Spectroscopic interaction studies of H2 receptor antagonists with levocetirizine

Patients with allergic rhinitis may also suffer abdominal pain, gastritis or peptic ulcer. In this condition patient may use levocetirizine with famotidine or ranitidine. These drugs have potential to interact with another drug and form complex. The aim of the present study is to evaluate the possible drug drug interaction with each other which may cause increase or decrease of therapeutic effects. For this purpose, validity of Beer Lambert law was checked, lone availability of famotidine (20gm), ranitidine (150gm) and levocetirizine (5mg) were studied in pH simulated to gastric juice (pH 1), pH 4, pH 7.4 and in pH 9 and finally percent availabilities of these drugs were calculated with the help of simultaneous equation. Results showed high percentage of levocetirizine in all pH as 300.32%, 514.41%, 173.38% and 220.68% in presence of famotidine but very low availability of famotidine as 5.36%, 35.38%, 51.87% and 10.89% in presence of levocetirizine. In the case of levocetirizine and ranitidine interaction, zero percent levocetirizine was available at pH 1and 9, 56.28% in pH 4 and 191.1% in pH 7.4. On the other hand, ranitidine was available as 95.36%, 127.93%, 41.47% and 144.3%. These results showed that percentage of all drugs were altered in presence of each other due to drug-drug interaction. This may be due to the charge transfer binding capabilities of the drugs which resulted in significantly changed availability of famotidine, ranitidine as well as levocetirizine.

Bacterial metabolism rescues the inhibition of intestinal drug absorption by food and drug additives

Food and drug products contain diverse and abundant small-molecule additives (excipients) with unclear impacts on human physiology, drug safety, and response. Here, we evaluate their potential impact on intestinal drug absorption. By screening 136 unique compounds for inhibition of the key intestinal transporter OATP2B1 we identified and validated 24 potent OATP2B1 inhibitors, characterized by higher molecular weight and hydrophobicity compared to poor or noninhibitors. OATP2B1 inhibitors were also enriched for dyes, including 8 azo (R-N=N-R') dyes. Pharmacokinetic studies in mice confirmed that FD&C Red No. 40, a common azo dye excipient and a potent inhibitor of OATP2B1, decreased the plasma level of the OATP2B1 substrate fexofenadine, suggesting that FD&C Red No. 40 has the potential to block drug absorption through OATP2B1 inhibition in vivo. However, the gut microbiomes of multiple unrelated healthy individuals as well as diverse human gut bacterial isolates were capable of inactivating the identified azo dye excipients, producing metabolites that no longer inhibit OATP2B1 transport. These results support a beneficial role for the microbiome in limiting the unintended effects of food and drug additives in the intestine and provide a framework for the data-driven selection of excipients. Furthermore, the ubiquity and genetic diversity of gut bacterial azoreductases coupled to experiments in conventionally raised and gnotobiotic mice suggest that variations in gut microbial community structure may be less important to consider relative to the high concentrations of azo dyes in food products, which have the potential to saturate gut bacterial enzymatic activity.

Pharmacokinetics and pharmacodynamics of olopatadine following administration via nasogastric tube to healthy horses

OBJECTIVE

To investigate the pharmacokinetics and antihistaminic effects (pharmacodynamics) of olopatadine in a small population of healthy horses after administration via nasogastric tube.

ANIMALS

4 healthy adult Thoroughbreds.

PROCEDURES

Olopatadine (0.1 mg/kg, once) was administered via nasogastric tube. Blood samples were collected at predetermined time points for pharmacokinetic analyses of the drug in plasma. Olopatadine effects were investigated by measurement of cutaneous wheals induced by ID histamine injection (0.1 mL [10 μg]/injection) at predetermined time points. Inhibition effect ratios were calculated on the basis of measured wheal size (area) after versus before olopatadine administration.

RESULTS

Mean ± SD maximum plasma olopatadine concentration was 48.8 ± 11.0 ng/mL approximately 1.5 hours after administration. Median terminal half-life was 6.11 hours. Mean ± SD maximal effect was 88.2 ± 4.9% inhibition approximately 3.5 hours after drug delivery, and the inhibition effect remained > 80% for 12.5 hours after treatment. No signs of adverse clinical effects were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested olopatadine may have a strong, long-term inhibitory effect against histamine-induced wheals in the skin of horses. Clinical research with a larger number of horses is warranted.

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.

Pharmacokinetics, Pharmacodynamics and Population Pharmacokinetic/Pharmacodynamic Modelling of Bilastine, a Second-Generation Antihistamine, in Healthy Japanese Subjects

BACKGROUND AND OBJECTIVES

Bilastine is a novel second-generation antihistamine for the symptomatic treatment of allergic rhinitis and urticaria. The objective of this study was to evaluate the pharmacokinetics, pharmacodynamics, and tolerability of bilastine following single and multiple oral doses in healthy Japanese subjects. The pharmacokinetic and pharmacodynamic profiles were compared with those reported in Caucasian subjects.

METHODS

In a single-blind, randomized, placebo-controlled, parallel-group, single- and multiple-ascending dose study, bilastine tablets were administered at single doses of 10, 20, and 50 mg (Part I), and once daily for 14 days at 20 and 50 mg (Part II).

RESULTS

After single oral doses, maximum plasma concentrations (C _max) were reached at 1.0-1.5 h postdose. Plasma exposure [C _max and area under the plasma concentration-time curve (AUC)] increased dose-proportionally at single doses of 10-50 mg. In repeated-dose administration, no remarkable differences were observed between Day 1 and Day 14 for C _max or AUC. For inhibitory effects on wheal and flare response, bilastine 20 and 50 mg showed significant inhibition from 1.5 h after administration as compared with placebo, and the significant effect persisted for 24 h after administration. The rates of adverse events (AEs) were comparable between bilastine and placebo in both Part I and Part II. In addition, no dose- or administration period-dependent tendency of increase in rate of AEs or worsening of severity was observed.

CONCLUSION

Bilastine exhibits similar single- and multiple-dose pharmacokinetic and pharmacodynamic characteristics in healthy Japanese subjects compared with those observed in Caucasian subjects in previous studies.

[Sex differences of P-glycoprotein functional activity and expression in rabbits]

The research consists in the investigation of the sex differences of P-glycoprotein functional activity and expression in Chinchilla rabbits. P-glycoprotein functional activity was assessed by the pharmacokinetics of its probe substrate--fexofenadine after its single oral administration. P-glycoprotein expression was investigated by immunohistochemistry method. It is shown that male's maximal concentration of fexofenadine, its areas under concentration-time curves, half-life and retention time were higher and its clearance was lower than female's. The efficient differences in pharmacokinetic parameters of fexofenadine confirm more intensive excretion and less intensive absorption in gastro-intestinal tract of fexofenadine. This data indicate that P-glycoprotein activity is more active in female than in male. Immunohistochemistry analysis shows that total liver and intestine P-glycoprotein expression is more intensive in females, than in males that correlates with its more active functioning.

Pharmacokinetics/Pharmacodynamics of Desloratadine and Fluoxetine in Healthy Volunteers

The authors assessed the potential for a pharmacokinetic/pharmacodynamic interaction between desloratadine and fluoxetine. This randomized, placebo-controlled, open-label study was conducted in 54 healthy volunteers. Subjects received 1 of 3 treatments: desloratadine 5 mg plus fluoxetine 20 mg, desloratadine 5 mg plus placebo, or fluoxetine 20 mg plus placebo. Serial electrocardiograms (ECGs) were performed at baseline and day 35. Treatment effects on C(max) and AUC were assessed. During coadministration of desloratadine with fluoxetine, the ratio of the mean log-transformed C(max) and AUC values for desloratadine following concomitant fluoxetine therapy revealed a small increase in C(max) values of 15% (90% confidence interval [CI], 95%-139%) but no increase for AUC values (90% CI, 82%-123%). Corresponding values for 3-OH desloratadine demonstrated small increases in mean log-transformed C(max) and AUC ratios: 17% (90% CI, 100%-136%) and 13% (90% CI, 96%-132%), respectively. Statistical evaluation of the ratio of the mean C(max) and AUC values for fluoxetine following concomitant desloratadine therapy revealed small decreases of 9% (90% CI, 72%-115%) and 11% (90% CI, 69%-113%), respectively. Corresponding values for norfluoxetine demonstrated modest increases in mean log-transformed C(max) and AUC ratios: 22% (90% CI, 100%-139%) and 18% (90% CI, 101%-136%), respectively. Coadministration of desloratadine with a potent inhibitor of CYP2D6 did not result in clinically relevant changes in its pharmacokinetic parameters. Desloratadine administration was not associated with clinically important changes in the pharmacokinetics of fluoxetine, a drug metabolized by CYP2D6. The most common adverse event in all groups was headache (65%). Desloratadine plus fluoxetine caused no significant changes in ECGs or ventricular rate.

