Psychometric aspects of antihistamines

Treatment of Allergic Rhinitis during Pregnancy

Background

Allergic rhinitis (AR) affecting ∼20–30% of women in childbearing age can be considered one of the most common group of medical conditions that complicate pregnancy. AR with symptoms of nasal obstruction, sneezing, and itching may require pharmacotherapy. However, there are concerns regarding the safety of different available agents that can be used during pregnancy with respect to both maternal and fetal well being.

Conclusions

The best first-line approach in the management of AR is avoidance of allergens. If environmental modification is ineffective, then the pharmacologic agents should be chosen. For symptoms of rhinorrhea, sneezing, or itching, intranasal cromolyn, with its excellent safety profile, should be considered as first-line therapy. If cromolyn is ineffective or poorly tolerated, first-generation (e.g., chlorpheniramine and tripelennamine) and second generation (e.g., cetirizine and loratadine) antihistamines can be given. Intranasal steroids (e.g., beclomethasone dipropionate, and budesonide) can be added to first-line therapy especially for severe nasal obstruction. There are no epidemiological studies with newer intranasal steroids (e.g., flunisolide, triamcinolone acetonide, fluticasone propionate, and mometasone furoate) during the first trimester of pregnancy. Immunotherapy has not proven to be teratogenic and is clinically useful in improving symptoms. Oral and topical decongestants can be considered as second-line therapy, for short-term relief, when no safer alternative is available.

Update on local allergic rhinitis

We here provide an update on the literature regarding local allergic rhinitis (LAR). In reviewing LAR, we have included an updated definition, classifications, mechanisms, comorbidities, and recommendations for diagnosis and treatment for LAR, as well as the defined research areas for future evidence-based studies. LAR is a localised nasal allergic response in the absence of systemic atopy characterised by local production of specific IgE (sIgE) antibodies, a TH2 pattern of mucosal cell infiltration during natural exposure to aeroallergens, and a positive nasal allergen provocation test response, with the release of inflammatory mediators. The localised allergic response of LAR is an important topic for the study of allergies. This review provides an update on the current knowledge of LAR.

The effects of fexofenadine at steady-state on sleep architecture: a study using polysomnography in healthy Korean volunteers

OBJECTIVES

To compare the effects of a first-generation antihistamine, chlorpheniramine, with those of the second-generation antihistamine, fexofenadine, at steady-state, on nocturnal sleep architecture in healthy Korean volunteers using polysomnography and the Multiple Sleep Latency Test. We evaluated whether a genetic polymorphism of multi-drug resistance 1 gene (MDR1) could produce variations in pharmacokinetic and pharmacodynamic parameters of fexofenadine.

DESIGN/METHODS

Ten healthy male volunteers received one capsule of fexofenadine 180 mg once each morning or chlorpheniramine 6 mg (2 mg in the morning and 4 mg after 12 h) for 3 days, in a single-site, randomized, double-blind, two-treatment, multiple-dosing, two-way crossover study, with a washout period of 7 days. Overnight polysomnography was measured on the second night of the treatment period. The Multiple Sleep Latency Test was carried out the next morning. Blood samples were taken for the assessment of fexofenadine pharmacokinetics and MDR1 genotyping on the third day.

RESULTS

Compared with baseline and fexofenadine, chlorpheniramine significantly increased the latency in rapid eye movement (REM) sleep, with no significant decrease in the percentage of REM sleep. No significant change in latency for REM sleep or percentage REM sleep after dosing with fexofenadine was observed. There was no significant change in the daytime sleepiness with fexofenadine and chlorpheniramine. The effects of MDR1 genotypes and haplotypes on the pharmacokinetics and pharmacodynamics of fexofenadine were not significant.

CONCLUSIONS

Our findings suggest that fexofenadine and chlorpheniramine at steady-state have no significant effect on nocturnal sleep variables and daytime sleepiness, when compared to baseline.

