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PubMed1992

Antihistamines and decongestants.

Drug therapy for allergic rhinitis is used either to prevent symptoms from occurring by short-circuiting the reaction and thus inhibiting the production of chemical mediators or to control symptoms after the target organs have been stimulated by these mediators. Antihistamines, the mainstay treatment of allergic rhinitis, are H1-receptor antagonists that bind competitively to histamine receptors. The older, classic antihistamines are effective in treating the symptoms of allergic rhinitis, but most are sedating because they cross the blood-brain barrier. They also have anticholinergic activity, which further restricts their use. The new, nonsedating antihistamines have overcome most of these limitations, and because they are long-acting, they require fewer daily dosages. Many still under development are quite potent and may be used for indications other than allergic rhinitis. Decongestants, sympathomimetic amines, are available both orally and topically as either short- or long-acting preparations. Topical decongestants should be used only for a short time to prevent rebound and ensuring overusage. These drugs interact with numerous antihypertensive medications and tricyclic antidepressants. Often combined with antihistamines, decongestants help offset their sedative effect.

Astemizole↗
PubMed1985

Terfenadine, a nonsedating antihistamine.

Terfenadine is an antihistamine recently approved for use in the U.S. Terfenadine possesses a unique chemical structure when compared with other antihistamines. It is a selective inhibitor of H1-receptors with little or no anticholinergic, antiserotoninergic, or antiadrenergic effects. Comparative studies have shown that terfenadine is as effective as other antihistamines in the treatment of allergic rhinitis and other hypersensitivity conditions. This drug produces a minimal amount of central nervous system (CNS) depression, which is documented by studies demonstrating that terfenadine and its metabolites do not readily pass into the CNS and have little affinity for central H1-receptors. The lack of CNS depression and anticholinergic effects, and the long duration of action that allows twice-a-day dosing make terfenadine an attractive alternative to other antihistamines.

Benzhydryl Compounds↗
PubMed1993

Cetirizine: a new, nonsedating antihistamine.

OBJECTIVE: To introduce cetirizine, a nonsedating antihistamine, and discuss its mechanism of action, chemistry, clinical and comparative trials, and adverse effects. DATA SOURCES: An English-language literature search of MEDLINE was conducted. STUDY SELECTION: Human clinical trials were selected for evaluation. DATA SYNTHESIS: Cetirizine, an investigational agent and a potent histamine1-antagonist is a piperazine derivative and carboxylated metabolite of hydroxyzine. As a second-generation, nonsedating antihistamine, cetirizine is associated with fewer adverse effects compared with first-generation antihistamines. It appears to be at least as effective as the other nonsedating antihistamines in the treatment of allergic rhinitis, chronic idiopathic urticaria, and pollen-induced asthma. The recommended adult dosage of this agent is 5 or 10 mg/d. CONCLUSIONS: Clinical studies indicate that cetirizine may be more beneficial in some ways than other available agents. Two of these advantages are a rapid onset of action and a once-daily dosing regimen. Future postmarketing surveillance is warranted to further document these findings.

Asthma↗
PubMed2003

Hydroxyzine from topical phospholipid liposomal formulations: evaluation of peripheral antihistaminic activity and systemic absorption in a rabbit model.

