title: Diphenhydramine produces local cutaneous analgesia in response to dorsal skin noxious stimuli in the rat.
abstract: Although diphenhydramine has been shown to produce longer duration of spinal block than lidocaine, few studies disclose its skin infiltrative anesthesia when compared with a long-lasting local anesthetic, bupivacaine. The purpose of this study was to investigate whether diphenhydramine elicited cutaneous analgesia in comparison with bupivacaine. After inhibition of cutaneous trunci muscle reflex via subcutaneous injection of drugs in rats, we examined the local anesthetic effect of diphenhydramine and bupivacaine as infiltrative cutaneous analgesia in a dose-dependent fashion. We showed that diphenhydramine, as well as bupivacaine displayed a dose-dependent cutaneous analgesia in response to dorsal cutaneous noxious stimuli. The relative potency (50% effective dose) was bupivacaine (0.023 [0.013-0.035]%) > diphenhydramine (0.078 [0.068-0.091]%; P < 0.001). On an equipotent basis, diphenhydramine had a similar duration of action to bupivacaine. Neither local injection of saline nor intraperitoneal administration of a large dose of diphenhydramine or bupivacaine produced cutaneous analgesia (data not shown). We conclude that diphenhydramine is less potent than bupivacaine at producing cutaneous analgesia. At equipotent doses for infiltrative cutaneous analgesia, the duration of action of diphenhydramine is equal to that of bupivacaine.
authors.affiliation: Department of Physical Therapy, Graduate Institute of Rehabilitation Science, China Medical University, 40402, Taichung, Taiwan; Department of Medical Research, Chi-Mei Medical Center, Yong Kang, 71004, Tainan, Taiwan.
authors.forename: Yu-Wen
authors.initials: YW
authors.lastname: Chen
authors.forename: Jann-Inn
authors.initials: JI
authors.lastname: Tzeng
authors.forename: Ting-Yun
authors.initials: TY
authors.lastname: Chen
authors.forename: Jhi-Joung
authors.initials: JJ
authors.lastname: Wang
authors.forename: Yu-Chung
authors.initials: YC
authors.lastname: Chen
authors.forename: Ching-Hsia
authors.initials: CH
authors.lastname: Hung
mesh_terms: D000698:Analgesia / Q000379:methods; D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002045:Bupivacaine / Q000008:administration & dosage / Q000494:pharmacology*; D003692:Delayed-Action Preparations; D004155:Diphenhydramine / Q000008:administration & dosage / Q000494:pharmacology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D008297:Male; D010146:Pain / Q000188:drug therapy; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000187:drug effects* / Q000473:pathology; D013997:Time Factors
chemical_list: D000700:Analgesics; D000779:Anesthetics, Local; D003692:Delayed-Action Preparations; D004155:Diphenhydramine; D002045:Bupivacaine
keywords: bupivacaine; diphenhydramine; dose-response curve; infiltrative cutaneous analgesia; subcutaneous injection