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PubMed1993

The effect of antihistamines on the immediate allergic response: a comparative review.

Antihistamines are believed to reduce the sneezing and rhinorrhea associated with allergic rhinitis, primarily by competitive antagonism of histamine for H1 cellular receptors, but additional mechanisms of action may contribute to their clinical efficacy. To improve our understanding of H1 antihistamine action, we studied the effects of pretreatment with terfenadine, cetirizine, ketotifen, azatadine, diphenhydramine, and azelastine on increases in vascular permeability, mast cell activation, and sneezing induced by nasal challenge with antigen. All studied antihistamines reduced sneezing, indicating that they all effectively antagonize histamine after its release. In addition, terfenadine and topically administered azatadine blocked the release of histamine. Studies with cetirizine and azelastine revealed that these antihistamines significantly reduced sulfidopeptide leukotriene levels. Terfenadine and azelastine also reduced kinin production. These results confirm that antihistamines are effective in reducing sneezing and, in some cases, vascular permeability. The findings of these studies also illustrate that the various antihistamines have multiple and different mechanisms of action that may have implications for their clinical uses.

Capillary Permeability↗
PubMed1997

Effects of antihistamines in adult asthma: a meta-analysis of clinical trials.

A meta-analysis of clinical trials of antihistamines was performed to assess the risk-benefit ratio of this therapeutic class in asthma. Double-blind randomized placebo-controlled trials assessing lung function changes under repeated use of antihistamine in adult asthma were selected, and the quality of studies was scored. Morning peak expiratory flow rate (PEFR) was the primary outcome: an effect size was computed for each study, with a 95% confidence interval (95% CI), and a mean effect size was computed, combining all studies. Effect sizes were also determined for secondary outcomes: evening PEFR, forced expiratory volume in one second (FEV1) and daily use of inhaled beta-agonists. Nineteen studies were included in the meta-analysis. Mean quality score of studies was 59.4%; asthma was generally uncontrolled at study inclusion. Altogether, 582 antihistamine-treated and 557 placebo-treated asthma patients were evaluable. Antihistamines had little effect on airway calibre (mean increase in morning PEFR: 13 L x min(-1); 95 CI: 8-18 L x min(-1)) and on use of inhaled beta-agonists (mean reduction in daily use: 0.4 doses; 95% CI: 0-0.8 doses). Sedation occurred more often with antihistamines than with placebo (p<0.001); additional side-effects were mentioned, including weight gain, altered taste, headache and dry mouth. Respiratory and systemic effects observed after repeated use of antihistamines do not support the use of these medications in the treatment of asthma; better designed studies could affect this appraisal.

Adolescent↗
PubMed1986

Ovarian function in ewes treated with antihistamines.

Ewes were treated systemically during the periovulatory period with the antihistamines diphenhydramine (H1-receptor antagonist) and(or) cimetidine (H2-receptor antagonist). None of the treatments prevented ovulation. However, the combination of drugs inhibited subsequent function of the corpus luteum (CL) as assessed by serum measurements of progesterone. Administration of antihistamines did not alter pituitary secretion of LH. Injection of small quantities of diphenhydramine and cimetidine into the antrum of the preovulatory follicle also caused aberrant luteal activity, but no blockade of ovulation. Intrafollicular injection of histamine reversed the inhibitory influence of antihistamines on the CL. Antihistamines suppressed preovulatory thecal edema and antral influx of plasma transudate containing LH. Thus, the effects of antihistamines appear to have been exerted at the follicular level. Function of matured CL was not compromised by peripheral administration of antihistamines. Actions of histamine within the preovulatory ovine follicle do not appear to be a prerequisite for ovulation, but apparently do have an impact on ensuing luteal function. We propose that a hyperemic reaction to histamine in preovulatory follicles enhances vascular filtration of LH. As a consequence, maximal permeation of the avascular granulosal layer of the follicle by LH leads to a normal luteinization response.

Animals↗
PubMedDate not supplied

Non-sedating antihistamines.

