Clinical pharmacology of the H1-receptor antagonists cetirizine and loratadine in children

Model-informed pediatric development applied to bilastine: Analysis of the clinical PK data and confirmation of the dose selected for the target population

Bilastine is a non-sedating second-generation H₁ antihistamine approved for treatment of allergic rhinoconjunctivitis (AR) and urticaria (U) in adults at the oral (p.o.) dose of 20 mg once daily (OD). Optimal attributes can be anticipated for its clinical use in pediatrics due to its favorable safety and tolerability and age-independent PD profile. The aim of this work was to characterize bilastine PK in children through population modeling of data from a limited sampling confirmatory clinical trial in children with AR or U. The objective was also to ascertain whether the proposed dose (10 mg/day) in the target pediatric subset aged 2-<12 years matches the systemic exposure seen in adults at the 20 mg/day dose. A popPK model characterizing bilastine PK behavior in children aged from 4 to <12 years treated with 10 mg oral bilastine daily was successfully developed and qualified. No relationship was found between bilastine PK and age or weight; stopping rules pre-stablished to finalize the trial, i.e., model completeness and no dependence of exposure on decreasing age, were thus fulfilled. On a second step, the popPK model in children was linked to the PD model in adults assuming the same PD as described in adults and used to compare the PD outcome between both populations. Finally, an allometric scaling method and a physiological approximation were used to evaluate the suitability of the selected dose in the youngest children, showing that children from 2 years were deemed to belong to the same population as well. The achievement of comparable PK (i.e., within the range) to that observed in adults after the therapeutic dose of 20 mg, together with the achievement of similar PD and additional integrative analysis, served to confirm the validity of the 10 mg daily dose for the target pediatric subset (2 to <12 years).

Model Informed Pediatric Development Applied to Bilastine: Ontogenic PK Model Development, Dose Selection for First Time in Children and PK Study Design

PURPOSE

Bilastine is an H₁ antagonist whose pharmacokinetics (PK) and pharmacodynamics (PD) have been resolved in adults with a therapeutic oral dose of 20 mg/day. Bilastine has favorable characteristics for use in pediatrics but the PK/PD and the optimal dose in children had yet to be clinically explored. The purpose is to: (1) Develop an ontogenic predictive model of bilastine PK linked to the PD in adults by integrating current knowledge; (2) Use the model to design a PK study in children; (3) Confirm the selected dose and the study design through the evaluation of model predictability in the first recruited children; (4) Consider for inclusion the group of younger children (< 6 years).

METHODS

A semi-mechanistic approach was applied to predict bilastine PK in children assuming the same PD as described in adults. The model was used to simulate the time evolution of plasma levels and wheal and flare effects after several doses and design an adaptive PK trial in children that was then confirmed using data from the first recruits by comparing observations with model predictions.

RESULTS

PK/PD simulations supported the selection of 10 mg/day in 2 to <12 year olds. Results from the first interim analysis confirmed the model predictions and design hence trial continuation.

CONCLUSION

The model successfully predicted bilastine PK in pediatrics and optimally assisted the selection of the dose and sampling scheme for the trial in children. The selected dose was considered suitable for younger children and the forthcoming safety study in children aged 2 to <12 years.

Inhibitory effects of 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate on allergic inflammatory responses in rat basophilic leukemia cells

Mast cells play crucial roles in the initiation of allergic inflammatory responses by releasing various mediators such as histamines, cytokines, and leukotrienes. In addition, signaling cascade pathways, such as the mitogen-activated protein kinase (MAPK) pathway, contribute to the regulation of mast cell degranulation. Accordingly, different research strategies have been pursued to develop anti-inflammatory and anti-allergic drugs by regulating these signaling pathways. The development of new drugs that inhibit mast cell degranulation may help in the treatment of allergies. In this study, we investigated the effects of coumarin derivatives on mast cell degranulation. The effect of coumarin derivatives on degranulation in rat basophilic leukemia (RBL)-2H3 cells was determined by a β-hexosaminidase assay and histamine assay. A coumarin derivative 1 (C1), 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate, inhibited degranulation in a dose-dependent manner and demonstrated maximum therapeutic effect when used at 25μM. Additionally, these compounds inhibited the phosphorylation of the extracellular signal-regulated kinase (ERK) pathway. Taken together, these results indicate that 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate inhibits mast cell degranulation by suppressing the activation of the ERK pathway and this inhibitory effect suggests potential therapeutic strategies towards the prevention of allergic disorders.

