Effectiveness of a Topical Formulation Containing Metronidazole for Wound Odor and Exudate Control

Cathy Kalinski, RN, BSN, CWCN, COCN; Mary Schnepf, RNC, MPH, ET; Debbie Laboy, RPh; Lucy Hernandez, MS, APRN, BC; Jeanne Nusbaum, RN; Brian McGrinder, RPh; Christopher Comfort, MD; Oscar M. Alvarez, PhD


Wounds. 2005;17(4):84-90. 

In This Article


The term "fungating" describes a condition of ulceration and proliferation that arises when malignant tumor cells infiltrate and erode the barrier properties of the skin. Figure 6 shows both these features in a patient with squamous cell carcinoma who was enrolled in this study. Areas of tumor growth are visible at the wound margins and on the patient's cheek together with the central area of ulceration. Fungating tumors may be complicated by sinus or fistula formation (Figure 7). Tumor infiltration of the skin involves the spread of malignant cells along pathways that offer minimal resistance between tissue planes, along small blood vessels (capillaries), lymphatic vessels, and in perineural spaces.[21] Fungating wounds may develop on a number of sites, the breast being the most common.[3] Melanoma, lymphoma, and cancers of the lung, stomach, head, neck, uterus, kidney, ovary, colon, and bladder also have the potential to invade the skin. The incidence or prevalence of fungating malignant wounds is unknown, as data are based on estimations rather than derived from population-based cancer registries. In a retrospective survey based on questionnaires, Thomas et al.[3,22] calculated an incidence of more than 2,400 per year (the majority being treated in radiotherapy and oncology units). The author concluded that these figures reflect a significant incidence.

The term "fungating" describes a condition of ulceration and proliferation, which arises when malignant tumor cells infiltrate and erode the barrier properties of the skin. This image shows both these features in a patient with squamous cell carcinoma. Areas of tumor growth are visible at the wound margins and on the patient's cheek and forehead, together with the central area of ulceration.

This is a fungating tumor (buttocks) in a patient with chondrosarcoma. These tumors are frequently complicated by sinus or fistula formation. Tumor infiltration of the skin involves the spread of malignant cells along soft tissue planes (which offer minimal resistance), along capillaries, lymphatic vessels, and in perineural spaces.

The clinical significance of the problem in relation to physical and psychological distress is well documented.[23] Several case studies describe vividly the embarrassment that a fungating wound causes the patient, owing principally to the problems of smell, exudate, and soiling of clothes.[3] The isolation endured through not being able to share the problem with professional caregivers, family members, and friends is also conveyed. Sims and Fitzgerald[24] studied the fear associated with a fungating wound and advancing disease, and Rutheford et al.[25] described the distressing associations of smell that may stay with the family even after the patient has died.

Most wound odor appears to be associated with the metabolic process of anaerobic bacteria. Devitalized and necrotic tissue is host to both anaerobic and aerobic bacteria. A vital source of energy for anaerobes is lipid that has been decomposed by aerobes and facultative anaerobes. Malodor is caused by the production of volatile fatty acids, ie, propionic, isobutyric, butyric, isovaleric, and valeric, during lipid catabolism. Acetic acid does not appear to have the same effect.[26] Most significant anaerobic infections involve 5 anaerobes.[26,27] These include Bacteroides fragilis, Bacteroides prevotella, Fusobacterium nucleatum, Clostridium perfringens, and anaerobic cocci. Other pathogenic organisms that may cause a pungent wound odor belong to the aerobic group of bacteria, the most common being Proteus, Pseudomonas, and Klebsiella.[5] In the authors' experience, fungating lesions and gangrenous wounds are most commonly associated with malodor. However, odor is very often a major symptom in other chronic wounds, such as large venous ulcers, pressure ulcers, neuropathic (diabetic) ulcers, and, less commonly, inflammatory ulcers.

Upon review of the literature, the authors were surprised to find numerous articles describing the use of metronidazole for malodorous wounds. Also, there is widespread agreement among wound care professionals that topical metronidazole is effective in controlling wound odor. Most clinicians that use or prescribe metronidazole for this purpose rely on the commercially available preparations (MetroGel [0.75% gel], Galderma Laboratories, Fort Worth, Tex, and NoritateTM [1% cream], Dermik, Berwyn, Pa). These commercially available formulations must be prescribed off label (in the US), since they are indicated for the treatment of inflammatory lesions and erythema of acne/rosacea. Every article that the authors reviewed describing the use of metronidazole to control wound odor reported positive results. These studies and case reports cited benefit from both commercially available and compounded (home-made) topical metronidazole formulations. Industry leaders cite the cost of clinical trials and a small market as deterrents to pursue wound odor control as a new indication, but with the growing chronic wound population, it merits further consideration.

Frequently, the commercially available topical metronidazole formulations are not reimbursed. Occasionally, it is because of the cost or because it is not indicated for this use. Ethically, the authors felt that all of the inpatients with fungating wounds should be treated with topical metronidazole. After studying the purchasing costs involved with the commercially available formulations, the authors asked the pharmacy to study the feasibility of compounding a metronidazole gel for the facility. It was agreed that the authors would study the pharmacy-compounded formulation on 20 consecutive patients with fungating malodorous wounds. The cost to the hospital for a 45g tube of MetroGel was approximately $43.50 compared to $1.68 for 60g (2oz jar) if the authors compounded their own.

In the authors' experience, metronidazole 0.75% gel formulated and compounded by the facility's pharmacists was very effective for the treatment of malodorous wounds. The response was noticeable just several hours after the initial application and continued throughout the 2-week study period. In most instances, a once-daily application was sufficient. In addition, 0.75% metronidazole gel was effective in controlling wound exudate. Treatment was safe (there were no adverse events related to the use of metronidazole 0.75% gel), easy, convenient, and cost effective.