Letters to the Editor: Opioid Calculator, Testosterone for SCI
Transdermal Fentanyl Calculations
I have found potential errors with your morphine equivalent dosing calculator. I tested the PPM Opioid Calculator1 against several sites, including New York and Washington states.
Your conversion from transdermal fentanyl (Duragesic), with no cross tolerance adjustment, appears to be wrong: 50 mcg/hr = 1200 mcg/day. This equals 120 MED.
Your calculator also appears incorrect from morphine oral to fentanyl transdermal.
Can you address, thanks.
Daniel Schwarz, MD, CMRO
The Center for Pain Recovery
Thank you for the interest in the PPM Opioid Calculator. You raise a very important question regarding the equivalence to and from fentanyl transdermal and morphine.
Of note, there is a very high variability in fentanyl transdermal absorption. When fentanyl transdermal was first introduced to the market, Johnson Johnson took a conservative approach in their recommendations for converting to their product from morphine. The unfortunate issue now is that if you convert backwards, it leaves you with a liberal conversion, and this is what is seen with all other calculators.
Donner and colleagues suggest a very different schematic that is less conservative for conversion to transdermal fentanyl, and probably more accurate.
Irrespective of how one converts to the other, as mentioned above, there is a large standard deviation with transdermal fentanyl absorption. For this reason, we took Donner’s conversion and the manufacturer’s conversion into account, and unlike other calculators, we have two equations in the background in order to keep it conservative in either direction. We feel this is important for safety reasons.
I have included two diagrams that illustrate the dosing of fentanyl (Figure 1 and Table 1).
Jeffrey Fudin, PharmD
VA Medical Center
Albany, New York
Dr. Fudin disclosed that his answer to this question was not prepared as part of his official government duties.
Testosterone For Spinal Cord Injury
I have read your articles and website and was immediately struck by how much sense testosterone replacement therapy (TRT) made for pain management.2
I work with individuals with spinal cord injuries (SCI) and many have a reliance on opioids as well as ongoing pain. Do you know if many physicians work with TRT as a modality for pain managment? I have spoken about your thesis with my clients and none of their physicians are versed with this approach.
New York, NY
Yoga and Wellness
Testosterone replacement has been around since the 1970s. However, there has been a sharp increase in the number of prescriptions for testosterone in the past decade. Chronic pain patients often have low serum testosterone levels. This is caused by both the condition and the treatments.
Pain itself can cause hyperarousal of the hypothalamic-pituitary-adrenal axis, depleting patients of hormones such as cortisol and testosterone.2 In addition, chronic opioid therapy causes hypogonadism. For both these conditions, testosterone replacement is a needed remedy. The only cases in which this would be contraindicated are patients with active cancer of the prostate, ovaries, and/or breast.
The scientific discovery that the central nervous system (CNS) makes several hormones is relatively new and, as of yet, poorly appreciated. Neurogenesis is promoted by some hormones, so some should be used for spinal cord injuries and other disorders. A recent PubMed search found 13 articles that mention TRT and SCI, but most are to treat hypogonadism in men with SCI.
Recent studies, however, have suggested that there is a link between testosterone replacement and an increased risk for heart disease and stroke.3,4 This has led the FDA to announce that they are going to investigate the safety of FDA-approved testosterone products.5 This has raised some concern among pain practitioners who want to know whether testosterone replacement is safe.
Despite these reports, testosterone replacement remains an essential element of chronic pain management in both males and females. Testosterone has 3 critical properties in pain patients: protection and regeneration of damaged neural tissue (peripheral and central); maintenance of opioid effectiveness, so dosage can be minimized; and prevention of opioid complications, including osteoporosis and muscle wasting.2
You are correct when you imply over-reliance on opioids and other symptomatic agents in pain management. Neurohormones are not a panacea, but they may provide some curative hope.
Forest Tennant, MD, DrPH