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PubMedDate not supplied

Chronic urticaria: clinical aspects and focus on a new antihistamine, levocetirizine.

Chronic urticaria (CU) involves release of histamine from mast cells and/or basophils, which in turn promotes the classic inflammatory cascade. The resultant symptoms can severely impact sufferers' quality of life and in severe cases prevent them from leading a normal existence, with consequent burdens on family and society. Rapid initiation of effective reliable therapy is important in combating CU, together with avoidance of triggers or exacerbating factors, if known. While newer immunologically-based therapies are beginning to be developed, antihistamines remain a cornerstone of effective therapy. Treatment should be tailored to individual patient circumstances, but in principle the choice of antihistamine component should be governed by the availability of evidence of rapid and prolonged efficacy specifically in CU and evidence of good tolerability and safety. Increasingly, evidence of beneficial effects on patient quality of life is also required for rational selection of an antihistamine from amongst those available. Levocetirizine is a new single-isomer antihistamine with a proven efficacy on chronic urticaria as documented in two recent clinical studies, which have included effectiveness and quality of life assessments.

Cetirizine↗
PubMedDate not supplied

Antihistamines: treatment selection criteria for pediatric seasonal allergic rhinitis.

Given the absolute numbers of children suffering from seasonal allergic rhinitis (SAR) and the fact that this number is rising, there is an unquestionable need for safe and effective treatments for the disease. The limited seriousness of the symptoms of SAR belies their true impact: the disease can have a profound effect on children's quality of life and impair learning performance. Furthermore, SAR has been linked to a number of comorbid conditions and forms part of the "allergic march" to more serious diseases such as asthma. Antihistamines are administered to relieve the symptoms of SAR, but they do not represent a homogeneous group. For example, older-generation antihistamines are associated with side effects such as impaired psychomotor performance. Newer-generation antihistamines must be evaluated individually based on their proven efficacy and safety so as to tailor treatment to each child's needs. Effective and safe treatment of SAR, with an antihistamine that does not cause sedation, should improve children's quality of life and could prevent the development of more serious conditions, thus reducing morbidity and possible future health care expenditure.

Child↗
PubMedDate not supplied

Cetirizine: a unique second-generation antihistamine for treatment of rhinitis and chronic urticaria.

The recent development of selective H1-antagonists that minimally cross the blood-brain barrier has greatly improved the management of allergic rhinitis and chronic urticaria. These new agents have much reduced anticholinergic and sedative side effects, which were the major drawbacks of the classic H1-antihistamines. Cetirizine, a new second-generation H1-antagonist, offers several properties that may further improve the treatment of allergic rhinitis and chronic urticaria. Cetirizine is the only antihistamine known to possess activity against both the histamine-mediated early phase of the allergic response and the late-phase response of immediate hypersensitivity characterized by migration of inflammatory cells to the site of the reaction. Its efficacy has been demonstrated in clinical trials of patients with seasonal rhinitis and urticaria. The most common side effects associated with cetirizine, such as sedation, are similar to those of other second-generation antihistamines. These properties, combined with a once-daily dosage regimen, should help improve patient compliance and optimize antihistamine therapy.

Cetirizine↗
PubMed1989

In vivo and in vitro effects of antihistamines on mast cell mediator release: a potentially important property in the treatment of allergic disease.

A nasal antigen challenge model of allergic individuals was used to evaluate whether antihistamines could inhibit human mast cell and basophil mediator release in vivo. In placebo-controlled trials, topically applied azatadine base, a tricyclic antihistamine with in vitro antirelease action, effectively reduced symptoms and mediator levels in nasal lavage fluids after antigen challenge, suggesting mast cell inhibition. Both terfenadine and cetirizine, systemically administered antihistamines, were clinically effective in reducing sneezing and changes in vascular permeability. Only terfenadine significantly reduced histamine in antigen-induced nasal secretions. However, cetirizine did reduce the level of leukotriene C4 in these fluids. These results indicate that some antihistamines may be capable of suppressing mediator release from nasal mast cells. The significance of this property in those compounds' overall clinical effect is unclear because of their other concomitant activities.

Administration, Intranasal↗
PubMed1987

Combined antihistamine antagonism of the flushing reaction to alcohol.

