Topical treatment of necrotic foot ulcers in diabetic patients: a comparative trial of DuoDerm and MeZinc. An open randomized controlled study was carried out of 44 diabetic patients with necrotic foot ulcers treated with adhesive zinc oxide tape (MeZinc) or with an adhesive occlusive hydrocolloid dressing (DuoDerm). Fourteen of the 21 patients treated with MeZinc had their necrotic ulcers improved by at least 50% compared to six out of 21 with the hydrocolloid dressing (P less than 0.025). Fifteen patients showed an increase in the area of necrosis during the course of the 5-week study and of these, 10 had been treated with the hydrocolloid dressing. 