Histamine-induced Wheal Research Articles

Comparative inhibition by oral bilastine, parenteral dexchlorpheniramine, and a new bilastine parenteral (i.v. and i.m.) formulation of histamine-induced wheal and flare response: A randomised phase I trial

BackgroundBilastine is a well-known non-sedating second-generation antihistamine authorised worldwide for the symptomatic treatment of allergic rhinoconjunctivitis (seasonal and perennial) and urticaria with proven efficacy and good safety and tolerability profile. When the oral route is not suitable or a rapid onset of action is preferred, parenteral formulations represent an effective treatment option. However, the parenteral formulations currently available are sedating antihistamines. The objective of this research was to compare the peripheral anti-H1 activity of different bilastine formulations (i.v., i.m. and oral) and dexchlorpheniramine among them also versus placebo. MethodsThis was a single-dose, randomized, crossover, double-blind, placebo-controlled, phase I clinical study performed on 25 adult healthy volunteers that compared the peripheral antihistaminic activity of a single dose of bilastine 12 mg i.v., bilastine 12 mg i.m., bilastine 20 mg oral tablets and dexchlorpheniramine 5 mg i.m. among them and versus placebo by inhibiting the histamine-induced wheal and flare (W&F) response. Pharmacokinetics, safety, and tolerability were also evaluated. ResultsAll bilastine formulations showed a rapid onset of action (15 min for parenteral and 30 min for the oral formulation), and the maximum effect in both wheal (i.v. 74.44 %; i.m.:74.29 %; oral 70,27 %) and flare area reduction (i.v. and i.m. 80.63 %; oral 77.67 %), was significantly larger compared to dexchlorpheniramine i.m. (25.85 % for wheal and 28.65 % for flare) and placebo (1.35 % for wheal and 4.02 % for flare). A more pronounced reduction in itching score was reached for bilastine oral, followed by i.m. and i.v. formulations. No serious adverse events (SAEs) were reported during the study, and 8 treatment-emergent adverse events (TEAEs) were reported by 5 subjects, all resolved without sequelae. For psychomotor assessments, dexchlorpheniramine i.m. showed a fast onset of drowsiness, as well as decreased attention and coordination when compared to all bilastine formulations and placebo. ConclusionsAll bilastine formulations showed a peripheral H1-blocking effect inducing a significantly greater inhibition of the wheal and flare response as compared to dexchlorpheniramine i.m. or placebo and provided a greater reduction of the itching sensation score. This study reconfirmed that bilastine has no sedative effect, even in a parenteral formulation. These results suggest that new bilastine parenteral formulation (i.v. or i.m.) may represent a suitable alternative for patients requiring immediate treatment of histamine-mediated type I hypersensitivity reactions, such as acute urticaria, or in those cases where oral administration is not possible.

Capsaicin Pretreatment Increases Mast Cell-Mediated But Not Histamine-Induced Wheal and Erythema Responses: A Proof-of-Concept Study

Capsaicin Pretreatment Increases Mast Cell-Mediated But Not Histamine-Induced Wheal and Erythema Responses: A Proof-of-Concept Study

Antihistamine activity of steam-exploded oak extract containing phenolic compounds

The aim of this study was to investigate the antihistamine activity of steam-exploded oak (Quercus variabilis) extract containing phenolic compounds. The antioxidant activity increased with residence time of the steam explosion process. The 50% EtOH extract had total phenolic compound content of 82.2 % and 46.2 mg GAE/g extract and vanillic acid, ferulic acid, and vanillin were identified. Treatment with 50% EtOH extract decreased the diameters of histamine-induced wheal and erythema responses in human volunteers. In patients with atopic dermatitis, topical administration of 50% EtOH extract led to significant diseases and improvement in terms of sleep disturbance, pruritus, xerosis, desire to scratch, and erythema. This study suggested that steam-exploded oak is rich in phenolic compounds with high antioxidant and antihistamine activities, and the extract may be a promising source of new antihistamine agents and pharmaceuticals.