The so-called Oriental flushing reaction associated with ingestion of small amounts of alcohol was antagonized by combined antihistamine administration. In stage one of the study, the flushing reaction to low doses of alcohol was produced in Orientals. Most subjects experienced a cutaneous flush, increase in skin temperature, decrease in blood pressure, increase in pulse rate and subjective symptoms such as dizziness, sleepiness, anxiety, headache, generalized weakness and nausea. One half of the group of subjects was then given diphenhydramine, 50 mg (H1 receptor antagonist) and cimetidine, 300 mg (H2 receptor antagonist) and the second half received placebo tablets before the administration of alcohol. The clearest difference between the antihistamine group and placebo group was in the skin flushing reaction. The antihistamine group showed a statistically significant reduction in the skin flush. The antihistamines also neutralized the systolic hypotension induced by the administration of alcohol.

Adult↗
PubMed1988

The relative safety and effectiveness of antihistamines.

More than sixty antihistamines are available for the treatment of dermatologic allergies. An appreciation of important differences between these agents is vital to the selection of a therapeutic regimen tailored to a patient's special needs. Duration of action varies among the agents. Data suggest that less frequent dosing schedules may be equally effective, while reducing adverse effects. The degree of sedation, a commonly-reported side effect, varies widely with different antihistamines. Data indicate that the pharmacokinetics of the available antihistamines differ in Orientals and Caucasians as well as in patients of different ages. Further research into possible genetic factors affecting the metabolism of these drugs is needed. In addition, to ensure the best possible quality of care, physicians should become thoroughly familiar with the biology and chemistry of the many antihistamines.

Drug Therapy, Combination↗
PubMed1988

[Allergy to topical antihistamines--discrepancy between the literature and clinical practice].

In a prospective study, 100 patients suffering from allergic contact dermatitis were tested for allergy to antihistamines. Diphenhydramine was chosen as test substance because it is the most widely used topical antihistamine in Europe and is, moreover, prescribed for several indications. Not one of the 100 patients proved to react positively on patch testing. The bad reputation among allergists of topically administered antihistamines, which is based on reports in the American literature claiming a high risk of epicutaneous sensitization, thus appears unjustified on the basis of our own data and the lack of European reports of this problem. The adverse findings in the USA may be due to their frequent use of a particularly potent contact sensitizer as emulsifier in topical preparations in general and antihistamines in particular.

Adolescent↗
PubMed1988

[Adverse effects of antihistaminics].

Of most antihistamines more or less pronounced sedative effects are known. In recently developed substances this effect is said to be less or absent. After some days of application the sedative effect may decrease, but it can be enhanced by simultaneous intake of psychotropic drugs, sedatives or alcohol. There are important interindividual differences. The Drug Commission of the German Medical Profession (AKdA) received reports concerning tiredness, somnolence (even with new antihistamines), CNS-stimulation, nervousness, insomnia and paroniria have also been observed. Furthermore cases of dyskinesia have been reported, which are already described in the literature after long term intake, as well as anticholinergic reactions. Despite of their use as antiallergic drugs, reports on hypersensitivity reactions due to antihistamines, up to anaphylactic reaction have been not infrequently received by the AKdA. In rare cases disturbances of blood cell formation have been reported besides observations of gastrointestinal disorders, increase of appetite and weight. Abuse of antihistamine containing drugs was reported mainly for combinations with psychotropic agents.

Histamine Antagonists↗
PubMed1986

Are antihistamine-decongestants of value in the treatment of acute otitis media in children?

Acute otitis media is the most common bacterial infection of childhood. The effectiveness of oral antihistamine-decongestant mixtures in the treatment of this illness remains controversial in clinical practice. In a double-blind randomized study, 82 children (aged under 15 years) with acute otitis media were treated with amoxicillin and either a decongestant-antihistamine mixture (Dimetapp) or placebo. All diagnoses required agreement between a family practice resident and the supervising family physician. Clinical course was assessed by symptom diaries completed by parents and by follow-up examination at approximately two weeks, which included pneumatic otoscopy. No statistically significant benefit of the antihistamine-decongestant mixture was shown in terms of resolution of the symptoms or prevention of the complications of acute otitis media. It is recommended that antihistamine-decongestants not be routinely added to an antibiotic in the treatment of acute otitis media in children.

Adolescent↗
PubMed1975

The effects of the H1 and H2 antihistamines on "allergic" histamine release and its inhibition by histamine.

