Antipruritic Effect of Topical Acetaminophen Gel in Histaminergic and Non-histaminergic Itch Provocation: A Double-blind, Vehicle-controlled Pilot Study
Leigh A. Nattkemper, Kaining Zhi, Kaeli E. Romero, Serena M. Shah, Terresa Ju, Kayla Fourzali, Rachel Shireen Golpanian, Flor MacQuhae, Yiong Huak Chan, David B. Lebo, Gil Yosipovitch
There is a need for new topical antipruritics that are effective on many types of itch. This study examined the antipruritic efficacy of a new formulation of topical acetaminophen. In vitro skin permeability studies showed that 2.5% and 5% formulations are able to rapidly deliver an adequate amount of the drug into the skin. In a double-blind, vehicle-controlled, randomized study in 17 healthy volunteers, 1%, 2.5% and 5% acetaminophen gels and a vehicle gel were applied to the skin prior to histaminergic and non-histaminergic itch induction and assessment of thermal pain thresholds. The 2.5% and 5% gel formulations significantly reduced the itch intensity time course and the area under the curve for both histamine and cowhage itch. No effect was noted on heat pain thresholds and no adverse effects were observed. These results suggest that topical acetaminophen would be a safe and effective over-the-counter medication for itch.
Topical acetaminophen gel was effective against both acute (histamine) and chronic (cowhage) models of induced itch, and did not cause any skin irritation or discoloration. Topical acetaminophen formulas may therefore be a safe and effective over-the-counter therapy for many types of itch.