The safety and efficacy of desloratadine for the management of allergic disease

Classics in Chemical Neuroscience: Deliriant Antihistaminic Drugs

Antihistaminic drugs are widely used clinically and have long been primarily known for their use to treat severe allergic conditions caused by histamine release. Antihistaminic drugs also exert central nervous system (CNS) effects, acting as anxiolytics, hypnotics, and neuroleptics. However, these drugs also have multiple serious neuropharmacological side-effects, inducing delirium, hyperarousal, disorganized behavior, and hallucinations. Due to their robust CNS effects, antihistamines are also increasingly abused, with occasional overdoses and life-threatening toxicity. Here, we discuss chemical and neuropharmacological aspects of antihistaminic drugs in both human and animal (experimental) models and outline their current societal and mental health importance as neuroactive substances.

Desloratadine ameliorates paclitaxel-induced peripheral neuropathy and hypersensitivity reactions in mice

Paclitaxel (PTX) serves as a primary chemotherapy agent against diverse solid tumors including breast cancer, lung cancer, head and neck cancer and ovarian cancer, having severe adverse effects including PTX-induced peripheral neuropathy (PIPN) and hypersensitivity reactions (HSR). A recommended anti-allergic agent diphenhydramine (DIP) has been used to alleviate PTX-induced HSR. Desloratadine (DLT) is a third generation of histamine H1 receptor antagonist, but also acted as a selective antagonist of 5HTR2A. In this study we investigated whether DLT ameliorated PIPN-like symptoms in mice and the underlying mechanisms. PIPN was induced in male mice by injection of PTX (4 mg/kg, i.p.) every other day for 4 times. The mice exhibited 50% reduction in mechanical threshold, paw thermal response latency and paw cold response latency compared with control mice. PIPN mice were treated with DLT (10, 20 mg/kg, i.p.) 30 min before each PTX administration in the phase of establishing PIPN mice model and then administered daily for 4 weeks after the model was established. We showed that DLT administration dose-dependently elevated the mechanical, thermal and cold pain thresholds in PIPN mice, whereas administration of DIP (10 mg/kg, i.p.) had no ameliorative effects on PIPN-like symptoms. We found that the expression of 5HTR2A was selectively elevated in the activated spinal astrocytes of PIPN mice. Spinal cord-specific 5HTR2A knockdown by intrathecal injection of AAV9-5Htr2a-shRNA significantly alleviated the mechanical hyperalgesia, thermal and cold hypersensitivity in PIPN mice, while administration of DLT (20 mg/kg) did not further ameliorate PIPN-like symptoms. We demonstrated that DLT administration alleviated dorsal root ganglion neuronal damage and suppressed sciatic nerve destruction, spinal neuron apoptosis and neuroinflammation in the spinal cord of PIPN mice. Furthermore, we revealed that DLT administration suppressed astrocytic neuroinflammation via the 5HTR2A/c-Fos/NLRP3 pathway and blocked astrocyte-neuron crosstalk by targeting 5HTR2A. We conclude that spinal 5HTR2A inhibition holds promise as a therapeutic approach for PIPN and we emphasize the potential of DLT as a dual-functional agent in ameliorating PTX-induced both PIPN and HSR in chemotherapy. In summary, we determined that spinal 5HTR2A was selectively activated in PIPN mice and DLT could ameliorate the PTX-induced both PIPN- and HSR-like pathologies in mice. DLT alleviated the damages of DRG neurons and sciatic nerves, while restrained spinal neuronal apoptosis and CGRP release in PIPN mice. The underlying mechanisms were intensively investigated by assay against the PIPN mice with 5HTR2A-specific knockdown in the spinal cord by injection of adeno-associated virus 9 (AAV9)-5Htr2a-shRNA. DLT inhibited astrocytic NLRP3 inflammasome activation-mediated spinal neuronal damage through 5HTR2A/c-FOS pathway. Our findings have supported that spinal 5HTR2A inhibition shows promise as a therapeutic strategy for PIPN and highlighted the potential advantage of DLT as a dual-functional agent in preventing against PTX-induced both PIPN and HSR effects in anticancer chemotherapy.