Pharmacokinetics in special populations

Pharmacokinetics are typically dependent on a variety of physiological variables (e.g., age, ethnicity, or pregnancy) or pathological conditions (e.g., renal and hepatic insufficiency, cardiac dysfunction, obesity, etc.). The influence of some of these conditions has not always been thoroughly assessed in the clinical studies of antiallergic drugs. However, the knowledge of the physiological grounds of the pharmacokinetics can provide some insight for predicting the potential alterations and guiding the initial prescription strategies. It is important to recognize that both pharmacokinetic and pharmacodynamic differences between populations should be considered. The available information on drugs used for the therapy of allergic diseases is reviewed in this chapter.

Clinical features and natural history of physical urticaria in children

Physical triggers are the most common precipitating factors for chronic urticaria in childhood. We investigate the natural history of physical urticaria (PU) and attempt to identify prognostic features. A retrospective study covering a 3 yr period (1999-2002) identified 82 children with PU seen in a tertiary referral centre. Parents of 53 children with PU responded to follow up by questionnaire and were included in the data analysis. The questionnaire ascertained symptom severity, remission status, effects of treatment and prognostic factors in determining resolution of the urticaria. Not all parents answered every question. Fisher's exact test was used to compare the remission and non-remission groups and Kaplan-Meir survival analysis was used to derive estimates of time to achieve remission. All 53 children with PU had chronic urticaria, with dermatographic, cholinergic and mixed subtypes of PU forming over 70% of the subtypes. Overall, 13% (6/45) of the children reported respiratory symptoms with the episodes of urticaria, and 67% (35/52) reported associated angioedema. In univariate analysis, a history of other allergic conditions in the child was associated with a greater chance of non-remission (p = 0.007). No significant difference in the age of onset of urticaria and duration of individual bouts was noted between the remission and non-remission groups. Episodes of urticaria were significantly less frequent (p = 0.02) in the remission group (monthly/weekly/daily - 70%/30%/0%) than the non-remission group (38%/34%/28%). Among the 20 children achieving remission, on average this occurred 30 months after onset of symptoms. In the survival analysis, the number of children becoming urticaria free was 11.6% (95% CI: 5.4%-23.9%) at 1 yr post-onset and 38.4% (95% CI: 25.9%-54.3%) 5 yr post-onset. In conclusion, based on this selected tertiary population, the prognosis for PU may not be as benign as has previously been reported. A history of allergic conditions and more frequent episodes of urticaria were associated with a poorer prognosis.

A survey of emergency department management of acute urticaria in children

OBJECTIVES

To describe emergency department management of acute urticaria in children and to determine factors associated with management strategies and adherence to practice guidelines.

METHODS

Self-administered cross-sectional survey mailed to all Section of Emergency Medicine members of the American Academy of Pediatrics (n = 1190) and 1000 randomly selected members of the American College of Emergency Physicians. Main outcome measure was proportion of respondents adhering to published guidelines. Factors associated with management strategies were analyzed using bivariate and logistic regression analyses.

RESULTS

Of 2190 surveys sent, 1137 (52.5%) were available for analysis. Respondents included 44.6% pediatric emergency physicians, 36.4% emergency physicians, and 15.3% pediatricians. First-generation histamine (H)1 antagonists alone were the most common therapy used on initial presentation of acute urticaria, followed by corticosteroids, H2 antagonists, and second-generation H1 antagonists, used by only 7.8%, despite their recommendation as first-line therapy. Physicians working in an emergency department as opposed to an urgent or primary care setting were less likely to use second-generation H1 antagonists (odds ratio [OR], 0.3 [0.1-0.7]). General emergency physicians were 2.6 times more likely to use H2 antagonists and more than 3 times as likely to use corticosteroids. Only 14.2% of physicians overall were familiar with guideline recommendations.

CONCLUSIONS

Minimal awareness and use of existing guidelines, and low concordance with published recommendations exist. Management practices vary and are influenced by training, practice setting, and clinical experience.

Inhibition of the histamine-induced weal and flare response: a valid surrogate measure for antihistamine clinical efficacy?

