Table 1.

Changes in wound histology induced by topical fentanyl

Group	Histologic score	Epidermal and dermal regeneration	Granulation tissue	Vasculature
PBS	1.2	Little epidermal and dermal regeneration	Thin granulation tissue	Altered angiogenesis (1-2 vessels per site). These vessels have a high degree of edema, hemorrhage with occasional congestion and thrombosis
Fentanyl	3.6	Complete epidermal and dermal regeneration	Thick granulation tissue	Newly formed capillaries (5-6 per site). There is moderate degree of perivascular and interstitial edema with congestion. There is no thrombosis or congestion. There is also the presence of slight perivascular edema

Histological scores on a scale of 1–4, where 1 represents little epidermal organization/thin granulation and 4 represents complete dermal organization/thick granulation.