Epileptic convulsions probably induced by desloratadine: a case report

Desloratadine, a second generation H1-antihistamine, is generally considered to be safe. We found only one article reporting four children with a family or disease history of epilepsy who developed the condition after desloratadine treatment, with all four patients recovering well. Here we describe a healthy boy who developed left-arm convulsions on day 68 after taking desloratadine, at which point the desloratadine treatment was immediately stopped. Investigations were completed on day 83 and the patient was diagnosed with epilepsy. He was prescribed sodium valproate combined with oxcarbazepine, topiramate, lamotrigine and clonazepam for 15 months, which did not control the convulsions. During the following 3 months the patient received sodium valproate combined with lacosamide, and on day 615 the seizures stopped and no further convulsions occurred. At the follow-up, his father reported that the boy's memory was not as good as it had been previously. The convulsions continued after the withdrawal of desloratadine; therefore, the pathological mechanism of convulsion and the treatment plan need further research.

The safety and tolerability profile of bilastine for chronic urticaria in children

Background

Urticaria is a condition defined by the development of wheals, angioedema or both. It is classified based on its duration as acute (≤ 6 weeks) or chronic (> 6 weeks). Chronic urticaria is less frequent than acute one in children, but it represents a debilitating condition, always needing treatment. Symptoms affect child's daily activities and disturb sleeping patterns, causing emotional distress and negatively influencing learning and cognition. Therefore, the management of chronic urticaria must point to a complete control of symptoms, taking into account tolerability and the patient quality of life.

Review of literature

The recently revised version of EAACI/GA²LEN/EDF/WAO guideline on the management of urticaria, in addition to recommending the use of second-generation H₁ antihistamines as the treatment of choice, gives particular attention to their use in the paediatric population. Bilastine has been studied in children; at the dose of 10 mg/once daily, it is licenced for the symptomatic relief of urticaria in children ≥ 6 to 11 years, in the European Union, in appropriate formulation, as oral solution or orodispersible tablet.

Conclusions

In line with the recent guideline recommendation for the use of second generation H₁ antihistamines in children we have reviewed the safety and tolerability profile of bilastine in children with chronic urticaria.

Brain histamine H1 receptor occupancy after oral administration of desloratadine and loratadine

Some histamine H1 receptor (H1R) antagonists induce adverse sedative reactions caused by blockade of histamine transmission in the brain. Desloratadine is a second-generation antihistamine for treatment of allergic disorders. Its binding to brain H1Rs, which is the basis of sedative property of antihistamines, has not been examined previously in the human brain by positron emission tomography (PET). We examined brain H1R binding potential ratio (BPR), H1R occupancy (H1RO), and subjective sleepiness after oral desloratadine administration in comparison to loratadine. Eight healthy male volunteers underwent PET imaging with [11C]-doxepin, a PET tracer for H1Rs, after a single oral administration of desloratadine (5 mg), loratadine (10 mg), or placebo in a double-blind crossover study. BPR and H1RO in the cerebral cortex were calculated, and plasma concentrations of loratadine and desloratadine were measured. Subjective sleepiness was quantified by the Line Analogue Rating Scale (LARS) and the Stanford Sleepiness Scale (SSS). BPR was significantly lower after loratadine administration than after placebo (0.504 ± 0.074 vs 0.584 ± 0.059 [mean ± SD], P < 0.05), but BPR after desloratadine administration was not significantly different from BPR after placebo (0.546 ± 0.084 vs 0.584 ± 0.059, P = 0.250). The plasma concentration of loratadine was negatively correlated with BPR in subjects receiving loratadine, but that of desloratadine was not correlated with BPR. Brain H1ROs after desloratadine and loratadine administration were 6.47 ± 10.5% and 13.8 ± 7.00%, respectively (P = 0.103). Subjective sleepiness did not significantly differ among subjects receiving the two antihistamines and placebo. At therapeutic doses, desloratadine did not bind significantly to brain H1Rs and did not induce any significant sedation.

[Drug use and driving]

Some drugs are known to impair driving because they can change the vision or hearing, and/or disrupt the intellectual or motor abilities: impaired vigilance, sedation, disinhibition effect, the coordination of movement disorders and the balance. The doctor during prescribing and the pharmacist during deliverance of drug treatment should inform their patients of the potential risks of drugs on driving or operating machinery. The driver has direct responsibility, who hired him and him alone, to follow the medical advice received. The pictograms on the outer packaging of medicinal products intended to classify substances according to their risk driving: The driver can whether to observe simple precautions (level one "be prudent"), or follow the advice of a health professional (level two "be very careful"), or if it is totally not drive (level three "danger caution: do not drive"). This classification only evaluates the intrinsic danger of drugs but not the individual variability. Medicines should be taken into account also the conditions for which the medication is prescribed. It is important to inform the patient on several points.