Hydroxyzine, an effective but sedating H1-antihistamine is given orally to treat allergic skin disorders. This study was performed to assess the peripheral H(1)-antihistaminic activity and extent of systemic absorption of hydroxyzine from liposomes applied to the skin. Using L-alpha-phosphatidylcholine (PC), small unilamellar vesicles (SUVs) and multilamellar vesicles (MLVs) containing hydroxyzine were prepared. Hydroxyzine in Glaxal Base (GB) was used as the control. Using a randomized, crossover design, each formulation, containing 10 mg of hydroxyzine, was applied to the shaved backs of 6 rabbits (3.08 +/- 0.05 kg). Histamine-induced wheal tests and blood sampling were performed at designated time intervals up to 24 hours. Compared with baseline, hydroxyzine from all formulations significantly suppressed histamine-induced wheal formation by 75% to 95% for up to 24 hours. Mean maximum suppression, 85% to 94%, occurred from 2 to 6 hours, with no differences among the formulations. The areas of plasma hydroxyzine concentration versus time area under the curve (AUCs) from PC-SUV and PC-MLV, 80.1 +/- 20.8 and 78.4 +/- 33.9 ng/mL/h, respectively, were lower than that from GB, 492 +/- 141 ng/mL/h (P < or =.05) over 24 hours. Plasma concentrations of cetirizine arising in-vivo as the active metabolite of hydroxyzine, from PC-SUV, PC-MLV, and GB, were similar with AUCs of 765 +/- 50, 1035 +/- 202, and 957 +/- 227 ng/mL/h, respectively (P < or =.05). Only 0.02% to 0.06% of the initial hydroxyzine dose remained on the skin after 24 hours. In this model, hydroxyzine from SUV and MLV had excellent topical H1-antihistaminic activity, and minimal systemic exposure occurred. Cetirizine formed in-vivo contributed to some of H1-antihistaminic activity.

Animals↗
PubMed1994

Antiallergic effect of ZCR-2060: antihistaminic action.

The antihistaminic effect of 2-[2-[4-(diphenylmethyl)-1-piperadinyl]ethoxy] benzoic acid maleate (ZCR-2060), a newly synthesized antiallergic agent, was investigated in both in vitro and in vivo studies. ZCR-2060 clearly antagonized histamine-induced contraction of isolated guinea pig ileum and trachea. In contrast, carbachol-, BaCl2- and 5-hydroxytryptamine-induced contractions of isolated guinea pig ileum were slightly inhibited by higher concentrations of ZCR-2060. 3H-Mepyramine specific binding to membranes from guinea pig lung and brain were markedly inhibited by ZCR-2060 in a concentration-dependent fashion. In the in vitro studies, the antihistaminic effect of ZCR-2060 was greater than those of cetirizine and terfenadine, but was less than that of ketotifen. In the in vivo studies, ZCR-2060 significantly inhibited the histamine-induced cutaneous reaction in rats, when administered orally 1 hr before the histamine injection. Moreover, ZCR-2060 has a long-lasting antihistaminic effect. In the in vivo studies, the antihistaminic effect of ZCR-2060 was found to be greater than that of cetirizine and terfenadine, and it was the same as that of ketotifen. Thiopental-induced sleep and spontaneous ambulatory activity in mice, however, were unaffected by ZCR-2060 at higher doses. These results indicate that ZCR-2060 has a potent, selective and long acting histamine H1-receptor antagonistic action without causing any unwanted CNS side effect.

Animals↗
PubMed1998

Therapeutic advantages of third generation antihistamines.

A third generation of antihistamines is emerging for the treatment of allergic rhinitis and chronic urticaria. First generation antihistamines are among the most widely used drugs in the world, and provide symptomatic relief from allergies and the common cold to millions of patients, mainly in OTC combination preparations. Their full potential is limited by the sedation caused by their effects on histamine receptors in the brain. Second generation antihistamines (terfenadine, astemizole, loratadine and cetirizine), which block peripheral H1 receptors without penetrating the blood-brain barrier, were developed and introduced from 1981 onwards to provide comparable therapeutic benefit without the CNS side-effects. Although largely successful in this goal, terfenadine and astemizole were found to cause potentially serious arrhythmias when plasma concentrations became elevated subsequent to impaired metabolism. It was established that the cardiac toxicity was mainly due to the parent drugs. As active metabolites could account for most of the clinical benefit, the goal for the third generation of antihistamines became to develop therapeutically active metabolites that were devoid of cardiac toxicity. The first of these drugs, fexofenadine (the active metabolite of terfenadine), was approved in July 1996, after an unusually rapid development programme. Its introduction set a new standard of safety that led the FDA to request the withdrawal of terfenadine in 1997 on the grounds that a safer version of an equivalent drug was now available. Norastemizole and descarboethoxy loratadine, the metabolites of astemizole and loratadine, respectively, are also in clinical development. These offer comparable or superior clinical benefits.