Antihistamines are effective therapy against histamine-mediated conditions, including seasonal and perennial allergic rhinitis and chronic urticaria. They may also have a therapeutic role to play in asthma. Until recently all antihistamines produced some degree of drowsiness, as well as having anticholinergic side effects. Several non-sedating antihistamines have now been developed. Evidence suggests that their freedom from central nervous system effects is due to their lack of penetration of the blood-brain barrier. They also have no appreciable binding to cholinergic receptors. Two of these non-sedating antihistamines, terfenadine and astemizole, have novel binding characteristics with the histamine H1 receptor, exhibiting irreversible binding at higher concentrations. In humans astemizole has a remarkably long half-life of elimination, on the order of 12 to 18 days for metabolites. Clinical trials have demonstrated that these newer antihistamines are as effective as classical antihistamines and that they have no greater incidence of central nervous system or anticholinergic side effects than placebo.

Animals↗
PubMed1999

Effect of antihistamines on epithelial cells.

Antihistamines have mostly been used in the management of allergic rhinitis, primarily for their symptomatic relief. Recent studies, however, have suggested that the non-sedating second-generation antihistamines also possess anti-inflammatory activity, and consequently may be useful in the management of inflammation in allergic airways disease. Several in vivo studies have demonstrated that antihistamines decrease inflammatory cell infiltration in allergic disease, mediator release from mast/basophil cells, and the expression of adhesion molecules on epithelial cells. Similarly, in vitro studies have demonstrated that antihistamines decrease the migration and activation of eosinophils and the release of pro-inflammatory mediators from mast/basophil cells, induced by immunological and non-immunological stimuli. More recent evidence suggests that the antihistamines may modulate airway inflammation by influencing the activity of airway epithelial cells, which due to their spatial arrangement and predominance in the airways, are thought to play a pivotal role in the aetiology of airway disease. We and others have demonstrated that antihistamines attenuate allergen- or chemical-induced expression and/or release of mediators which influence the activity of inflammatory cells, such as eosinophils, mast cells, basophils and lymphocytes, known to be involved in the pathogenesis of allergic airway diseases. Collectively, these studies suggest that second-generation H1-histamine receptor antagonists may have potential use either as safe anti-inflammatory alternatives to corticosteroids, or as rescue medication in combination with corticosteroids, for the management of severe airway disease.

Animals↗
PubMedDate not supplied

The role of nonsedating antihistamines in asthma therapy.

There is well-established evidence that histamine plays a significant role as a chemical mediator in asthma. However, although antihistamines are commonly used for the treatment of allergic rhinitis, their use in asthma has been somewhat controversial. Mechanistically, their application for asthma appears logical. In addition to their effects at the histamine receptor, antihistamines, in a dose-dependent fashion, inhibit the release of preformed mediators such as histamine and mediators synthesized de novo including the metabolities of arachidonic acid from mast cells and basophils. Antihistamines also show, in a concentration-dependent manner, anti-inflammatory and immunomodulatory activity through their effects on epithelial cells, endothelial cells, macrophages, eosinophils, and T lymphocytes. Clinically, there appears to be a link between allergic rhinitis and asthma such that treatment of the upper airway has been shown to benefit lower airway disease. Of interest is that although antihistamines have been shown to reduce asthma symptoms and improve quality of life, generally, they have not, at doses sufficient to control rhinitis, improved objective measures of lung function. This could potentially be achieved, in a fashion similar to that observed in concentration-dependent in vitro studies, by using higher medication levels. However, most antihistamines, both first- and second-generation, cannot be used above recommended doses without causing unacceptable side effects including sedation and psychomotor function impairment. As newer antihistamines with improved therapeutic indices have been developed, asthma studies can and must be conducted to evaluate high-dose therapy with the potential of reaping the anti-inflammatory and immunomodulatory effects of these drugs.

Animals↗
PubMed2003

[A potential of positron emission tomography in the drug development of non-sedative antihistamines].

Histamine H1 receptor antagonists, or antihistamines, are very effective for treatment of various allergic disorders such as seasonal rhinitis and urticaria. Sometimes antihistamines induce sedative CNS side effects that might result in dangerous traffic accidents. That is why a lack of sedation is important for development of new antihistamines. It is clear that all antihistamines have a potential to produce subjective (sleepiness, fatigue etc.) and objective sedation (impaired performance), dependent on the histaminergic mechanisms involved in the control of arousal. We have proposed the usefulness of H1 receptor occupancy measurement with Positron Emission Tomography (PET) using 11C-doxepin as a tracer. The PET measurement is currently included as one of the three major factors defined by the international Consensus Group on New Generation Antihistamines (CONGA) for evaluation of antihistamines: 1) incidence of subjective sleepiness, 2) objective and psychomotor functions, and 3) PET measurement of H1 receptor occupancy. Merit of PET measurement is that we can directly calculate the receptor occupancy for each separate drug while the former two should be discussed based on the difference between placebo and active placebo. PET will be used more actively in the development of various new drugs in future.

