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Application of a mathematical topological pattern of antihistaminic activity for the selection of new drug candidates and pharmacology assays.

Molecular topology was used to achieve a mathematical model capable of classifying compounds according to their antihistaminic activity and low sedative effects. By application of this model of activity to databases containing chemical reagents and drugs exhibiting other pharmacological activity, we selected 30 compounds with possible antihistaminic activity. After those with possible sedative effects were discarded, activity tests were performed with five chemical reagents and three drugs searching for in vivo antihistaminic activity. The obtained results indicate that compounds such as 4-[(E)-2-(1,3-benzothiazol-2-yl)vinyl]-N,N-dimethylaniline (AH2), 2-ethyl-9,10-dimethoxyanthracene (AH4), and 2,4-bis(alpha,alpha-dimethylbenzyl)phenol (AH5) showed antihistaminic activity above terfenadine, the reference drug, whereas others, for instance, pergolide, miconazole, trihexyphenidyl, 2-(dibenzylamino-3-phenyl-1-propanol (AH1), and N-benzylquininium chloride (AH3), were less active than terfenadine.

Aniline Compounds↗

A comparison of the clinical efficacy and safety of intranasal fluticasone propionate and antihistamines in the treatment of rhinitis.

Adequate management of allergic rhinitis is needed to avoid its considerable adverse social, clinical, and economic impact. Both topical intranasal steroids and oral or topical antihistamines are recognised as effective treatments for this condition. In comparative studies, however, intranasal steroids and, in particular, fluticasone propionate aqueous nasal spray (FPANS), have afforded consistently better symptomatic relief, and have a greater beneficial effect on quality of life. Furthermore, the addition of an antihistamine to FPANS therapy has generally produced little further benefit. Intranasal administration is associated with a low systemic absorption of fluticasone propionate and, following regular use of FPANS, placebo, or an oral antihistamine, no significant differences were seen between treatment groups in plasma or urinary cortisol. Overall, therefore, the data indicate that FPANS is superior to second-generation antihistamines in the management of allergic rhinitis.

Administration, Intranasal↗

H1-antihistaminic activity of cetirizine and fexofenadine in allergic children.

The clinical pharmacology of H1-antihistamines has not yet been optimally studied in children and other special groups of patients. Our objective was to determine the onset, extent, and duration of H1-antihistaminic activity of cetirizine and fexofenadine in the pediatric population. We performed a prospective, randomized, placebo-controlled, double-blind, crossover, single-dose study of these H1-antihistamines in 15 allergic children, mean+/-SEM age 8.8+/-0.5 years. We used suppression of the histamine-induced wheal and flare as the primary outcome. Compared with pre-dose baseline, cetirizine 10 mg suppressed the wheals significantly (p<or=0.05) from 2 to 24 h and the flares significantly from 1 to 24 h, achieving 77+/-SEM 10% to 86+/-9% suppression of the wheal from 2 to 7 h and 85+/-6% to 88+/-6% suppression of the flare from 2 to 24 h, inclusive. Compared with baseline, fexofenadine 30 mg did not suppress the wheals or flares significantly at any time, achieving 40+/-9% to 54+/-9% wheal suppression from 2 to 7 h and 45+/-11% to 68+/-9% flare suppression from 2 to 7 h, inclusive. Compared with placebo, cetirizine suppressed the wheals and flares significantly from 2 to 24 h. Compared with placebo, fexofenadine suppressed the wheals significantly at 4 and 6 h, and the flares from 4 to 7 h. Cetirizine suppressed the wheals and flares significantly more than fexofenadine at 2 h (wheals), and at 3 and 24 h (flares). Placebo did not suppress the wheals and flares significantly at any time. In children age 6-11 years, cetirizine 10 mg has a rapid onset of H1-antihistaminic activity, a 24-h duration of action, and greater H1-activity than fexofenadine 30 mg. Higher doses of fexofenadine should be tested in children.

Anti-Allergic Agents↗

Chromatographic analysis of phenethylamine-antihistamine combinations using C8, C18 or cyano columns and micellar sodium dodecyl sulfate-pentanol mixtures.