Journal Article↗
PubMed1988

Antihistamine blockade of alcohol-induced flushing in orientals.

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, an increase in skin temperature, a decrease in blood pressure, an increase in pulse rate and subjective symptoms such as dizziness, sleepiness, anxiety, headache, generalized weakness and nausea. Before the administration of alcohol, one-half of the subjects were given 50 mg of diphenhydramine (H1 receptor antagonist) and 300 mg of cimetidine (H2 receptor antagonist). The second half received placebo tablets. The clearest difference between the antihistamine group and placebo group was in the skin flushing reaction. The antihistamine group showed a significant reduction in the skin flush. The antihistamine also neutralized the systolic hypotension induced by the administration of alcohol. The possible importance of histamine in the expression of sensitivity to alcohol is considered. The relevance to genetic susceptibility for development of alcoholism is discussed.

Adolescent↗
PubMed2004

Central nervous system side effects of first- and second-generation antihistamines in school children with perennial allergic rhinitis: a randomized, double-blind, placebo-controlled comparative study.

OBJECTIVE: Allergic rhinitis is common and on the rise. Antihistamines are the mainstay of treatment and are the most commonly prescribed drugs in Singapore. Treatment-related sedation and its effect on cognition are a major concern. First- and second-generation antihistamines show varying degrees of sedation, but to date, objective studies in children are lacking. The objective of this study was to assess the sedating effect of cetirizine (second-generation antihistamine) and chlorpheniramine (first-generation antihistamine) compared with placebo using an objective neurophysiological test. METHODS: This was a prospective, double-blind, placebo-controlled, randomized, single-dose, 3-way crossover study. Twenty-four children aged 7 to 14 years with allergic rhinitis completed the study. All children were randomly allocated to medication sequences and received 3 different drugs on 3 different days, at least 1 week apart. The P300 event-related potential was used as an objective test of sedation. Subjective assessment was by a visual analog scale. RESULTS: Chlorpheniramine and cetirizine increased P300 latency when compared with baseline. No significant increase was obtained with placebo. The significant increase in P300 latency was not accompanied by significant change in subjective somnolence as measured by the visual analog scale. CONCLUSION: We have shown that cetirizine has sedative properties in children. The lack of correlation between P300 latency and the visual analog scale indicates that sedation induced by these drugs may not be subjectively noted.

Adolescent↗
PubMed2005

Preclinical pharmacology of bilastine, a new selective histamine H1 receptor antagonist: receptor selectivity and in vitro antihistaminic activity.

OBJECTIVE: This study aimed to establish the receptor selectivity and antihistaminic activity of bilastine, a new selective antihistamine receptor antagonist. DESIGN AND METHODS: In vitro experiments were conducted using a receptor binding screening panel and guinea-pig and rat tissues. Antihistaminic activity was determined using H1 receptor binding studies and in vitro H1 antagonism studies conducted in guinea-pig tissues and human cell lines. Receptor selectivity was established using a receptor binding screening panel and a receptor antagonism screening conducted in guinea-pig, rat and rabbit tissues. Inhibition of inflammatory mediators was determined through the Schultz-Dale reaction in sensitised guinea-pig ileum. RESULTS: Bilastine binds to histamine H1-receptors as indicated by its displacement of [3H]-pyrilamine from H1-receptors expressed in guinea-pig cerebellum and human embryonic kidney (HEK) cell lines. The studies conducted on guinea-pig smooth muscle demonstrated the capability of bilastine to antagonise H1-receptors. Bilastine is selective for histamine H1-receptors as shown in receptor-binding screening conducted to determine the binding capacity of bilastine to 30 different receptors. The specificity of its H1-receptor antagonistic activity was also demonstrated in a series of in vitro experiments conducted on guinea-pig and rat tissues. The results of these studies confirmed the lack of significant antagonism against serotonin, bradykinin, leukotriene D4, calcium, muscarinic M3-receptors, alpha1-adrenoceptors, beta2-adrenoceptors, and H2- and H3-receptors. The results of the in vitro Schultz-Dale reaction demonstrated that bilastine also has anti-inflammatory activity. CONCLUSIONS: These preclinical studies provide evidence that bilastine has H1- antihistamine activity, with high specificity for H1-receptors, and poor or no affinity for other receptors. Bilastine has also been shown to have anti-inflammatory properties.

