Wheal Suppression Research Articles

Effect of itraconazole on the pharmacokinetics and pharmacodynamics of fexofenadine in relation to the genetic polymorphism

Our objective was to evaluate the effect of itraconazole, a P-glycoprotein inhibitor, on the pharmacokinetics and pharmacodynamics of fexofenadine, a P-glycoprotein substrate, in relation to the multidrug resistance 1 gene (MDR1) G2677T/C3435T haplotype. A single oral dose of 180 mg fexofenadine was administered to 7 healthy subjects with the 2677GG/3435CC (G/C) haplotype and 7 with the 2677TT/3435TT (T/T) haplotype. One hour before the fexofenadine dose, either 200 mg itraconazole or placebo was administered to the subjects in a double-blinded, randomized, crossover manner with a 2-week washout period. Histamine-induced wheal and flare reactions were measured to assess the effects on the antihistamine response. In the placebo phase, pharmacokinetic parameters of fexofenadine showed no statistically significant difference between 2 MDR1 haplotypes; the area under the curve from time 0 to infinity (AUC(0-infinity)) of fexofenadine in the T/T and G/C groups was 5194.0 +/- 1910.8 and 4040.4 +/- 1832.2 ng.mL(-1).h(-1), respectively (P = .271), and the oral clearance (CL/F) was 530.9 +/- 191.1 and 806.0 +/- 355.3 mL.h(-1).kg(-1), respectively (P = .096). The disposition of itraconazole, a substrate of P-glycoprotein, was not significantly different between the 2 haplotypes. After itraconazole pretreatment, however, the differences in fexofenadine pharmacokinetics became statistically significant; the mean fexofenadine AUC(0-infinity) in the T/T group was significantly higher than that in the G/C group (15,630.6 +/- 5070.0 and 9252.9 +/- 2044.1 ng/mL.h, respectively; P = .007), and CL/F of the T/T subjects was lower than that of the G/C subjects (167.0 +/- 33.3 and 292.3 +/- 42.2 mL.h(-1).kg(-1), respectively; P < .001). Itraconazole pretreatment caused more than a 3-fold increase in the peak concentration of fexofenadine and the area under the curve to 6 hours compared with the placebo phase. This resulted in a significantly higher suppression of the histamine-induced wheal and flare reactions in the itraconazole pretreatment phase compared with those in the placebo phase. The effect of MDR1 G2677T/C3435T haplotypes on fexofenadine disposition are magnified in the presence of itraconazole. Itraconazole pretreatment significantly altered the disposition of fexofenadine and thus its peripheral antihistamine effects.

Similar rapid onset of action and magnitude of effect of fexofenadine and cetirizine as assessed by inhibition of histamine-induced wheal-and-flare reaction

Histamine-induced wheal-and-flare studies are useful, objective tests for determining differences in the peripheral H1-receptor blockade activities of antihistamines. To evaluate the time of occurrence of 95% inhibition of histamine-induced wheal and flare after administration of fexofenadine hydrochloride, 180 mg, or cetirizine, 10 mg. Forty-two volunteers (aged 18-60 years) were included in a randomized, double-blind, crossover study. Skin prick tests were undertaken using histamine (100 mg/mL) before treatment and 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, and 4.0 hours after treatment. Wheal and flare areas were evaluated, and the time to occurrence of 95% inhibition and the frequency of subjects exhibiting 95% inhibition before median time to 95% inhibition were calculated. Mean +/- SD time to 95% wheal inhibition was 2.46 +/- 0.71 hours with fexofenadine and 2.55 +/- 0.57 hours with cetirizine. The estimated mean difference between fexofenadine and cetirizine (-7 minutes in favor of fexofenadine; 2-sided 95% confidence interval, -21 to +7 minutes) was not statistically significant (P = .34). For wheal, 29% of subjects receiving fexofenadine and 24% receiving cetirizine achieved 95% inhibition before the median time of inhibition (2.5 hours). An exact permutation test yielded a P = .37. For flare, 26% of subjects receiving fexofenadine and 10% receiving cetirizine achieved 95% inhibition before the median time of inhibition (3 hours; P = .12 by exact permutation test). Fexofenadine and cetirizine have comparable onset of action times and similar frequencies of inhibition, as evaluated by the occurrence of 95% inhibition of histamine-induced wheal and flare.

