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

Cutaneous vaccination with coated microneedles prevents development of airway allergy

Allergy cases are increasing worldwide. Currently allergies are treated after their appearance in patients. However, now there is effort to make a preventive vaccine against allergies. The rationale is to target patient populations that are already sensitized to allergens but have yet to develop severe forms of the allergic disease, or who are susceptible to allergy development but have not yet developed them. Subcutaneous injections and the sublingual route have been used as the primary mode of preventive vaccine delivery. However, injections are painful, especially considering that they have to be given repeatedly to infants or young children. The sublingual route is hard to use since infants can't be trained to hold the vaccine under their tongue. In the present study, we demonstrate a microneedle (MN)-based cutaneous preventive allergy treatment against ovalbumin (Ova)-induced airway allergy in mice. Insertion of MNs coated with Ova as a model allergen and CpG oligonucleotide as an adjuvant (MNs-CIT) into the skin significantly induced Ova specific systemic immune response. This response was similar to that induced by hypodermic-needle-based delivery of Ova using the clinically-approved subcutaneous immunotherapy (SCIT) route. MNs-CIT regulated Th2 cytokines (IL-4, IL-5 & IL-13) and anti-inflammatory cytokines (IL-10) in the bronchoalveolar fluid, and IL-2 and IFN-γ cytokines in restimulated splenocyte cultures. Absence of mucus deposition inside the bronchiole wall and low collagen around the lung bronchioles after Ova-allergen challenge further confirmed the protective role of MNs-CIT. Overall, MNs-CIT represents a novel minimally invasive cutaneous immunotherapy to prevent the progression of Ova induced airway allergy in mice.

Antihistamine therapy in allergic rhinitis

Antihistamines have long been a mainstay in the therapy for allergic rhinitis. Many different oral antihistamines are available for use, and they are classified as first generation or second generation based on their pharmacologic properties and side-effect profiles. The recent introduction of intranasal antihistamines has further expanded the role of antihistamines in the treatment of allergic rhinitis. Certain patient populations, such as children and pregnant or lactating women, require special consideration regarding antihistamine choice and dosing as part of rhinitis therapy.

Selecting the Optimal Oral Antihistamine for Patients with Allergic Rhinitis

Allergic rhinitis (AR) is now recognised as a global health problem that affects 10-30% of adults and up to 40% of children. Each year, millions of patients seek treatment from their healthcare provider. However, the prevalence of AR maybe significantly underestimated because of misdiagnosis, under diagnosis and failure of patients to seek medical attention. In addition to the classical symptoms such as sneezing, nasal pruritus, congestion and rhinorrhoea, it is now recognised that AR has a significant impact on quality of life (QOL). This condition can lead to sleep disturbance as a result of nasal congestion, which leads to significant impairment in daily activities such as work and school. Traditionally, AR has been subdivided into seasonal AR (SAR) or perennial AR (PAR). SAR symptoms usually appear during a specific season in which aeroallergens are present in the outdoor air such as tree and grass pollen in the spring and summer and weed pollens in the autumn (fall); and PAR symptoms are present year-round and are triggered by dust mite, animal dander, indoor molds and cockroaches. Oral histamine H(1)-receptor antagonists (H(1) antihistamines) are one of the most commonly prescribed medications for the treatment of AR. There are several oral H(1) antihistamines available and it is important to know the pharmacology, such as administration interval, onset of action, metabolism and conditions that require administration adjustments. When prescribing oral H(1) antihistamines, the healthcare provider must take into account the clinical efficacy and weigh this against the risk of adverse effects from the agent. In addition to the clinical efficacy, potential for improvement in QOL with a particular treatment should also be considered.

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.

Histamine skin test reactivity following single and multiple doses of azelastine nasal spray in patients with seasonal allergic rhinitis

OBJECTIVE

To determine whether azelastine nasal spray suppresses the dermal response to epicutaneous histamine in allergic patients and the duration of suppression after azelastine use is discontinued.

METHODS

Seventy-eight patients with seasonal allergic rhinitis were entered into this randomized, double-blind, parallel-group, placebo-controlled study. Patients received either azelastine nasal spray (2 sprays per nostril twice daily) or placebo nasal spray for 14 days. Skin tests were performed 5 hours after the first dose of study drugs to determine the effect of a single dose of azelastine nasal spray on the wheal-and-flare response to histamine. At the end of the 14-day treatment period, skin tests were performed 5 hours after the last dose of study drugs and at 24-hour intervals thereafter, until each patient's wheal-and-flare response to histamine (1.0 and 5.0 mg/mL) returned to within 20% of baseline values.