Animals↗
PubMed1999

Clinical assessment of antihistamines in rhinitis.

The first line of treatment for allergic rhinitis must be identification and avoidance as far as possible of the relevant allergens. This is rarely completely successful and so pharmaceutical treatment is also needed. Antihistamines are effective in allergic rhinitis, which comprises approximately 80% of rhinitis found in children and 30% in adults. Antihistamines antagonize the effect of histamine at the H1 receptor and their major clinical effects are related to this. They are effective against rhinorrhoea, itch and sneezing but have little effect on nasal obstruction. Clinical trials show between 36% and 80% of patients experiencing good to excellent symptom relief (approximately twice that induced by placebo), in seasonal allergic rhinitis; between 55% and 86% of patients experience moderate to excellent symptom relief in perennial allergic rhinitis. Meta-analysis reveals that antihistamines are inferior to corticosteroids in allergic rhinitis therapy. Antihistamines are generally well tolerated, although serious cardiac dysrhythmias have occurred with terfenadine and astemizole. Their place in therapy is probably as sole agent in mild, intermittent rhinitis and in combination with topical corticosteroids in more severe disease not controlled by corticosteroids alone.

Arrhythmias, Cardiac↗
PubMed2000

The changing face of antihistamines and cardiac adverse drug reactions: a clinical perspective.

Recent times have witnessed a qualitative shift in the recognition and management of adverse drug effects. Many of them occur in organs that are unconnected to the primary target of pharmacological action. Out of these, cardiac side-effects have drawn particular attention because of their potential to cause death. Starting with the early observations on antibiotics such as macrolides, followed by fluoroquinolones and others, the focus has now shifted to the antihistamine class of drugs which are used extensively by patients all over the world, thanks to the ever increasing levels of environmental pollution. The occurrence of prolonged QTc interval following treatment with terfenadine leading to ventricular tachycardia of torsades de points variety with a potentially fatal outcome has forced many regulatory authorities of the world to clamp a ban the use of this drug. Alerted by these developments, studies on a new member, followed by fluoroquinolones and others, the focus has now shifted to the antihistamine class of drugs which are used extensively by patients all over the world, thanks to the ever incresing levels of envrionmental pollution. The occurrence of prolonged QTc interval following treatment with terfenadine leading to ventricular tachycardia of torsades de points variety with a potentially fatal outcome has forced many regulatory authorities of the world to clamp a ban use of this drug. Alerted by these developments, studies on a new member of non-sedating antihistamine class viz, fexofenadine, have been reviewed especially because of the structural similarity between terfenadine and fexofenadine. It is now clear that despite the closeness of its chemical structure to terfenadine fexofenadine behaves in a different manner and does not affect the electrophysiology of the heart muscle tissue, as proved by data from extensive clinical trials as well as membrane models in vitro. Interestingly, the solitary false alarm that was sounded on the drug by a group of workers in the Netherlands was later rectified by the same group. Clinically speaking, the cardiovascular safety of fexofenadine has been convincingly demonstrated at various dose levels and various time intervals, alone and together with other drugs of potential toxigenicity. All things put together, it appears reasonable to conclude that fexofenadine is free from cardiovascular ADRs of clinical significance. It could also be concluded that cardiac side-effects of antihistamines is not a class effect.

Cardiovascular Diseases↗
PubMed2001

A descriptive analysis of the use and cost of new-generation antihistamines in the treatment of allergic rhinitis: a retrospective database analysis.

