The peroxidative metabolism of tenoxicam produces excited species

The peroxidative metabolism of the nonsteroid anti-inflammatory oxicams generates metabolites of the type expected from a dioxetane intermediate. Therefore, electronically excited metabolites may be expected. Consistent with this possibility, both direct and sensitized light emission are observed when tenoxicam is exposed to horseradish peroxidase or when added to leukocytes, where it undergoes a myeloperoxidase-catalyzed aerobic oxidation. The similarity between peroxidative metabolism with concomitant oxygen uptake and photodegradation brought about by singlet oxygen addition to the substrate is pointed out. As a whole, the results strengthen the view that electronically excited species should also be considered when analyzing the effect(s) of xenobiotics.