Histamine plays a central role in allergic responses. Inhibition of the weal and flare response to histamine is a traditional pharmacodynamic tool to measure the activity of H(1)-receptor antagonists. The time course and duration of cutaneous weal and flare inhibition are often used as surrogate measures of clinical efficacy. Pharmacodynamic differences among antihistamines are often interpreted to indicate differences in clinical efficacy. A systematic review of literature from 1980 to 2006 regarding the histamine induced weal and flare was undertaken. Search terms included 'histamine', 'skin test', 'weal', 'flare', and 'antihistamine'; retrieved articles were searched for relevant studies not identified initially. Data from human studies on the inhibition of the weal and flare by second-generation antihistamines were extracted and assessed. A literature search from 1980 to 2006 was undertaken for comparative studies of second-generation antihistamines in the clinical settings of allergic rhinitis (AR) and chronic idiopathic urticaria; data extracted from these studies underwent systematic review. Differences were noted among second-generation antihistamines in terms of their ability to inhibit the histamine-induced weal and flare. Corresponding differences in terms of clinical efficacy in AR and chronic urticaria were not identified following a systematic review. The reasons for the disconnect between pharmacodynamic effects and clinical efficacy may include differences between the route and concentration of histamine, the involvement of mediators other than histamine in the allergic response, and the short time course of pharmacodynamic studies. The histamine-induced weal and flare response is a pharmacodynamic test that should not be used to compare the clinical efficacy of different antihistamines, and is not an adequate alternative to clinical end-point assessments in AR or chronic idiopathic urticaria.

Treatment in the pediatric emergency department is evidence based: a retrospective analysis

BACKGROUND

Our goal was to quantify the evidence that is available to the physicians of a pediatric emergency department (PED) in making treatment decisions. Further, we wished to ascertain what percentage of evidence for treatment provided in the PED comes from pediatric studies.

METHODS

We conducted a retrospective chart review of randomly selected patients seen in the PED between January 1 and December 31, 2002. The principal investigator identified a primary diagnosis and primary intervention for each chart. A thorough literature search was then undertaken with respect to the primary intervention. If a randomized control trial (RCT) or a systematic review was found, the intervention was classified as level I evidence. If no RCT was found, the intervention was assessed by an expert committee who determined its appropriateness based on face validity (RCTs were unanimously judged to be both unnecessary and, if a placebo would have been involved, unethical). These interventions were classified as level II evidence. Interventions that did not fall into either above category were classified as level III evidence.

RESULTS

Two hundred and sixty-two patient charts were reviewed. Of these, 35.9% did not receive a primary intervention. Of the 168 interventions assessed, 80.4% were evidence-based (level I), 7.1% had face validity (level II) and 12.5% had no supporting evidence (level III). Of the evidence-based interventions, 83.7% were supported by studies with mostly pediatric patients.

CONCLUSION

Our study demonstrates that a substantial proportion of PED treatment decisions are evidence-based, with most based on studies in pediatric patients. Also, a large number of patients seen in the PED receive no intervention.

Experimental models for the evaluation of treatment of allergic rhinitis

OBJECTIVE

To review the experimental models used for the clinical evaluation of treatments for allergic rhinitis.

DATA SOURCES

Peer-reviewed clinical studies and review articles were selected from the PubMed database using the following relevant keywords: allergic rhinitis in combination with efficacy, wheal and flare, nasal challenge, park, cat room, or exposure unit. Regulatory guidance documents on allergic rhinitis were also included.

STUDY SELECTION

The authors' knowledge of the field was used to limit references with emphasis on recent randomized and controlled studies. References of historical significance were also included.

RESULTS

Traditional outpatient studies are universally accepted in the evaluation of treatment for allergic rhinitis. Experimental models provide ancillary information on efficacy at different stages of treatment development. Skin histamine and allergen challenge, as well as direct nasal challenge with histamine and allergen, are often used as early steps in assessing drug efficacy. Exposure units, park settings, and cat rooms better approximate real life by drawing on the natural mode of allergen exposure and delivering the sensitizing allergen to allergic individuals in the ambient air. Park studies make use of allergens in the outdoors, whereas cat rooms and exposure units present the sensitizing allergens indoors, with the latter providing consistent predetermined allergen levels. Exposure unit and park studies are acknowledged for the determination of onset of action and are also suited to the measurement of duration of effect and other measures of efficacy. Onset and duration of effect are 2 important pharmacodynamic properties of antihistamines and nasal corticosteroids as determined by the Allergic Rhinitis and Its Impact on Asthma and the European Academy of Allergology and Clinical Immunology workshop group.