Cetirizine from topical phosphatidylcholine liposomes: Evaluation of peripheral antihistaminic activity and systemic absorption in a rabbit model

This study was performed to assess the peripheral H(1)-antihistaminic activity and extent of systemic absorption of cetirizine from liposomes applied to the skin. Cetirizine was incorporated into small unilamellar vesicles (SUV) and multilamellar vesicles (MLV) prepared using L-alpha-phosphatidylcholine, and into Glaxal Base (GB), used as the control. In a randomized, cross-over study, each formulation, containing 10 mg of cetirizine, was applied to depilated areas on the backs of six rabbits (3.08+/-0.05 kg). Histamine-induced wheal tests and blood sampling were performed before cetirizine application and at designated times for up to 24 h. Compared with the baseline, histamine-induced wheal formation was suppressed by cetirizine in SUV and MLV from 0.5-24 h and by cetirizine in GB from 0.5-8 h, p</=0.05. Maximum wheal suppression by cetirizine in SUV and MLV ranged from 90.6%+/-4.9% to 89.0%+/-3.8% and 98.0%+/-1.3% to 94.0%+/-2.3%, respectively, from 6 to 8 h. The plasma cetirizine AUC of 201+/-24.2 ng.h/ml from SUV was lower than from PC-MLV, 334.6+/-65.1 ng.h/ml and from GB, 248.3+/-34.6 ng.h/ml. After 24 h, the percent of the cetirizine dose remaining on the backs of the rabbits from SUV was lower than from both MLV and GB, p</=0.05. In this model, cetirizine from both SUV and MLV had excellent topical H(1)-antihistaminic effects, while systemic exposure to cetirizine from SUV was reduced.

Cetirizine from topical phosphatidylcholine-hydrogenated liposomes: Evaluation of peripheral antihistaminic activity and systemic absorption in a rabbit model

Cetirizine, an effective, minimally sedating, second-generation H1-antihistamine is widely used orally to treat allergic skin disorders. This study was performed to assess the peripheral H1-antihistaminic activity and extent of systemic absorption of cetirizine from liposomes applied to the skin. Cetirizine was incorporated into small unilamellar vesicles (SUV) and multilamellar vesicles (MLV) prepared using L-alpha-phosphatidylcholine hydrogenated (HPC), and into Glaxal Base (GB) as the control. In a randomized, crossover study, each formulation, containing 10 mg of cetirizine, was applied to the depilated backs of 6 rabbits (3.08 +/- 0.05 kg). Histamine-induced wheal tests and blood sampling were performed before cetirizine application and at designated times for up to 24 hours afterwards. Compared with baseline, histamine-induced wheal formation was suppressed by cetirizine in SUV only at 24 hours, in MLV from 0.5 to 24 hours, and in GB from 0.5 to 8 hours (P < or = .05). Wheal suppression by cetirizine in SUV at 24 hours (91.7% +/- 5.2%) and in MLV from 1 to 24 hours (93.8% +/- 2.2% to 76.2% +/- 6.5%) was greater than in GB (36.5% +/- 7.4% to 60.6% +/- 14.2%) from 1 to 24 hours (P < or = .05). Faster onset, as well as greater and more persistent suppression was obtained from cetirizine in MLV. Plasma cetirizine concentrations from MLV (area under the curve [AUC] of 221.2 +/- 42.3 ng x hr/mL) were lower than from GB (AUC of 248.3 +/- 34.6 ng.hr/mL). In this model, cetirizine from MLV had excellent topical H(1)-antihistamine activity, while systemic exposure was reduced, compared with cetirizine from GB.