RESULTS

A single dose of azelastine nasal spray did not significantly alter the wheal-and-flare response to histamine. The wheal response was within 20% of the baseline value in 82% and 88% (1.0 and 5.0 mg/mL of histamine, respectively) of the patients 5 hours after discontinuing 14 days of treatment with azelastine nasal spray. Wheal responses were within 20% of baseline values 48 hours after treatment was discontinued, whereas flare responses returned to within 20% of baseline within 48 hours in 92% of the patients.

CONCLUSIONS

Azelastine nasal spray should be discontinued for at least 48 hours before beginning allergy skin test procedures.

Efficacy and safety of topical azelastine compared with topical mitomycin C in patients with allergic conjunctivitis

PURPOSE

To compare the efficacy and safety of topical azelastine with topical mitomycin C (MMC) in patients with allergic conjunctivitis.

METHODS

Sixty-three patients (29 male, 29 female; 34 in the age range of 6 to 65 years) with allergic conjunctivitis were enrolled in this study. The patients were randomly assigned to receive topical azelastine 0.02% (n = 31) or topical MMC (0.2 mg/10 mL) (n = 31) four times daily for 3 months. Follow-up examinations were done at 2 weeks to examine side effects of the medications and again at 4 weeks to assess the outcome of treatment. The eyes were examined for relief of symptoms, cure of signs, and the appearance of side effects with use of these drugs.

RESULTS

The mean age of the patients in this study was 34.8 +/- 17.3 years. The age of patients in the MMC group was significantly higher than patients in the azelastine group (mean +/- SD, 25.2 +/- 13.5 years). More patients in the MMC group had relief of symptoms like redness [25 (80.7%) in the MMC group versus 19 (55.9%) in the azelastine group; p= 0.033], photophobia [11 (35.5%) in the MMC group versus six (17.7%) in the azelastine group; not significant], discharge [17 (54.8%) in the MMC group versus 11 (32.3%) in the azelastine group; not significant], and foreign body sensation [21 (67.7%) in the MMC group versus 16 (47.1%) in the azelastine group; not significant], while more patients in the azelastine group had relief of lacrimation [14 (41.2%) in the azelastine group versus 10 (32.3%) in the MMC group; not significant] and pain [12 (35.3%) in the azelastine group versus eight (25.8%) in the MMC group; not significant]. The MMC group also showed a greater decrease in follicles [31 (100.0%) in the MMC group versus six (17.7%) in the azelastine group; p= 0.0001] and papillae [29 (93.6%) in the MMC group versus four (11.8%) in the azelastine group; p= 0.0001]. Both drugs were found to be equally effective in relieving itching [18 (58.1%) in the MMC group versus 18 (52.9%) in the azelastine group; not significant]. In the MMC group, 27 (87.1%) patients had conjunctival hyperemia, 28 (90.3%) patients had episcleritis, and 29 (93.6%) patients had irritation. The use of topical azelastine did not cause any adverse event.

CONCLUSIONS

Though this was a short-term study, we found topical MMC to be more effective than topical azelastine in the treatment of allergic conjunctivitis both in terms of relief of symptoms and resolution of signs. The use of topical MMC in low doses does not cause any significant adverse effect.

The comparison of the efficacy and safety of cetirizine, oxatomide, ketotifen, and a placebo for the treatment of childhood perennial allergic rhinitis

BACKGROUND

There has been no study comparing the long-term effects of ketotifen, oxatomide, and cetirizine for the treatment of perennial allergic rhinitis among children.

OBJECTIVE

We conducted a study to compare the efficacy of the three agents for the treatment of perennial allergic rhinitis among children.

METHODS

The study consisted of a double-blind, placebo-controlled, randomized design, comprising 69 perennial allergic rhinitis patients with mite allergy, aged 6 to 12 years, randomly assigned to 1 of 4 test treatment groups for 3 months: 19 in the cetirizine group (10 mg daily), 18 in the ketotifen group (1 mg, twice daily), 16 in the oxatomide group (1 mg/kg, twice daily), and 16 in the placebo group. We used the nasal symptom score of diary card and the Pediatric Rhinoconjunctivitis Quality of Life Questionnaire and eosinophil cation protein peripheral blood total eosinophil count and immunoglobulin E level, eosinophil proportion from a nasal smear, and nasal peak expiratory flow rate to evaluate the effect of the four agents.

RESULTS

Cetirizine was significantly more effective at reducing the mean rhinorrhea score compared with oxatomide for both weeks 8 and 12 (P < 0.01). Before the end of week 12, cetirizine was significantly more effective than ketotifen (P < 0.01). Cetirizine and oxatomide significantly decreased the mean Pediatric Rhinoconjunctivitis Quality of Life Questionnaire score compared with the placebo for week 12 (P < 0.05).

CONCLUSIONS

Cetirizine was more effective than oxatomide and ketotifen for the relief of nasal congestion and rhinorrhea, and was responsible for significantly decreasing the eosinophil representation of a posttreatment nasal smear.