Drug Evaluation↗
PubMed1986

N-substituted 11-(4-piperidylene)-5,6-dihydro-11H-benzo-[5,6]cyclohepta [1,2-b]pyridines. Antihistamines with no sedating liability.

Conversion of the basic tertiary amino function of the potent antihistamine, azatadine (Optimine), to neutral carbamate function results in compounds which retain significant antihistamine activity with little or no CNS effects. In guinea pigs the N-ethoxycarbonyl derivative 4 had the same antihistamine potency as terfenadine, a clinically used non-sedating antihistamine. In mice, 4 was a potent antihistamine while lacking CNS effects. The 8-chloro-N-ethoxycarbonyl 5 (loratadine, Sch 29851) was the most potent antihistamine in the series, had no CNS side effects, and was selected for clinical evaluation.

Animals↗
PubMed1980

Antihistamines as prophylaxis against side reactions to intravenous fluorescein.

Systemic antihistamines were administered prior to dye injection in 50 patients undergoing fluorescein angiography. The patients were monitored for side effects. Venous blood samples were obtained before and at three, ten and thirty minutes after intravenous administration of sodium fluorescein and analyzed for histamine levels. Three patients (6%) developed minor side effects of nausea or dizziness; this compares to an incidence of 21% in a previous series of patients from our institution untreated with antihistamines. A three-fold increase in plasma histamine levels occurred in 28% of patients following fluorescein and antihistamine injection; this compares with a 26% incidence of increase in plasma histamine in patients receiving fluorescein without antihistamines (as determined in a previous study). Prophylactic antihistamines should be considered in patients undergoing fluorescein angiography if they have a history of previous allergies or side reactions during prior fluorescein studies. However, complete prophylaxis against severe side reactions to fluorescein injections is not assured with antihistamines.

Adolescent↗
PubMed1996

Effects of H1- and H2-antihistamines on platelet-activating factor and bradykinin-induced inflammatory responses in human skin.

Previous studies show that oral antihistamines affect the weal and flare response to intradermal injections of the inflammatory mediators platelet-activating factor (PAF) and bradykinin (BK). The aim of this study was to compare the effects of terfenadine (an H1-antagonist) and cimetidine (an H2-antagonist) on weal and flare responses to PAF and BK in healthy non-atopic human volunteers. The effects of doxepin on PAF responses were investigated, as there is evidence that doxepin may have direct anti-PAF effects in addition to its known antihistaminic actions. Terfenadine significantly reduced weal and flare responses to PAF (mean reduction 53 and 73%, respectively) and flare responses to BK (mean reduction 78%) but had no effect on weal responses to BK. Doxepin significantly reduced both weal and flare responses to PAF (mean reduction 43 and 68%, respectively, at higher doses of PAF). Cimetidine had no effect on weal or flare responses to PAF or BK. These findings suggest that the flare response to intradermal BK is mediated via histamine release while the weal response is not. The effects of the various antagonists of PAF-induced responses suggest that its effects too may be mediated via histamine, the similarity of the effects of terfenadine and doxepin on these responses indicating that the effects of doxepin may be due to its known antihistamine activity rather than to any specific PAF-antagonistic properties. Platelet-activating factor (PAF) is a phospholipid which is released from a wide range of cell types and also from vascular endothelium. PAF is formed by the conversion of ether-linked phospholipids initially to the biologically inactive lyso-PAF and then by acetylation to PAF. Intradermal injection of PAF in human skin causes vasodilatation and increased vascular permeability, producing a weal and flare response with accompanying pruritus. Bradykinin (BK) is a vasoactive polypeptide formed by the action of enzymes known as kallikreins on inactive precursors called kininogens. Its effects include an increase in blood flow and vascular permeability and stimulation of the release of prostaglandins and histamine. On intradermal injection in human skin it causes a weal and flare response with associated pain rather than pruritus. Previous studies have suggested that the weal and flare response to PAF may be mediated in part by histamine release. Given that BK is known to cause histamine release it appears possible that the responses to both compounds may be modified by conventional antihistamines. Experiments based on this premise have found that antihistamines have a pronounced effect on the flare response to PAF but a less marked effect on weal responses. The weal response to BK was unaffected by systemic antihistamines but studies have produced conflicting results with regard to effects on the flare response. The aim of this study was to compare the effects of terfenadine (an H1-antagonist) and cimetidine (an H2-antagonist) on PAF- and BK-induced weal and flare responses in healthy, non-atopic human volunteers. Based on the treatment of cold urticaria it has been suggested that doxepin, which has known H1- and H2-antagonistic effects, may in addition show specific anti-PAF activity. We compared the effects of doxepin on PAF-induced intradermal responses with those of terfenadine and cimetidine in this study.