Multiple-Dose Pharmacokinetics and Safety of Desloratadine in Subjects With Moderate Hepatic Impairment

Desloratadine, a nonsedating histamine H(1)-receptor antagonist, is metabolized to 3-hydroxy (3-OH) desloratadine. Impaired hepatic function could result in increased exposure to desloratadine. This study assessed possible differences in the pharmacokinetics and safety of desloratadine and 3-OH desloratadine in subjects (N = 21) with moderate hepatic dysfunction or normal liver function. Subjects were given desloratadine 5 mg once daily for 10 days and were assessed in several pharmacokinetic parameters. A similar degree of plasma protein binding to desloratadine and 3-OH desloratadine was observed in healthy volunteers and subjects with moderate hepatic impairment. All subjects with hepatic impairment were normal metabolizers. Three subjects with normal liver function, all African American, were identified as poor metabolizers. Exposure to desloratadine in the poor metabolizers was 2.6- to 6.5-fold greater than in other subjects with normal liver function. Eleven treatment-related adverse events, all mild to moderate in severity, were reported. Results suggest that subjects with moderate hepatic impairment experienced a greater increase in desloratadine exposure than subjects with normal liver function. Poor metabolizers had more exposure to desloratadine than normal metabolizers with or without hepatic impairment. Desloratadine administered at a daily dose of 5 mg was well tolerated.

Use of second generation H1 antihistamines in special situations

Antihistamine drugs are one of the therapeutic classes most used at world level, at all ages and in multiple situations. Although in general they have a good safety profile, only the more recent drugs (second generation antihistamines) have been studied specifically with regard to the more important safety aspects. Given the variety of antihistamine drugs, they cannot all be considered equivalent in application to various special clinical situations, so that the documented clinical experience must be assessed in each case or, in the absence of such, the particular pharmacological characteristics of each molecule for the purpose of recommendation in these special situations. In general, there are few clinical studies published for groups of patients with kidney or liver failure, with concomitant multiple pathologies (such as cardiac pathology), in extremes of age (paediatrics or geriatrics) and in natural stages such as pregnancy or lactation, but these are normal situations and it is more and more frequent (among the elderly) for antihistamine drugs to be recommended. This review sets out the more relevant details compiled on the use of antihistamines in these special situations.

Safety profile of bilastine: 2nd generation H1-antihistamines

Bilastine is a new H1 antagonist with no sedative side effects, no cardiotoxic effects, and no hepatic metabolism. In addition, bilastine has proved to be effective for the symptomatic treatment of allergic rhinoconjunctivitis and urticaria. Pharmacological studies have shown that bilastine is highly selective for the H1 receptor in both in vivo and in vitro studies, and with no apparent affinity for other receptors. The absorption of bilastine is fast, linear and dose-proportional; it appears to be safe and well tolerated at all doses levels in healthy population. Multiple administration of bilastine has confirmed the linearity of the kinetic parameters. The distribution in the brain is undetectable. The safety profile in terms of adverse effects is very similar to placebo in all Phase I, II and III clinical trials. Bilastine (20 mg), unlike cetirizine, does not increase alcohol effects on the CNS. Bilastine 20 mg does not increase the CNS depressant effect of lorazepam. Bilastine 20 mg is similar to placebo in the driving test. Therefore, it meets the current criteria for medication used in the treatment of allergic rhinitis and urticaria.

Preparation and evaluation of fexofenadine microemulsions for intranasal delivery

To enhance the solubility and bioavailability of poorly absorbable fexofenadine, microemulsion system composed of oil, surfactant and co-surfactant was developed for intranasal delivery. Phase behavior, particle size, viscosity and solubilization capacity of the microemulsion system were characterized. Histopathology and in vivo nasal absorption of the optimized microemulsion formulations were also investigated in rats. A single isotropic region was found in the pseudo-ternary phase diagrams developed at various ratios with Lauroglycol 90 as oil, Labrasol as surfactant and Plurol Oleique CC49 or its mixture with PEG-400 (1:1) as cosurfactant. An increase in the microemulsion region in pseudo-ternary phase systems was observed with increased surfactant concentration. The optimized microemulsion formulations showed higher solubulization of fexofenadine, i.e., F1 (22.64 mg/mL) and F2 (22.98 mg/mL), compared to its intrinsic water solubility (1.51 mg/mL). Nasal absorption of fexofenadine from these microemulsions was found to be fairly rapid. Tmax was observed within 5 min after intranasal administration at 1.0 mg/kg dose, and the absolute bioavailability (0-4 h) was about 68% compared to the intravenous administration in rats. Our results suggested that these microemulsion formulations could be used as an effective intranasal dosage form for the rapid-onset delivery of fexofenadine

Effects of silybinin, CYP3A4 and P-glycoprotein inhibitor in vitro, on the bioavailability of loratadine in rats

The effect of silybinin on the pharmacokinetics of orally and intravenously administered loratadine in rats was investigated. Pharmacokinetic parameters of loratadine were determined in rats following oral (4 mg x kg(-1)) and intravenous (1 mg x kg(-1)) administration to rats in the presence and absence of silybinin (0.3, 1.5 and 6 mg x kg(-1)). Compared to those animals in an oral control group (given loratadine alone), the area under the plasma concentration-time curve (AUC) and the peak plasma concentration (C(max)) of loratadine were increased significantly (P < 0.05 for 1.5 mg x kg(-1), P < 0.01 for 6 mg x kg(-1)) by 50.0-76.7% and 65.4-90.1%, respectively, by silybinin. Consequently, the absolute bioavailability of loratadine in the presence of silybinin (1.5 and 6 mg x kg(-1)) was 8.6-10.2%, which was significantly (1.5 mg x kg(-1), P < 0.05; 6 mg x kg(-1), P < 0.01) enhanced compared to that in oral control group (5.8%). Moreover, the relative bioavailability of loratadine was 1.50- to 1.77-fold greater than that in the control group. In contrast, silybinin had no effect on any pharmacokinetic parameters of loratadine given intravenously, implying that coadministration of silybinin could inhibit the cytochrome P450 (CYP) 3A4-mediated metabolism of loratadine, resulting in reducing gastrointestinal and hepatic first-pass metabolism, and the P-glycoprotein (P-gp) efflux pump in the small intestine. Silybinin significantly enhanced the oral bioavailability of loratadine, suggesting that concurrent use of silybinin and loratadine should be monitored closely for potential drug interactions.

Levocetirizine for the treatment of allergic rhinitis and chronic idiopathic urticaria in adults and children

BACKGROUND

Levocetirizine (LCZ) is a second-generation antihistamine that was approved in January 2008 for the relief of symptoms of seasonal allergic rhinitis (SAR), perennial allergic rhinitis (PAR), and chronic idiopathic urticaria (CIU) in adults and children aged > or = 6 years.

OBJECTIVES

This article reviews the available literature on the pharmacokinetics and pharmacodynamics, clinical efficacy and tolerability, and effect on quality of life (QoL) of LCZ.

METHODS

A search of the English-language literature was performed using the following databases: MEDLINE (1966-February 2009), International Pharmaceutical Abstracts (19 70-February 2009), Database of Abstracts of Reviews of Effectiveness, Cochrane Database of Systematic Reviews, EMBASE Drugs & Pharmacology (1991-February 2009), Blackwell Synergy, CINAHL Plus with Full Text, EBSCOhost, ScienceDirect, and Wiley Interscience. The search terms were levocetirizine, allergic rhinitis, chronic idiopathic urticaria, antihistamine, pharmacokinetics, quality of life, drug interactions, case reports, and cost. Publications describing studies of > or = 2 weeks' duration that concerned the efficacy, tolerability, pharmacoeconomics, and/or QoL effects of LCZ were included in the review.

