Sensitization of Naive Beagles by Intradermal Injection of an Ascaris Antigen: Induction of a Model of Skin Allergy

Inhibitory effect of topical adelmidrol on antigen-induced skin wheal and mast cell behavior in a canine model of allergic dermatitis

BACKGROUND

Adelmidrol is a semisynthetic derivative of azelaic acid and analogue of the anti-inflammatory compound palmitoylethanolamide (PEA). Based upon its physicochemical properties, adelmidrol is suitable for topical application. The main objective of the present study was to evaluate the efficacy of a topical adelmidrol emulsion on early and late inflammatory responses in hypersensitive dogs. Repeated intradermal injections of Ascaris suum extract were performed in both lateral thoracic areas of six conscious hypersensitive Beagle dogs, topically treated during 8 consecutive days. Adelmidrol (2%) was applied to one side and vehicle to the other. 24 hours after the last antigen challenge, two biopsies (adelmidrol- and vehicle-treated side) were obtained for each dog at the antigen injection site.

RESULTS

A significant reduction in the antigen-induced wheal areas was observed on the 4th and 7th day of adelmidrol treatment. Moreover, cutaneous mast cell numbers were significantly decreased in biopsies obtained after 8 consecutive days of topical adelmidrol treatment.

CONCLUSIONS

The results obtained in the present study show that topical treatment with adelmidrol might represent a new therapeutic tool in controlling the early and late allergic inflammatory skin responses in companion animals.

Clinical pharmacology of alcaftadine, a novel antihistamine for the prevention of allergic conjunctivitis

PURPOSE

In this report, we characterize the in vitro pharmacokinetic properties of a new antihistamine, alcaftadine. In addition, we report results from phase 1 studies of several ophthalmic formulations of alcaftadine and examine the pharmacokinetic properties of one formulation in detail.

METHODS

In vitro pharmacology employed a human liver microsome assay combined with index substrates or inhibitors for specific cytochromes. Metabolic fate of (14)C-alcaftadine was determined by high-performance liquid chromatography-based separation of parent compound from metabolites. Plasma protein binding was determined by equilibrium dialysis using (3)H-labeled alcaftadine and (3)H-labeled alcaftadine carboxylic acid metabolite. Relative tolerability (comfort) of 4 concentrations and 3 formulations of alcaftadine ophthalmic solution was assessed in 2 double-masked, randomized, placebo-controlled, contralateral studies in which formulations were compared to Tears Naturale II (placebo) in normal adult subjects. Data analysis focused on the mean differences in subject-reported drop comfort scores (within each dose level, at each time point) and compared the study-treatment eye with the placebo eye. Pharmacokinetics of alcaftadine 0.25% ophthalmic solution were determined in an open-label, single-center study after a single bilateral dose and after 7 days of once-a-day bilateral doses in healthy subjects 18-55 years old.

RESULTS

Alcaftadine is not significantly metabolized by microsomal cytochromes, but it is rapidly converted to the carboxylic acid metabolite by one or more cytosolic enzymes. Neither the parent compound nor its carboxylic acid metabolite displayed significant plasma protein binding. Over a range of formulations and concentrations (0.05%-0.5%), alcaftadine was well tolerated and subjects reported little or no discomfort or taste perversion in any treatment group. Pharmacokinetic studies showed that both the parent compound and the carboxylic acid metabolite reach peak serum levels within minutes of administration and fall below detectable levels within 3 h of dosing.

CONCLUSIONS

Based upon pharmacokinetic and phase 1 studies, the novel antihistamine alcaftadine is an appropriate drug for use as an ophthalmic formulation for prevention and treatment of ocular allergic conditions such as allergic conjunctivitis (alcaftadine ophthalmic solution 0.25% was recently approved for use by the FDA). Topical administration of alcaftadine 0.25% ophthalmic solution was well tolerated and had an acceptable safety profile.