OBJECTIVE: This retrospective database analysis was conducted to evaluate the use and cost of new-generation antihistamines (i.e., those that are nonsedating) in the treatment of allergic rhinitis in a managed care population. STUDY DESIGN: The study is a retrospective database review of medical and pharmacy-related claims linked by episodes of care. METHODS: Patients who had been diagnosed as having allergic rhinitis and had at least 1 prescription claim were identified from a database containing patient-level medical and pharmacy-related claims. The treatment patterns of patients with allergic rhinitis who met the study criteria were documented for a 12-month period in which the use of nonsedating antihistamines was described and the associated costs of various medications were assessed. Subanalyses of patients categorized by comorbidity status were also performed. RESULTS: A total of 202,426 patients participated in the study. Nonsedating antihistamines were used by 71% of the patients; the most commonly prescribed drugs were loratadine and fexofenadine. The mean annual charges per patient for the treatment of allergic rhinitis in the study population were $465.21 (standard deviation [SD], 548). The greatest departmental cost was that of pharmacy-related charges (mean, $236.02; SD, 233); the next highest cost was that of outpatient charges (mean, $216.31; SD, 396). Comparisons of departmental charges indicated the use of loratadine was associated with significantly higher treatment costs than that of fexofenadine in a number of patient subgroups. CONCLUSION: In this analysis, loratadine was associated with significantly higher treatment charges than was fexofenadine. This result was observed consistently across different stratifications of patients, including the presence of comorbid respiratory infection, concomitant use of nasal steroids, and the presence of asthma and/or sinusitis. These results provided useful insights into the differential costs associated with the use of nonsedating antihistamines in the treatment of rhinitis.

Adolescent↗
PubMed2001

The costs of nonsedating antihistamine therapy for allergic rhinitis in managed care: an updated analysis.

OBJECTIVE: To update a prior study evaluating the use and costs of new-generation antihistamines for the treatment of allergic rhinitis in a managed care population. STUDY DESIGN: A retrospective database review of rhinitis-related medical and pharmacy-related claims during a treatment period of 12 months. METHODS: Patients who had been diagnosed as having allergic rhinitis and had at least 1 prescription claim were identified from a database containing patient-level medical and pharmaceutical claims. The treatment patterns for patients meeting study criteria were documented for a 12-month period to describe how nonsedating antihistamines are being used in allergic rhinitis, and to assess the associated costs of various medications. Subanalyses of patients categorized by comorbidity status were also performed. RESULTS: A total of 105,696 patients were included in this updated analysis, covering calendar year 1999. Nonsedating antihistamines were used by 68% of the sample, with loratadine and fexofenadine being the most commonly prescribed agents. The mean annual rhinitis-specific charge for fexofenadine-treated patients was $409 (standard deviation [SD] 727), which was significantly lower compared with charges for loratadine-treated patients, $424 (SD 740), P = .0144, or cetirizine-treated patients, $444 (SD 625), P < .0001. This trend was also observed in comparisons of patient subgroups. CONCLUSIONS: Consistent with our prior study, loratadine and cetirizine were generally associated with significantly higher treatment charges than fexofenadine. This result was observed across different stratifications of patients, including those with comorbid respiratory illness, concomitant use of nasal steroids, and asthma and/or sinusitis. These results provide further useful insights into the differential costs associated with the use of nonsedating antihistamines for allergic rhinitis treatment.

Adolescent↗
PubMed2002

Antihistamines in the management of canine atopic dermatitis: a retrospective study of 171 dogs (1992-1998).

Antihistamines were prescribed for 178 of 271 dogs with a diagnosis of atopic dermatitis at the Veterinary Medical Teaching Hospital of the University of California, Davis from 1992 to 1998. Fifty-four percent of 166 dogs given antihistamines responded favorably to these treatments, with 27% of the responses rated as good and 27% rated as moderate. Diphenhydramine and hydroxyzine were the most commonly used antihistamines and were the most frequently effective. Chlorpheniramine and clemastine were administered less frequently and had much lower positive response rates. Responses to antihistamines as a group were significantly better in dogs having onset of clinical signs at younger ages (odds ratios for 1-year increase in age = 0.72, 95% confidence interval = 0.57 to 0.91, P =.005).