RESULTS

In 4 studies in adult patients with moderate to severe PAR, LCZ 5 mg/d was associated with significant improvements in symptom scores for sneezing, rhinorrhea, and ocular/nasal pruritus at 4 to 6 weeks compared with placebo (P < or = 0.05). In 3 studies, nasal congestion scores were significantly improved within 4 to 6 weeks compared with placebo (P < 0.001). LCZ 5 mg/d was associated with improvements compared with placebo in scores for the ability to do housework, complete work activities, and engage in outdoor activities at 6 months (P < or = 0.011). In a 6-week study in children with moderate to severe SAR, LCZ 5 mg/d was associated with significant improvements compared with placebo in sneezing, rhin-orrhea, and itchy nose (P < 0.004); significant improvements in symptoms from baseline were also seen in a 4-week study in adults with SAR (P < 0.001). One study in patients with SAR reported no significant difference between LCZ and fluticasone compared with fluticasone monotherapy in terms of improvement in QoL, nasal airflow obstruction, sneezing, or pruritus. In a 6-week study in patients with moderate to severe CIU, LCZ 5 mg/d was significantly more effective than placebo in reducing overall CIU symptoms (P < 0.05). In two 4-week studies, one comparing LCZ 5 mg/d with placebo and the other comparing it with desloratadine (DSL), LCZ was significantly more effective than either comparator in terms of improvement in scores for pruritus severity (P < or = 0.001 vs placebo; P < 0.004 vs DSL) and duration (P < or = 0.001 vs placebo; P = 0.009 vs DSL). LCZ was significantly more effective than placebo (but not DSL) in reducing the number and size of wheals (both, P = 0.001). In a 12-week, open-label, crossover study, patients reported significantly longer symptom relief with cetirizine than LCZ (P < 0.005). The most commonly reported adverse events in two 6-month studies in adults with PAR treated with LCZ 5 mg/d included headache (23.8%), pharyngitis (19.4%), influenza (14.6%), fatigue (8.3%), and somnolence (8.3%). There is serious concern about the possibility of febrile seizures in infants treated with LCZ. Three pharmacoeconomic studies of LCZ 5 mg/d were identified, one comparing it with placebo in patients with PAR, one comparing it with placebo in patients with CIU, and another comparing it with second-generation antihistamines and montelukast in patients with PAR. Because of design limitations and differences in comparators in these studies, it was not possible to determine the cost-effectiveness of LCZ in the treatment of PAR or CIU.

CONCLUSIONS

In the studies reviewed, LCZ 5 mg/d was effective in reducing symptoms of PAR, SAR, and CIU and improving QoL, with an acceptable tolerabili-ty profile. There is a need for studies of longer durations, head-to-head comparisons against other anti-histamines, drug-interaction studies, safety studies in infants, and cost-effectiveness analyses.

Metabolism of loratadine and further characterization of its in vitro metabolites

The present study demonstrated that in addition to CYP3A4 and CYP2D6, the metabolism of loratadine is also catalyzed by CYP1A1, CYP2C19, and to a lesser extent by CYP1A2, CYP2B6, CYP2C8, CYP2C9 and CYP3A5. The biotransformation of loratadine was associated with the formation of desloratadine (DL) and further hydroxylation of both DL and the parent drug (loratadine). Based on the inhibition and correlation studies contribution of CYP2C19 in the formation of the major circulating metabolite DL seems to be minor. Reported clinical results suggest that the steady state mean (%CV) plasma Cmax and AUC(24hr) of loratadine were 4.73 ng/ml (119%) and 24.1 ng.hr/ml (157%), respectively, after dosing with 10 mg loratadine tablets for 10 days. High inter-subject variability in loratadine steady-state data is probably due to the phenotypical characteristics of CYP2D6, CYP2C19, and CYP3A4. The relative abundance of CYP3A4 in the human liver exceeds that of CYP2C19 and CYP2D6 and therefore the contribution of CYP3A4 in the metabolism of loratadine should be major (approximately 70%).

New oral H1 antihistamines in children: facts and unmeet needs

BACKGROUND

Second-generation antihistamines differ from first-generation ones because of their elevated specificity and affinity for peripheral H1-receptors and because of their lower penetration to the central nervous system, having fewer sedative effects as a result. Over the last few years, new compounds with different pharmacokinetic properties have been synthesized. More recent improvements of the molecules, generally in the form of active metabolites, led to the synthesis of new-generation antihistamines.

METHODS

Recommendations on the minimum criteria that would have to be met for compounds to be classified as new-generation antihistamines have been recently established by a consensus statement. In the past, the pharmacokinetics and pharmacodynamics of H1 antihistamines have not been optimally investigated in the pediatric population, especially in infants and young children.

RESULTS

The pharmacology of second-generation H1 antihistamines has been investigated relatively deeper than old antihistamines in children. In the pediatric population, clinical studies with new-generation antihistamines are still limited in number and, with rare exceptions, of brief duration. Comparative trials on the efficacy and safety between different compounds are also lacking.

CONCLUSIONS

Properly designed, long-term trials with new-generation H1 antihistamines need to be performed in single age groups, in order to better define the effects of these drugs in all pediatric population.

Disposition of loratadine in healthy volunteers

The absorption, metabolism and excretion of carbon-14-labeled loratadine (LOR, SCH 29851, Claritin) administered orally to healthy male volunteers were evaluated. Following a single oral 10-mg dose of [(14)C]LOR ( approximately 102 microCi), concentrations of LOR and desloratadine (DL; a pharmacologically active descarboethoxy metabolite of LOR) were determined in plasma. Metabolites in plasma, urine and feces were characterized using a liquid chromatography-mass spectrometry system (LC-MS) connected in line with a flow scintillation analyzer (FSA). Maximum plasma LOR and DL concentrations were achieved at 1.5 h and 1.6 h, respectively; thus, LOR was rapidly absorbed but also rapidly metabolized as indicated by these similar t(max) values. Metabolite profiles of plasma showed that LOR was extensively metabolized via descarboethoxylation, oxidation and glucuronidation. Major circulating metabolites included 3-hydroxy-desloratadine glucuonide (3-OH-DL-Glu), dihydroxy-DL-glucuronides, and several metabolites resulting from descarboethoxylation and oxidation of the piperidine ring. LOR was completely metabolized by 6 h post-dose. LOR-derived radiocarbon was excreted almost equally in the urine (41%) and feces (43%). About 13% of the dose was eliminated in the urine as 3-OH-DL-Glu. DL accounted for less than 2% of the dose recovered in the urine and only trace amounts of LOR were detected. 3-OH-DL was the major fecal metabolite ( approximately 17% of the dose). The combined amount of 5- and 6-hydroxy-DL contributed to an additional 10.7% of the dose in feces. Approximately 5.4% and 2.7% of the dose were excreted in the feces as unchanged drug and DL, respectively.

Metabolism and excretion of loratadine in male and female mice, rats and monkeys

The metabolism and excretion of loratadine (LOR), a long-acting non-sedating antihistamine, have been evaluated in male and female mice, rats and monkeys. Following a single (8 mg kg-1) oral administration of [14C]LOR, radioactivity was predominantly eliminated in the faeces. Profiling and characterization of metabolites in plasma, bile, urine and faeces from male and female mice, rats and monkeys showed LOR to be extensively metabolized with quantitative species and gender differences in the observed metabolites. In all species investigated, the primary biotransformation of LOR involved decarboethoxylation to form desloratadine (DL), subsequent oxidation (hydroxylation and N-oxidation) and glucuronidation. More than 50 metabolites were profiled using liquid chromatography-mass spectrometry (LC-MS) with in-line flow scintillation analysis (FSA) and characterized using LC-MSn techniques. The major circulating metabolite in male rats is a DL derivative in which the piperidine ring was aromatized and oxidized to pyridine-N-oxide. Much lower levels of the pyridine-N-oxide metabolite were observed in female rat plasma. In contrast, the relative amount of DL was notably higher in female than in male rats. The major circulating metabolite in either gender of mouse and male monkey is a glucuronide conjugate of an aliphatic hydroxylated LOR; in the female monkey, the major circulating metabolite is formed through oxidation of the pyridine moiety and subsequent glucuronidation. Qualitatively similar metabolic profiles were observed in the mouse, rat and monkey urine and bile, and the metabolites characterized resulted from biotransformation of LOR to DL, hydroxylation of DL and subsequent glucuronide conjugation. 5-Hydroxy-desloratadine was the major faecal metabolite across all three species irrespective of gender.

Visualization of first-pass drug metabolism of terfenadine by MALDI-imaging mass spectrometry

The aim of this article is to focus on the implementation and the application of matrix-assisted laser desorption/ionization-imaging mass spectrometric system (MALDI-IMS) to determine the disposition or biotransformation pathway of terfenadine and its active metabolite, fexofenadine in mouse and rat whole-body tissue sections. Whole-body MALDI-IMS data showed that the poor oral bioavailability of terfenadine was largely due to high first-pass metabolism in the intestines and the liver before the compound reached systemic circulation.

Some pharmacokinetic aspects of the lipophilic terfenadine and zwitterionic fexofenadine in humans

Fexofenadine, an active metabolite of the second-generation histamine H1 receptor antagonist (antihistamine) terfenadine, does not have the disadvantage of QT prolongation. In addition, unlike first-generation antihistamines, it is associated with few CNS adverse effects. Chemically, fexofenadine has a zwitterionic structure that makes it an interesting molecule for use as an oral drug. Fexo-fenadine has negligible hepatic metabolism in humans, and is recovered mainly in the faeces in an unchanged form after oral administration. The absolute oral bioavailability of fexofenadine in humans is not known because of a lack of studies of intravenous administration of this agent. Its apparent elimination half-life (t1/2) ranges from 3 to 17 hours and is highly dependent on study design, i.e. the length of blood sampling. This large discrepancy might be associated with a 'flip-flop' phenomenon caused by slow absorption of the zwitterionic molecule. This review summarises the available literature related to the absorption, elimination and excretion of fexofenadine and terfenadine. Based on these data, the volume of distribution, t1/2 and oral bioavailability of fexofenadine in humans are estimated. Understanding these pharmacokinetic aspects of this drug might be very useful for medicinal chemists utilising fexofenadine/terfenadine as an example for designing zwitterionic compounds to combat cardiotoxicity and other issues related to basic and lipophilic molecules.

