title: Experimental evaluation of cyadox phototoxicity to Balb/c mouse skin.
abstract: BACKGROUND
  Cyadox is a veterinary drug mainly used as an effective antimicrobial promoter in animal husbandry. It was reported that the other quinoxaline-1,4-dioxide compounds had phototoxicity, but only few data are reported on phototoxicity of cyadox. This study was performed to evaluate the phototoxicity of cyadox on skin.
  
  
  METHODS
  Eighty mice were equally divided into eight groups. Five groups with ultraviolet A (UVA) irradiation for 2 h (21 J/cm2) were administered at doses of 0, 10, 50, 200 mg/kg cyadox and 50 mg/kg olaquindox, respectively, and others as controls without irradiation administered at doses of 0, 200 mg/kg cyadox and 50 mg/kg olaquindox, respectively. Drugs were administered by gavage once daily with a suspension in 0.8% carboxymethyl-cellulose for consecutive 4 days. After administration, a recovery period of 7 days was arranged. Histopathological examination of auricular skin was performed on days 5 and 12. Measurement of auricular thickness, gross pathology and erythema score were conducted once daily.
  
  
  RESULTS
  Cyadox groups (200, 50 and 10 mg/kg) with irradiation had erythema and oedema of auricular skin with dose-response relationship, which gradually convalesced after dosing and irradiation ceased. Severe erythema, oedema and necrosis of auricles were observed on olaquindox group with irradiation.
  
  
  CONCLUSIONS
  The phototoxicity of cyadox was mild and reversible, which demonstrated a good safety profile of cyadox in terms of phototoxicity.
authors.affiliation: National Reference Laboratory of Veterinary Drug Residues and MOA Key Laboratory of Food Safety Evaluation, Huazhong Agricultural University, Wuhan, Hubei, China.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: He
authors.forename: Guijie
authors.initials: G
authors.lastname: Fang
authors.forename: Yulian
authors.initials: Y
authors.lastname: Wang
authors.forename: Zhichao
authors.initials: Z
authors.lastname: Wei
authors.forename: Daju
authors.initials: D
authors.lastname: Wang
authors.forename: Shiqi
authors.initials: S
authors.lastname: Zhou
authors.forename: Shengxian
authors.initials: S
authors.lastname: Fan
authors.forename: Zanghui
authors.initials: Z
authors.lastname: Yuan
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004890:Erythema / Q000139:chemically induced*; D051379:Mice; D008807:Mice, Inbred BALB C; D011810:Quinoxalines / Q000633:toxicity; D012867:Skin / Q000187:drug effects* / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D011810:Quinoxalines; C020728:cyadox