Acupuncture for the Treatment of Allergic Rhinitis: A Systematic Review and Meta-Analysis

Background

Because acupuncture may modulate the immune system, it has been proposed as a useful treatment for patients with allergic rhinitis (AR). Here, we assessed the evidence for the clinical efficacy of acupuncture for the management of AR patients by performing a systematic review and meta-analysis of the published literatures.

Methods

By searching PubMed, EMBASE, the Cochrane clinical trials database, and the China National Knowledge Infrastructure from 1980 through July 11, 2013, we collected and analyzed the randomized controlled trials (RCTs) of acupuncture for the treatment of AR patients to assess its efficacy and safety.

Results

Thirteen full papers that met our inclusion criteria were included, and a total of 2365 participants, including 1126 as treatment group and 1239 as control group, were enrolled. Compared with control group, acupuncture treatment group exerted a significant reduction in nasal symptom scores (weighted mean difference [WMD]: -4.42, 95% confidence interval [CI]: -8.42 to -0.43, p = 0.03), medication scores (WMD: 1.39, 95% CI: -2.18 to -0.61, p = 0005), and serum IgE (WMD: -75.00, 95% CI: -91.17 to -58.83, p < 0.00001). Data relating to Rhinitis Quality of Life Questionnaire (RQLQ) and 36-Item Short-Form (SF-36) component score in included studies were analyzed, which ultimately point to the efficacy of acupuncture treatment in improving quality of life in AR patients. No fatal events were reported in any of the included studies, and no serious systemic reaction, which needed treatment in the hospital, was related to the acupuncture treatment.

Conclusion

Our meta-analysis suggests that that acupuncture could be a safe and valid treatment option for AR patients.

Safety evaluation of desloratadine in allergic rhinitis

INTRODUCTION

Desloratadine is a biologically active metabolite of second-generation antihistamine loratadine. It is also indicated for the treatment of allergic diseases, including allergic rhinitis.

AREAS COVERED

A Medline search was conducted to identify preclinical and clinical studies of desloratadine. This was supplemented with additional articles obtained from online sources. The focus of this review is on the safety profile of desloratadine.

EXPERT OPINION

The review of these data indicates that the safety profile of desloratadine is similar to other second-generation antihistamines. Desloratadine is highly selective for histamine H₁-receptors, does not cross the blood-brain barrier (BBB), and has minimal adverse events (very low sedation rate), with a better safety and tolerability than first-generation antihistamines. Desloratadine is safe and well tolerated without having central nervous system (CNS) or cardiovascular effects and with low drug interaction.

Treatment strategies in urticaria

Urticaria is a common group of disorders encountered in dermatology and in a variety of other fields. In particular, acute urticaria and angiooedema are common medical emergencies, which are treated in the first instance in the Accident and Emergency Department, whereas chronic urticaria poses a challenge in the long-term treatment. This review presents the latest evidence about the treatment for urticaria and is based on the most recent international guidelines (GA(2)LEN, Global Allergy and Asthma Network, 2009). Patients with acute and chronic urticaria are often not treated appropriately and this review provides a guide for any clinician to treat the underlying cause as well as the symptoms of this disorder according to the latest evidence. Many new therapies are available to patients with urticaria refractory to common therapies and it is important to consider second- and third-line therapies.

Acupuncture for allergic rhinitis: a systematic review

OBJECTIVE

To systematically evaluate the effectiveness of acupuncture for treating or preventing allergic rhinitis (AR).

DATA SOURCES

We retrieved data from 17 electronic databases, nonelectronic searches of conference proceedings, our own files of articles, and bibliographies of located articles.

STUDY SELECTION

All randomized clinical trials (RCTs) of acupuncture for AR were considered for inclusion if they included placebo controls or were controlled against a comparator intervention.

RESULTS

One hundred fifteen possibly relevant studies were identified and 12 RCTs met our inclusion criteria. The methodologic quality of the individual trials was variable. Our review includes 7 trials of high quality that met standards of methodologic rigor. All RCTs tested the effectiveness of acupuncture on AR symptoms and none on its curative value. Three RCTs failed to show superiority of acupuncture for treating or preventing symptoms for seasonal AR compared with placebo acupuncture. For perennial AR, 1 study reported favorable effects of acupuncture on a rhinitis symptoms score and 1 found positive results for a nasal symptoms score compared with placebo acupuncture (n = 152; standard mean difference, 0.45; 95% confidence interval, 0.13-0.78; P = .006; heterogeneity: chi2 = 0.45, P = .50, I2 = 0%). Two RCTs compared acupuncture with oral pharmacologic medications. Their results were in favor of acupuncture.