The chromatographic behaviour of binary and ternary mixtures of several phenethylamines (phenylephrine, phenylpropanolamine, ephedrine, pseudoephedrine and methoxyphenamine) and antihistamines (pheniramine, carbinoxamine, doxylamine, chlorpheniramine, dexchlorpheniramine, dexbrompheniramine, diphenhydramine, tripolidine, azatadine and phenyltoloxamine), found in cough-cold pharmaceutical preparations, was studied using C8, C18 and cyano columns, micellar mobile phases of sodium dodecyl sulfate (SDS) and pentanol and UV detection. Using a C8 column and mobile phases of 0.05 mol l-1 SDS-6% v/v pentanol or 0.15 mol l-1 SDS-2% v/v pentanol at pH 7, more than 30 different phenethylamine-antihistamine combinations can be resolved in < 15 min. Intra- and inter-day repeatabilities and reproducibilities evaluated at three different drug concentrations (0.5, 5 and 25 micrograms ml-1, n = 10) were below 1.6, 2.5 and 2.4%, respectively. The drug amounts found in 18 formulations agreed with those declared by the manufacturers within the tolerance limits, and with those obtained using a mobile phase of 55% v/v methanol at pH 7. No interference was observed from other accompanying drugs such as acetylsalicylic acid, ascorbic acid, betamethasone, bromhexine, caffeine, codeine, dextromethorphan, paracetamol, prednisolone, salicylamide and tartrazine. The proposed procedure has the advantage over the conventional aqueous-organic procedure of using a small amount of organic solvent, which is highly retained in the SDS solution. The efficiencies are also greater. On the other hand, in the micellar system, the retentions of phenethylamines and antihistamines are similar, although the compounds can be easily resolved. In contrast, using the methanol-water mobile phase, the phenethylamines are weakly retained, whereas the antihistamines usually show a high retention.

Chromatography↗

Standard treatment: the role of antihistamines.

Histamine-1 (H1) antihistamines are the first-line drug for the treatment of urticaria. Major progress has been achieved in recent years both in the understanding of their ligands, the H1-histamine receptors, and therefore in the mechanisms of their pharmacologic effects, as well as in the development of safer antihistamines with low or no sedating effects and no interactions on the level of potassium channels leading to QT-prolongations and interactions on the level of cytochrome P450 isoenzymes. This development has brought antihistamines very close to the ideal antihistamines that are desired by clinicians to treat most types of urticaria in patients who have to take these drugs for a long time.

Cyclizine↗

Antihistamines in severe/chronic rhinitis.

Oral antihistamines generally represent the first line of treatment (after allergen avoidance) in mild seasonal allergic rhinitis (SAR), and in perennial allergic rhinitis (PAR) where symptoms are intermittent. They are safe, effective and easily administered. First-generation antihistamines experienced problems mainly with sedation and anticholinergic activity. Second-generation antihistamines are safer and have largely eliminated these effects, although a very small number of patients taking terfenadine or astemizole have developed a characteristic ventricular dysrhythmia, 'torsade de pointes'. Ebastine is a potent second-generation H1-blocker that compares well with others in the class. It demonstrates no interaction with alcohol, does not induce sedation and has no clinically relevant effect on QTc interval at up to five times the maximum recommended dose. Ebastine acts rapidly to relieve symptoms of allergic rhinitis (including stuffiness) and has a long duration of action, allowing once-daily dosing. Whilst comparable in efficacy to other second-generation antihistamines at 10 mg, ebastine also has the advantage of flexible dosing. Thus, the lower dose of 10 mg is effective for treatment of mild SAR or PAR, and the dose can be increased to 20 mg once daily for control of patients with severe or chronic symptoms.

Butyrophenones↗

Preclinical pharmacology of desloratadine, a selective and nonsedating histamine H1 receptor antagonist. 1st communication: receptor selectivity, antihistaminic activity, and antiallergenic effects.

