Efficacy of a New Tonic Containing Urea, Lactate, Polidocanol, and <b><i>Glycyrrhiza inflata</i></b> Root Extract in the Treatment of a Dry, Itchy, and Subclinically Inflamed Scalp

TLDR

Cutaneous application of local anesthetic bases can alter pain, itch, and thermal sensations by acting on nociceptors and thermoreceptors. The study aims to characterize the pharmacodynamic response of nonionic surfactants, such as polidocanol, by measuring thermal thresholds after cutaneous application. Thermal thresholds were measured with a thermal sensory analyzer after applying nonionic surfactants and compared to those obtained with local anesthetic bases including mepivacaine, bupivacaine, prilocaine, lidocaine, EMLA, and a triple mixture. None of the tested surfactants altered thermal thresholds, likely due to their high molecular weight, whereas prilocaine, lidocaine, and their mixtures produced potent local anesthesia but showed no significant pharmacodynamic differences among them.

Abstract

With cutaneously applied local anesthetic bases various effects may be observed, such as a decrease in pricking pain and a change in burning, itch, and thermal sensations. These effects occur after skin penetration and may be attributed to the action of the anesthetics on nociceptors and thermoreceptors, i.e., on C and A delta nerve fibers, respectively. As little is known about the pharmacodynamic response of nonionic surfactants with a potentially anesthetic action such as polidocanol, this study characterizes nonionic surfactants pharmacodynamically by measuring thermal thresholds with a thermal sensory analyzer after cutaneous application. The results obtained with the nonionic surfactants were compared with data resulting from the cutaneous application of local anesthetic bases such as mepivacaine, bupivacaine, prilocaine, lidocaine, the 1:1 mixture of lidocaine and prilocaine contained in EMLA and a triple mixture consisting of lidocaine, prilocaine and tetracaine (1:1:1). The results show that none of the investigated surfactants affect thermal thresholds probably due to their high molecular weight. The same was observed with the anesthetics mepivacaine and bupivacaine. In contrast, prilocaine, lidocaine, the 1:1 mixture of lidocaine and prilocaine and the triple mixture consisting of lidocaine, prilocaine and tetracaine (1:1:1) proved to be potent local anesthetics. However, their pharmacodynamic responses do not differ significantly from each other.