Allergens↗
PubMed2002

H1-antihistamines in the elderly.

In the elderly, H1-antihistamine therapy is commonly prescribed for treatment of rhinitis, conjunctivitis, pruritus, eczema, urticaria, and for prophylaxis of anaphylactoid reactions. Second-generation H1-receptor antagonists provide excellent, safe, and effective alternatives to first-generation antihistamines in this population, as in younger patients. As with all medications, the choice of which agent to use must be tailored to the needs of the individual. Treatment should be planned with consideration of concomitant medications and potential drug-drug interactions and drug-disease interactions. First-generation antihistamines should not be used for treatment of allergic rhinitis or urticaria in the elderly. Age-related physiological changes can enhance or complicate the actions of H1-receptor antagonists, especially when these drugs are taken concurrently with other medications and/or in the presence of comorbid disease. Adjustments in dosages are necessary when some agents are used in patients with renal and/or hepatic disease; however, overall, the use of the newer nonsedating antihistamines is safe, effective, and gratifying in the elderly.

Aged↗
PubMed2002

[Cutaneous drug eruption with two antihistaminic drugs of a same chemical family: cetirizine and hydroxyzine].

BACKGROUND: H1-antihistamines are widely used to relieve symptoms of allergic disorders. A few skins reactions to H1-antihistamines have been described in the literature. We report the first case of cutaneous drug eruption as fixed drug eruption with 2 antihistamines of the same chemical family: cetirizine and hydroxyzine. CASE REPORT: A 73 year-old man was admitted because of a third cutaneous eruption with the same morphologic features of the same sites as before. The first and second eruption appeared after 4 hours of cetirizine intake, the third eruption appeared after 4 hours of hydroxyzine intake. Healing was obtained after stopping the medication. Histology showed induced drug reaction. Patch tests with cetirizine and hydroxyzine were negative, except false positivity with dimethylsulfoxide vehicles. DISCUSSION: The diagnosis of cutaneous drug eruption as non pigmenting fixed drug eruption related to cetirizine and hydroxyzine was retained. Allergy to both H1 antihistamines can be explained by the fact that they've got the same chemical node that is piperazine, and by the fact that cetirizine is the main metabolite of hydroxyzine. Oral test provocation was omitted because the patient had already reexposed himself to the drugs. To identify the drug responsible for fixed drug eruption, peroral provocation tests are the most valuable method, but carry the risk of a strong reaction. Some authors use patch tests, but their positivity is inconstant. Their interest in fixed drug eruption is undergoing assessment.

Aged↗
PubMed2003

[Antihistamine drugs in the treatment of allergic skin diseases].

Antihistaminic therapy is widely used in the treatment of allergic dermatoses. Second generation antihistamines due to their pharmacokinetic mechanism depending on the wide extra-receptor anti-inflammatory and anti-allergic actions are used in the treatment of diseases, in which the main pathogenetic role is played by various allergic mechanisms and inflammatory cellular processes. The modern views on etiopathogenesis and antihistaminic treatment of allergic skin diseases are presented in this paper. The course of allergic inflammation, role of histamine and its receptors, taking into consideration the biological effects of their suppression and influence on the course of early and late phase of allergic reaction, are discussed. A review of classical and second generation antihistamines has been done, taking into account their usefulness in the treatment of acute and chronic urticaria, angioedema, atopic dermatitis, different forms of eczema and various drug-induced reactions.

Histamine H1 Antagonists↗
PubMedDate not supplied

Antihistamine onset of action: the importance to the patient.

Although some older antihistamines have a relatively slow onset of action, modern agents indicate an efficacy between 1 and 3 hours of administration. For patients who use antihistamines regularly, a short onset of action is relatively unimportant. When antihistamines are used as needed, either because of poor compliance or in accordance with emerging therapeutic guidelines, antihistamines with a short onset of action are preferable.

Histamine H1 Antagonists↗