Xiaochen Gu

Suppression of the early and late cutaneous allergic responses using fexofenadine and montelukast.

BACKGROUNDnThe relative contribution of histamine and the cysteinyl leukotrienes to the early and late cutaneous allergic responses (ECAR and LCAR) can be studied using antagonists of these mediators.nnnOBJECTIVEnTo determine the relative suppression of the ECARs and LCARs using standard doses of an H1-receptor antagonist, a cysteinyl leukotriene1-receptor antagonist, and the two antagonists administered concurrently.nnnMETHODSnWe carried out a prospective, randomized, double-blind, placebo-controlled, four-way crossover study in 12 highly allergic participants. Intradermal tests with standardized allergen, and with histamine phosphate, LTD4, and saline controls were performed on 5 different test days as follows: pretreatment baseline and at steady state immediately after the seventh and last dose of a 1-week course of treatment with once-daily fexofenadine, 120 mg; montelukast, 10 mg; fexofenadine and montelukast administered concurrently; or placebo. On each test day, the skin test results were read at intervals from 0.25 to 24 hours after the intradermal injections were performed.nnnRESULTSnAfter allergen injection, compared with baseline, all treatment regimens significantly decreased the ECAR and LCAR. After allergen injection, compared with placebo, fexofenadine significantly decreased the ECAR and the LCAR from 0.25 to 2 hours and at 8 hours. Montelukast did not significantly decrease the ECAR or LCAR. Fexofenadine and montelukast administered concurrently were not more effective than fexofenadine alone at any time. In the control skin tests, compared with placebo, fexofenadine, but not montelukast, significantly decreased the histamine-induced response, and montelukast, but not fexofenadine, significantly decreased the LTD4-induced response.nnnCONCLUSIONSnFexofenadine and montelukast administered concurrently were not significantly more effective than fexofenadine alone in decreasing the ECAR and LCAR. Montelukast does not need to be discontinued before allergen skin testing. Further studies of the effect of concurrent treatment with higher doses of a histamine antagonist and a leukotriene modifier on the allergic response in the skin are needed.

Epinephrine absorption after different routes of administration in an animal model

The administration of epinephrine is the most important initial treatment in systemic anaphylaxis.

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-α-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<.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<.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.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 H1-antihistamine activity, while systemic exposure was reduced, compared with cetirizine from GB.

Hydroxyzine from topical phospholipid liposomal formulations: Evaluation of peripheral antihistaminic activity and systemic absorption in a rabbit model

Hydroxyzine, an effective but sedating H1-antihistamine is given orally to treat allergic skin disorders. This study was performed to assess the peripheral H1-antihistaminic activity and extent of systemic absorption of hydroxyzine from liposomes applied to the skin. Using L-α-phosphatidylcholine (PC), small unilamellar vesicles (SUVs) and multilamellar vesicles (MLVs) containing hydroxyzine were prepared. Hydroxyzine in Glaxal Base (GB) was used as the control. Using a randomized, crossover design, each formulation, containing 10 mg of hydroxyzine, was applied to the shaved backs of 6 rabbits (3.08±0.05 kg). Histamine-induced wheal tests and blood sampling were performed at designated time intervals up to 24 hours. Compared with baseline, hydroxyzine from all formulations significantly suppressed histamine-induced wheal formation by 75% to 95% for up to 24 hours. Mean maximum suppression, 85% to 94%, occurred from 2 to 6 hours, with no differences among the formulations. The areas of plasma hydroxyzine concentration versus time area under the curve (AUCs) from PC-SUV and PC-MLV, 80.1±20.8 and 78.4±33.9 ng/mL/h, respectively, were lower than that from GB, 492±141 ng/mL/h (P<.05) over 24 hours. Plasma concentrations of cetirizine arising in-vivo as the active metabolite of hydroxyzine, from PC-SUV, PC-MLV, and GB, were similar with AUCs of 765±50, 1035±202, and 957±227 ng/mL/h, respectively (P<.05). Only 0.02% to 0.06% of the initial hydroxyzine dose remained on the skin after 24 hours. In this model, hydroxyzine from SUV and MLV had excellent topical H1-antihistaminic activity, and minimal systemic exposure occurred. Cetirizine formed in-vivo contributed to some of H1-antihistaminic activity.