Evaluation of the onset and duration of effect of azelastine eye drops (0.05%) versus placebo in patients with allergic conjunctivitis using an allergen challenge model

OBJECTIVE

The trial evaluated the effectiveness of the investigational antihistaminic and antiallergic compound Azelastine Eye Drops (AZE) in the treatment of allergic conjunctivitis using an allergen challenge model.

DESIGN

Randomized, double-blind, placebo-controlled, paired-eye study.

PARTICIPANTS

Adults with a history of allergic conjunctivitis (>/=2 years) who were asymptomatic throughout the trial, had a positive skin test (cat dander, grass, or ragweed pollen within the last year), and had a positive conjunctival reaction (score 2+ or more for itching and redness in both eyes on a 0-4 scale) during two separate conjunctival provocation tests (CPT) before randomization.

METHODS

Eighty patients underwent a 2-week screening period (visits 1 and 2) that included a CPT during visit 1 to establish the allergen threshold dose and a second confirmatory CPT performed at visit 2. Eye symptom assessments for itching (evaluated by patient) and conjunctival redness (evaluated by physician) were performed 5 and 10 minutes after CPT using a 5-point scale (from 0 = none to 4+ = severe). Qualified patients were randomized to receive one drop of AZE (0.015 mg of azelastine hydrochloride) in one eye and one drop of placebo in the other eye 20 minutes before CPT at visit 3 (onset) and 8 or 10 hours before CPT at visit 4 (duration).

MAIN OUTCOME MEASURES

Individual severity scores for itching (evaluated by patient) and conjunctival redness (evaluated by physician) for each eye at 3, 5, and 10 minutes after CPT at visits 3 and 4 using a 5-point scale (0 = none to 4+ = very severe).

RESULTS

Each of the 80 randomized patients completed the trial. Mean itching and conjunctival redness scores at visit 3 (onset) were significantly lower (P: < 0.001) in the AZE-treated eyes than in the placebo-treated eyes. At visit 4 (duration), mean itching and conjunctival redness scores (P: </= 0.003) for the 8-hour group and mean itching scores (P: </= 0.001) for the 10-hour group were significantly lower in the AZE-treated eyes than in the placebo-treated eyes. Significant differences in mean tearing and chemosis severity scores were also seen at visit 3 (onset) and visit 4 (duration) in the AZE-treated eyes when compared with the placebo-treated eyes. Treatment with AZE was well tolerated.

CONCLUSIONS

Therapy of experimentally induced allergic conjunctivitis with AZE was highly effective, with an onset of action seen within 3 minutes and a duration of effect of at least 8 to 10 hours.

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.

Inhibition of leukotriene synthesis by terfenadine in vitro

To determine the inhibitory mechanisms of terfenadine on the synthesis of leukotriene C4 (LTC4), an important mediator in allergic diseases, we evaluated the action of terfenadine on the IgE-dependent production of LTC4 in rat basophilic leukaemia 2H3 cells. Rat IgE-loaded cells were stimulated with anti-IgE in the presence or absence of various concentrations of terfenadine and the level of LTC4 released into the medium was measured by performing a specific radio immunoassay. Terfenadine inhibited the synthesis of LTC4 to 67.2% at a concentration of 5 microg/ml. LT synthesis was directly suppressed by inhibition of 5-lipoxygenase (5-LO) through calcium ion-independent mechanisms, and was also possibly suppressed by inhibition of cytosolic phospholipase A2 and 5-LO by blocking the influx of intracellular calcium ion that was initiated by IgE-related stimulation.

Executive summary

Allergic rhinitis is now recognized as a major cause of morbidity that significantly impairs function and quality of life. Moreover, it is now widely held that the pathophysiologic mechanisms causing nasal allergy contribute, or predispose many individuals, to the development of other airway diseases, including asthma. Allergic rhinitis may well be a factor in 24% of children with otitis media with effusion (OME), and perhaps 28% of cases of chronic sinusitis. As many as 78% of persons with asthma aged 15 to 30 years have elevated serum IgE antibodies to five common aeroallergens. In many instances, nasal allergy signals the presence of more severe disease.

Considerable evidence now suggests that early and appropriate intervention can improve the quality of life and productivity of patients with allergic rhinitis, enhance the academic performance of children, and reduce the prevalence of airway complications. The goal of treatment has shifted from mere symptom alleviation to blocking the pathophysiologic mechanisms that cause chronic allergic inflammation and leave patients vulnerable to airway infections. The earlier in a patient's life that this can be accomplished, the better the anticipated consequences.