Comparative activity of cetirizine and desloratadine on histamine-induced wheal-and-flare responses during 24 hours

Cetirizine and desloratadine are antihistamines active in the treatment of symptoms associated with seasonal allergic rhinitis and chronic urticaria. To compare the antihistamine activity of desloratadine, the active metabolite of loratadine, with that of cetirizine in the skin wheal-and-flare responses during 24 hours. This was a double-blind, randomized, placebo-controlled, single oral dose, crossover study. Skin reaction to histamine (100 mg/mL), administered by prick tests, was measured by the wheal and flare surface areas for 24 hours (before treatment and at 0.5, 1, 2, 3, 4, 6, 8, 10, 12, and 24 hours). Eighteen healthy volunteers (mean age, 33.9 years; 13 women) participated in this study. The areas under the curves of the wheal-and-flare responses as a function of time (primary efficacy variables) were compared using analysis of variance. A highly significant overall treatment effect (P < .001) was detected for wheal and flare inhibition, with the activity of cetirizine and desloratadine significantly superior to that of placebo (P < .001). In addition, the activity of cetirizine was significantly superior to that of desloratadine (P < .001). With desloratadine, only 3 of the 18 subjects achieved a wheal inhibition of at least 70%, occurring between 2 and 4 hours, whereas all subjects using cetirizine reached a wheal inhibition of at least 70% between 0.5 and 3 hours (median time, 1.7 hours). The difference between the 2 active drugs was highly significant (P < .001). The median duration of wheal inhibition of at least 70% was zero with placebo and desloratadine and was 21.9 hours with cetirizine (P < .001). No serious adverse events were reported, and no subject withdrew from the study due to an adverse event. Cetirizine was associated with significantly greater suppression of skin reactivity to histamine compared with desloratadine during 24 hours after a single dose, with a consistent duration of action for cetirizine, as previously reported.

Fexofenadine HCl 180 mg provides greater and faster histamine-induced flare suppression than desloratadine 5 mg

Rationale Limited data exist comparing the peripheral H 1-receptor antagonist activities of the newer-generation antihistamines, fexofenadine and desloratadine. Methods In a randomized, placebo-controlled, double-blind, crossover histamine-induced wheal and flare study, non-allergic subjects received fexofenadine HCl 180 mg, desloratadine 5 mg or placebo. Histamine (1.8 mg/mL) skin pricks were performed pre-dose, 20, 40 and 60 minutes post-dose, hourly until 12 hours and at 23 and 24 hours. Primary endpoint: difference between baseline and post-dose flare measurements. Secondary endpoints: onset and time to maximum percent suppression. Onset of suppression was the first time a difference in flare (≥5 mm) or wheal (≥1 mm) diameter occurred between antihistamine and placebo from baseline on two consecutive measurements. Results Fexofenadine significantly suppressed histamine-induced flares versus placebo from 2–24 hours ( p<0.05), and versus desloratadine from 2–6 hours post-dose ( p<0.01). Desloratadine significantly suppressed flares versus placebo from 6–10 hours, and at 12 and 24 hours ( p<0.05). Onset for flare suppression was 60 minutes for fexofenadine and 5 hours for desloratadine. Fexofenadine significantly suppressed wheals versus desloratadine from 2–4 hours ( p<0.001), 6–9 hours ( p<0.05), and at 12 hours ( p<0.05); onset time was 60 minutes for both antihistamines. For fexofenadine, maximum suppression of flares (84.7%) and wheals (67.8%) occurred at 6 hours. For desloratadine, maximum flare and wheal suppression occurred at 10 hours (51.4%) and 7 hours (30.6%), respectively. Conclusions Fexofenadine HCl 180 mg has a faster onset of action at suppressing histamine-induced flare, and provides greater overall flare and wheal suppression than desloratadine 5 mg.

