRD) complex. Because of its clinical features as well as pathomorphological and histopathological lesions it can be considered an independent disease. Therefore, concepts of treatment deviating from conventional BRD have to be applied. In addition to antibiotic therapy, therefore, the effect of treatment with the antihistamine Diphenylhydramin (Benadryl-parenteral, Parke Davis) was checked. For the evaluation the internal body temperature was used as measure. With the additional daily application of the antihistamine to the antibiotic therapy the animals were faster without fever. The difference was significant.

Animals↗

PubMed1995

Positron emission tomographic study of central histamine H1-receptor occupancy in human subjects treated with epinastine, a second-generation antihistamine.

Histamine H1-receptor occupancy in the human brain was measured in healthy young volunteers by positron emission tomography (PET) using [11C]doxepin. d-Chlorpheniramine, a selective and classical antihistamine, occupied 76.8 +/- 4.2% of the averaged values of available histamine H1 receptors in the frontal cortex after its administration in a single oral dose of 2 mg. Epinastine, a non-sedative antihistamine, occupied 13.2 +/- 18.5% of the available H1 receptors in the human frontal cortex after its administration in a single oral dose of 20 mg. There was significant correlation between H1 receptor occupancy by epinastine and its plasma concentration in each subject. PET data on the human brain were essentially compatible with those on H1-receptor occupancy in the guinea pig brain as determined by an in vivo binding technique, although for the same H1-receptor occupancy, the dose was less in humans than in guinea pigs. Our PET studies demonstrated that receptor occupancy by a second-generation H1 antagonist, epinastine, was less than 20% of the total H1 receptors, and that the low receptor occupancy was closely related to the low incidence of central side effects.

Adult↗

PubMedDate not supplied

[Antihistaminics].

The antihistamines are drugs who compete for the histamine receptor H-1, blocking the liberation of autacoid mediators, that is the reason for their action in allergic diseases. It's important to know the pharmacodynamics and pharmacokinetics of these drugs in order to choose the best one for the patient, looking for the ones who have less side effects and work better. We show a summary of the principal antihistamines, their actions and side effects.

Eicosanoids↗

PubMed1978

Studies on antihistaminic action. II: In vitro and in vivo effect of chlorpheniramine and its analogs on the uptake and retention of 5-hydroxytryptamine by rabbit blood platelets.

We have previously shown that the antihistaminic drug, chlorpheniramine maleate (CTM) increased blood histamine levels more rapidly than it did the blood 5-hydroxytryptamine (5-HT) levels in the rabbit (Sankar, Li and Santare, 1974). The present studies show that, while the in vitro addition of CTM to isolated rabbit blood platelets inhibited the platelet uptake of labeled 5-HT-14C, its administration to rabbits increased such in vitro uptake by platelets isolated from recipient animals. This is possibly due to the enhancement of release (depletion) of 5-HT from platelets in vivo. Such depleted platelets, will take up larger amounts of 5-HT on in vitro incubation. Our studies also show increased levels of blood 5-HT within minutes after administration of CTM to rabbits, further indicating that CTM deplets the platelets of their 5-HT on in vivo administration. Our present studies show that D-CTM is more active than brompheniramine in this system, while the fluorine derivative is least active. It is postulated that the antecedent release of histamine and 5-HT from tissues by antihistamines, renders further anaphylactic challenge or hypersensitivity episode less severe.

Animals↗

PubMed1996

Antiasthma activity of the novel antihistamine E-4716 in guinea pigs in vivo.

The effects of E-4716, a novel antihistamine compound, on histamine-induced bronchoconstriction, platelet activating factor (PAF)- or antigen-induced airway hyperreactivity, eosinophil infiltration, and airway microvascular leakage were compared with those of reference drugs in guinea pigs in vivo. E-4716 (300 microg/kg, i.v. or i.p.) suppressed histamine-induced bronchoconstriction in nonsensitized anesthetized guinea pigs and effectively inhibited acetylcholine-induced bronchial hyperreactivity in nonsensitized animals 24 h after PAF aerosol exposure. E-4716 also attenuated antigen-induced acute respiratory distress and suppressed histamine-induced airways hyperreactivity in conscious sensitized animals 24 h after antigen exposure, but did not affect the increased number of eosinophils in the bronchoalveolar lavage fluid. E-4716 300 microg/kg, i.v. or 1 mg/ml by inhalation (60 breaths) inhibited both PAF- and antigen-induced airway microvascular leakage. This in vivo profile of activity, comprising antihistamine, antihyperreactivity and antiexudative effects, suggests that E-4716 is of potential therapeutic value as an antiasthma and/or antiallergic drug.

Analysis of Variance↗

PubMed1996

5-Lipoxygenase inhibitory and antihistamine activities of linetastine.

The ability of linetastine (TMK688, 1-[¿5'-(3"-methoxy-4"-ethoxycarbonyloxyphenyl)-2',4'-pentadieno yl¿ aminoethyl]-4-diphenylmethoxypiperidine, CAS 110501-66-1) to inhibit leukotriene production and to antagonize the effect of histamine was examined in comparison with the ability of azelastine, an antiallergic drug having an antihistamine activity. Linetastine and its active metabolite TMK777 (1-[¿5'-(3"-methoxy-4"-hydroxyphenyl)-2',4'-pentadienoyl¿ aminoethyl]-4-diphenylmethoxypiperidine, CAS 101619-11-8) inhibited the release of leukotrienes B4 and C4 from calcium ionophore-stimulated human leukocytes. The respective IC50 values of leukotriene B4 were 1.2 x 10(-7) mol/l and 8.6 x 10(-8) mol/l, and those of leukotriene C4 were 1.5 x 10(-7) mol/l and 7.1 x 10(-8) mol/l. Azelastine also inhibited the release of leukotriene B4 and C4, but its IC50 values were higher than 1 x 10(-5) mol/l. Linetastine at 1-10 mg/kg p.o. inhibited the increase in leukotriene B4 and C4 production in the lungs during late asthmatic responses in actively sensitized guinea-pigs. The effect of 3.2 mg/kg lasted for more than 16 b. Since repeated oral administration of linetastine, 1 mg/kg once a day for 7 successive days, showed the same inhibitory effect on the increase in respiratory resistance and the leukotriene production as single oral administration, the effect of linetastine was neither tachyphylactic nor cumulative. Azelastine at 10 mg/kg had no effect on the leukotriene production. Linetastine TMK777 and azelastine dose-dependently inhibited the histamine-induced contraction of isolated guinea-pig trachea in a noncompetitive manner, the respective pD2 values were 7.28, 7.98 and 8.07. Linetastine inhibited histamine-induced bronchoconstriction dose-dependently at 1-10 mg/kg (p.o.) in guinea-pigs, and the effect lasted for more than 24 h. Repeated oral administration of linetastine, 0.32 to 3.2 mg/kg once a day for 7 successive days inhibited the histamine-induced bronchoconstriction, the same as single oral dosing. Azelastine at 0.32 mg/kg p.o. also showed antihistamine activity. In conclusion, linetastine inhibits both the production of leukotrienes and the effect of histamine at almost the same dose and the effects were long lasting.

Animals↗