Desloratadine (descarboethoxyloratadine, CAS 100643-71-8) is an active metabolite of loratadine (CAS 79794-75-5) that exhibits qualitatively similar pharmacodynamic activity with a relative oral potency in animals 2.5-4 times greater than loratadine. Its antihistaminic effect lasts 24 h. Desloratadine was shown to be a selective H1 antagonist with more potent antihistaminic activity in vitro than either loratadine or terfenadine (CAS 50679-08-8), as indicated by its displacement of 3H-mepyramine from H1 receptors in rat brain, guinea pig brain, and guinea pig lung, and by its antagonism of histamine-induced contractions of guinea pig ileum. Antihistaminic activity and anitallergic effects also were observed in vivo. After oral administration, desloratadine was 2.5 to 4 times more potent than loratadine in protecting against histamine-induced lethality in the guinea pig and paw edema in the mouse; after topical administration, it was almost 10 times more potent in antagonizing histamine-induced increases in nasal microvascular permeability in the guinea pig. Histamine-induced changes in pulmonary resistance and compliance were also prevented by oral administration of desloratadine and loratadine in the monkey. An oral antiallergic effect was demonstrated by important reductions of acute bronchospasm in the allergic monkey and potent inhibition of allergic cough in the guinea pig. These preclinical studies provide evidence that desloratadine is an antihistaminic agent with a greater potency than loratadine and, together with results from numerous published studies, suggest an antiallergic effect of desloratadine.

Animals↗

A randomized, placebo-controlled trial of the effect of antihistamine or corticosteroid treatment in acute otitis media.

OBJECTIVES: To determine whether the adjunctive drugs antihistamine and corticosteroid improve immediate and long-term outcomes of acute otitis media (AOM). STUDY DESIGN: Children with AOM (3 mos-6 y) were enrolled in a randomized, double-blind, placebo-controlled trial. All 179 children received one dose of intramuscular ceftriaxone and were assigned to receive either chlorpheniramine maleate (0.35 mg/kg/d) and/or prednisolone (2 mg/kg/day) or placebo for 5 days. Main outcome measures were rate of treatment failure during the first 2 weeks, duration of middle ear effusion, and rate of recurrences of AOM to 6 months. RESULTS: Clinical outcomes and recurrence rates did not differ significantly with treatment. Children who received antihistamine alone had significantly longer duration of middle ear effusion (median, 73 days) than subjects in other treatment groups (median, 23 to 36 days, P=.04). Temporary normalization of tympanometric findings on day 5 occurred more frequently in the corticosteroid-treated group (P=.04). CONCLUSIONS: Five-day treatment with antihistamine or corticosteroid, in addition to antibiotic, did not improve AOM outcomes. Antihistamine use during an acute episode of OM should be avoided, since the drug may prolong the duration of middle ear effusion. The efficacy of 7- to 10-day treatment of AOM with corticosteroid, in addition to antibiotic, deserves further investigation.

Acute Disease↗

Continuous infusion interleukin-2 and antihistamines in metastatic kidney cancer.

A prior randomized trial suggested a possible survival advantage favoring the combination of histamine and subcutaneous interleukin-2 (IL-2), compared to IL-2 alone in patients with metastatic melanoma. It has been postulated previously that antihistamines may, therefore, actually be antagonistic to IL-2 and thus interfere with its antitumor activity. We have previously shown no such antagonistic effect in patients with melanoma receiving IL-2 and antihistamines when reviewing the known literature. We sought to determine whether there was any negative effect of the combination in patients with metastatic kidney cancer. A PubMed literature search between 1985 and 2005 was done. High-dose continuous (or constant) infusion (CIV) interleukin-2 was used as the reference therapy because of the relatively constant IL-2 levels generated by this approach. Studies in which cimetidine, ranitidine, or famotidine were regularly scheduled and administered concurrently with IL-2 were included. Thirteen studies were identified. A total of 47 patients responded to therapy. Total response rate = 22%; 95%; Confidence Interval: 17%-28%. Eleven complete responses were noted. Complete response rate = 5%; 95% Confidence Interval: 3%-9%. These response rates are consistent with previously noted IL-2 response rates. In this study of CIV IL-2 and antihistamines, this combination appears to be active in metastatic kidney cancer. There appears to be no negative effect of antihistamine on the CIV IL-2 response rate in this disease.

Adjuvants, Immunologic↗

Enhanced cancer growth in mice administered daily human-equivalent doses of some H1-antihistamines: predictive in vitro correlates.

