Diphenhydramine produces local cutaneous analgesia in response to dorsal skin noxious stimuli in the rat

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.     

Cutaneous lesions of Kikuchi's disease: Evolution of histopathological findings

We report a 38‐year‐old male patient who presented with cutaneous lesions mimicking widespread discoid lupus erythematosus with high‐grade fever, arthralgia and lymphadenopathy. Additional lymph node and skin biopsies, however, revealed karyorrhectic debris without neutrophils and numerous CD68‐positive cells, a characteristic finding of Kikuchi's disease (KD). Comparing skin biopsies on different occasions, we could see different forms of histopathology. The histopathology of skin lesions of KD may vary during the clinical course, which may reflect the stage of the disease.