Diclofenac (ATC code: M02A A15) for topical administration is safety classified as Probably not porphyrinogenic because of minimal systemic exposure and because diclofenac for systemic use (ATC code: M01A B05) is classified as Probably not porphyrinogenic (PNP). For more details of the metabolism of diclofenac please refer to the monograph of diclofenac for systemic use (ATC code: M01A B05).

About 6% of a dose is absorbed after topical administration of 2.5 grams diclofenac gel on 500 cm2 of skin. Occlusion for 10 hours increases the systemic exposure three times. Maximum plasma concentration is about a 100 times less than after per oral administration of the same dose (SPC).

Uneventful use reported in 10 patients with acute porphyria. ATC code: M02A B05 (systemic exposure): uneventful use reported in 41 patients with acute porphyria.