BACKGROUND: Present studies of drug-induced tumor growth promotion have evolved from earlier investigations into the mechanism of action of N,N-diethyl-2-[4-(phenylmethyl)phenoxy[ethanamine.HCl, a tamoxifen derivative which potently inhibits lymphocyte mitogenesis in vitro and stimulates tumor growth in vivo. It is thought that potency to bind to intracellular histamine receptors (HIC), some of which are on cytochromes P450, may correlate with tumor growth-promoting activity. PURPOSE: We assessed the effectiveness of five in vitro assays in predicting in vivo tumor growth stimulation by the H1-antihistamines loratadine, astemizole, cetirizine, hydroxyzine, and doxylamine. METHODS: Potency of each agent was ranked 1-5 in each of the following in vitro assays: 1) inhibition of [3H]histamine binding to microsomal HIC, 2) inhibition of histamine binding to microsomal P450, 3) inhibition of the P450-catalyzed demethylation of aminopyrine, 4) inhibition of lymphocyte mitogenesis, and 5) stimulation of tumor colony formation. An overall rank score was assigned to each drug and correlated with tumor growth stimulation in vivo. Two laboratories conducted in vivo studies in a blinded fashion. Female C57BL and C3H mice were given a subcutaneous injection on day 1 of syngeneic B16F10 melanoma cells (5 x 10(5)) or C-3 fibrosarcoma cells (1 x 10(5)), respectively. Mice were randomly assigned to treatment groups, then received a single, daily intraperitoneal injection of an estimated human-equivalent dose (or range of doses) of antihistamine or vehicle control for 18-21 days before being killed. Tumors were surgically removed and wet weights compared statistically among groups. RESULTS: The cumulative potency of each drug in affecting tumor growth or growth mechanisms in the five in vitro assays ranked as follows: Loratidine and astemizole ranked highest and were equally potent, followed in decreasing order by hydroxyzine, doxylamine, and cetirizine. A significant correlation (r = .97; P < .02) was observed between the rank order of potency of the antihistamines in all five in vitro assays and the rank order to enhance tumor growth in vivo: Loratidine and astemizole significantly (P < .001) promoted the growth of both melanoma and fibrosarcoma, hydroxyzine significantly (P < .001) promoted the growth of melanoma, while doxylamine and cetirizine did not promote the growth of either tumor. CONCLUSION: Data demonstrate that the in vitro assays predicted the propensity of each H1-antihistamine to stimulate cancer growth in vivo. IMPLICATION: These in vitro tests may prove valuable to screen potential tumor growth promoters.

Animals↗

Efficacy and central nervous system impairment of newer-generation prescription antihistamines in seasonal allergic rhinitis.

Allergic rhinitis is a highly prevalent disorder and oral antihistamines are often used to manage patient symptoms. Older-generation antihistamines, such as diphenhydramine and chlorpheniramine, are effective at relieving the symptoms of seasonal allergic rhinitis (SAR); however, they are associated with adverse events, including sedation and impairment, at, or above, the recommended dose. Newer-generation antihistamines, such as desloratadine, cetirizine and fexofenadine, were developed to minimize adverse events. In this article, studies examining newer-generation antihistamines in adults and children were reviewed. The clinical evidence confirms that desloratadine, cetirizine and fexofenadine are effective at managing the symptoms of SAR in adults and children; however, cetirizine is more likely to cause sedation. Physician intervention is paramount to SAR symptom management. It is essential that appropriate treatment relieves SAR symptoms with absent or minimal adverse events. This is particularly important for those patients involved in skilled and cognitive activities or safety-critical jobs.

Central Nervous System↗

Single and repeated dose comparison of three antihistamines and phenylpropanolamine: psychomotor performance and subjective appraisals of sleep.