Antigen-induced, IgE-mediated release of histamine from human basophiles is an in vitro model of allergic reacttions; it is blocked by extracellular histamine, presumably as a result of its ability to increase adenosine 3',5'-monophosphate (cyclic AMP) levels. The H1 antihistamines do not antagonize these effects of histamine but at approximately equal to 1 mM cause histamine release and at approximately equal to 0.1mM inhibit antigen-induced histamine release. The phenothiazine antihistamines are 10-30 fold more potent inhibitors than the rest; other tricyclic antidepressant drugs share this activity. The mechanism of this inhibition, which occurs in both the 1 degree and 2 degree stages of histamine release, is not known but it is not due to partial agonist activity since the anti-H1 drugs cause a significant fall in cyclic AMP levels. The anti-anaphylactic effects of the H1 antagonists probably play no therapeutic role but we suggest that drugs structurally similar to the phenothiazine antihistamines should be developed for clinical testing. The H2 antihistamines block histamine-induced inhibition of histamine release and the increase in cyclic AMP levels, but neither cause nor inhibit histamine release. The K-B values for the anti-H2 drugs (burimamide approximately equal to 5 muM); metiamide approximately equal to 0.5muM); are similar to those described for other H2 receptors.

Animals↗
PubMed1981

In vitro antagonism of benzodiazepine binding to cerebral receptors by H1 and H2 antihistamines.

Antihistamines directed at either the H1 or H2 histamine receptor have the well-known side effect of sedation. The mechanism for the CNS depressant action of antihistamines is unknown. We examine here the possibility that the mechanism may involve modulation of the cerebral benzodiazepine receptor. We demonstrate that cimetidine and pyrilamine are competitive antagonists of 3H-benzodiazepine binding to human cerebral receptor in vitro. The inhibition of radioligand binding was not specific for benzodiazepine receptor, however, since antihistamines also antagonized binding to GABA, opiate, and muscarinic acetylcholine receptor. The interaction of antihistamine with CNS receptors other than histamine receptor may explain, at least in part, the side effect of sedation.

Binding, Competitive↗
PubMed1982

A kinetic study of the antihistaminic effect of terfenadine.

Kinetics of the antihistaminic effect of alpha-[4-(1,1-dimethylethyl)phenyl]-4-(hydroxydiphenylmethyl)-1- piperidinebutanol (terfenadine, RMI 9918, Triludan, Teldane, resp.) were examined in the isolated guinea pig ileum and spirally cut tracheal strip preparations. In the isolated guinea pig ileum, terfenadine produced a parallel or competitive shift (3.16 X 10(-8) and 10(-7) mol/l) as well as a nonparallel or unsurmountable shift (3.16 X 10(-7) and 10(-6) mol/l) of the histamine dose response curves. Using the dose ratio test, it was concluded that terfenadine competes at the same receptors as chlorpheniramine, namely, the histamine H1-receptors. The antihistaminic effects of terfenadine, both the competitive and unsurmountable effects, were difficult to reverse by washout techniques whereas the nonspecific effects (against acetylcholine and barium chloride) could be readily washed out. The unsurmountable antagonism of histamine by terfenadine may result from a slow dissociation of terfenadine from the histamine H1-receptor. When terfenadine (2 mg/kg) or chlorpheniramine (2 mg/kg) was administered systemically, either orally or intraperitoneally, to guinea pigs and the antihistaminic effect assessed in vitro (isolated ileal strips and tracheal strips) terfenadine consistently produced a longer duration of action than chlorpheniramine. It is concluded that terfenadine is a potent, selective histamine H1-receptor antagonist; the kinetics of association/dissociation of terfenadine with histamine H1-receptors may account for the long-lasting antihistaminic effect in various animal models.

Animals↗
PubMedDate not supplied

[Non-sedative antihistaminics in the treatment of chronic urticaria].

Antihistamines are the drugs of choice in the symptomatic relief of chronic idiopathic urticaria; however, the usefulness of classic antihistamines has been limited by side effects. In the 1980s a new class of antihistamines has been developed that maintains effectiveness and produces less side effects (eg anticholinergic side effects, daytime sedation, etc). This review analyzes each of the new nonsedating antihistamines commercially available in Spain (astemizole, ebastine, cetirizine, loratadine and terfenadine) and evaluates its clinical efficacy and safety in the treatment of chronic idiopathic urticaria.

Chronic Disease↗
PubMed1995

Antihistamines: the old and the new.

