Dynamics of systemic quinidine photoallergy in the mouse

Photoallergy to systemically administered quinidine was induced in the mouse, and the minimal time for sensitization as well as the duration of the allergy were studied. When groups of female albino mice, pretreated with cyclophosphamide, were exposed to quinidine 100 mg/kg i.p. followed by 0.1 J/cm2 UVB and 5.0 J/cm2 UVA, a positive challenge reaction, measured as ear edema, could be registered as early as the third day after induction and peaked on days 5-12. When animals photosensitized as above were photochallenged after 7 days, and again after 2 and 8 months, strong reactions were obtained on all 3 occasions, suggesting a duration of systemically induced photoallery to quinidine of more than 8 months. In the absence of quinidine, no photosensitivity could be demonstrated with UVA only. Phototoxicity controls were negative. These results suggest that photoallergy induced by systemic administration behaves similarly to contact and photocontact allergy.