1 In a double-blind cross-over study, nine healthy male students received placebo, brompheniramine 12 mg), carbinoxamine (12 mg), clemastine (1 mg), and phenylpropanolamine (50 mg) orally. Three doses of each drug were given: at 08.30 h and 21.00 h on the first day of treatment and at 08.30 h on the following day. 2 Psychomotor skills and subjective feelings were recorded before and 2, 6 and 12 h after the first dose on day 1 as well as before and 2 and 6 h after the third dose on day 2. Subjective appraisals of sleep were requested on the morning of day 2. 3 All antihistamines tended to cause subjective drowsiness on the first day of treatment. Drowsiness was felt for a maximum of 2 h after carbinoxamine, 6 h after brompheniramine, and 12 h after clemastine. In contrast to antihistamines, phenylpropanolamine made subjects more alert and quick witted. Tolerance to the antihistamine-induced drowsiness developed on the second day. 4 Divided attention, tracking, speed anticipation and sleep were not affected by any drug. Carbinoxamine slowed reactions 2 h after the first dose, but no impairment was measured in objective tests after brompheniramine or clemastine. 5 Phenylpropanolamine improved reaction speed and reaction accuracy and enhanced flicker recognition throughout the study. Phenylpropanolamine plasma levels and improvement in flicker fusion test results correlated with each other on day 2. 6 The results suggest that phenylpropanolamine and the antihistamines studied are comparatively harmless to psychomotor performance and driving skills.

Adult↗

A gap in surface therapy: topical antihistamines.

Allergic and non-allergic rhinitis have been treated by many drugs with different modes of action such as topical disodium cromoglycate and ipratropium bromide, systemic antihistamines and corticosteroid drugs and topical corticosteroids. Yet, these therapies are not entirely satisfactory for all symptoms. The rationale for the topical, intranasal use of antihistamines in patients is discussed. Topical antihistamine agents are administered in order to avoid the side effects of systematically applied medications, and to reach higher local drug concentrations. H1 receptors of the nasal mucosa play an important role in the physiopathology of allergic and non-allergic rhinitis and even of infectious rhinitis. Most studies using topical antihistamines in rhinitis, had an experimental physiopathological aim and did not explore clinical efficacy. Recently, topical application of levocabastine--a potent H1 antagonist--yielded good clinical results in allergic conjunctivitis, seasonal allergic rhinoconjunctivitis, and non allergic perennial rhinitis.

Administration, Topical↗

Oral antihistamines for the symptom of nasal obstruction in persistent allergic rhinitis--a systematic review of randomized controlled trials.

BACKGROUND: Oral antihistamines are recommended by a World Health Organisation working group as a first-line pharmacological treatment in mild persistent allergic rhinitis. There is, however, uncertainty with respect to their effectiveness for a common symptom, that of nasal obstruction. OBJECTIVE: To test the null hypothesis that oral antihistamines have no effect on the symptom of nasal obstruction in a clinical setting in patients with persistent allergic rhinitis. METHODS: Protocol based review of double-blind randomized controlled trials of oral antihistamine (i.e. drugs considered to act as a histamine receptor type-1 antagonist) vs. placebo. A search was carried out for published and unpublished trials. Individuals had to be age 12 years or older (with a diagnosis confirmed by skin prick tests, IgE blood tests or nasal allergen challenge), experiencing their normal allergen exposure. A symptom score for nasal obstruction had to be recorded. Predetermined quality criteria were applied. Treating their data as 4-point scores, a meta-analysis was carried out for studies, which provided enough data to be pooled. RESULTS: Meta-analysis found a weighted mean difference of -0.52 in favour of treatment for patient-assessed symptom scores (95% confidence interval (CI)-0.73,-0.31, P<0.00001), and of -0.33 in favour of treatment for healthcare worker assessed scores (95% CI -0.49, -0.16, P = 0.0001). CONCLUSION: Oral antihistamines cause statistically significant improvement in the symptom of nasal obstruction in patients with persistent allergic rhinitis.

Administration, Oral↗

Sedation in allergic rhinitis is caused by the condition and not by antihistamine treatment.