Second-Generation Antihistamines

Antihistamines are useful medications for the treatment of a variety of allergic disorders. Second-generation antihistamines avidly and selectively bind to peripheral histamine H1 receptors and, consequently, provide gratifying relief of histamine-mediated symptoms in a majority of atopic patients. This tight receptor specificity additionally leads to few effects on other neuronal or hormonal systems, with the result that adverse effects associated with these medications, with the exception of noticeable sedation in about 10% of cetirizine-treated patients, resemble those of placebo overall. Similarly, serious adverse drug reactions and interactions are uncommon with these medicines. Therapeutic interchange to one of the available second-generation antihistamines is a reasonable approach to limiting an institutional formulary, and adoption of such a policy has proven capable of creating substantial cost savings. Differences in overall efficacy and safety between available second-generation antihistamines, when administered in equivalent dosages, are not large. However, among the antihistamines presently available, fexofenadine may offer the best overall balance of effectiveness and safety, and this agent is an appropriate selection for initial or switch therapy for most patients with mild or moderate allergic symptoms. Cetirizine is the most potent antihistamine available and has been subjected to more clinical study than any other. This agent is appropriate for patients proven unresponsive to other antihistamines and for those with the most severe symptoms who might benefit from antihistamine treatment of the highest potency that can be dose-titrated up to maximal intensity.

Emerging safety issues regarding long-term usage of H(1)receptor antagonists

The second generation histamine H(1)-receptor antagonists are important therapeutic tools in the treatment of atopic disease and may also have a place as an adjunct therapy for those patients whose allergic asthma coexists with allergic rhinitis. They are amongst the most widely prescribed and safest drugs in the world. However, as second generation H(1)-receptor antagonists are used to treat non-life threatening conditions, the risk of adverse effects is of vital importance. For many, the potential for sedation by some of the newer antihistamines still remains an issue, while there have recently been widespread concerns regarding the potential for cardiotoxicity and the impact of drug-drug interactions associated with some second generation H(1)-receptor antagonists. Consequently, progress with this class of drugs should involve not only increased efficacy but also improvements in their safety and specificity. Moreover, there is a trend towards using second generation H(1)-receptor antagonists as long-term therapy rather than confining their use to treating the short-term manifestations of allergic disease. To this end, a number of novel, potent and safe antihistamines have been developed which are either metabolites of active drugs or enantiomers. This review will examine some of the safety issues associated with established and newer second generation drugs particularly in relation to their long-term usage in adults and children.

Long-term evaluation of the impact of the h1-receptor antagonist cetirizine on the behavioral, cognitive, and psychomotor development of very young children with atopic dermatitis

The impact of the prolonged use of cetirizine at high dose (0.25 mg/kg twice a day over 18 mo) on behavior and cognitive ability was examined in a double-blind, randomized, placebo-controlled trial (ETAC-Early Treatment of the Atopic Child) designed to establish whether it was possible to prevent young children (1-2 y old at study entry) with atopic dermatitis from developing asthma. Well-validated and standardized measures of behavior (Behavior Screening Questionnaire) and cognition (McCarthy Scales of Children's Abilities) were used. In addition, the ages of attainment of psychomotor milestones were established. These measures were taken between an average of 32 and 53 mo of age, both during the study treatment with cetirizine or placebo and after the study treatment had been discontinued. The Behavior Screening Questionnaire was completed at least once on approximately 300 children in each group and on approximately 200 children on five occasions. The McCarthy Scales of Children's Abilities were administered to approximately 100 in each group at three different times. There were no significant differences between the cetirizine and placebo groups on either of the behavior and cognition measures or in psychomotor milestones during or after the study treatment. These findings suggest that there are no adverse effects on behavior or learning processes associated with the prolonged use of cetirizine in young children with atopic dermatitis.

Lack of effect of single and repeated doses of levocetirizine, a new antihistamine drug, on cognitive and psychomotor functions in healthy volunteers

AIMS

Levocetirizine (R-cetirizine), is the active enantiomer of cetirizine, an antihistamine indicated in the treatment of allergic rhinitis and chronic idiopathic urticaria. The purpose of this trial was to analyse the effects of levocetirizine single and multiple doses on CNS using integrated measures of cognitive and psychometric performance.

METHODS

A battery of psychometric tests was used: critical flicker fusion (CFF), choice reaction time (CRT), body sway (BS), learning memory test (LMT) and subjective assessments of alertness compared with placebo. Nineteen (19) healthy male volunteers received either levocetirizine 5 mg (therapeutic dose), diphenhydramine 50 mg or placebo once daily for 5 consecutive days (3-way cross-over). Diphenhydramine was used as a positive control. CFF tests were performed on days 1 and 5 at baseline and up to 24 h following drug intake. Subjects used the Bond-Lader visual analogue scales (VAS) to assess their mood and vigilance.