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

To investigate the pharmacokinetics and antihistaminic effects (pharmacodynamics) of olopatadine in a small population of healthy horses after administration via nasogastric tube. 4 healthy adult Thoroughbreds. 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. 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. 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.

High volume of polysorbate‐containing (Tween® 80) solutions induces false‐positive results in intradermal test

Intradermal test is used to detect causative allergens in IgE-mediated hypersensitivity. The surfactant polysorbate 80 can be added to intradermal test solutions to more reliably dissolve the allergen and ensure a constant bioavailability of the injected allergen. Polysorbate 80 has, however, some histamine-releasing properties which could blur the difference to the histamine-induced wheal. Routinely serving as a control. Allergen-free polysorbate 80 containing (0.005%) test solutions were therefore systematically tested at different injection volumes to see whether polysorbate can falsify skin reactions and if yes whether conditions can be identified to avoid this. In a partly blinded study, 30 patients were tested intracutaneously at the back: each received at three separate sites 0.05 mL of polysorbate-containing solvent, 0.02 mL polysorbate-containing solvent as well as 0.02 mL polysorbate-free solvent. After 15 min, wheal and erythema were documented and planimetrically quantified. Unexpectedly 23 of 30 (77%) patients showed false-positive test reactions to the volume of 0.05 mL of the polysorbate-containing solvent whereas the polysorbate-containing solvent with 0.02 mL and the polysorbate-free solvent with 0.02 mL injection volume had no reinforcing effect on skin test reaction. Different volumes of polysorbate-containing solutions, all recommended by manufacturers for intradermal tests, may significantly influence test results. The study shows that a polysorbate 80 used at 0.005% in solvents for intradermal test to provide a better bioavailability of allergens produces false-positive reactivity in a surprising and a hitherto unknown 77% if the 0.05 mL volume is injected. It is, therefore, mandatory to strictly adhere to an intradermal test volume of 0.02 mL as only then falsifying effects of the polysorbate additive are avoided, and comparable test results are ensured.

Effect of Topical Steroids on Skin Prick Test: A Randomized Controlled Trial

IntroductionTopically applied corticosteroids on the skin can significantly inhibit the wheal response to allergens in skin prick test (SPT). The duration of this effect is unknown. The aim of this study is to investigate the duration of the inhibitory effect of topical corticosteroids on SPT.MethodsTwenty-two healthy subjects were included in a single-blinded randomized study. All subjects were skin prick tested using a standard inhalant allergen panel. The subjects were randomized to treat either the left or right forearm with Betnovat® cream (group III steroid) once a day for 10 days. Subsequently, the subjects were skin prick tested the following 5 days and at day 8 on both forearms.ResultsAt baseline, the 22 individuals had positive SPT for a total of 72 allergens. Compared with the untreated arm, the mean size of the wheals was significantly reduced on day 1 (12 h after end of treatment) by 0.56 mm (95 % confidence interval (CI) [0.06; 1.06], p = 0.03) for allergens and 0.70 mm [0.32; 1.09] (p = 0.001) for histamine. On day 2 (36 h after end of treatment), the mean difference between treated and untreated arm was 0.47 mm [−0.08; 0.85] (p = 0.02) for allergen-induced wheals and 0.22 mm [−0.21; 0.64] (p = 0.31) for histamine-induced wheal. On day 3, 4, 5, and 8, there was no significant difference.ConclusionsTreatment with topical steroid significantly inhibited the response to SPT for 36 h but for less than 3 days. In addition, we demonstrated that topical applied corticosteroids inhibit the mean wheal size of the positive histamine control for a shorter time than for the allergens. Consequently, positive response to histamine control is not a valid marker for reliable skin prick test in steroid-treated patients.Plain Language SummaryPlain language summary available for this article.

Prediction of the Efficacy of Antihistamines in Chronic Spontaneous Urticaria Based on Initial Suppression of the Histamine- Induced Wheal.