Several pharmacologic agents provide antihistamine effects by acting at the H1 histamine receptor site. The classic agents are relatively nonselective, resulting in a wide range of effects, both therapeutic and undesirable. The newer agents preferentially block peripheral H1 receptor sites and, consequently, have fewer side effects, including sedation. Antihistamines are useful in the treatment of allergic conditions, Parkinson's disease, insomnia and some forms of nausea, and provide symptomatic relief of cough and other conditions associated with respiratory tract infections. Certain agents may play a role in the treatment of asthma and anorexia. Selection of a specific agent should be based on cost and the minimization of side effects. The classic antihistamines provide an inexpensive and highly effective means of treating histamine-mediated symptoms. The bothersome central nervous system side effects can be alleviated by taking the drugs at bedtime; their prolonged tissue half-life allows dosing once or twice a day for 24-hour clinical relief. The newer, more expensive nonsedating antihistamines are acceptable alternatives for patients who are incapable of tolerating the effects of classic agents.

Histamine Antagonists↗
PubMed1978

[Histamine-liberating effect of antihistaminics on the isolated rat mast cells].

Research Allergological Laboratory of the USSR Academy of Medical Sciences and Laboratory of Pharmacology, S. Ordzhonikidze Research Chemico-Pharmaceutical Institute, Moscow. Among the tested new antihistaminic drugs (quinuclidine derivatives) quinuclidyl-3-(O-tolyl) carbinol possessed histamine releasing action (HRA) on the isolated rat mast cells. In used concentrations (up to 0.4 mmol) all phenothiazines (promethazine, phenethazine, chlorpromazine, methylene blue) had HRA. There was no correlation between the HRA and the antihistaminic activity of the tested drugs. Histamine release induced by antihistaminic drugs and a steep dose-response curve, was produced at low temperature and was not inhibited under conditions of inhibition of energy-dependent stage of 48/80-induced histamine release. It was concluded that the tested antihistaminic drugs which had HRA were non-selective histamine releasers.

Animals↗
PubMed1994

Role of antihistamines in allergic disease.

Both first-generation and second-generation antihistamines effectively reduce symptoms of sneezing, rhinorrhea, and nasal pruritus in individuals with allergic disease. These agents act as competitive inhibitors of histamine (a principal mediator of the allergic response) at various target-organ sites. Although the classic, first-generation antihistamines are unable to halt the allergic reaction once it has begun, emerging evidence has suggested that newer, second-generation agents may interfere with the release of inflammatory mediators from mast cells or may inhibit eosinophil chemotaxis. These effects may confer additional clinical benefit. Also, the second-generation agents produce fewer adverse reactions, including a marked reduction in sedation. Contrary to previous recommendations, recent findings have suggested that antihistamines may not necessarily be contraindicated in patients who have both asthma and allergic rhinitis. A greater understanding of the mechanisms of action and clinical effects of both older-generation and newer-generation antihistamines should help define optimal therapeutic strategies in the future.

Histamine Antagonists↗
PubMed1993

The new H1 antihistamines. Treatment of urticaria and other clinical problems.

The new H1 antihistamines are a major therapeutic advancement in the treatment of allergic disorders such as urticaria and allergic rhinitis. Their efficacy combined with greatly reduced sedating and anticholinergic side effects makes the new class of H1 antihistamines the first-line treatment in the management of urticaria and mild angioedema. The choice of a particular low-sedating H1 antihistamine depends on pharmacokinetic considerations, the severity of the problem (systemic steroids and epinephrine are the first-line treatment for severe angioedema), and the requirement for limiting the frequency of administration. The efficacy of the new H1 antihistamines in the treatment of itch due to atopic eczema and systemic disease remains uncertain, and further controlled clinical trials are needed to elucidate their possible role in these conditions.

Astemizole↗
PubMed1993

Effects of H2-antihistamines in murine models of immediate hypersensitivity and chronic inflammation.

Effects of H2-antihistamines alone and in combination with H1-antihistamines on immediate hypersensitivity and chronic inflammation in mice and rats were investigated. The mouse PCA reaction was inhibited partially by a minimum effective dose of diphenhydramine and blocked completely when administered simultaneously with either famotidine, ranitidine or cimetidine. There was similar synergism between H1- and H2-antihistamines in inhibiting the PCA-like reaction in rat paw. Famotidine alone was able to inhibit those two reactions in a large oral dose of 100 mg/kg. A five-day course of therapy with H2-antihistamines alone or in combination with pyrilamine, suppressed effectively the chronic swelling induced in the hind paw of BUF rats. From these results, it is deduced that simultaneous blockage of both histamine H1- and H2-receptors may be necessary for sufficient inhibition of the microvascular permeability increase in some kinds of anaphylactic reactions, and that histamine, mainly interacting with H2-receptors, may take an important role for activation of a certain phase of chronic inflammation where bone destruction, blood capillary growth and mast cell degranulation involve.

Animals↗