Administration, Oral↗
PubMedDate not supplied

Antiallergic properties of antihistamines.

Histamine is a major mediator of the allergic reaction, and histamine H1-receptor antagonists have a long history of clinical efficacy in a variety of allergic disorders. The pathogenesis of allergic disease is complex, involving not only histamine and mast cell-derived tryptase, but also eosinophil and neutrophil derived mediators, cytokines, and intercellular adhesion molecules (ICAM-1). A number of "in vitro" and "in vivo" studies have been performed to assess the clinical effectiveness of antihistamines in inhibiting the allergen-induced inflammatory process in the skin and mucosa. In vitro human studies have shown that high concentration of second generation antihistamines can block inflammatory mediator release from basophils and mast cells, and reduce ICAM-1 expression in epithelial cell lines. In vivo studies have also shown an effect on the allergen-induced inflammatory reaction; both oral and intranasal antihistamines cause a reduction in nasal symptoms and inflammatory cell influx. Analysis of secretory fluids and tissues after challenge indicates that antihistamines interfere with mediator release. Recruitment of inflammatory cells to the site of the allergic insult is also disturbed by antihistamines of second-generation, suggesting that these drugs may inhibit upregulation of molecules involved in cell adhesion and migration, and perhaps they may interfere with the cytokine cascade through their ability of stabilizing mast cells and of limiting the incursion of inflammatory cells. This article reviews available human data on the antiallergic effects of antihistamines.

Butyrophenones↗
PubMed1998

Pharmacokinetic overview of oral second-generation H1 antihistamines.

Specific H1 antihistamines have become the standard of treatment for relief of symptoms associated with seasonal allergic rhinitis. First-generation antihistamines are small lipophilic molecules that are associated with numerous adverse events largely because of their propensity to cross the blood-brain barrier and their cholinergic activity. Second-generation antihistamines, being more lipophobic, offer the advantages of a lack of CNS and cholinergic effects such as sedation and dry mouth, which are commonly seen in first-generation antihistamines. Their longer duration of action also enables a more patient-friendly dosing regimen which increases patient compliance. This paper reviews the pharmacokinetic properties of these second-generation agents and is intended to provide comparisons that help explain differences in dosing profiles and drug interactions for members of this class of drugs. With the announced withdrawal of terfenadine from the U.S. market in early 1997, 4 second-generation antihistamines are currently widely available: astemizole, loratadine, cetirizine, and fexofenadine. Terfenadine and astemizole both produce significant cardiac QT interval prolongation that may progress to a rare but fatal cardiac ventricular tachycardia known as torsades de pointes. While only terfenadine has been withdrawn due to its adverse effects profile, significant warnings were recently issued for astemizole. The pharmacokinetic profiles of loratadine and cetirizine are reflective of the advantages of these agents as non-cardiotoxic antihistamines. With respect to the newest agent fexofenadine, the major metabolite of terfenadine, published reports are minimal, but its pharmacokinetics differs from that of terfenadine.

Astemizole↗
PubMed2004

Decongestants and antihistamines for acute otitis media in children.