Antihistamines are the first line of treatment for chronic spontaneous urticaria. However, there is no effective method to predict whether an antihistamine will have a beneficial clinical effect or not. To assess whether the change in histamine-induced wheal and flare measurements 24 hours after administration of antihistamine can predict the efficacy of treatment. We performed a multicenter, triple-blind, randomized study. Patients received a daily oral dose of cetirizine, fexofenadine, bilastine, desloratadine, or ebastine over 8 weeks. After 4 weeks, a higher dose of antihistamine was administered to patients who did not experience a clinical response. A histamine skin prick test was carried out at baseline and 24 hours after the first dose of antihistamine. Disease severity (Urticaria Activity Score [UAS]), response to the histamine skin prick test, and impact on the patient's quality of life (Dermatology Life Quality Index [DLQI]) were determined every 2 weeks. The study population comprised 150 patients (30 per group) and 30 controls. Twenty-four hours after administration of antihistamine, inhibition of the histamine wheal by >75% was significantly associated with better UAS and DLQI scores. The safety and efficacy of the 5 antihistamines were similar. After updosing, rates of disease control (DLQI score <5) increased from 58.7% to 76.7%. Measurement of the histamine-induced wheal can predict which patients will have a strong clinical response to antihistamines but has limited utility for identifying nonresponders. The clinical significance of these data could be relevant in the search for new urticaria treatment regimens.

Measurement and interpretation of skin prick test results.

BackgroundThere are several methods to read skin prick test results in type-I allergy testing. A commonly used method is to characterize the wheal size by its ‘average diameter’. A more accurate method is to scan the area of the wheal to calculate the actual size. In both methods, skin prick test (SPT) results can be corrected for histamine-sensitivity of the skin by dividing the results of the allergic reaction by the histamine control. The objectives of this study are to compare different techniques of quantifying SPT results, to determine a cut-off value for a positive SPT for histamine equivalent prick -index (HEP) area, and to study the accuracy of predicting cashew nut reactions in double-blind placebo-controlled food challenge (DBPCFC) tests with the different SPT methods.MethodsData of 172 children with cashew nut sensitisation were used for the analysis. All patients underwent a DBPCFC with cashew nut. Per patient, the average diameter and scanned area of the wheal size were recorded. In addition, the same data for the histamine-induced wheal were collected for each patient. The accuracy in predicting the outcome of the DBPCFC using four different SPT readings (i.e. average diameter, area, HEP-index diameter, HEP-index area) were compared in a Receiver-Operating Characteristic (ROC) plot.ResultsCharacterizing the wheal size by the average diameter method is inaccurate compared to scanning method. A wheal average diameter of 3 mm is generally considered as a positive SPT cut-off value and an equivalent HEP-index area cut-off value of 0.4 was calculated. The four SPT methods yielded a comparable area under the curve (AUC) of 0.84, 0.85, 0.83 and 0.83, respectively. The four methods showed comparable accuracy in predicting cashew nut reactions in a DBPCFC.ConclusionsThe ‘scanned area method’ is theoretically more accurate in determining the wheal area than the ‘average diameter method’ and is recommended in academic research. A HEP-index area of 0.4 is determined as cut-off value for a positive SPT. However, in clinical practice, the ‘average diameter method’ is also useful, because this method provides similar accuracy in predicting cashew nut allergic reactions in the DBPCFC.Trial registration: Trial number NTR3572

Preliminary Investigations of the Anti-asthmatic Properties of the Aqueous Extract of Justicia pectoralis (Fresh Cut).