The clinical pharmacology of brompheniramine in children

BACKGROUNDnBrompheniramine has been widely used in the treatment of allergic rhinitis and other disorders during the past 4 decades. There are no published studies of its clinical pharmacology in children.nnnOBJECTIVESnThis study was performed to test the hypothesis that brompheniramine would have a prompt onset of action and a 24-hour duration of action in children.nnnMETHODSnBefore brompheniramine 4 mg was ingested, and at intervals from 0.5 to 30 hours thereafter, blood samples were obtained for quantitation of plasma brompheniramine concentrations by means of HPLC. Concurrently, epicutaneous tests with histamine phosphate were performed; wheals and flares were traced at 10 minutes, and the areas were measured by using a computerized digitizing system.nnnRESULTSnIn 14 children, mean age 9.5 +/- 0.4 years (SEM), the peak brompheniramine concentration was 7.7 +/- 0.7 ng/mL, and the time at which peak concentrations occurred was 3.2 +/- 0.3 hours. The terminal elimination half-life was 12.4 +/- 1.1 hours, and the oral clearance was 20.2 +/- 2.1 mL/min/kg. Compared with predose areas, the wheals and flares produced by histamine phosphate 1 mg/mL were significantly decreased from 0.5 to 30 hours and from 1 to 30 hours, respectively (P <.05), with mean maximum inhibition at 12 (52% +/- 9%) and 6 hours (72% +/- 10%), respectively.nnnCONCLUSIONSnIn children a single dose of brompheniramine produces prompt, long-lasting peripheral H1 -blockade. Revised dosage regimens may be needed in this population.

813 Can epinphrine inhalations by substituted for epinephrine injection in children at risk for systemic anaphylaxis

BACKGROUNDnFor out-of-hospital treatment of anaphylaxis, inhalation of epinephrine from a pressurized metered-dose inhaler is sometimes recommended as a noninvasive, user-friendly alternative to an epinephrine injection.nnnOBJECTIVEnTo determine the feasibility of administering an adequate epinephrine dose from a metered-dose inhaler in children at risk for anaphylaxis by assessing the rate and extent of epinephrine absorption after inhalation.nnnMETHODSnWe performed a prospective, randomized, observer-blind, placebo-controlled, parallel-group study in 19 asymptomatic children with a history of anaphylaxis. Based on the childs weight, 10, 15, or 20 carefully supervised epinephrine or placebo inhalations were attempted. Before dosing, and at intervals from 5 to 180 minutes after dosing, we monitored plasma epinephrine concentrations, blood glucose, heart rate, blood pressure, and adverse effects.nnnRESULTSnEleven children (mean +/- standard error of the mean: 9 +/- 1 years and 33 +/- 3 kg) in the epinephrine group were able to inhale 11 +/- 2 (range: 3-20) puffs, equivalent to 74% +/- 7% of the precalculated dose or 0.078 +/- 0.009 mg/kg. They achieved a mean peak plasma epinephrine concentration of 1822 +/- 413 (range: 230-4518) pg/mL at 32.7 +/- 6.2 minutes. Eight children (10 +/- 1 years of age and 33 +/- 5 kg) in the placebo group were able to inhale 12 +/- 2 (range: 8-20) puffs, 89% +/- 3% of the precalculated dose, and had a peak endogenous plasma epinephrine concentration of 1316 +/- 247 (range: 522-2687) pg/mL at 44.4 +/- 16.7 minutes. In the children receiving epinephrine compared with those receiving placebo, mean plasma epinephrine concentrations were not significantly higher at any time, mean blood glucose concentrations were significantly higher from 10 to 30 minutes, mean heart rate was not significantly different at any time, and mean systolic and diastolic blood pressures were not significantly increased at most times. After the inhalations of epinephrine or placebo, the children complained of bad taste and many experienced cough or dizziness. After inhaling epinephrine, 1 child developed nausea, pallor, and muscle twitching.nnnCONCLUSIONSnDespite expert coaching, because of the number of epinephrine inhalations required and the bad taste of the inhalations, most children were unable to inhale sufficient epinephrine to increase their plasma epinephrine concentrations promptly and significantly. Therefore, we urge caution in recommending epinephrine inhalation as a substitute for epinephrine injection for out-of-hospital treatment of anaphylaxis symptoms in children.