Relative potency of fexofenadine HCl 180 mg, loratadine 10 mg, and placebo using a skin test model of wheal-and-flare suppression

H1-receptor antagonists differ in their ability to produce peripheral H1-blockade. Suppression of histamine-induced flares and wheals is a useful objective test for measuring these differences. To evaluate the relative potency of fexofenadine HCI 180 mg, loratadine 10 mg, and placebo (PBO) in suppressing histamine-induced flares and wheals and compare the onset, duration, and maximum suppression of histamine achieved with each agent. Thirty healthy volunteers were enrolled in this randomized, double-blind, single-dose, crossover study. Flares and wheals induced by skin-prick testing with histamine 1.8 mg/mL were measured before treatment, every 20 minutes during the first hour after dosing, and thereafter hourly between 2 and 12 hours and between 23 and 25 hours postdose. Fexofenadine was significantly more effective than loratadine in suppressing the histamine-induced flare response at hours 2 through 7 and 10 through 12 and produced greater flare suppression than did PBO at hours 2 through 25. Onset of flare suppression occurred 2 hours after dosing with fexofenadine and 4 hours after dosing with loratadine. Likewise, fexofenadine was superior to loratadine in suppressing the wheal response from hours 1 through 12 and was more effective than PBO at hours 1 through 12, 24, and 25. Throughout the 25-hour measurement interval, the magnitude of difference in both wheal and flare suppression consistently favored fexofenadine over loratadine. In a skin test model of wheal-and-flare suppression, fexofenadine showed rapid distribution into the skin compartment with faster onset of action and greater potency vs loratadine.

Clinical pharmacology of H1-antihistamines in the skin

Background: The extent of the distribution of H1-antihistamines into the skin and H1-antihistamine activity in the skin are clinically relevant in the treatment of allergic skin disorders. Methods: In a prospective, randomized, double-blind, parallel-group, multiple-dose study, we gave fexofenadine 180 mg, loratadine 10 mg, or chlorpheniramine 8 mg to 21 men (7 in each group). Before dosing and at 1, 3, 6, 9, and 24 hours after the first antihistamine dose as well as at 168, 192, and 216 hours after the first dose (ie, 12, 36, and 60 hours after the seventh and last consecutive daily H1-antihistamine dose), we measured fexofenadine, loratadine, or chlorpheniramine concentrations in plasma and in skin tissue samples obtained through use of punch biopsies, along with suppression of histamine-induced skin wheals and flares. Loratadine metabolites, including desloratadine and its metabolites, were not measured, and chlorpheniramine metabolites were not measured. Results: All 21 participants completed the study. Skin/plasma fexofenadine ratios ranged from 1.2 ± 0.5 at 1 hour to 110 ± 74 at 24 hours, and skin fexofenadine concentrations exceeded loratadine and chlorpheniramine skin concentrations at each test time. This was reflected in significant wheal and flare suppression by fexofenadine in comparison with loratadine at 3 hours and in comparison with chlorpheniramine at 6 and 9 hours (wheal) and from 3 to 24 hours and at 192 hours (flare). Compared with fexofenadine, loratadine significantly suppressed the wheal at 192 hours, and compared with chlorpheniramine, it significantly suppressed the wheal at 9 hours and the flare at 24 and 192 hours. At no time did chlorpheniramine suppress the wheal or flare significantly more than fexofenadine or loratadine. Conclusions: In skin disorders for which H1-antihistamines are recommended, these results support the use of fexofenadine or loratadine, and they indicate the need for reexamination of the use of chlorpheniramine. (J Allergy Clin Immunol 2002;110:777-83.)

Tecastemizole induces a rapid and sustained inhibition of wheal and flare reactions

Tecastemizole induces a rapid and sustained inhibition of wheal and flare reactions