Justicia pectoralis (fresh cut plant), family Acantheceae, is a herb that is native to central America and the Caribbean. A crude extract prepared from the leaves of Justicia pectoralis is commonly used in Jamaican ethnotraditional medicine to reduce difficulty in breathing and suppress wheezing in asthmatic individuals. To investigate the anti-inflammatory and antihistamine activity of an aqueous extract of Justicia pectoralis. In in vivo experiments, guinea pigs were sensitized by the method of Weinrich and Undem (1987). The effect of water on the wheals was assessed in the control group, n = 4. The effect of 3.3 mg of the crude extract was noted in histamine-induced wheals over a period of three hours. The extract was injected via intraperitoneal injections. In in vitro experiments, 3.3 mg of crude sample was tested for its effectiveness against histamine-induced tracheal contraction caused by cumulative dosing of histamine. The crude extract was efficacious in reducing the formation of histamine-induced wheals (p < 0.05). Results obtained from in vitro studies indicated that the crude extract (3.3 mg) caused significant reduction in tracheal smooth muscle contraction resulting from cumulative doses of histamine (p < 0.05). However, as the histamine doses increased, fresh cut extract was not able to maintain inhibition of histamine-induced tracheal smooth muscle contraction. This is an indication that the extract showed competitive reversible antagonism, possibly at histamine receptors. A crude extract of the leaves Justicia pectoralis reduced the formation of histamine-induced wheals in sensitized guinea pigs (p < 0.05) and also reduced histamine-induced tracheal smooth muscle contractions (p < 0.05). It blocked the effect of contraction produced by histamine in the airways; this property supports folklore claims for its use as an antihistamine.

The reservoir effect of topical steroids in vitiliginous skin: A cross-sectional study.

Prolonged and frequent use of topical steroids may lead to decrease in efficacy as well as many local adverse effects. Stratum corneum has a unique property of reservoir effect. To study the reservoir effect of topical steroids in a steroid-responsive condition which may enable a decrease in the dosing frequency of topical steroids. A cross-sectional study design was used. Patients with at least three vitiliginous patches of more than 2 cm 2 present over the trunk or limbs were included. Exclusion criteria were topical or systemic corticosteroid use within the previous 4 weeks, antihistamine use within the previous 7 days, history of any allergy in the past and immunosuppression. Clobetasol propionate cream was applied on the first vitiliginous area (site A) and fluticasone propionate ointment was applied on the second vitiliginous area (site B). The third vitiliginous area, site C (control site) was left without applying any medication. Histamine-induced wheal suppression test was performed on each site, at the same time of the day, on every consecutive day following steroid application, until the values obtained at sites A and B approached those obtained at site C. SPSS software for Windows, version 16.0 was used for statistical analysis. The mean and standard deviation of the various studied parameters were calculated for various treatment groups and compared using analysis of variance (ANOVA) test. Forty patients were included in the study. The average wheal volumes and average erythema sizes at sites A and B were significantly smaller than the corresponding values at site C for up to 5 days after applying medication (P < 0.001). The presence of a cutaneous reservoir of topical steroid was confirmed based on its suppressive effect on the wheal and flare response to histamine. It is not certain that the concentration that suppresses histamine-induced wheal and flare is sufficient for therapeutic efficacy in vitiligo. The reservoir effect of topical clobetasol propionate and fluticasone propionate persisted for 5 days in vitiliginous skin. Hence, it may be possible to reduce the frequency of topical steroid application in vitiligo.

Comparison of effects of 5 and 10 mg oral desloratadine and levocetirizine on histamine-induced wheal and flare response in healthy volunteers

Background: Levocetirizine and desloratadine are mostly used as H1-antihistamines in the treatment of allergic disease in 5 and 10 mg doses. Objective: In this study, the efficacy of single oral dosages of 5 and 10 mg desloratadine and levocetirizine were compared by using histamine-induced wheal and flare reactions. Methods: Eighty healthy volunteers were randomized for four double-blinded treatment with desloratadine 5 and 10 mg and levocetirizine 5 and 10 mg. Wheal and flare responses were produced by histamine. Measurements were performed just before the ingestion of antihistamines (baseline) and afterward at 30, 60, 240 min and 24 h. The values obtained for each antihistamine were compared with baseline values. Results: It was found that except the flare reactions at 30th min, levocetirizine 5 and 10 mg suppressed histamine-induced wheal and flare reactions more than desloratadine 5 and 10 mg did. There were not any significant differences between desloratadine 5 and 10 mg in all periods. Levocetirizine 10 mg suppressed wheal and flare reactions significantly more than levocetirizine 5 mg only at 24th h. Conclusion: In this study, it was observed that levocetirizine 5 and 10 mg had a higher activity than desloratadine 5 and 10 mg.

