Insignificant systemic exposure. Two references consider it (probably) safe. Did not induce ALAS1 in rat.

Gel 2.5%. Analgetic and antiinflammatory gel for dermal application. Bioavailability after percutaneous administration about 5%. South African list: use with care. French list: authorized

Uneventful use reported in 19 patients with acute porphyria.