The Editors’ Choice

The Editors’ Choice

Skin concentrations of H1-receptor antagonists

Background: H1-receptor antagonists are widely used in the treatment of allergic skin disorders. Objective: We sought to evaluate the extent of fexofenadine and diphenhydramine distribution into the skin concomitantly with their peripheral H1-receptor antagonist activity. Methods: In a prospective, randomized, double-blind, parallel-group study, 7 men received 120 mg of fexofenadine, and 7 received 50 mg of diphenhydramine. Before dosing; at 1, 3, 6, 9, and 24 hours after the first dose; and at 168 hours (steady-state), 12 hours after the seventh and last daily dose, blood samples and skin punch biopsy specimens were obtained, and epicutaneous tests with histamine phosphate, 1 mg/mL, were performed. Results: Fexofenadine penetrated the skin to a significantly greater extent than diphenhydramine at 6, 9, 24, and 168 hours (P ≤ .05). Maximum skin/plasma ratios of both the H1-antagonists (41.3 ± 7.8 for fexofenadine and 8.1 ± 4.4 for diphenhydramine) were obtained at 24 hours. Fexofenadine also produced significantly greater suppression of wheals at 3, 6, and 9 hours and of flares at 3, 6, 9, and 168 hours compared with diphenhydramine (P ≤ .05). Conclusion: In disorders in which the presence and the effects of H1-receptor antagonists in the skin are clinically relevant, our results support the use of fexofenadine and indicate the need to re-examine the role of diphenhydramine. (J Allergy Clin Immunol 2001;107:526-30.)

Activity of ebastine (10 and 20 mg) and cetirizine at 24 hours of a steady state treatment in the skin of healthy volunteers

We have compared the inhibitory effects of ebastine (10 mg), ebastine (20 mg) and cetirizine (10 mg) on histamine-induced wheal and flare skin reactions 24 h following a 6-day-long treatment. This was a double-blind, randomised, crossover, placebo-controlled study involving 24 healthy volunteers (18-65 years) with negative skin prick tests and the absence of specific IgEs to common allergens. Subjects were randomised to receive each of the following treatments once daily for 6 days: ebastine (10 mg), ebastine (20 mg), cetirizine (10 mg) or placebo with a washout period of 5 days. Twenty-four hours after the last dose of each treatment, histamine skin prick tests were performed (0, 0.5, 1, 2.5, 5, 10, 20, 50, 100 and 200 mg/mL), and wheal and flare responses were measured. All active treatments produced significant inhibition of the wheal responses compared to placebo (P < 0.001). Wheal response inhibition was significantly better with 20 mg of ebastine compared with 10 mg of ebastine and 10 mg of cetirizine. In a comparison to histamine concentrations required to produce a wheal surface area of 10 mm2, 20 mg of ebastine was also significantly better than ebastine 10 mg and cetirizine (P < 0.001), and 10 mg ebastine was significantly better than cetirizine (P < 0.05). Highly significant (P < 0.001) effects on the flare response were observed with each active treatment compared to placebo, with no difference between groups. The frequency of adverse events, primarily somnolence, was similar among the four treatment groups. Our results clearly indicate that ebastine, at either recommended dosage of 10 and 20 mg, and cetirizine produced significant inhibition of the histamine-induced wheal and flare reaction compared to placebo for up to 24 h. A superior efficacy of 20 mg of ebastine is observed compared with 10 mg of ebastine and 10 mg of cetirizine on the skin wheal response 24 h after the last dose of a 6-day-long treatment. This study clearly proves ebastine to be an effective, truly once-daily antihistamine.

Mizolastine: antihistaminic activity from preclinical data to clinical evaluation

Mizolastine, a new H1-receptor antagonist, is highly selective for histamine H1 receptors and has no anticholinergic, antiadrenergic, or antiserotonin activity. It is rapidly absorbed after oral ingestion, with peak plasma concentrations occurring at 1.5 h. The distribution and terminal elimination half-life values are 2 and 13 h, respectively, in healthy young adult volunteers. Half-life values are longer in the elderly and in subjects with chronic renal insufficiency; however, the differences are not large enough to be clinically relevant or to necessitate a dose adjustment in these populations. Mizolastine produces prompt, sustained, peripheral blockade of histamine H1 receptors in the skin. Suppression of the histamine-induced wheal and flare begins 40-60 min after ingestion of a 10-mg dose, peaks at 3-4 h, lasts for at least 24 h, and does not decrease during regular once-daily dosing. The amount of wheal suppression is comparable to that produced by other leading new H1-receptor antagonists. These pharmacokinetic and pharmacodynamic studies of mizolastine provide its clinical pharmacology 'signature'. They also provide the scientific rationale for recommending a once-daily 10-mg dose and suggest that the efficacy and effectiveness of mizolastine will be widely confirmed in allergic disorders, especially rhinitis and urticaria.

