Effectiveness of a Topical FormulationContaining Metronidazole forWound Odor and Exudate Control
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Fungating tumors, pressure ulcers, and other chronic wounds are frequently the source of offensive odors that distress patients, family, and healthcare professionals. These odors often limit the patients’ contact with others and have a negative psychological impact on all concerned. The social embarrassment caused by a malodorous wound heightens the misery of advanced and uncontrolled disease, deepening the person’s sense of helplessness, worthlessness, and social isolation at the time when support of family and friends is crucial.1 Smell carries a social stigma and may cause a patient to feel guilty and ashamed. It can inhibit sexuality and intimacy with a loved one resulting in depression.2
Fungating wounds are the visible markers of underlying malignant disease.3 The wound develops from a local tumor extending into the epithelium and its supporting lymph and blood vessels. As the mass increases and loses its vascularity, capillaries rupture, and necrosis and subsequent infection develop. This produces a malodorous purulent wound.4 For patients, odor is often the most distressing complication of their wounds and poses a considerable challenge to caregivers.
Nonsporing anaerobes that colonize cutaneous lesions release volatile fatty acids as metabolic end products that are responsible for the characteristic putrid odor.5,6 Deodorizers and ventilation7 and charcoal dressings that absorb these fatty acids8 seldom adequately control this odor.
The deodorizing effect of metronidazole9–13 has been shown to correlate with eradication of anaerobic infection,9 but systemic administration is often associated with adverse events, such as nausea and vomiting, and the ban on alcohol necessary with oral metronidazole may further impair patients’ quality of life.14 Topical application of metronidazole for the treatment of malodorous skin ulcers has been studied previously. Finlay et al.7 conducted a multicenter trial that prospectively evaluated metronidazole 0.75% gel on 47 patients with benign and malignant malodorous wounds. Decreased odor was reported on 95% of the patients after 14 days of treatment. There was a significant decrease in anaerobic organism cultured but no significant changes in the growth of aerobic bacteria. In this same study, patients also reported significantly less pain, but there was no control for the gel vehicle or wound dressing used. In a double-blind placebo-controlled trial,11 metronidazole 0.8% gel was reported to be beneficial in the reduction of odor from fungating primary or metastatic tumors. The difference in odor between the active and placebo-treated wounds was clinically evident but not statistically significant because of the study’s small sample size (11 patients). There are numerous other articles (case studies or anecdotal experience) reporting the reduction of wound odor with topically applied metronidazole.15–19
The purpose of this study was 2-fold: 1) to evaluate the effectiveness of 0.75% metronidazole on the eradication of odor in patients with large fungating tumors and 2) to compare the costs associated with using a commercial product versus a formulation compounded by the authors’ hospital pharmacy.
Study medication. The Calvary Hospital Pharmacy formulated metronidazole 0.75% gel as follows: 3.6g of metronidazole USP (Gallipot Inc., St Paul, Minn) were blended with 10mL of propylene glycol (Paddock Labs, Minneapolis, Minn) to produce a gelatin. Upon dispersion, 480mL of hydroxypropyl methylcellulose (Liqua-Gel®, Paddock Labs) was added and slowly blended until the metronidazole powder dissolved. The metronidazole 0.75% gel was packaged in either 2 or 4oz jars and labeled.