title: Single dose parenteral hyposensitization to poison ivy urushiol in guinea pigs.
abstract: Studies were carried out in guinea pigs to evaluate the potential for single dose hyposensitization to poison ivy urushiol dermatitis. Sensitization was induced by topical application of 1 mg of poison ivy urushiol to the back of the neck. In the first series of studies, three different analogs of poison ivy urushiol were studied: 1) a mixture of pentadecyl and heptadecyl catechols (PDC/HDC), the saturated side chain analog of the natural urushiol mixture; 2) a mixture of the diacetate esters of PDC and HDC (PDC/HDC Ac), the esterified form of the saturated sidechain analogs; 3) 2-n-pentadecyl hydroquinone diacetate (HQ Ac). Each of these compounds was administered as 5 mg of the free catechol i.m. each week for three weeks. A vehicle group received only corn oil injections. Reactivity to poison ivy urushiol (PIU) challenge was evaluated in skin tests at 1 and 5 weeks post-treatment. PDC/HDC Ac induced a marked reduction in both the incidence and the severity of lesions induced by PIU at both 1 and at 5 weeks post-treatment. Other analogs were ineffective at 5 weeks post-treatment, and were less effective than PDC/HDC Ac at 1 week post-treatment. In a second series of experiments, the efficacy of PDC/HDC Ac was evaluated in both single and multiple dose regiments. One treatment group received 5 mg of PDC/HDC Ac intramuscularly each week for 4 weeks, while another treatment group received a single dose of 20 mg PDC/HDC Ac i.m. Corresponding vehicle control groups were also included. At 1 week post-treatment in the single dose group, the PDC/HDC Ac was only modestly effective, with some reduction of severity of lesions at the higher challenge doses of PIU. However, at 4 and 7 weeks post-treatment, both the incidence and the severity of the lesions at all challenge doses were reduced. In the multiple dose group, the incidence and severity of lesions are reduced at 1 week and 4 weeks post-treatment (4 weeks and 7 weeks after the initial dose) but were not significantly different from the single dose group. These findings indicate that the diacetate ester of PDC/HDC is an effective hyposensitizer to poison ivy urushiol, and that this hyposensitization can be reasonably accomplished in a single dose treatment regimen.
authors.affiliation: Research Institute of Pharmaceutical Sciences, University of Mississippi, University 38677, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Walker
authors.forename: E S
authors.initials: ES
authors.lastname: Watson
authors.forename: M A
authors.initials: MA
authors.lastname: elSohly
mesh_terms: D000818:Animals; D002396:Catechols / Q000008:administration & dosage* / Q000737:chemistry / Q000633:toxicity*; D011040:Dermatitis, Toxicodendron / Q000628:therapy*; D003888:Desensitization, Immunologic / Q000379:methods*; D004195:Disease Models, Animal; D005069:Evaluation Studies as Topic; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D007273:Injections, Intramuscular; D012882:Skin Tests
chemical_list: D002396:Catechols; C003747:urushiol