Second-generation antihistamines: a comparative review.

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

Inhibitory effects of rupatadine on mast cell histamine release and skin wheal development induced byAscaris suum in hypersensitive dogs

The present studies were performed to compare the cutaneous antiallergic effects of rupatadine, a new potent dual antagonist of histamine and platelet-activating factor (PAF), with those of loratadine (an H1-antihistamine) and SR-27417A (a PAF antagonist). Two experimental models were used: an in vivo skin challenge by Ascaris suum extract administered intradermically in conscious hypersensitive dogs and an in vitro assay of Asc S 1 antigen-induced histamine release from isolated canine skin mast cells. In antigen-induced skin inflammation, both rupatadine and loratadine administered orally inhibited wheal formation in a dose-dependent manner at the studied doses. At the 0.1 mg/kg dose, maximum inhibition values for rupatadine and loratadine were similar, but the effect of rupatadine lasted 24 h, whereas loratadine's effect disappeared after 8 h. At the 1 mg/kg dose, the two compounds behaved similarly, with maximum effects of about 65% (4 h after treatment) and activity lasting more than 24 h in both cases. At the 10 mg/kg dose, rupatadine and loratadine exhibited maximum effects of 84 and 64% in wheal inhibition 2 and 4 h after drug administration, respectively. SR-27417A did not inhibit ascaris-induced wheal at the doses studied (1 and 10 mg/kg p.o.). In isolated canine skin mast cells, rupatadine and loratadine inhibited antigen-induced histamine release in a concentration-dependent manner. Rupatadine was more potent than loratadine at each concentration studied (100 nM–30 μM). Maximum inhibitory effects were 83 and 67% for rupatadine and loratadine, respectively, after a 30 μM concentration. Rupatadine, with an IC50 value of 5.3 μM, was about fourfold more potent than loratadine, with an IC50 value of 19 μM. SR-27417A exhibited no effect in our experimental model. Moreover, neither loratadine or rupatadine showed cytotoxic or prodegranulating effects at any concentration, whereas SR-27417A was cytotoxic at the highest concentration (30 μM). Thus, rupatadine is effective in controlling inflammatory reactions in dog skin and the effect may be partly due to its modulation of mast cell degranulation, but not to its PAF-antagonist properties. Drug Dev. Res. 44:49–55, 1998. © 1998 Wiley-Liss, Inc.

Appraisal of the validity of histamine-induced wheal and flare to predict the clinical efficacy of antihistamines

Antihistaminic drugs have been used successfully for many years in the treatment of allergic diseases. Second-generation antihistamines have fewer sedating side effects than first-generation agents, and the number of newer drugs available for clinical use is growing. Various methods have been used to assess antihistaminic activity, the most popular of which is the epicutaneous histamine-induced wheal and flare. This test relies on the ability of epicutaneously injected histamine to bring about the wheal and flare, a neurovascular response that involves reflex vasodilation (flare) and local swelling caused by plasma extravasation (wheal). Antihistamines have been compared on the basis of their ability to block the histamine-induced wheal and flare in the skin. Results of these trials have been applied to predict the global antiallergic efficacy of various antihistamines. This review has examined the reliability of suppression of the histamine wheal and flare reaction in the skin to predict an antihistamine's clinical efficacy in two common allergic diseases, seasonal allergic rhinitis and chronic idiopathic urticaria. Although histamine is one mediator in the allergic response in the skin and nasal mucosa, many other agents are important modulators of the allergic response. In addition, the major structural and functional differences that exist between the nasal mucosa and the skin affect the type of local response. These manifest themselves as differences between the responses to antigen and histamine challenge in the skin and the nose. The allergic responses in these tissues are not simply the consequence of one chemical but are the result of a cascade of interactions among various cells and mediators. The clinical manifestations of these complex interactions obviously cannot be fully replicated by injection of one chemical mediator, histamine, into the outer layer of the skin. Studies with antihistamines have shown that certain drugs, such as cetirizine, are more suppressive than others (loratadine, terfenadine) in controlling the histamine-induced wheal and flare reaction in the skin. When the clinical efficacy of these medications is compared in clinical trials in seasonal allergic rhinitis and chronic idiopathic urticaria, all are equally efficacious in controlling symptoms. Although the histamine-induced wheal and flare reaction can serve as a useful clinical pharmacologic test to assess dose-response relations for an antihistamine, its lack of correlation with clinical responses among antihistamines indicates that this model should not be used to predict or compare clinical efficacies of antihistamines in seasonal allergic rhinitis and chronic idiopathic urticaria. (J Allergy Clin Immunol 1997;99:S798-806.)