CONCLUSIONS

All challenge models serve as important instruments in the evaluation of antiallergic medications and provide additional information to complement traditional studies.

Levocetirizine in children: evidenced efficacy and safety in a 6-week randomized seasonal allergic rhinitis trial

Studies evaluating newer antihistamines in children are few. Levocetirizine is a potent and highly selective H1-antihistamine with a proven efficacy in adults. Primary objective was to assess the efficacy of levocetirizine 5 mg once-daily in reducing seasonal allergic rhinitis (SAR) symptoms, as measured by Total Four Symptom Score (T4SS = sum of sneezing, rhinorrhea, nasal and ocular pruritus), over the first 2 wk of treatment. Efficacy over 4 and 6 wk of treatment, effect on nasal congestion and on health-related quality of life as measured by PRQLQ (Paediatric Rhinoconjunctivitis Quality of Life Questionnaire) were among the major secondary objectives. A double-blind, randomized, placebo-controlled study including 177 children with a documented SAR (to grass and/or weed) for at least a year and having a mean baseline T4SS > or = 6 (out of 12). Children evaluated daily the severity of T4SS and nasal congestion on a scale from 0 (absent) to 3 (severe). PRQLQ responses were assessed on a scale from 0 (not bothered) to 6 (extremely bothered) and analysed descriptively. Global evaluation of disease evolution judged by investigators, parents and children was made on a scale from 1 (marked worsening) to 7 (marked improvement). For the primary objective, levocetirizine was statistically highly superior to placebo with a difference in adjusted means of 1.29 (95% CI: 0.66-1.92) in favour of levocetirizine (p < 0.001). The effect of levocetirizine was almost twice that of placebo (94.1% relative improvement over placebo). Nasal congestion was improved with levocetirizine reaching maximum difference to placebo of 0.31 (p < 0.05), a relative improvement over placebo of 77.5%. PRQLQ scores at week 2 improved with levocetirizine more than with placebo (0.85 vs. 0.51, respectively) remaining larger after 4 and 6 wk of treatment. In the study, 84.3%, 80.9%, 80.9% of children had their disease evolution rated as slightly-to-markedly improved by, respectively, the investigators, the parents and children themselves. Incidence of treatment-emergent adverse events was similar in both groups (33.7% with levocetirizine; 30.7% with placebo). No child in the levocetirizine group discontinued treatment because of adverse events. The 6-wk duration of this study was longer than the usual 2-4-wk duration for similar studies and shows that levocetirizine controls SAR symptoms in children over the entire pollen season.

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.

Cetirizine: a review of its use in allergic disorders

Cetirizine is a selective, second-generation histamine H1 receptor antagonist, with a rapid onset, a long duration of activity and low potential for interaction with drugs metabolised by the hepatic cytochrome P450 system. Cetirizine was generally more effective than other H1 receptor antagonists at inhibiting histamine-induced wheal and flare responses. Cetirizine is an effective and well tolerated agent for the treatment of symptoms of seasonal allergic rhinitis (SAR), perennial allergic rhinitis (PAR) and chronic idiopathic urticaria (CIU) in adult, adolescent and paediatric patients. In adults with these allergic disorders, cetirizine was as effective as conventional dosages of ebastine (SAR, PAR, CIU), fexofenadine (SAR), loratadine (SAR, CIU) or mizolastine (SAR). This agent was significantly more effective, and with a more rapid onset of action, than loratadine in 2-day studies in environmental exposure units (SAR). In paediatric patients, cetirizine was as at least as effective as chlorphenamine (chlorpheniramine) [SAR], loratadine (SAR, PAR) and oxatomide (CIU) in the short term, and more effective than oxatomide and ketotifen (PAR) in the long term. Cetirizine was effective in reducing symptoms of allergic asthma in adults and reduced the relative risk of developing asthma in infants with atopic dermatitis sensitised to grass pollen or house dust mite allergens. It had a corticosteroid-sparing effect in infants with severe atopic dermatitis and was effective in ameliorating reactions to mosquito bites in adults. Cetirizine was well tolerated in adults, adolescents and paediatric patients with allergic disorders. In adult, adolescent and paediatric patients aged 2-11 years, the incidence of somnolence with cetirizine was dose related and was generally similar to that with other second-generation H1 receptor antagonists. Although, its sedative effect was greater than that of fexofenadine in some clinical trials and that of loratadine or fexofenadine in a postmarketing surveillance study. In infants aged 6-24 months, the tolerability profile of cetirizine was similar to that of placebo. Cetirizine did not have any adverse effects on cognitive function in adults, or cognitive function, behaviour or achievement of psychomotor milestones in paediatric patients. Cetirizine was not associated with cardiotoxicity.