RESULTS

In contrast to diphenhydramine, when compared with placebo, levocetirizine did not modify the CFF (primary endpoint), regardless of the dosing scheme (-1.62 Hz [-2.61, -0.64] and -0.81 Hz [-1.80, 0.19], respectively, 3 h after dosing on day 1). CRT was decreased with both levocetirizine and placebo up to 5 h after dosing on day 1 and up to 3 h after dosing on day 5. Body sway data were similar with levocetirizine and placebo but increased with diphenhydramine. LMT was similar in all three groups. No relevant difference between placebo and levocetirizine was recorded by the subjects on their assessment of alertness using the VAS, whilst decreased alertness was reported following diphenhydramine 50 mg.

CONCLUSIONS

This study showed that levocetirizine does not produce any deleterious effect on cognitive and psychometric functions compared with placebo in healthy male volunteers.

Sedation, cognition, and antihistamines

First-generation antihistamines are well-known to cause subjective drowsiness. A myriad of studies has also been published that suggest a clear relationship between the use of these drugs and objective performance impairment. Although not all of the tests used in these studies have been validated, the data are fairly consistent, and suggest a difference between earlier (first-generation) sedating antihistamines and the newer (second-generation) nonsedating antihistamines.

New insights into the second generation antihistamines

Second generation antihistamines are recognised as being highly effective treatments for allergy-based disease and are among the most frequently prescribed and safest drugs in the world. However, consideration of the therapeutic index or the benefit/risk ratio of the H1 receptor antagonists is of paramount importance when prescribing this class of compounds as they are used to treat non-life threatening conditions. There are many second generation antihistamines available and at first examination these appear to be comparable in terms of safety and efficacy. However, the newer antihistamines in fact represent a heterogeneous group of compounds, having markedly differing chemical structures, adverse effects, half-life, tissue distribution and metabolism, spectrum of antihistaminic properties, and varying degrees of anti-inflammatory effects. With regard to the latter, there is growing awareness that some of these compounds might represent useful adjunct medications in asthma therapy. In terms of safety issues, the current second generation grouping includes compounds with proven cardiotoxic effects and others with the potential for adverse drug interactions. Moreover, some of the second generation H1 antagonists have given cause for concern regarding their potential to cause a degree of somnolence in some individuals. It can be argued, therefore, that the present second generation grouping is too large and indistinct since this was based primarily on the concept of separating the first generation sedating compounds from nonsedating H1 antagonists. Although it is too early to talk about a third generation grouping of antihistamines, future membership of such a classification could be based on a low volume of distribution coupled with a lack of sedating effects, drug interactions and cardiotoxicity.

Sedation and antihistamines: a review of inter-drug differences using proportional impairment ratios

The use of antihistamines (AHs) has until recently been associated with a number of undesirable side effects, the most troublesome of which is sedation. There are two aspects to sedation. The first, an objectively determined measure based on the results of psychometric tests from controlled trials, and the second, the subject's response to the administration of a drug. Since AHs are largely used in ambulant patients, a complete evaluation of sedation should be performed through standardised objective and subjective tests, shown to be sensitive to the central effects of AHs.An extensive review of the literature identified 76 studies of H(1) receptor antagonists in healthy volunteers, in which assessment of sedation was the primary objective. Results from studies published in peer-reviewed journals which employed a placebo condition as well as a positive internal control using a crossover design were analysed to determine the extent to which a particular antihistamine produced impairments on a battery of psychometric tests. The impairment index for each antihistamine was calculated and subsequently compared with the impairment index obtained for all other AHs.The calculation of this proportional impairment ratio enabled the sedative potential of an individual antihistamine to be identified relative to all other AHs and thus allowed the ranking of AHs with respect to their ability to cause impairments of cognitive and psychomotor function.Findings from this review clearly demonstrate that there are distinct classes of AHs with respect to their ability to impair cognitive function and psychomotor performance. Copyright 2000 John Wiley & Sons, Ltd.