CONCLUSIONS

The evidence for the effectiveness of acupuncture for the symptomatic treatment or prevention of AR is mixed. The results for seasonal AR failed to show specific effects of acupuncture. For perennial AR, results provide suggestive evidence of the effectiveness of acupuncture.

Desloratadine for the Relief of Nasal and Non-nasal Allergy Symptoms: An Observational Study

Introduction

The rates of allergic rhinitis, allergic asthma, and atopic eczema range from 6% to 16% globally. Second-generation antihistamines have been shown to be safe and effective for the treatment of symptoms of allergic disease. This study investigated the efficacy and safety of desloratadine, a nonsedating second-generation antihistamine, in the treatment of common allergy symptoms.

Methods

In this open-label, uncontrolled, non-randomized, observational study, subjects (N = 973) with allergy symptoms were given desloratadine 5 mg daily for 3 weeks. Nasal, ocular, and dermal symptom severity was rated as asymptomatic, mild, moderate, or severe; changes in the percentage of subjects in each severity category were assessed. Overall efficacy and tolerability of desloratadine treatment were evaluated separately by physicians and subjects.

Results

Allergic rhinitis was the most frequent diagnosis, occurring in 59.0% of subjects. Approximately 40% of subjects had received previous treatment with other antihistamines, systemic/topical glucocorticosteroids, or beta-sympathicomimetics. Slightly more than half of subjects received concomitant medication during the study; 263 (53.0%) of those used intranasal steroids. A significant reduction in severity scores was observed in all symptom subgroups (P < 0.001). Desloratadine efficacy was judged to be excellent or good by 90.2% of physicians and 88.6% of subjects; 82.5% of investigators and 80.9% of subjects considered it more effective than previous therapy. The tolerability of desloratadine was rated excellent or good by 97.0% of both groups. Thirty-one subjects (3.2%) experienced adverse events.

Conclusions

In an open-label, uncontrolled, non-randomized, observational study allergy symptoms improved significantly in subjects treated with desloratadine.

How to prescribe antihistamines for chronic idiopathic urticaria: desloratadine daily vs PRN and quality of life

BACKGROUND

Chronic idiopathic urticaria (CIU) impairs quality of life (QoL). Currently, no consensus exists regarding how second-generation H(1)-antihistamines (proven to control CIU symptoms) should be taken long-term: as daily treatment or only when symptoms return (PRN). We sought to determine which regimen improves or better maintains QoL in CIU: desloratadine (DL) daily or PRN.

METHODS

Subjects with CIU initially responding to DL 5 mg/day for 4 weeks were randomized for an additional 8 weeks, to DL 5 mg/day (arm 1: 'continuous', n = 46) or to DL only on days when urticarial wheals were present (arm 2: "PRN", n = 60). To ensure blinding, treatment was presented in both arms as a combination of daily treatment (arm 1: DL; arm 2: placebo), plus a "rescue" tablet (arm 1: placebo; arm 2: DL) to be taken only in case of symptoms. The main outcome measure was QoL assessed by the VQ-Dermato, a validated French QoL instrument, and the Dermatology Life Quality Index (DLQI).

RESULTS

At 4 and 8 weeks after randomization, subjects taking continuous DL showed statistically significant improvements in VQ-Dermato Global Index score (P = 0.001 and P = 0.016, respectively) and dimension scores for daily living activity, mood state, and social functioning vs subjects taking DL PRN. Improvement in DLQI score at Week 4 was also significantly greater with continuous DL (P = 0.001).

CONCLUSION

Continuous daily therapy with DL 5 mg is a better regimen than PRN treatment to maintain or improve QoL in subjects with CIU.