BACKGROUND: Acute otitis media (AOM) is a common and important source of morbidity in children, although most cases resolve spontaneously. While frequently recommended, decongestant and antihistamine therapy is of unclear benefit. OBJECTIVES: To determine the efficacy of decongestant and antihistamine therapy in children with AOM on outcomes of AOM resolution, symptom resolution, medication side effects, and complications of AOM. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2003); MEDLINE (January 1966 to December 2003), EMBASE (January 1990 to July 2003) and reference lists of articles for this updated review. We also contacted study authors and pharmaceutical companies. SELECTION CRITERIA: Randomized controlled trials evaluating decongestant or antihistamine treatment for children with AOM were included. Patient-oriented outcomes were considered most relevant. There were no quality or language restrictions. DATA COLLECTION AND ANALYSIS: Investigators independently evaluated studies for inclusion, performed validity assessments, and completed data extraction. Dichotomous data were pooled to generate relative risks; homogeneity was assessed using approximate chi-square tests. MAIN RESULTS: Fifteen trials involving 2695 people were included. Only the combined decongestant-antihistamine group demonstrated statistically lower rates of persistent AOM at the two week period (fixed relative risk (RR) 0.76; 95% confidence interval (CI) 0.60 to 0.96; number needed to treat (NNT) 10). No benefit was found for early cure rates, symptom resolution, prevention of surgery or other complications. There was a five to eight -fold increased risk of side effects for those receiving an intervention, which reached statistical significance for all decongestant groupings. Validity sub analyses demonstrated that lower quality studies found benefit, while analysis of those studies with higher validity scores found no benefit of treatment. REVIEWERS' CONCLUSIONS: Given lack of benefit and increased risk of side effects, these data do not support the use of decongestant treatment in children with AOM. There was a small statistical benefit from combination medication use but the clinical significance is minimal and study design may be biasing the results. Thus, the routine use of antihistamines for treating AOM in children cannot be recommended.

Acute Disease↗
PubMed2006

Antihistamines and/or decongestants for otitis media with effusion (OME) in children.

BACKGROUND: Otitis media with effusion (OME) is common and may cause hearing loss with associated developmental delay. Treatment remains controversial. The effectiveness of antihistamines, decongestants and antihistamine/decongestant combinations in promoting the resolution of effusions has been assessed by randomized controlled trials. OBJECTIVES: The objective of this review is to determine whether antihistamine, decongestant, or combination therapy is effective in treating children who present with OME. SEARCH STRATEGY: The Cochrane Ear, Nose and Throat Disorders Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1 2006), EMBASE (1974 to 2006), MEDLINE (1951 to 2006) and a gray literature database were searched using a search strategy created by an experienced medical librarian. The date of the last search was March 2006. Reference lists from included studies and relevant reviews were searched by hand; pharmaceutical manufacturers of antihistamines and decongestants and first authors of included studies were contacted to identify other potentially relevant studies. SELECTION CRITERIA: Randomized controlled trials (RCTs) using antihistamines, decongestants or antihistamine/decongestant combinations as treatment for OME in children were selected. We excluded trials that randomized on the basis of acute otitis media (AOM) even though OME was also studied in follow up. DATA COLLECTION AND ANALYSIS: Data were extracted from the published reports by two authors independently using standardized data extraction forms and methods. The methodological quality of the included studies was independently assessed by two authors. Dichotomous results were expressed as a relative risk with 95% confidence intervals using a fixed-effect model when homogeneous and a random-effects model when heterogeneous. Nearly all outcomes analysed were homogeneous. Continuous results were discussed qualitatively. Statistical analysis was conducted using RevMan software. MAIN RESULTS: No statistical or clinical benefit was found for any of the interventions or outcomes studied. However, treated study subjects experienced 11% more side effects than untreated subjects (number needed to treat to harm = 9). AUTHORS' CONCLUSIONS: Because the pooled data demonstrate no benefit and some harm from the use of antihistamines or decongestants alone or in combination in the management of OME, we recommend against their use.

Child↗
PubMed1990

Solubilization of salicylamide and acetaminophen by antihistamines in aqueous solution.

The effect of self-association of the antihistaminic drugs pheniramine, chlorpheniramine, and brompheniramine as their maleate salts on the solubilization of salicylamide and acetaminophen in aqueous solution has been investigated. The total solubility of salicylamide increased nonlinearly at lower antihistamine concentrations (less than 0.4 M), but reached limiting linearity (slope = 0.34 mol/mol of antihistamine) at higher concentrations (up to 0.8 M). Salicylamide solubility increases are approximately 10-fold at high concentrations (0.6-0.8 M) of antihistamine, while acetaminophen solubility increases are about fivefold at similar antihistamine concentrations. The solubilization data were analyzed with a stepwise self-association model. Based on a dimer model, the experimental and theoretical log excess salicylamide solubility profiles were in good agreement (r2 = 0.982) except at the lowest chlorpheniramine maleate concentrations. Such deviation at the lowest concentrations increased when trimer and 11-mer models were utilized. To account for this deviation, a monomer-dimer model based on interaction with both the chlorpheniramine maleate monomer and dimer was proposed. This model was in excellent agreement (r2 = 0.996) with the solubility data.