Antihistamines: models to assess sedative properties, assessment of sedation, safety and other side-effects

Behavioural changes are produced by any drug that enters the central nervous system. These psychoactive effects include changes in alertness, concentration, attention, memory, cognition, psychomotor accuracy, skilled performance and affect. Changes in psychological performance may affect the safety of both the individuals taking the drug and of those people coming into contact with them. The aims of psychopharmacological performance tests are to describe the nature, extent and severity of these changes and identify drugs without deleterious effects upon performance. Use of traditional antihistamines has until recently been associated with a number of undesirable side-effects, the most troublesome of which is sedation. There are two aspects to sedation. Firstly, an objectively determined one based on the results of psychometric tests from controlled trials and secondly, the subjects response to the administration of a drug. Although the second generation of antihistamines have a much more favourable therapeutic index, use of these agents has also been reported to cause varying degrees of sedation. As antihistamines are largely used by ambulant patients, a complete evaluation of sedation should be performed through standardized objective tests, shown to be sensitive to the central effects of antihistamines as well as reliable ratings of subjective experiences. An extensive review of the literature has identified a number of tests which appear to be sensitive to the central effects of antihistamines. These include tests of psychomotor performance, sensori-motor co-ordination speed, information processing, sensory skills as well as physiological measures and subjective rating scales. Using this battery of cognitive and psychomotor tests, it is evident that only a very limited number of antihistamines can claim to be virtually free of both objective and subjective sedative effects, although the second generation of antihistamines are generally less impairing than the original ones; when prescribed at their recommended doses.

Second-generation antihistamines: a comparative review

Second-generation histamine H1 receptor antagonists (antihistamines) have been developed to reduce or eliminate the sedation and anticholinergic adverse effects that occur with older H1 receptor antagonists. This article evaluates second-generation antihistamines, including acrivastine, astemizole, azelastine, cetirizine, ebastine, fexofenadine, ketotifen, loratadine, mizolastine and terfenadine, for significant features that affect choice. In addition to their primary mechanism of antagonising histamine at the H1 receptor, these agents may act on other mediators of the allergic reaction. However, the clinical significance of activity beyond that mediated by histamine H1 receptor antagonism has yet to be demonstrated. Most of the agents reviewed are metabolised by the liver to active metabolites that play a significant role in their effect. Conditions that result in accumulation of astemizole, ebastine and terfenadine may prolong the QT interval and result in torsade de pointes. The remaining agents reviewed do not appear to have this risk. For allergic rhinitis, all agents are effective and the choice should be based on other factors. For urticaria, cetirizine and mizolastine demonstrate superior suppression of wheal and flare at the dosages recommended by the manufacturer. For atopic dermatitis, as adjunctive therapy to reduce pruritus, cetirizine, ketotifen and loratadine demonstrate efficacy. Although current evidence does not suggest a primary role for these agents in the management of asthma, it does support their use for asthmatic patients when there is coexisting allergic rhinitis, dermatitis or urticaria.

Intranasal azelastine. A review of its efficacy in the management of allergic rhinitis

Azelastine, a phthalazinone compound, is a second generation histamine H1 receptor antagonist which has shown clinical efficacy in relieving the symptoms of allergic rhinitis when administered as either an oral or intranasal formulation. It is thought to improve both the early and late phase symptoms of rhinitis through a combination of antihistaminic, antiallergic and anti-inflammatory mechanisms. Symptom improvements are evident as early as 30 minutes, after intranasal administration of azelastine [2 puffs per nostril (0.56mg)] and are apparent for up to 12 hours in patients with seasonal allergic rhinitis (SAR). The effect on nasal blockage is variable: in some studies objective and/or subjective assessment showed a reduction in blockage, whereas in other studies there was no improvement. Intranasal azelastine 1 puff per nostril twice daily is generally as effective as standard doses of other antihistamine agents including intranasal levocabastine and oral cetirizine, ebastine, loratadine and terfenadine at reducing the overall symptoms of rhinitis. The relative efficacies of azelastine and intranasal corticosteroids (beclomethasone and budesonide) remain unclear. However, overall, the corticosteroids tended to improve rhinitis symptoms to a greater extent than the antihistamine. Azelastine was well tolerated in clinical trials and postmarketing surveys. The most frequently reported adverse events were bitter taste, application site irritation and rhinitis. The incidence of sedation did not differ significantly between azelastine and placebo recipients and preliminary report showed cardiovascular parameters were not significantly altered in patients with perennial allergic rhinitis (PAR).

CONCLUSION

Twice-daily intranasal azelastine offers an effective and well tolerated alternative to other antihistamine agents currently recommended for the symptomatic relief of mild to severe SAR and PAR in adults and children (aged > or = 12 years in the US; aged > or = 6 years in some European countries including the UK). The rapid onset, confined topical activity and reduced sedation demonstrated by the intranasal formulation of azelastine may offer an advantage over other antihistamine agents, although this has yet to be confirmed.

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.