Multidrug resistance-associated protein 2 is primarily responsible for the biliary excretion of fexofenadine in mice

Previous studies implicated P-glycoprotein (P-gp) as the major transport protein responsible for the biliary excretion of fexofenadine (FEX). However, FEX biliary excretion was not impaired in P-gp- or breast cancer resistance protein (Bcrp)-knockout mice or multidrug resistance-associated protein 2 (Mrp2)-deficient rats. The present study tested the hypothesis that species differences exist in the transport protein primarily responsible for FEX biliary excretion between mice and rats. Livers from Mrp2-knockout (Mrp2KO) mice and Mrp2-deficient (TR(-)) rats were perfused in a single-pass manner with 0.5 muM FEX. N-(4-[2-(1,2,3,4-Tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918) (10 muM) was employed to inhibit P-gp and Bcrp. The biliary excretion rate of FEX was decreased 85% in Mrp2KO relative to wild-type mice (18.4 +/- 2.2 versus 122 +/- 34 pmol/min/g liver). In mice, more than 50% of FEX unbound intrinsic biliary clearance (CL(bile, int)(') = 3.0 ml/h/g liver) could be attributed to Mrp2 (Mrp2-dependent CL(bile, int)(') approximately 1.7 ml/h/g liver), with P-gp and Bcrp playing a minor role (P-gp- and Bcrp-dependent CL(bile, int)(') approximately 0.3 ml/h/g liver). Approximately one third of FEX CL(bile, int)(') was attributed to unidentified mechanisms in mice. In contrast to mice, FEX biliary excretion rate (245 +/- 38 and 250 +/- 25 pmol/min/g liver) and CL(bile, int)(') (9.72 +/- 2.47 and 6.49 +/- 0.68 ml/h/g liver) were comparable between TR(-) and control Wistar rats, respectively, suggesting that unidentified transport mechanism(s) can completely compensate for the loss of Mrp2 function in rats. Mrp2 clearly plays a major role in FEX biliary excretion in mice. In conclusion, remarkable species differences exist in FEX hepatobiliary transport mechanisms.

Levocetirizine does not prolong the QT/QTc interval in healthy subjects: results from a thorough QT study

OBJECTIVE

To conduct a thorough QT study of levocetirizine, a non-sedating antihistamine, in accordance with International Conference on Harmonisation (ICH) E14 guidance.

METHODS

The study was designed as a single-dose, placebo and positive-controlled, four-way crossover, randomised trial in which 52 healthy male and female subjects participated. Levocetirizine (5 and 30 mg) and placebo were administered double-blind, and the positive control, moxifloxacin (400 mg), was open-label. Electrocardiograms (ECGs) were obtained by continuous Holter monitoring at various time points (three per time point) during a 24-h period at baseline and after each treatment. The ECGs were read centrally in a blinded manner. QT intervals were corrected for heart rate using a gender- and study-specific correction (QTcSS) and Fridericia's correction (QTcF). The largest QTc time-matched and baseline-subtracted difference between each active drug and the placebo (largest delta delta QTcSS) was derived from a mixed-effect analysis of variance.

RESULTS

The one-sided 95% upper limits of the largest delta delta QTcSS for levocetirizine were 5.7 ms (5 mg) and 3.9 ms (30 mg), with mean estimates of 2.9 and 1.1 ms, respectively. Similar results were obtained for the delta delta QTcF data. Statistically, moxifloxacin significantly lengthened the QTcSS, with a one-sided 95% lower limit of the largest delta delta QTcSS of 10.5 ms and a mean estimate of 13.4 ms. There was no relationship between the measured delta QTcSS and the plasma concentration of levocetirizine, whereas a statistically significant linear relationship was observed with the plasma concentration of moxifloxacin [slope estimate 0.004 ms/(ng/mL); 95% confidence interval: 0.003-0.005].

CONCLUSIONS

Overall, the results of this thorough QT study indicate that the methodology of the trial was valid and sensitive enough to demonstrate the absence of effect of levocetirizine at both therapeutic (5 mg) and supra-therapeutic (30 mg) doses on cardiac repolarisation.

Peripheral and central H1 histamine receptor occupancy by levocetirizine, a non-sedating antihistamine; a time course study in the guinea pig

BACKGROUND AND PURPOSE

The H(1) receptor occupancy (H1RO) in brain is an indicator of central side effects of antihistamines. Here, we determined the kinetics of central and peripheral H1RO by levocetirizine in relation to its brain and plasma concentration, and investigated the role of the blood-brain barrier in any delay in brain H1RO.

EXPERIMENTAL APPROACH

Concentration-time profiles in plasma and brain were obtained after 0.1 and 1 mg kg(-1) oral doses of levocetirizine in guinea pigs. H1RO in brain was measured ex vivo using [3H]-mepyramine and, in the periphery, by measuring the degree of inhibition of histamine-induced contractions of isolated guinea pig ileum.

KEY RESULTS

The concentration-time profile of levocetirizine indicated lower levels (partition coefficient, K(p)=0.06-0.08), higher t(max) (2-4 h vs 1-1.5 h) and longer terminal half-life (4-5.6 h vs 2.1-2.8 h) in brain than plasma. The H1RO at 0.1 and 1 mg kg(-1) were 75% and 97%, respectively, at 1 hr in the periphery and, in the brain, were <20% and 28-67% respectively, at all time points studied. Brain H1RO vs plasma concentrations profile showed a delay, but not when compared to brain concentrations.

CONCLUSIONS AND IMPLICATIONS

This study demonstrates an effective peripheral antihistamine effect of levocetirizine without central adverse effects at the dose close to human therapeutic dose. The slow increase in H1RO in the brain with time was caused by slow blood-brain barrier transport of levocetirizine. This demonstrates the importance of measuring time course of brain H1RO in relation to brain concentrations of drugs.

BIOEQUIVALENCE OF TWO FEXOFENADINE FORMULATIONS IN HEALTHY HUMAN VOLUNTEERS AFTER SINGLE ORAL ADMINISTRATION

AIM

A randomized, two-way, crossover, bioequivalence study was conducted in 25 fasting, healthy, male volunteers to compare two brands of fexofenadine 180 mg tablets, FEXOFENADINE 180 mg Film Tablet (Drogsan A.S., Ankara, Turkey) as test and Telfast 180 mg Tablet (Aventis Pharma, Frankfurt am Main, Germany) as a reference product.

METHOD

One tablet of either formulation was administered after 10 h of overnight fasting. After dosing, serial blood samples were collected during a period of 48 hours. Plasma samples were analysed for fexofenadine by a validated HPLC method. The pharmacokinetic parameters AUC(0-48), AUC(0-alpha), C(max), T(max), K(el), T(1/2), and CL were determined from plasma concentration-time profiles for both formulations and were compared statistically.

RESULTS AND CONCLUSIONS

The analysis of variance (ANOVA) did not show any significant difference between the two formulations and 90% confidence intervals (CI) fell within the acceptable range, satisfying the bioequivalence criteria of the FDA. Based on these statistical inferences it was concluded that the two brands exhibited comparable pharmacokinetics profiles and that Drogsan's Fexofenadine is equivalent to Telfast of Aventis Pharma, Frankfurt am Main, Germany.

Clinical efficacy and pharmacokinetic profiles of intranasal and oral cetirizine in a repeated allergen challenge model of allergic rhinitis

BACKGROUND

Intranasal and oral antihistamines are effective in treating allergic rhinitis. Studies comparing these routes of administration of an antihistamine regarding efficacy and pharmacokinetic profile are lacking.

OBJECTIVE

To compare topical and oral routes of administration of cetirizine regarding efficacy, plasma exudation, and systemic drug levels in a repeated allergen challenge model of allergic rhinitis.

METHODS

Oral cetirizine dihydrochloride, 10 mg once daily, and topical cetirizine dinitrate in a dose corresponding to 4.4 mg of the dihydrochloride salt twice daily were given to grass pollen-sensitive individuals for 12 days in a double-blind, placebo-controlled, crossover design. Timothy grass pollen allergen challenges were given once daily for 7 days using a nasal spray device. Nasal symptoms and peak inspiratory flow were recorded in the morning, 10 minutes after allergen challenge, and in the evening. The pharmacokinetics of the treatments was monitored in 8 patients. The remaining 28 patients were challenged topically with histamine 12 and 24 hours after the final topical and oral cetirizine doses, respectively. Nasal lavage levels of alpha2-macroglobulin were determined to evaluate histamine-induced mucosal plasma exudation.