Acetaminophen↗
PubMed1979

Effects of a histamine synthesis inhibitor and antihistamines on the sexual behavior of female rats.

Intraventricular administration of alpha-hydrazinohistidine, a histamine synthesis inhibitor, at different doses and times before testing produced a significant decrease of lordotic responses and sexual receptivity in ovariectomized estrogen plus progesterone-primed female rats. The H1-antihistamines pyrilamine and chlorfeniramine and the H2-antihistamine metiamide, injected in the lateral ventricle, significantly decreased the lordosis quotient but did not modify receptivity; antihistamine-injected rats showed no soliciting behavior. Exploratory activity was decreased by both alpha-hydrazinohistidine and metiamide but not by the H1-antihistamines. It is concluded that treatments which either deplete histamine or block their receptors can alter female copulatory responsiveness. The mechanism of this antihistamine effect appears to be unrelated to that of other side effects, such as motor impairment, sedation, or local anesthesia.

Animals↗
PubMed1986

Interaction studies in mice of SCH 29851, a potential non-sedating antihistamine, with commonly used therapeutic agents.

SCH 29851 was studied for its ability to interact with selected drugs used in man. The non-sedating antihistamine terfenadine and the sedating antihistamine diphenhydramine were also studied for comparison. SCH 29851 at 80 mg/kg po in mice, a dose about 50 times its ED50 for blocking histamine-induced paw edema in the same species, potentiated the anticonvulsant effects of diazepam. At the high dose of 320 mg/kg po, about 80 times its ED50 for antihistamine effects, SCH 29851 potentiated the ability of high doses of ethanol and hexobarbital to induce loss of righting reflexes (LRR). However, no potentiation was seen when SCH 29851 was studied with lower doses of ethanol or phenobarbital that had anticonvulsant effects but did not cause LRR. At this high dose of 320 mg/kg po, SCH 29851 also did not interact with the antihypertensive drugs propranolol and alpha-methyldopa, the anti-ulcer drug cimetidine, the nasal decongestant pseudoephedrine, or the CNS stimulant d-amphetamine. A nearly identical profile of interactions was seen with terfenadine, including potentiation of diazepam at 50 times its antihistamine ED50, potentiation of ethanol- and barbiturate-induced LRR at 80 times its antihistamine ED50, and lack of interaction effects at 320 mg/kg po with each of the other tested drugs. The demonstration in this study of the significant interactions between diphenhydramine and many of the tested drugs is consistent with the clinical experience in man that this drug does have sedating properties and significant interactions with drugs like ethanol and diazepam.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Impact of CYP2D6*10 on H1-antihistamine-induced hypersomnia.

OBJECTIVE: This study investigated the relevance of the cytochrome P450 (CYP) 2D6 genotype to the adverse drug reactions (ADRs) of H1-antihistamines and the level of sedation. METHODS: Japanese participants in a health screening program were asked to describe any past history of ADRs. Any subjects reporting ADRs induced by H1-antihistamines were then individually interviewed and defined as cases. Excessive daytime sleepiness, which had occurred in the cases as an H1-antihistamine-induced ADR, was assessed by the Epworth sleepiness scale (ESS), and an ESS score >or=12 was considered hypersomnia. CYP2D6*4, *5, *14, and *10 were genotyped by a panel of polymerase chain reaction techniques. RESULTS: Out of 2,074 participants, 100 cases (M:F = 37:63, mean age 51.9 +/- 9.2 years) were eligible for analysis. The most common etiological drug was chlorpheniramine, which is the most frequently used H1-antihistamine in Japan. CYP2D6*10 allele and genotypes were more frequently found in the cases than in the healthy Japanese population in a large study (P < 0.005 and P = 0.039, respectively), but no difference was observed in the null alleles and genotypes. The ESS scores in 75 cases (M:F=25:50) who had experienced excessive daytime sleepiness were 9.5 +/- 5.5 in men and 12.9 +/- 6.1 in women (P < 0.001, cases vs. 34 subjects without symptoms; P = 0.001 men vs. women). The occurrence of hypersomnia increased as the number of CYP2D6 mutant alleles increased (P = 0.045). CONCLUSION: The results suggest that the presence of the CYP2D6*10 allele is a risk factor for development of H1-antihistamine-induced ADRs in Japanese.

Asian People↗