The Inhibition by Levocetirizine and Fexofenadine of the Histamine-induced Wheal and Flare Response in Healthy Caucasian and Japanese Volunteers

This randomized, double-blind, placebo-controlled crossover study compared inhibition by one 5 mg dose of levocetirizine with two 60 mg doses of fexofenadine separated by 12 h of histamine-induced wheal and flare responses in 9 Caucasian and 9 Japanese healthy male volunteers. Levocetirizine was more inhibitory than fexofenadine on wheal, flare and pruritus (p < 0.005). Variability, evaluated from the standard deviation of inhibition, ranged from 14% to 23.2% for levocetirizine and 65.4% to 112.4% for fexofenadine. Levocetirizine had a faster onset of action (30-90 min versus 2 h), shorter time to maximum effect (3-4 versus 3-6 h) and longer duration of action (at least 24 h versus ~12 h) than fexofenadine. The plasma levels of levocetirizine rose more quickly, reached higher levels, were more consistent and decreased slower than those of fexofenadine. There were no clinically significant ethnic differences in responsiveness to the drugs.

Antihistamines do not inhibit the wheal induced by the intradermal injection of autologous serum in resistant chronic idiopathic urticaria

Some patients with chronic idiopathic urticaria (CIU) are resistant to conventional doses of antihistamines (AHs). This study was designed to check whether the skin wheal and flare reaction produced by the intradermal injection of autologous serum (AS) and by histamine differs in AH-resistant and AH responder CIU patients. CIU patients with treatment failure under fexofenadine at 180 mg q.d. increased their daily dose of AH to 4 tablets daily. Those with significant improvement of urticaria activity score under fexofenadine at 180 mg were included in the CIU group. Subjects with treatment failure despite a full 8-week fourfold fexofenadine treatment were included in the resistant CIU (R-CIU group). The control group consisted of sex- and age-matched patents with allergic rhinitis. The AS skin test and intradermal histamine-induced wheal and flare reaction were performed at baseline (without AH), after 8 and 16 weeks (under AH treatment). Forty-six subjects were included in the CIU group, 21 were in the R-CIU group, and 44 were in the control group. Under AH therapy, the skin reaction to intradermal histamine injection was significantly diminished in all study groups. In the R-CIU group, fexofenadine at 180 mg did not suppress AS-induced wheal reaction (5.96 ± 2.25 mm; p = 0.85), and with a fourfold AH dose some reduction of AS-induced wheal (3.79 ± 1.74 mm; p = 0.008) was observed but remained larger than in the CIU (2.31 ± 1.12; p = 0.006) and control groups (2.52 ± 1.36; p = 0.037). AHs do not inhibit the wheal induced by the intradermal injection of AS in R-CIU.

Effects of single therapeutic doses of promethazine, fexofenadine and olopatadine on psychomotor function and histamine-induced wheal- and flare-responses: a randomized double-blind, placebo-controlled study in healthy volunteers