RESULTS

During the last 3 days of the repeated allergen challenge model, chronic symptoms were established. Both treatments reduced symptoms 10 minutes after allergen challenge (P < .001 vs placebo). Neither treatment reduced morning and evening symptoms or nasal peak inspiratory flow. Topical, but not oral, cetirizine reduced histamine-induced plasma exudation (P < .01 vs placebo) when systemic drug levels were similar in the 2 treatment regimens.

CONCLUSIONS

Topical and oral cetirizine reduced acute nasal symptoms produced by allergen challenges in patients with established chronic symptoms. There were also antihistaminic effects of topical cetirizine not related to systemic drug levels.

Evaluation of the effect of levocetirizine on nasal mucociliary clearance in allergic rhinitis patients by rhinoscintigraphy

OBJECTIVE

The purpose of this study was to assess the effect of levocetirizine on nasal mucociliary clearance in allergic rhinitis patients using rhinoscintigraphy.

METHODS

Twenty patients with allergic rhinitis (12 males and eight females, mean age 37.7 +/- 10.5 years) were evaluated. All the patients received levocetirizine (5 mg x day(-1)) for 4 weeks, and the speed of nasal mucociliary clearance was assessed before and after treatment. Twenty healthy controls (11 males and nine females, mean age 39.4 +/- 7.8 years) were also evaluated.

RESULTS

The clearance values obtained for the treated group before and after treatment were significantly lower than those of the control group (P = 0.0001), but there was no significant difference in clearance speeds before and after treatment in the patient group (P = 0.444).

CONCLUSION

The study demonstrated that levocetirizine did not affect the speed of nasal mucociliary clearance in allergic rhinitis patients, and that nasal mucociliary clearance can easily be evaluated by rhinoscintigraphy.

Desloratadine dose selection in children aged 6 months to 2 years: comparison of population pharmacokinetics between children and adults

AIMS

The aim of this study was to identify the dose of desloratadine in children aged > or =6 months- < or =2 years that would yield a single-dose target exposure (AUC) comparable with that in adults taking 5 mg desloratadine as syrup.

METHODS

In a phase 1, single-dose, open-label, pharmacokinetic study in 58 children aged > or =6 months- <1 year and > or =1 year- < or =2 years were randomly assigned to desloratadine syrup 0.625 mg (1.25 ml) and 1.25 mg (2.5 ml), respectively. Because the volume of blood that could be collected from individual subjects was limited, a population pharmacokinetic approach was used to estimate the pharmacokinetics of desloratadine. Safety was assessed based on results of screening and postdose physical examinations, laboratory safety tests, vital signs, and adverse events.

RESULTS

The apparent clearance (CL/F) of desloratadine, population estimate (%CV), in children aged > or =6 months- <1 year was 27.8 l h(-1) (35) and corresponding values in children > or =1 year- < or =2 years was 35.5 l h(-1) (51), compared with 137 l h(-1) (58) for adults. The CL/F ratios (children to adults) indicated that doses of 1 mg for > or =6 months- <1 year and 1.25 mg for > or =1 year- < or =2 years would result in similar systemic exposure to that observed in adults receiving the recommended 5 mg dose. Desloratadine was well tolerated with no safety issues.

CONCLUSIONS

Doses of 1.0 and 1.25 mg in children aged > or =6 months- < or =2 years should result in an exposure to desloratadine similar to that of adults receiving doses of 5 mg.

Enhancing effect of surfactants on fexofenadine·HCl transport across the human nasal epithelial cell monolayer

The effect of various surfactants (sodium cholate, sodium taurocholate, Tween 80 and Poloxamer F68) on enhancing the transepithelial permeability of fexofenadine.HCl was evaluated in a human nasal epithelial cell monolayer model. The cytotoxicity of the surfactants on the human nasal epithelial cells was evaluated by the MTT assay. A dose-dependent reduction of cell viability was observed at higher than critical micelle concentration (CMC) of the surfactants, and the IC50 of non-ionic surfactants (Tween 80 and Poloxamer F68) was higher than that of ionic surfactants (sodium cholate and sodium taurocholate). The TEER values significantly decreased after 2 h incubation with the ionic surfactants, but were recovered after 24 h in the fresh culture media. Ionic surfactants significantly increased the transepithelial permeability (P(app)) of fexofenadine.HCl compared to the non-ionic surfactants. The reduction of TEER values upon exposing the cell monolayer to the surfactants for 2 h correlated well with the P(app) of fexofenadine.HCl, which suggests that the permeation-enhancing mechanism of the ionic surfactants is by altering the tight junction property of the paracellular pathway. F-actin staining showed that the effect of ionic surfactants on the tight junction is temporary and reversible, which is consistent with the TEER value recovery within 24 h. These results imply that ionic surfactants are potentially useful permeation enhancers for nasal delivery of hydrophilic compounds, such as fexofenadine.HCl. This study also indicated the usefulness of the human nasal epithelial cell monolayer model not only for evaluating the in vitro nasal drug transport but also for studying the mechanism and toxicity of enhancers.

Verapamil, but not probenecid, co-administration can convert desloratadine to a sedating antihistamine in mice

The possibility that non-sedating antihistamines could elicit sedation in mice due to drug-induced inhibition of brain PgP was evaluated by measuring the ability of desloratadine alone or in combination with verapamil to cause ataxia in mice. Also, the concentrations of desloratadine in plasma and in brain homogenates were measured by liquid chromatography-mass spectrometry. Relative to methylcellulose (control) treatment, verapamil plus desloratadine decreased rotarod performance of mice. Plasma concentrations of desloratadine appeared comparable in the mice treated with either desloratadine or verapamil plus desloratadine, however the rate of decline of desloratadine from brain tissue was slower in mice treated with verapamil plus desloratadine compared to mice treated with desloratadine only. These data suggest that inhibition of brain PgP can convert desloratadine to a sedating antihistamine in mice.

Determination of fexofenadine enantiomers in human plasma with high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatography (HPLC) method was developed as an assay for fexofenadine enantiomers in human plasma. Fexofenadine enantiomers were separated using a mobile phase of 0.5% KH(2)PO(4)-acetonitrile (65:35, v/v) on a Chiral CD-Ph column at a flow rate of 0.5 ml/min and measurement at 220 nm. Analysis required 400 microl of plasma and involved solid-phase extraction with an Oasis HLB cartridge, which gave recoveries for both enantiomers from 67.4 to 71.8%. The lower limit of quantification was 25 ng/ml for (R)- and (S)-fexofenadine. The linear range of this assay was between 25 and 625 ng/ml (regression line r(2)>0.993). Inter- and intra-day coefficients of variation were less than 13.6% and accuracies were within 8.8% over the linear range for both analytes. This method can be applied effectively to measure fexofenadine enantiomer concentrations in clinical samples.

Pharmacokinetics of fexofenadine enantiomers in healthy subjects

Fexofenadine, a substrate of P-glycoprotein and an organic anion transporter polypeptide, is commonly used to assess P-glycoprotein activity in vivo. The purpose of this study was to elucidate the pharmacokinetics of each fexofenadine enantiomer. After a single oral dose of racemic fexofenadine (60 mg), the plasma and urine concentrations of fexofenadine enantiomers were measured over the course of 24 h in six healthy subjects. The mean plasma concentration of R(+)-fexofenadine was higher than that of S(-)-fexofenadine. The area under the plasma concentration-time curve (AUC(0-infinity)) and the maximum plasma concentration (C(max)) of R(+)-fexofenadine were significantly greater than those of the S(-)-enantiomer (P = 0.0018 and 0.0028, respectively). The R/S ratios of AUC and C(max) of fexofenadine were 1.75 and 1.63, respectively. The oral clearance and renal clearance of S(-)-fexofenadine were significantly greater than that of R(+)-fexofenadine (P = 0.0074 and 0.0036). On the other hand, the stereoselective metabolism of fexofenadine using recombinant CYP3A4 was investigated; however, fexofenadine enantiomers were not metabolized by CYP3A4. Fexofenadine is transported by both P-glycoprotein and OATP and is not metabolized by intestinal CYP3A. Our findings suggest that the affinity of P-glycoprotein for S(-)-fexofenadine is greater than its affinity for the R(+)-enantiomer. Thus, P-glycoprotein is likely to have chiral discriminatory abilities.