CONCLUSION

Cetirizine is well established in the treatment of symptoms of SAR, PAR or CIU. It demonstrated a corticosteroid-sparing effect and reduced the relative risk of developing asthma in sensitised infants with atopic dermatitis. Cetirizine was effective in the treatment of allergic cough and mosquito bites; however, its precise role in these indications has yet to be clearly established. On the basis of its favourable efficacy and tolerability profile and rapid onset of action, cetirizine provides an important option for the treatment of a wide range of allergic disorders.

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.

H1-antihistaminic activity of cetirizine and fexofenadine in allergic children

The clinical pharmacology of H1-antihistamines has not yet been optimally studied in children and other special groups of patients. Our objective was to determine the onset, extent, and duration of H1-antihistaminic activity of cetirizine and fexofenadine in the pediatric population. We performed a prospective, randomized, placebo-controlled, double-blind, crossover, single-dose study of these H1-antihistamines in 15 allergic children, mean+/-SEM age 8.8+/-0.5 years. We used suppression of the histamine-induced wheal and flare as the primary outcome. Compared with pre-dose baseline, cetirizine 10 mg suppressed the wheals significantly (p<or=0.05) from 2 to 24 h and the flares significantly from 1 to 24 h, achieving 77+/-SEM 10% to 86+/-9% suppression of the wheal from 2 to 7 h and 85+/-6% to 88+/-6% suppression of the flare from 2 to 24 h, inclusive. Compared with baseline, fexofenadine 30 mg did not suppress the wheals or flares significantly at any time, achieving 40+/-9% to 54+/-9% wheal suppression from 2 to 7 h and 45+/-11% to 68+/-9% flare suppression from 2 to 7 h, inclusive. Compared with placebo, cetirizine suppressed the wheals and flares significantly from 2 to 24 h. Compared with placebo, fexofenadine suppressed the wheals significantly at 4 and 6 h, and the flares from 4 to 7 h. Cetirizine suppressed the wheals and flares significantly more than fexofenadine at 2 h (wheals), and at 3 and 24 h (flares). Placebo did not suppress the wheals and flares significantly at any time. In children age 6-11 years, cetirizine 10 mg has a rapid onset of H1-antihistaminic activity, a 24-h duration of action, and greater H1-activity than fexofenadine 30 mg. Higher doses of fexofenadine should be tested in children.

Paediatric issues relating to the pharmacotherapy of allergic rhinitis

The prevalence of allergic rhinitis in children has risen significantly over the last two decades. Important comorbidities like asthma have grown in parallel due to a complex mix of environmental and genetic factors. These conditions have similar allergic inflammatory mechanisms, which raises the possibility of treating both conditions by targeting shared inflammatory mediators pharmacologically. The first line treatment for paediatric allergic rhinitis is a topical nasal corticosteroid or a non-sedating antihistamine. Available intranasal corticosteroids show superior symptom control to second-generation antihistamines. However, most topical steroids and non-sedating antihistamines have equivalent clinical efficacy within their respective classes, so the choice of agent depends on safety and tolerability. Ideally, topical nasal steroids should exhibit high local receptor binding affinity and low systemic bioavailability, allied with a lack of long-term growth suppression in children and adolescents. Regular use of topical steroids is advisable, but intermittent and prophylactic use is also effective. Second-generation antihistamines are effective and some have no adverse cardiac or sedative effects. Non-sedating antihistamine treatment can ameliorate rhinitis-induced decrements in learning. alpha-Adrenergic nasal decongestants provide short-term benefit, but topical agents can cause rebound symptoms. Prophylactic treatment with chromones is safe and effective, but multiple daily dosing is needed. Ipratroprium bromide nasal spray is useful as an intermittent therapy for mild disease or as add-on treatment, but its effect is limited to the control of rhinorrhoea. Children with allergic rhinitis should receive pharmacotherapy if allergen avoidance measures are ineffective, ideally with a topical intranasal steroid or a second-generation antihistamine.