Since most first-generation antihistamines have undesirable sedative effects on the central nervous systems (CNS), newer (second-generation) antihistamines have been developed to improve patients’ quality of life. However, there are few reports that directly compare the antihistaminic efficacy and impairment of psychomotor functions. We designed a double-blind, placebo controlled, crossover study to concurrently compare the clinical effectiveness of promethazine, a first-generation antihistamine, and fexofenadine and olopatadine, second-generation antihistamines, by measuring their potency as peripheral inhibitors of histamine-induced wheal and flare. Further, we investigated their sedative effects on the CNS using a battery of psychomotor tests. When single therapeutic doses of fexofenadine (60 mg), olopatadine (5 mg) and promethazine (25 mg) were given in a double-blind manner to 24 healthy volunteers, all antihistamines produced a significant reduction in the wheal and flare responses induced by histamine. In the comparison among antihistamines, olopatadine showed a rapid inhibitory effect compared with fexofenadine and promethazine, and had a potent effect compared with promethazine. In a battery of psychomotor assessments using critical flicker fusion, choice reaction time, compensatory tracking, rapid visual information processing and a line analogue rating scale as a subjective assessment of sedation, promethazine significantly impaired psychomotor function. Fexofenadine and olopatadine had no significant effect in any of the psychomotor tests. Promethazine, fexofenadine and olopatadine did not affect behavioral activity, as measured by wrist actigraphy. These results suggest that olopatadine at a therapeutic dose has greater antihistaminergic activity than promethazine, and olopatadine and fexofenadine did not cause cognitive or psychomotor impairment.

Comparative inhibition by bilastine and cetirizine of histamine-induced wheal and flare responses in humans

Comparison of bilastine and cetirizine in inhibiting skin wheal and flare responses over 24h. Twenty-one healthy male volunteers (aged 19-44years). Volunteers were randomised to receive single oral doses of 20 or 50mg bilastine, 10mg cetirizine or placebo before provocation of wheal and flare responses to 100mg/ml histamine by skin prick 1.5, 4, 8, 12 and 24h later. There were no significant differences between overall inhibitions of wheal or flare by 20mg bilastine and 10mg cetirizine. Bilastine was faster in onset than cetirizine, inhibitions of wheal and flare at 1.5h being 89±3 versus 44±14% (P=0.011) and 85±4 versus 45±14% (P=0.016), respectively (Student's t test). At 1.5h, both wheals and flares were inhibited by >70% in 11/12 volunteers taking bilastine and 3/11 taking cetirizine (P=0.003, Fisher's exact test). There were no significant differences between the drugs at later times. Bilastine 50mg had a longer duration of action than bilastine 20mg. Both 20mg bilastine and 10mg cetirizine are effective and of long duration in reducing histamine-induced wheal and flare responses, the major difference between the two drugs being the more rapid onset of action of bilastine.

Effect of prednisolone and cetirizine on D. farinae and histamine-induced wheal and flare response in healthy dogs

Prednisolone and antihistamines are highly potent drugs in the treatment of atopic dermatitis and widely used in humans and dogs. In some atopic patients in which antihistamines, corticosteroids or other drugs have already been administered intradermal testing (IDT) may be necessary. The aim of the present study was to compare the effects of cetirizine and prednisolone on IDT results. Thirty healthy dogs (average age 5.9 ± 0.6 years) were randomly assigned to three groups. Treatment groups were administered prednisolone (1 mg/kg BW daily, tapering dosage; group I), cetirizine (1mg/kg BW daily; group II) and placebo (group III) respectively for one week. In the second week, none of the dogs received any medications. IDT was performed prior to drug administration and results obtained were considered as the baseline response. Second and third IDTs were performed at the end of the first and second week, respectively. In groups I and II IDT reactivity was reduced at the end of first week (p<0.05). After drug discontinuation the reactivity almost returned to baseline at the end of the 2-week period, with the exception of the prednisolone group for D.farinae . Prednisolone and cetirizine have significant effects on IDT reactions and must be withdrawn by veterinary practitioners up to 2 weeks prior to IDT.

Itraconazole and Rifampin Alter Significantly the Disposition and Antihistamine Effect of Ebastine and Its Metabolites in Healthy Participants