Determination of loratadine and its active metabolite in human plasma by high-performance liquid chromatography with mass spectrometry detection

A new sensitive and selective liquid chromatography coupled with mass spectrometry (LC/MS/MS) method for quantification of loratadine (LOR) and its active metabolite descarboethoxyloratadine (DSL) in human plasma was validated. After addition of the internal standard, metoclopramide, the human plasma samples (0.3 ml) were precipitated using acetonitrile (0.75 ml) and the centrifuged supernatants were partially evaporated under nitrogen at 37 degrees C at approximately 0.3 ml volume. The LOR, DSL and internal standard were separated on a reversed phase column (Zorbax SB-C18, 100 mmx3.0 mm i.d., 3.5 microm) under isocratic conditions using a mobile phase of an 8:92(v/v) mixture of acetonitrile and 0.4% (v/v) formic acid in water. The flow rate was 1 ml/min and the column temperature 45 degrees C. The detection of LOR, DSL and internal standard was in MRM mode using an ion trap mass spectrometer with electrospray positive ionisation. The ion transitions were monitored as follows: 383-->337 for LOR, 311-->(259+294+282) for DSL and 300-->226.8 for internal standard. Calibration curves were generated over the range of 0.52-52.3 ng/ml for both LOR and DSL with values for coefficient of determination greater than 0.994 by using a weighted (1/y) quadratic regression. The lower limits of quantification were established at 0.52 ng/ml LOR and DSL, respectively, with an accuracy and precision less than 20%. Both analytes demonstrated good short-term, long-term, post-preparative and freeze-thaw stability. Besides its simplicity, the sample treatment allows obtaining a very good recovery of both analytes, around 100%. The validated LC/MS/MS method has been applied to a pharmacokinetic study of loratadine tablets on healthy volunteers.

Lack of dose-dependent effects of itraconazole on the pharmacokinetic interaction with fexofenadine

The aim of this study was to determine the inhibitory effect of itraconazole at different coadministered doses on fexofenadine pharmacokinetics. In a randomized four-phase crossover study, 11 healthy volunteers were administered a 60-mg fexofenadine hydrochloride tablet alone on one occasion (control phase) and with three different doses of 50, 100, and 200 mg of itraconazole simultaneously on the other three occasions (itraconazole phase). Although the elimination half-life and the renal clearance of fexofenadine remained relatively constant, a single administration of itraconazole with fexofenadine significantly increased mean area under the plasma concentration-time curve (AUC(0-infinity)) of fexofenadine (1701/3554, 4308, and 4107 ng h/ml for control; 50 mg, 100 mg, and 200 mg of itraconazole, respectively). Although mean itraconazole AUC(0-48) from 50 mg to 200 mg increased dose dependently from 214 to 772 ng h/ml (p = 0.003), no significant difference was noted in the three parameters, AUC (p = 0.423), C(max) (p = 0.636), and renal clearance (p = 0.495), of fexofenadine among the three doses of itraconazole. Itraconazole exposure at a lower dose (50 mg) compared with the clinical dose (200 mg once or twice daily) had the maximal effect on fexofenadine pharmacokinetics, even though itraconazole plasma concentrations gradually increased after higher doses. These findings suggest that the interaction may occur at the gut wall before reaching the portal vein circulation, and the inhibitory effect must be saturated by substantial local concentrations of itraconazole in the gut lumen after 50-mg dosing.

Effects of single and multiple doses of itraconazole on the pharmacokinetics of fexofenadine, a substrate of P-glycoprotein

AIMS

We determined whether or not the extent of drug interaction of fexofenadine by itraconazole is time-dependent.

METHODS

In a randomized two-phase crossover study, itraconazole was administered orally for 6 days, and, on days 1, 3 and 6, fexofenadine was administered simultaneously. On another occasion, fexofenadine was administered alone.

RESULTS

Itraconazole increased fexofenadine AUC(0, infinity), and the % change for difference was 178% (95% CI 1235, 3379), 205% (95% CI 1539, 3319) and 169% (95% CI 1128, 2987) on days 1, 3 and 6 of the 6 day treatment, respectively.

CONCLUSIONS

The extent of drug interaction by itraconazole was not time-dependent.

Review of desloratadine for the treatment of allergic rhinitis, chronic idiopathic urticaria and allergic inflammatory disorders

Desloratadine is a once-daily, non-sedating, non-impairing, selective histamine H1-receptor antagonist. It relieves the symptoms of seasonal allergic rhinitis (including nasal obstruction and congestion, and morning symptoms), perennial allergic rhinitis and chronic idiopathic urticaria by blocking multiple critical steps in the systemic allergic cascade and downregulating key allergy-induced inflammatory mediators. It also relieves asthma symptoms and decreases rescue medication use in patients with seasonal allergic rhinitis and comorbid asthma. Numerous clinical studies have demonstrated that desloratadine is safe, well tolerated and free of serious cardiac effects. Pharmacokinetic studies have demonstrated a low propensity for drug-drug or drug-food interactions. This review outlines the mechanism of action, efficacy and safety of desloratadine for the treatment of allergic inflammatory disorders.

Severe arrhythmia as a result of the interaction of cetirizine and pilsicainide in a patient with renal insufficiency: first case presentation showing competition for excretion via renal multidrug resistance protein 1 and organic cation transporter 2

A 72-year-old woman with renal insufficiency who was taking oral pilsicainide (150 mg/d) complained of feeling faint 3 days after she was prescribed oral cetirizine (20 mg/d). She was found to have a wide QRS wave with bradycardia. Her symptoms were relieved by termination of pilsicainide. The plasma concentrations of both drugs were significantly increased during the coadministration, and the cetirizine concentration decreased on cessation of pilsicainide despite the fact that treatment with cetirizine was continued, which suggested that the fainting was induced by the pharmacokinetic drug interaction. A pharmacokinetic study in 6 healthy male volunteers after a single dose of either cetirizine (20 mg) or pilsicainide (50 mg), or both, found that the renal clearance of each drug was significantly decreased by the coadministration of the drugs (from 475 +/- 101 mL/min to 279 +/- 117 mL/min for pilsicainide and from 189 +/- 37 mL/min to 118 +/- 28 mL/min for cetirizine; P = .008 and .009, respectively). In vitro studies using Xenopus oocytes with microinjected human organic cation transporter 2 and renal cells transfected with human multidrug resistance protein 1 revealed that the transport of the substrates of these transporters was inhibited by either cetirizine or pilsicainide. Thus elevated concentrations of these drugs as a result of a pharmacokinetic drug-drug interaction via either human multidrug resistance protein 1 or human organic cation transporter 2 (or both) in the renal tubular cells might have caused the arrhythmia in our patient. Although cetirizine has less potential for causing arrhythmias than other histamine 1 blockers, such an interaction should be considered, especially in patients with renal insufficiency who are receiving pilsicainide.

The relative bioavailability of loratadine administered as a chewing gum formulation in healthy volunteers

OBJECTIVE

The aim of this study was to investigate the pharmacokinetics of loratadine and its active metabolite desloratadine after single-dose administration of loratadine as a conventional tablet, orally disintegrating tablet (smelt tablet) and a chewing gum formulation with and without the collection of saliva.

METHODS

Twelve healthy male volunteers participated in a four-period cross-over trial evaluating the effect of dosage forms on the pharmacokinetics of a single dose of loratadine. Loratadine was administered as two 10-mg conventional tablet, two 10-mg smelt tablet, a 30-mg portion of medicated chewing gum without collection of saliva and a 30-mg portion of medicated chewing gum with collection of saliva. Blood samples were taken at predefined sampling points 0-24 h after medication, and the plasma concentrations of loratadine and desloratadine were determined by high-performance liquid chromatography. Each study period was separated by a wash-out period of at least 7 days.

RESULTS

The mean dose-corrected area under the plasma concentration-time curve extrapolated to infinity AUC(0-infinity) for the chewing gum formulation was statistically significantly increased compared to the tablet formulation (geometric mean ratio: 2.68; 95%CI: 1.75-4.09). Desloratadine pharmacokinetic parameters from the chewing gum formulation were not statistically significantly different from the conventional tablet. Neither loratadine nor desloratadine pharmacokinetics of the smelt tablet formulation were statistically significantly different from the conventional tablet formulation. Plasma concentrations of desloratadine following the administration of loratadine as chewing gum with saliva collection were very low.

CONCLUSION

Our study showed that formulation of loratadine as a medicated chewing gum results in an almost threefold increase in relative bioavailability. This is most likely due to a bypass of first-pass metabolism as this study suggests that approximately 40% of the absorbed loratadine was absorbed via the oral mucosa.

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.

Bioavailability of two oral formulations of loratadine 20 mg with concomitant ketoconazole: An open-label, randomized, two-period crossover comparison in healthy Mexican adult volunteers

BACKGROUND

Loratadine is a long-acting antihistamine with selective peripheral histamine H(1)-receptor antagonistic activity and fewer sedative effects compared with conventional antihistamines, and is widely used in Mexico. Although several generic formulations of loratadine are available in Mexico, based on a literature search, information concerning the bioavailability of each formulation in the Mexican population is not available.

OBJECTIVE

The aim of this study was to compare the bioavailability and tolerability of 2 oral formulations of loratadine 20 mg (two 10-mg tablets) used in Mexico: Sensibit (test formulation; Laboratorios Liomont S.A. de C.V., Mexico City, Mexico) and Clarityne (reference formulation; Schering-Plough S.A. de C.V., Mexico City, Mexico) in healthy volunteers.