Dual effect of a new compound, rupatadine, on edema induced by platelet-activating factor and histamine in dogs: Comparison with antihistamines and PAF antagonists

The antihistamine-H1 and antiplatelet activating factor (PAF) activities of seven compounds, including rupatadine, a new antiallergic drug, were studied in healthy beagle dogs using a new experimental model that allows simultaneous testing of PAF and histamine reactions in the same animal. The method was based on the measurement of wheal area induced in dogs' skin by intradermal injection of PAF (1.5 μg) or histamine (2.5 μg). Rupatadine and the H1-antihistamine drugs cetirizine, levocabastine, and loratadine, administered orally at doses of 1 or 10 mg/kg showed similar maximum potencies (75–85% of wheal inhibition) 4–8 h after treatment. Levocabastine was the longest-acting compound (55% and 69% inhibition 24 h after administration of 1 or 10 mg/kg, respectively). Rupatadine, loratadine, and cetirizine behaved similarly, showing 34% and 58% inhibition at 24 h at the same doses. Dual PAF and histamine antagonist SCH-37370 exhibited mild anti-H1 activity, the maximum effect being 27% at 10 mg/kg. Pure PAF antagonists WEB-2086 and SR-27417 showed no effect against histamine-induced wheals. Only rupatadine, SR-27417A, SCH-37370, and WEB-2086 showed PAF antagonist activity, whereas pure antihistamines were inactive. The most potent PAF antagonist was SR-27417A, with a maximum effect of 56% and 80% at 1 and 10 mg/kg, respectively. Rupatadine and WEB-2086 antagonized PAF-induced wheal response, although they showed less maximum effect and shorter duration of action than SR-27417A. SCH-37370 exhibited only slight PAF antagonist activity at 10 mg/kg. Overall, the histamine- and PAF-induced wheal model in dogs proved useful for independent evaluation of histamine and PAF antagonist properties of the tested compounds, as pure antagonists blocked the effect of only one of the mediators. Rupatadine was the only one of the seven compounds studied that showed potent dual activity against PAF and histamine. Drug Dev. Res. 39:12–18 © 1997 Wiley-Liss, Inc.

Plasma and skin suction-blister-fluid pharmacokinetics and time course of the effects of oral mizolastine.