Disposition of desloratadine in healthy volunteers

The absorption, metabolism and excretion of desloratadine (DL, Clarinex) were characterized in six healthy male volunteers. Subjects received a single oral 10-mg dose of [(14)C]DL ( approximately 104 microCi). Blood, urine and feces were collected over 240 h. DL was well absorbed; drug-derived radioactivity was excreted in both urine (41%) and feces (47%). With the exception of a single subject, DL was extensively metabolized; the major biotransformation pathway consisted of hydroxylation at the 3 position of the pyridine ring and subsequent glucuronidation (3-OH-DL-glucuronide or M13). In five of the six subjects, DL was slowly eliminated (mean t((1/2)) = 19.5 h) and persisted in the plasma for 48-120 h post-dose. This is in contrast to a t((1/2)) of approximately 110 h and quantifiable plasma DL concentrations for the entire 240-h sampling period in one subject, who was identified phenotypically as a poor metabolizer of DL. This subject also exhibited correspondingly lower amounts of M13 in urine and 3-OH-DL (M40) in feces. Disposition of DL in this subject was characterized by slow absorption, slow metabolism and prolonged elimination. Further clinical studies confirmed the lack of safety issues associated with polymorphism of DL metabolism (Prenner et al. 2006, Expert Opinion on Drug Safety, 5: 211-223).

Non-sedating antihistamines in the treatment of chronic idiopathic urticaria using patient-reported outcomes

BACKGROUND

Chronic idiopathic urticaria (CIU) greatly impairs quality of life (QoL). Thus, patient-reported outcome (PRO) measures, using validated scoring instruments, are probably the most accurate tools available for assessing the efficacy of medications that treat CIU, such as second-generation antihistamines.

RESEARCH METHODS

A structured search of the MEDLINE database was conducted to identify English-language papers published between 1 January 1991 and 30 September 2007 on the treatment of CIU with the second-generation antihistamines cetirizine, desloratadine, fexofenadine, and levocetirizine, and their effects on patient-reported QoL. We used the following search terms alone or in combination: 'chronic idiopathic urticaria'; 'pruritus'; 'wheals'; 'hives'; 'second-generation antihistamines'; 'cetirizine'; 'desloratadine'; 'fexofenadine'; 'levocetirizine'; and 'quality of life'.

SCOPE

We evaluated the effects of second-generation antihistamines on the QoL of subjects with CIU using desloratadine as a treatment model. Desloratadine was selected because it is the most frequently assessed non-sedating second-generation antihistamine in QoL studies in patients with CIU.

FINDINGS

Desloratadine 5 mg QD improved QoL in numerous PRO studies. Treatment with desloratadine significantly (p < 0.05) lowered (better) scores in three studies (n = 364) that used validated dermatology-specific scoring instruments. Three 6-week double-blind, placebo-controlled trials (n = 553) found that desloratadine significantly (p < 0.05) improved patient-reported pruritus, sleep disruption, and interference with daily activities. Desloratadine was associated with a low incidence of adverse events and an overall tolerability profile similar to placebo.

LIMITATIONS

Limitations in this review include divergence in search practices that may lead to omission of relevant research, unintentional error in data transfer, inconsistency in quality of selected papers, and potential publication bias against papers that report results from small studies.

CONCLUSIONS

The favorable impact of second-generation antihistamines on the QoL of patients with CIU was demonstrated using desloratadine, the most frequently investigated drug in this field, as a treatment model.

Allergic rhinitis in family practice: the role of levocetirizine in clinical care

Allergic rhinitis is one of the most common presentations of allergic disorders in the United States, affecting more than 20% of the population. Chronic rhinitis affects patients' quality of life and exacerbates comorbid conditions. Its widespread burden affects society by substantially decreasing worker and scholastic productivity. Allergic rhinitis is typically managed with pharmacotherapy to alleviate symptoms and control comorbid conditions, yet many of these agents carry their own burden due to bothersome and sometimes severe side effects that can compromise patient safety. A new generation of non- or less-sedating antihistamines has recently emerged. These agents offer the promise of enhanced efficacy and tolerability. Of these agents, levocetirizine is the latest antihistamine introduced in the United States. It appears to be safe and effective for the treatment of allergic rhinitis. In addition to covering the above topics, this article reviews the value of levocetirizine for the treatment of allergic rhinitis based on its pharmacologic and pharmacokinetic profile, its efficacy compared with placebo and other new-generation antihistamines, and its safety and tolerability.

Effects of desloratadine and alcohol coadministration on psychomotor performance

OBJECTIVE

This study was set up to evaluate the effects of desloratadine 7.5 mg daily, with and without alcohol, on sedation and psychomotor performance.