The present study was performed to elucidate the effects of itraconazole and rifampin on the pharmacokinetics and pharmacodynamics of ebastine, a nonsedative H1 receptor antagonist. In a 3-way crossover sequential design with 2-week washouts, 10 healthy participants were pretreated with itraconazole for 6 days, rifampin for 10 days, or neither. After oral administration of 20 mg ebastine, blood and urine samples were collected for 72 and 24 hours, respectively, and histamine-induced wheal and flare reactions were measured to assess the antihistamine response for 12 hours. Itraconazole pretreatment decreased the oral clearance of ebastine to 10% (P < .001) and increased the AUC(infinity) of the active metabolite, carebastine, by 3-fold (P < .001). On the other hand, rifampin pretreatment decreased the AUC(infinity) of carebastine to 15% (P < .001), with an enormous reduction in the oral bioavailability of ebastine and significantly reduced histamine-induced skin reactions. From these results, the disposition of ebastine and carebastine seems to be significantly altered by coadministration of itraconazole or rifampin. The antihistamine response after ebastine dosing would be decreased following rifampin pretreatments.

Study of reservoir effect of clobetasol propionate cream in an experimental animal model using histamine-induced wheal suppression test

Background:Topical corticosteroids used in various dermatological diseases several times a day led to an increase risk of side effects. By demonstrating a significant reservoir of corticosteroids in the stratum corneum, one can maximize their efficacy and safety as therapeutic agents.Aim:The study was designed to demonstrate a reservoir of topically applied corticosteroid clobetasol propionate cream experimentally in rabbits using histamine-induced wheal suppression test.Materials and Methods:The work was carried out on albino rabbits, as rabbit skin is akin to human skin, using a topical steroid. The topical steroid clobetasol propionate 0.05% cream was applied on the back of rabbit, and after 1-h occlusion histamine-induced wheal suppression test was performed and wheal area measured at 10 min till day 7. Statistical analysis was done by ANOVA followed by “Post Hoc” test.Results:Maximum wheal suppression was seen on day 1 (P < 0.001). Interday comparison of mean wheal size showed no significant difference (P > 0.05) on day 2, 3, and 4 as compared to day 1. Day 5-7 show highly significant difference (P < 0.001) as compared to day 1, thereby suggesting that the reservoir effect of topical clobetasol propionate 0.05% cream persisted till day 4.Conclusions:This work demonstrated that histamine-induced wheal by the topical steroid clobetasol propionate 0.05% cream was suppressed till day 4, indicating that the reservoir of topical corticosteroid persisted till day 4.

Effects of Olopatadine Hydrochloride, a Histamine H1 Receptor Antagonist, on Histamine‐Induced Skin Responses

Effects of olopatadine hydrochloride, a histamine H1 receptor antagonist, on histamine-induced skin responses were evaluated in 10 healthy subjects in comparison with placebo, fexofenadine hydrochloride, and bepotastine besilate. Olopatadine significantly suppressed histamine-induced wheal, flare, and itch, starting 30 minutes after oral administration. Olopatadine was more effective than fexofenadine and bepotastine. None of the drugs studied impaired performance of word processing tasks. These results suggest that olopatadine can suppress skin symptoms caused by histamine soon after administration.

Responses to Intradermal Injections of Substance P in Psoriasis Patients with Pruritus

Background: Various mediators have been suggested for the pathogenesis of pruritus in psoriasis. Methods: To investigate cutaneous responses of substance P in pruritic lesional and nonlesional areas of psoriasis patients and in healthy controls, substance P, saline and histamine were injected intradermally. After each injection, pruritus, flare and wheal were recorded. Results: There was no statistical difference in the latency period, duration, area under the curve and maximum intensity of pruritus evoked by substance P (10^–5 and 10^–6 mol/l) between psoriasis and healthy control skin. Substance P (10^–5 mol/l) induced a tendency to a greater intensity of pruritus in lesional compared to nonlesional psoriatic skin (p = 0.08). Histamine produced a shorter itch latency period (p < 0.05) and a lower maximum intensity of pruritus (p = 0.05) in lesional psoriasis skin than in healthy control skin. No significant difference in flare area was observed between the psoriasis patients and healthy controls. The histamine-induced wheal was smaller in psoriasis patients than in healthy individuals (p < 0.05). Conclusion: Intradermally injected substance P induced pruritus, flare and wheal in psoriasis patients. However, these responses did not differ significantly from those of the healthy controls.