To investigate plasma and skin suction-blister-fluid pharmacokinetics of oral mizolastine in order to determine whether the drug concentration in the fluid of suction-induced skin blisters could better predict the antihistamine activity than the plasma concentration. Department of Internal Medicine, Université Paris 6. Ten healthy male volunteers. The volunteers (mean age 26.8 years, mean weight 75.8 kg) received a single 10-mg oral dose of mizolastine at 1000 hours. The pharmacokinetic study included 11 plasma and 9 blister fluid samples and blister epidermal-roof specimens. Mizolastine was assayed by high-performance liquid chromatography (HPLC). Each volunteer also received nine intradermal injections of 5 micrograms histamine. Antihistamine activity was assessed as the post-treatment percentages of changes in the histamine-induced relative wheal and flare areas versus baseline. Mizolastine mean Cmax (SD) and median tmax were, respectively, 380 ng.ml-1 and 0.8 h in plasma, and 21.8 ng.ml-1 and 10 h in blister fluid. Mizolastine could not be quantified in the epidermis. The maximal histamine-induced relative flare inhibition was 72.5% and was attained at the median time of 3 h post-dosing and therefore was delayed by 2.2 h with respect to the plasma tmax. Mean relative wheal inhibition, although lower, showed the same time profile. A direct relationship could not be found between drug concentrations in blister fluid and antihistamine activity. Simulated concentrations in the peripheral compartment better explain the maximum inhibition effect on flare, observed 3 h post-dosing, with a flatter hysteresis loop obtained when plotting relative flare inhibition versus plasma or blister-fluid drug concentrations. The mizolastine concentrations in the skin suction-blister fluid were not predictive of the antihistamine activity.

Quantitation of H 1-receptor antagonists in skin and serum

Background: Cetirizine and hydroxyzine produce prompt, long-lasting peripheral H 1-blockade in skin. We hypothesized that after oral administration of these H 1-receptor antagonists, skin concentrations would be higher than serum concentrations and would correlate with peripheral H 1 blockade. Methods: In a randomized, double-blind, parallel-group study in 13 healthy subjects, skin biopsies, venipunctures, and epicutaneous tests with histamine were performed before ingestion of 10 mg cetirizine or 50 mg hydroxyzine and 1, 3, 6, 9, and 24 hours after administration. Subjects then took 10 mg cetirizine or 50 mg hydroxyzine at 21:00 hours for 6 consecutive days. All tests were repeated at 168 hours (steady state), 12 hours after the last dose. Results: Skin cetirizine concentrations were lower than serum cetirizine concentrations from 1 to 9 hours but were higher at 24 hours and equivalent at 168 hours (steady state). Skin hydroxyzine concentrations were higher than serum hydroxyzine concentrations at all test times. After hydroxyzine dosing, cetirizine, the active metabolite of hydroxyzine arising in vivo, was found in skin and serum. Single doses of cetirizine or hydroxyzine produced highly significant suppression of wheals and flares from 3 to 24 hours inclusive, and this suppression was maintained at steady state. Conclusions: Cetirizine and hydroxyzine enter the skin readily, and their sustained high concentrations in skin after single or multiple dosing may contribute to their well-known efficacy in symptomatic treatment of urticaria and other skin disorders in which histamine plays a role. (J A LLERGY C LIN I MMUNOL 1995;95:759-64.)

Effect of the H2-receptor antagonist cimetidine, on the pharmacokinetics and pharmacodynamics of the H1-receptor antagonists hydroxyzine and cetirizine in rabbits.

The effects of coadministration of the H2-receptor antagonist cimetidine on the pharmacokinetics and pharmacodynamics of the H1-receptor antagonists hydroxyzine and cetirizine were studied in rabbits. A single dose of hydroxyzine, 10 mg (Experiment A), or cetirizine, 10 mg (Experiment B), was given intravenously on three occasions: 2 weeks before cimetidine administration, after cimetidine, 100 mg/kg, had been given every 12 hr for 1 week, and 2 weeks after the cimetidine was discontinued. Serum concentrations of hydroxyzine and cetirizine, the active metabolite of hydroxyzine arising in vivo (Experiment A), or cetirizine (Experiment B) were measured by HPLC. The pharmacologic effects of hydroxyzine and cetirizine were monitored by measuring the suppression of histamine-induced wheals, using an IBM-PC and digitizer. The hydroxyzine and cetirizine half-life and AUC0-->infinity values were significantly increased and the systemic clearance rates were significantly decreased in the presence of cimetidine. Similar results were obtained when cetirizine was administered de novo. Wheal suppression produced by hydroxyzine or cetirizine was increased and prolonged in the presence of cimetidine. The synergism observed between hydroxyzine or cetirizine and cimetidine in suppression of the histamine-induced cutaneous response may be due to a pharmacokinetic interaction.