RESEARCH METHODS

In a double-blind, placebo-controlled, four-way crossover trial, 25 adult patients were randomized to desloratadine 7.5 mg, desloratadine 7.5 mg plus alcohol, placebo, or placebo plus alcohol. Alcohol was weight adjusted to an average blood alcohol concentration of 0.1%. Assessments included the modified Romberg test, Stanford Sleepiness Scale, Digit Symbol Substitution Test, Serial Add Subtract Reaction Time Test, and the Psychomotor Vigilance Test. The primary variable was the mean score of each of the five tests averaged over the treatment period, expressed as the mean percent change from baseline.

RESULTS

Across these assessments, differences between desloratadine alone or with alcohol versus placebo alone or without alcohol, were not significant, whereas most differences between desloratadine and placebo alone versus desloratadine and placebo with alcohol were significant (p < 0.01). Thus, with or without alcohol, desloratadine 7.5 mg does not increase sedation or impair psychomotor performance. Most adverse events (AEs) were mild-to-moderate in severity, with the most frequently reported individual AEs being headache, fatigue, nausea, vomiting, and dry mouth. The study does have potential limitations. The measures used are restricted to a particular profile of the known effects of alcohol only, and the relatively high doses of alcohol used alone demonstrate effects on psychomotor function and attention.

CONCLUSIONS

A single dose of desloratadine does not potentiate alcohol-mediated CNS impairment. Desloratadine alone or in combination with alcohol was safe and well tolerated.

Desloratadine for chronic idiopathic urticaria: a review of clinical efficacy

Chronic idiopathic urticaria (CIU) is a disabling affliction that considerably limits patients' daily activities and interferes with sleep. Clinical studies have shown that histamine H1-receptor antagonists (antihistamines) are highly effective for inhibiting the hives/wheals and pruritus associated with CIU, as well as improving patients' quality of life. Desloratadine is a rapid-acting, once-daily, nonsedating selective H1-receptor antagonist/inverse receptor agonist with proven clinical efficacy in patients with CIU. It has 10-20 times the in vivo H1 receptor-binding affinity of loratadine, its parent compound, and 52-194 times the H1 receptor-binding affinity of cetirizine, ebastine, loratadine, and fexofenadine. Desloratadine displays linear pharmacokinetics after oral administration. Age and sex have no apparent effect on the drug's metabolism and elimination, and food does not affect its bioavailability or absorption. Desloratadine also exerts anti-inflammatory effects via mechanisms that are independent of H1-receptor antagonism. Results from randomized, double-blind, placebo-controlled studies of 6 weeks' duration in adults and adolescents with moderate-to-severe CIU indicate that desloratadine significantly minimizes the severity of pruritus, reduces the number and size of hives, and improves disease-impaired sleep and daily activities. Improvements were noted after a single dose of desloratadine and were maintained over 6 weeks of treatment. Desloratadine was safe and well tolerated in clinical trials of patients with CIU. The adverse effect profile of desloratadine in adults, as well as in children aged from 6 months to 11 years, is comparable to that of placebo. Evaluations of cognitive and psychomotor performance in adults indicate no impairment of function with dosages of desloratadine 5 mg/day. In conclusion, desloratadine is an important therapeutic option for prompt and enduring symptom relief in patients with moderate-to-severe CIU. In addition to efficacy and safety, desloratadine affords a convenient administration regimen, rapid onset of action, and an absence of drug-drug or drug-food interactions. Other important prescribing considerations are that, unlike all first-generation and some second-generation antihistamines, desloratadine is nonsedating at its clinically approved dosage and does not impair psychomotor function.

Adult and paediatric poor metabolisers of desloratadine: an assessment of pharmacokinetics and safety

Antihistamines are widely used to treat allergic rhinitis (AR) and chronic idiopathic urticaria (CIU) in adults and children. Desloratadine is a once-daily oral antihistamine with a favourable sedation profile that is approved for the treatment of AR and CIU. Phenotypic polymorphism in the metabolism of desloratadine has been observed, such that some individuals have a decreased ability to form 3-hydroxydesloratadine, the major metabolite of desloratadine; such individuals are termed 'poor metabolisers of desloratadine'. This review describes the prevalence of poor metabolisers of desloratadine, quantifies the exposure to desloratadine in poor metabolisers and demonstrates that the increased exposure in poor metabolisers is independent of age when administered at age-appropriate doses. Furthermore, this review demonstrates that the increased exposure to desloratadine in poor metabolisers is not associated with any changes in the safety and tolerability profile of desloratadine, including cardiovascular safety.