METHODS

This open-label, randomized, 2-period crossover study was conducted at Universidad Autónoma de Nuevo León, Monterrey, Nuevo León, Mexico. Eligible subjects were healthy male Mexican volunteers aged > or=18 years. Subjects were randomly assigned to receive a single 20-mg dose (two 10-mg tablets) of the test or reference formulation, followed by a 2-week washout period, followed by the same dose of the alternate formulation. A 400-mg dose of ketoconazole (2 doses in 24 hours) was administered to each subject before the administration of each formulation, and a 200-mg dose of ketoconazole was given together with each formulation (ie, a total of 600 mg of ketoconazole was administered). Doses were administered after a 12-hour overnight fast. For analysis of pharmacokinetic properties, including C(maX), AUC(0-t), and AUC(0-infinity), blood samples were drawn at 0.25, 0.5, 0.75, 1, 1.25, 1.5, 2, 2.5, 3, 5, 8, 12, 16, and 22 hours after dosing. The formulations were considered bioequivalent if the geometric mean ratios of C(maX) and AUC were within the predetermined equivalence range of 80% to 125%. Tolerability was assessed by monitoring vital signs and subject interview regarding the potential presence of adverse events (AEs).

RESULTS

Thirty-two subjects were enrolled in the study (mean age, 22 years [range, 18-28 years]; mean weight, 68.9 kg [range, 58-79 kg]; mean height, 170.8 cm [range, 158-183 cm]). Sixteen subjects received the test formulation first. No period or sequence effect was observed. The 90% CIs for the corresponding ratios of CmaX, AUC(0-t), and AUC(0-infinity) were 81.43% to 106.01%, 83.12% to 100.23%, and 84.06% to 101.10% (all, P < 0.05), meeting the predetermined criteria for bioequivalence. Similar results were found for data without a logarithmic transformation. No AEs were reported throughout the study.

CONCLUSIONS

In this small study in healthy Mexican volunteers, a single, 20-mg dose of the test formulation of loratadine was found to be bioequivalent to that of the reference formulation based on the rate and extent of absorption when concomitantly administered with ketoconazole. Both formulations were well tolerated.

BRAIN DISTRIBUTION OF CETIRIZINE ENANTIOMERS: COMPARISON OF THREE DIFFERENT TISSUE-TO-PLASMA PARTITION COEFFICIENTS: Kp, Kp,u, AND Kp,uu

The objective of this study was to compare the blood-brain barrier (BBB) transport and brain distribution of levo- (R-CZE) and dextrocetirizine (S-CZE). Microdialysis probes, calibrated using retrodialysis by drug, were placed into the frontal cortex and right jugular vein of eight guinea pigs. Racemic CZE (2.7 mg/kg) was administered as a 60-min i.v. infusion. Unbound and total concentrations of the enantiomers were measured in blood and brain with liquid chromatography-tandem mass spectrometry. The brain distribution of the CZE enantiomers were compared using the parameters K(p,) K(p,u,) K(p,uu), and V(u,br). K(p) compares total brain concentration to total plasma concentration, K(p,u) compensates for binding in plasma, whereas K(p,uu) also compensates for binding within the brain tissue and directly quantifies the transport across the BBB. V(u,br) describes binding within the brain. The stereoselective brain distribution indicated by the K(p) of 0.22 and 0.04 for S- and R-CZE, respectively, was caused by different binding to plasma proteins. The transport of the CZE enantiomers across the BBB was not stereoselective, since the K(p,uu) was 0.17 and 0.14 (N.S.) for S- and R-CZE, respectively. The K(p,uu) values show that the enantiomers are effluxed to a large extent across the BBB. The V(u,br) of approximately 2.5 ml/g brain was also similar for both the enantiomers, and the value indicates high binding to brain tissue. Thus, when determining stereoselectivity in brain distribution, it is important to study all factors governing this distribution, binding in blood and brain, and the BBB equilibrium.

Levocetirizine: pharmacokinetics and pharmacodynamics in children age 6 to 11 years

BACKGROUND

The pharmacokinetics and pharmacodynamics of medications may differ between children and adults, necessitating different dose regimens for different age groups. Levocetirizine, the active enantiomer of cetirizine, is used in the treatment of allergic rhinitis and chronic urticaria in Europe. Its pharmacokinetics and pharmacodynamics have not yet been studied prospectively in school-age children.

OBJECTIVES

This study was performed to investigate levocetirizine pharmacokinetic disposition and pharmacodynamics in relation to skin reactivity to histamine in children aged 6 to 11 years.

METHODS

Blood samples were obtained at predose baseline and at defined intervals up to and including 28 hours after a 5-mg levocetirizine dose. Concurrently, epicutaneous tests with histamine phosphate, 1 mg/mL, were performed. Wheals and flares were traced at 10 minutes, and the areas were measured with a computerized digitizing system.

RESULTS

In children aged 8.6 +/- 0.4 years (+/- SEM), the peak levocetirizine concentration was 450 +/- 37 ng/mL, and the time at which peak concentrations occurred was 1.2 +/- 0.2 hours. The terminal elimination half-life was 5.7 +/- 0.2 hours, the oral clearance was 0.82 +/- 0.05 mL/min/kg, and the volume of distribution was 0.4 +/- 0.02 L/kg. Compared with predose areas, the wheals and flares produced by histamine phosphate were significantly decreased from 1 to 28 hours, inclusive (P < .05). Mean maximum inhibition of wheals and flares occurred from 2 to 10 hours (97% +/- 1%) and from 2 to 24 hours (93% +/- 1%), respectively.

CONCLUSIONS

Levocetirizine had an onset of action within 1 hour and provided significant peripheral antihistaminic activity for 28 hours after a single dose. Once-daily dosing may be optimal in children aged 6 to 11 years, as it is in adults.

[Study on determination of desloratadine in human serum and its pharmacokinetics by HPLC/MS]

OBJECTIVE

To study the determination of desloratadine in human serum and its pharmacokinetics in healthy volunteers.

METHODS

A single oral dose of 10 mg desloratadine was given to 18 healthy volunteers. The serum concentrations of desloratadine were determined by HPLC-MS assay. The pharmacokinetics parameters of desloratadine tablets were calculated with program 3P97.

RESULT

The main pharmacokinetics parameters of desloratadine tablets were as followsút(max)(1.611 +/-0.366)h, C(max) (4.455+/-1.990)microg x L(-1), AUC(0-t) (58.50+/-21.34)microg x L(-1) x h(-1), AUC(0-infinity) (60.59+/-22.32)microg x L(-1) x h(-1), t(1/2(ke)) (20.303+/-5.833)h, Ke (0.0372+/-0.0116)h(-1) and CL(0.1838+/-0.0563)L x h(-1).

CONCLUSION

Desloratadine tablet is absorbed quicker in the 18 healthy volunteers than the reports and its peak blood concentration reached at 1.5 h after oral administration with t(1/2) 20 h.

A review of the second-generation antihistamine ebastine for the treatment of allergic disorders

Ebastine is a once-daily, non-sedating, selective, long-acting, second-generation antihistamine. The use of ebastine is indicated in patients suffering from intermittent and persistent allergic rhinitis and chronic idiopathic urticaria. Ebastine 10 mg/day, appears as effective as other second-generation antihistamines, such as cetirizine and loratadine. Ebastine 20 mg/day is indicated in patients with moderate and severe allergic symptoms. No cardiovascular effects of ebastine are described, although there is a pharmacokinetic interaction when ketoconazole or macrolides are co-administered. Ebastine has no relevant effects on the psychomotor performance. Even with ebastine 20 mg/day skilled performance does not appear to be impaired. Furthermore, ebastine 5-10 and 2.5 mg, appears to be efficient and can be used safely in children 6-11 and 2-5 years of age, respectively. Ebastine appears to be a safe, effective and well-tolerated second-generation antihistamine in the treatment of allergic rhinitis and chronic idiopathic urticaria.

[Circadian rhythms in the toxic effects of the histamine antagonist cetirizine in mice]

Cetirizine is a second generation histamine H(1) receptor antagonist used to provide symptomatic relief of allergic signs caused by histamine release. The aim of the study was to learn whether the survival and the motor incoordination (ataxia) side effect of cetirizine administration is dosing time-dependent.

MATERIALS AND METHODS

A total of 240 male Swiss mice, 10 weeks of age were synchronized for 3 weeks by 12 h light (rest span)/12 h dark (activity span). Different doses of cetirizine were administered orally at fixed times during the day to determine both the sublethal (TD(50)) and lethal (LD(50)) doses, which were, respectively, 55 +/- 0.35 and 750 +/- 0.40 mg/kg. In the chronotoxicologic study a single dose of cetirizine (DL(50)) was administered to comparable groups of animals at six different circadian stages [1, 5, 9, 13, 17, 21 h after light onset (HALO)].