Sedation is regarded as a common side-effect of most H1-antihistamines. This view must be accepted, yet can hardly be assessed under treatment of allergic disorders. Since central sedative potency is hard to evaluate, different methods of measurement have been introduced in the four phases of clinical investigation. While tests of high complexity in early trials can detect true central effects, they seem to have the disadvantage of not taking into consideration the important interactions of drugs with the disorder. Therefore, we used a visual analog scale (VAS) as an instrument to demonstrate sedative effects in five clinical studies carried out between 1989 and 1994 with a total number of 1070 patients. Thereby, we could assess the result of the different components of the central interaction. In 1989, in a double-blind, placebo-controlled trial, we could show that the vigilance of patients suffering from seasonal allergic rhinitis increased significantly more under treatment with an antihistamine (mizolastine) than under placebo. From 1992 until 1994, we compared azelastine nasal spray either by the double-dummy technique with oral antihistamines (cetirizine, loratadine, and astemizole) or by the double-dummy or placebo-controlled design with monotherapy or combined therapy with azelastine tablets. A marked or statistically significant improvement of vigilance was found for all compounds (loratadine: P < 0.0001; cetirizine: P < 0.0254; and azelastine nasal spray: P < 0.1409 to P < 0.0001). Even when taking azelastine as oral application, patients, in spite of the warning, reported a similar increase in vigilance (P < 0.2628 to P < 0.0001). Finally, we assessed the range of physiologic vigilance using the same VAS in healthy volunteers. In conclusion, we could prove that in all trials the baseline values of vigilance of untreated symptomatic patients were far below physiologic condition and improved under treatment to the upper range of healthy persons. Therefore, any sedative properties of modern H1-antihistamines should not limit their therapeutic use, since the truly threatening sedation results from the disorder itself.

Arousal↗

Additive benefits of EFAs in dogs with atopic dermatitis after partial response to antihistamine therapy.

It has been reported that 20 to 70 per cent of atopic cases in the dog can be controlled with antihistamines, though the effective antihistamine cannot be predetermined. Combination therapy with essential fatty acids (EFAs) and antihistamines has been shown to be useful in dogs. All of the work published to date has been performed in open studies, without the use of placebo, and in dogs where the aim has been to control pruritus as a symptom rather than that caused specifically by atopy. The aim of this study was to assess the combined effects of four antihistamines; hydroxyzine, chlorpheniramine, cyproheptadine and clemastine; with both an EFA supplement and a placebo of olive oil, in 25 dogs to control pruritus in clinically proven cses of atopy.

Animals↗

Antihistamines.

Antihistamines and their drug-drug interactions are reviewed in depth. The metabolism of "classic" or sedating antihistamines is coming to light through in vivo and in vitro studies. The polymorphic CYP 2D6 metabolic enzyme appears to be potently inhibited by many of these over-the-counter medications. The history of the discontinued "second-generation" antihistamines terfenadine and astemizole is reviewed to remind the reader why the understanding of the cytochrome P450 system became increasingly important when the cardiotoxicity of these drugs became apparent. The "third-generation" nonsedating antihistamines are also listed and compared. They have been exhaustively scrutinized for drug-drug interactions and cardiotoxicity, and they appear to have no serious drug-drug interactions at recommended doses.

Astemizole↗

Effect of decongestant with or without antihistamine on eustachian tube function.

In an attempt to determine the effect of a decongestant with or without an antihistamine on the ventilatory function of the eustachian tube (ET), two separate studies were conducted in 50 children who had had chronic or recurrent otitis media with effusion (OME) and in whom tympanostomy tubes had been inserted previously. The first was a double-blind study that compared the effect of an oral decongestant, pseudoephedrine hydrochloride, with that of a placebo in 22 children who developed an upper respiratory infection (URI) during an observation period. Certain measures of ET function were significantly elevated above baseline values during the URI, which was attributed to intrinsic mechanical obstruction of the ET. It was found that the oral decongestants tended to alter these parameters of ET function in the direction of the baseline (preURI) values. Even though the effect was statistically significant, the favorable changes in measurements of tubal function were only partial and were more prominent on the second day of the trial after the subjects had received four doses of the decongestant. However, the administration of nasal spray of 1% ephedrine appeared to have no apparent effect on ET function in these children. The second study was a double-blind crossover design. In this study of 28 children who did not have a URI, the effect of a decongestant-antihistamine combination (pseudoephedrine hydrochloride and chlorpheniramine maleate) was compared with that of a placebo. When the subjects were given the decongestant-antihistamine medication, there were favorable changes in certain ET function measures which were not observed when they received the placebo. Again, the response differences between the two groups were statistically significant. Even though these two studies indicated that an oral decongestant appeared to affect favorably the ET function of children who had a URI, and that the combination of an oral decongestant and antihistamine had a similar effect on tubal function in children without a URI, an evaluation of the efficacy of these commonly employed medications must await the results of controlled clinical trials in children with OME.

Adolescent↗