Even Medicinal Maggots Carry Warnings

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by Deboshree Roy, MSC and Ron Sherman MD, MSC, DTM&H

Most wound care therapists are well acquainted with the benefits of maggot debridement therapy (MDT) by now, but may not be as informed about its adverse events. As an intern with the BTER Foundation, one of my projects was to review records of adverse events and potential complications by examining data from published studies, regulatory documents, and the quality control files shared by one producer of medicinal maggots, Monarch Labs (Irvine, California). Now nearing the end of my 6-month study, who better to share my discoveries with than the wound care experts that visit the WoundSource blog?

The package insert is the best place to begin a search for real and potential adverse events, but it does not always convey the element of probability and relative risk. For example, one adverse event may be quite severe but very rare; another may be quite common but merely an inconvenience. In weighing the risks and benefits of a set of treatment options, it is imperative to consider both the severity and the probability of adverse events, along with the associated warnings and contraindications. For the purpose of this discussion, and as a practical matter, we would suggest that the most important adverse events associated with maggot therapy --- each occurring in over 1% of cases --- are pain, anxiety, and the inconvenience of late deliveries.

Managing Pain Associated with Maggot Debridement Therapy

When medical grade maggots are first applied, they are too small to be felt. Besides, most patients have no significant sensation in their wounds, anyway. But as the larvae quickly debride the wound and grow, they may become large enough to be felt by some patients --- particularly those with pre-existing wound pain. Pain is generally described as brief and sharp, or throbbing and pressure-like. The former probably represents the rough-bodied maggots crawling over nerves; the latter may be a response to the maggots pushing into (or out from) confined spaces.

Maggot-associated pain occurs in less than 30% of patients, and most often after 48 hours of therapy, when the maggots are satiated, finished working, and trying to escape. Thus, the pain is generally predictable and treatable. Those patients with pre-existing wound pain should be warned and given access to analgesics. When their pain is no longer controllable with analgesics, the maggot dressings should be removed, even if this is before the scheduled time for removal, and even if this means that they would require a second cycle to attain complete debridement. Above all, the maggots should not be left in place beyond 48 hours, because by that time over 50% of the maggots will be trying to escape, and the pressure within the dressing will increase dramatically. Once the maggots are removed, the maggot-associated pain ceases. Some therapists apply lidocaine or other topical analgesics to the wound, but to date no studies have looked at the efficacy of this practice.

Mitigating Maggot-Related Anxiety

Anxiety is probably the second most common adverse event surrounding maggot therapy, though we have no good data to suggest how common or significant a problem this is. It is clear, though, that anxiety is a greater problem in persons without wounds (including health care workers and administrators) than it is in the wounded patients themselves. It appears that patients are better able to evaluate and manage their anxiety, putting it into the context of their chronic, draining, stinking, life-altering, limb-threatening wound. The best way to treat or prevent anxiety is through education, and by allowing individuals to speak with, or see interviews of former patients and therapists. Anxiolytic medication is rarely needed, but is occasionally requested. Twenty-four hour access to a competent wound care team member is also helpful in controlling anxiety.

Avoiding Late Deliveries of Perishable Maggots

The third most common problem associated with maggot therapy is delayed delivery of the maggots. This is actually the most commonly reported adverse event reported with Medical Maggots™ (Monarch Labs, Irvine, California), with an incidence of approximately 1.5% of all deliveries. Late deliveries are a problem because medicinal maggots are highly perishable and should be used within 24 hours of delivery. They are often requested to arrive a few hours before the procedure, and if they arrive late they may not reach the clinic until after the patient’s appointment time. This is particularly problematic for outpatient treatments.

Mind you, a late delivery rate of 1.5% is actually well-below the industry standard for courier services. Still, it is a major inconvenience, no matter how rarely it occurs. This inconvenience can be minimized if the maggots are scheduled to arrive the day before the anticipated treatment. In this way, even if the package is stuck overnight it should still arrive by the next morning. Additionally, if it fails to arrive as intended the day before, there is still time for Monarch Labs to send out a replacement for delivery the next morning, still before the scheduled treatment.

The Importance of Reporting Adverse Events

The BTER Foundation's Adverse Events watch was initiated several years ago, and will continue indefinitely. Remember always to report problems to the manufacturer. Not only is that our most reliable source of data, but also it is the only way that problems can be recognized, quantified, and ultimately mitigated or eliminated.

Recommended Reading:
Sherman RA. Maggot Therapy Takes Us Back to the Future of Wound Care: New and Improved Maggot Therapy for the 21st Century. J Diabetes Sci Technol. 2009;3:336-44.
Sherman RA. Maggot therapy for foot and leg wounds. Int J Low Extrem Wounds. 2002;1:135-42.
Steenvoorde P, Buddingh TJ, van Engeland A, Oskam J. Maggot therapy and the "yuk" factor: an issue for the patient? Wound Repair Regen. 2005;13:350-2.
Thomas S, Jones M, Wynn K, Fowler T. The current status of maggot therapy in wound healing. Br J Nurs. 2001;10(22 Suppl): S5–8, S10, S12.

About The Authors
Ron Sherman MD, MSC, DTM&H has led a long career at the forefront of biotherapy, pioneering the development of medicinal maggots for over 25 years. He is now retired from his faculty position at the University of California, but continues to volunteer as Director and Board Chair of the BTER Foundation, and as Laboratory Director of Monarch Labs.

Deboshree Roy graduated with an M.Sc. in Biochemistry from Mumbai University in India in 2010. Roy now works as a Writing & Communications Intern at the BTER Foundation while studying at the Keck School of Medicine (University of Southern California) to obtain an M.S. in Applied Biostatistics & Epidemiology.

The views and opinions expressed in this blog are solely those of the author, and do not represent the views of WoundSource, Kestrel Health Information, Inc., its affiliates, or subsidiary companies.

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Medical maggots also can cause severe bleeding, as would be expected when one considers the mechanism of action. In this trial, 10 of the 37 patients had treatment failure, usually resulting from excess bleeding. http://www.medicalnewstoday.com/articles/235008.php

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