RESULTS

The survival was statistically significant dosing time-dependent (chi(2) = 16.73; P < 0.001). Drug dosing at 17 HALO resulted in 83.3% survival rate whereas drug dosing at 5 HALO was only 23.25%. Cosinor analysis revealed a statistically significant circadian (period approximately 24 h) rhythmic component in survival. Lowest (20%) and highest (88%) ataxia occurred when cetirizine was administered, respectively, at 17 and 5 HALO. Cosinor analysis revealed a statistically significant circadian (period approximately 24 h) rhythmic component in ataxia.

CONCLUSION

Our results reveal that the best safety is shown when cetirizine is administered in the middle of the dark (activity) span of the mice, since it produces some side effects: ataxia and hyperthermia. Taking into account of the hour administration of cetirizine, improves treatment efficacy and permit the best control of allergic diseases.

EFFECT OFCYP2D6*10ALLELE ON THE PHARMACOKINETICS OF LORATADINE IN CHINESE SUBJECTS

Loratadine is known to be a substrate for both CYP3A4 and CYP2D6 based on a previous in vitro study. In view of the large interindividual variability in loratadine pharmacokinetics and the greater genetically determined variability of CYP2D6 activity than of CYP3A4 in vivo, we hypothesized that CYP2D6 polymorphisms may contribute to the pharmacokinetic variability of loratadine. The purpose of this study was to evaluate the effect of CYP2D6 genotype (specifically the CYP2D6*10 allele) on the pharmacokinetics of loratadine in Chinese subjects. Three groups of healthy male Chinese subjects were enrolled: group I, homozygous CYP2D6*1 (*1/*1, n=4); group II, heterozygous CYP2D6*10 (*1/*10 or *2/*10, n=6); and group III, homozygous CYP2D6*10 (*10/*10, n=7) carriers. Each subject received a single oral dose of 20 mg of loratadine under fasting conditions. Multiple blood samples were collected over 48 h, and the plasma concentrations of loratadine and its metabolite desloratadine were determined by high-performance liquid chromatography. In comparing homozygous CYP2D6*10 (group III) to heterozygous CYP2D6*10 (group II) to homozygous CYP2D6*1 (group I) subjects, loratadine oral clearance values were 7.17+/- 2.54 versus 11.06+/-1.70 versus 14.59+/-2.43 l/h/kg, respectively [one-way analysis of variance (ANOVA), p<0.01], and the corresponding metabolic ratios [area under the plasma concentration-time curve (AUC)(desloratadine)/AUC(loratadine)] were 1.55+/-0.73 versus 2.47+/- 0.46 versus 3.32+/- 0.49, respectively (one-way ANOVA, p<0.05), indicating a gene-dose effect. The results demonstrated that CYP2D6 polymorphism prevalent in the Chinese population significantly affected loratadine pharmacokinetics.

Retrospective population pharmacokinetics of levocetirizine in atopic children receiving cetirizine: the ETAC study

AIMS

To evaluate the population pharmacokinetics of levocetirizine in young children receiving long-term treatment with cetirizine.

METHODS

Data were available from a randomized, double-blind, parallel group and placebo-controlled study of cetirizine in 343 young children between 12 and 24 months of age at entry, who were at high risk of developing asthma, but were not yet affected (ETAC study). Infants received oral drops of cetirizine at 0.25 mg kg(-1) twice daily for 18 months. Plasma concentration of the active enantiomer levocetirizine was determined in blood samples collected at months 3, 12 and 18 (1-3 samples per child). A one-compartment open model was fitted to the data using nonlinear mixed effects modelling (NONMEM). The influence of weight, age, gender, BSA and other covariates on CL/F and V/F was evaluated.

RESULTS

CL/F increased linearly with weight by 0.044 l h(-1) kg(-1) over an intercept of 0.244 l h(-1), and V/F increased linearly with weight by 0.639 l kg(-1). Population estimates in children with weights of 8 and 20 kg were 0.60 and 1.13 l h(-1) for CL/F, and 5.1 and 12.8 l for V/F, respectively, with interpatient variabilities of 24.4% and 14.7%. Weight-normalized estimates of CL/F and V/F were higher than in adults. The estimated relative bioavailability was 0.28 in 12% of instances of suspected noncompliance. Levocetirizine pharmacokinetics were not influenced by severe allergy or aeroallergen sensitization. Results on the effects of concomitant medications or diseases were inconclusive due to limited positive cases. AUC(ss), calculated in compliant subjects using posterior estimates of the final model, was 1952 (1227-3319) microg l(-1) h (mean, min-max), a value similar to that in adults after intake of 5 mg oral solution (2036 (1414-2827) microg l(-1) h.

CONCLUSIONS

The model suggests that administration of levocetirizine 0.125 mg kg(-1) twice daily in children 12-48 months of age or weighing 8-20 kg yields the same exposure as in adults taking the recommended dose of 5 mg once daily.

Evaluation of pharmacokinetic interaction between cetirizine and ritonavir, an HIV-1 protease inhibitor, in healthy male volunteers

BACKGROUND

Serious adverse effects have been observed with some non-sedative H1-antihistamines (terfenadine and astemizole) when they were associated with drugs known to inhibit their metabolism. However, this is not a class effect, and this interaction should be considered on a case-by-case basis. The aim of this study was to evaluate the potential of pharmacokinetic interaction between cetirizine and ritonavir, the most potent cytochrome P450 (CYP) inhibitor.

METHODS

An open-label, single-center, one-sequence crossover pharmacokinetic study was conducted in three running periods: cetirizine (CTZ) alone, ritonavir (RTV) alone and then CTZ plus RTV. For each period, steady-state pharmacokinetics were obtained. RTV and CTZ plasma concentrations were determined using validated liquid chromatography methods. The statistical method was based on a 90% confidence interval (CI) for the ratio of population geometric means (combination/drug alone) for each drug and for each parameter [area under the plasma concentration versus time curve (AUC(0-tau,ss)), value of maximum plasma concentration (C(max,ss))] and compared to bioequivalence ranges 80-125% and 70-143% for AUC(0-tau,ss) and C(max,ss), respectively.

RESULTS

Among the 17 male subjects enrolled (26.4 +/- 8.6 years), 16 completed the study (1 withdrawal after the first period). The RTV pharmacokinetic parameter values were not affected by CTZ co-treatment. With RTV, a 42% increase in the CTZ AUC(0-tau,ss) (3406 versus 4840 microgh/l, 90% CI of 128-158%), a 53% increase in the CTZ elimination half-life (7.8 h versus 11.9 h, P = 0.001), a slight increase (15%) in the CTZ apparent volume of distribution (V(d,ss)/f) (34.7 l versus 39.8 l, P = 0.035), a 29% decrease in the CTZ apparent total body clearance (49.9 ml/min versus 35.3 ml/min, P < 0.001) and bioequivalent C(max,ss) (374 microg/l versus 408 microg/l) were observed. No serious drug related adverse effects were notified.

CONCLUSIONS

CTZ does not significantly affect the pharmacokinetic parameters of RTV, and the association does not, thus, require a modification of the dosage of the protease inhibitor. The increased extent of exposure to CTZ in healthy subjects, in the presence of RTV administered at high doses, remained in the same range as previously observed in the elderly or in mildly renally impaired subjects.

Central effects of fexofenadine and cetirizine: measurement of psychomotor performance, subjective sleepiness, and brain histamine H1-receptor occupancy using 11C-doxepin positron emission tomography

Histamine H1-receptor (H1R) antagonists, or antihistamines, often induce sedative side effects when used for the treatment of allergic disorders. This study compared the sedative profiles of the second-generation antihistamines, fexofenadine and cetirizine, using 3 different criteria: subjective sleepiness evaluated by the Stanford Sleepiness Scale, objective psychomotor tests (simple and choice reaction time tests and visual discrimination tests at 4 different exposure durations), and measurement of histamine H1-receptor occupancy (H1RO) in the brain. Subjective sleepiness and psychomotor performance were measured in 20 healthy Japanese volunteers at baseline and 90 min after administration of fexofenadine 120 mg or cetirizine 20 mg in a double-blind, placebo-controlled crossover study. Hydroxyzine 30 mg was included as a positive control. H1RO was measured using positron emission tomography (PET) with (11)C-doxepin in 12 of the 20 subjects, and a further 11 volunteers were recruited to act as controls. In psychomotor tests, fexofenadine was not significantly different from placebo and significantly less impairing than cetirizine on some tasks, as well as significantly less impairing than hydroxyzine on all tasks. For subjective sleepiness, fexofenadine was not significantly different from placebo, whereas cetirizine showed a trend toward increased sleepiness compared with fexofenadine and placebo. H1RO was negligible with fexofenadine (-0.1%) but moderately high with cetirizine (26.0%). In conclusion, fexofenadine 120 mg is distinguishable from cetirizine 20 mg, as assessed by H1RO and psychomotor testing.