A panel of experts was convened in Amsterdam, The Netherlands, on 2 September 1996, to explore these issues and their impact on allergy prevention and treatment in primary care. Their undertaking was supported by an unrestricted educational grant from Schering‐Plough Pharmaceuticals.

Clinical comparison of histamine H1-receptor antagonist drugs

Nearly 40 million Americans have symptoms of upper respiratory allergies, making antihistamines among the most frequently used pharmacologic agents. Although there are mediators of allergic symptoms in addition to histamine, therapy for allergic rhinitis and urticaria has focused upon the use of antihistamines. The classic histamine H1-receptor antagonists, however, are not selective for the H1 site and produce a variety of dopaminergic, serotonergic, and cholinergic responses leading to considerable adverse effects in the central nervous system consequent to both their pharmacologic nonselectivity and their ability to penetrate the blood-brain barrier readily. The second-generation antihistamines were a major advance in the therapy of allergic rhinitis, because they do not penetrate the blood-brain barrier as rapidly and are also designed for greater specificity at H1-receptor. Given their greater selectivity for the H1-receptor, they cause fewer undesirable central nervous system actions, whereas their efficacy is similar to that of the classic antihistamines used in the treatment of allergic rhinitis. Selecting among these antihistamines for the treatment of allergic rhinitis has focused on their pharmacokinetics and adverse effect profiles. The potential cardiotoxic effects of some antihistamines when their metabolism is inhibited requires caution in prescribing these agents. The antiallergic and antiasthmatic effects of several newer antihistamines are being explored. For the clinician, making the therapeutic decision among H1-receptor antagonists requires a comprehensive knowledge of their diverse effects.

The effect of cetirizine and loratadine on codeine-induced histamine release in human skin in vivo assessed by cutaneous microdialysis

OBJECTIVE AND DESIGN

To determine whether or not cetirizine and loratadine inhibit codeine- induced histamine release in human skin in vivo, we conducted a placebo-controlled double-blind trial in which histamine release was assessed by dermal microdialysis.

SUBJECTS

A group of ten normal volunteers were studied, each subject visiting the laboratory on three occasions with intervals of at least 2 weeks between visits.

TREATMENT

Cetirizine, loratadine (both 10 mg) or placebo was given orally 4 h before provocation of weal and flare responses in the skin by intradermal injection of 25 microliters of 3 or 10 mg/ml codeine 1 mm from the centre of individual 216 microns diameter microdialysis fibres inserted in the dermis.

METHODS

Dialysate was collected at 2 min intervals for 4 min before and 20 min after codeine injection and histamine assayed spectrofluorometrically. Weal and flare responses to codeine were assessed in the opposite arm.

RESULTS

Histamine concentrations in the microdialysis fibre outflow with 3 and 10 mg/ml codeine were maximal at 2-4 min when 910 +/- 156 and 1194 +/- 304 nM respectively were found in the placebo group. Cetirizine and loratadine did not modify either the kinetics or total histamine release while significantly (p < 0.01) inhibiting weal and flare responses.

CONCLUSIONS

Neither cetirizine nor loratadine inhibited codeine-induced histamine release or modified the time course of its release in human skin in vivo when given in clinically used doses which are sufficient to significantly reduce weal and flare responses.

Comparison of intranasal triamcinolone acetonide with oral loratadine for the treatment of patients with seasonal allergic rhinitis

This multicenter, double-blind, randomized, controlled, parallel-group study compared the safety and efficacy of intranasal triamcinolone acetonide with oral loratadine in relieving symptoms of ragweed-induced seasonal allergic rhinitis. Patients from community-based allergy practices with a history of at least two seasons of seasonal allergic rhinitis verified by a positive skin test received either once-daily treatment with intranasal triacinolone acetonide 220 micrograms plus 1 placebo capsule or oral loratadine 10 mg plus placebo nasal spray. Other medications for rhinitis were prohibited. Changes in rhinitis symptoms were assessed by using patient evaluations, physician global evaluations, and withdrawal rates. Efficacy was evaluated in 274 of 298 patients randomized to treatment (134 to triamcinolone acetonide and 140 to loratadine). Mean total nasal symptom scores for weeks 1, 2, 3, and 4 and the overall score showed greater improvement (P = 0.001) with triamcinolone acetonide than with loratadine. Improvement in all rhinitis symptoms was significantly greater with triamcinolone acetonide than with loratadine; there was a trend for greater improvement in ocular symptoms with triamcinolone acetonide. Physicians' global evaluations indicated triamcinolone acetonide provided moderate-to-complete relief in 78% of patients compared with 58% of loratadine-treated patients (P < or = 0.0001). Both treatments were well tolerated; headache was the most commonly reported adverse event in both groups. Intranasal triamcinolone acetonide was significantly more effective than oral loratadine in relieving the symptoms of seasonal allergic rhinitis.