Opioid Calculator Apps: Then and now

2020; Volume 21, No 11, November

Opioid Calculator Apps: Then and now

Dr. Romayne Gallagher

By Romayne Gallagher, MD
IAHPC App Reviewer

Opioid rotation is defined as switching the route of administration or switching from one opioid to another. Intolerable adverse effects (nausea, confusion, persistent sedation etc.), development of analgesic tolerance, or inadequate analgesia despite titration are the usual reasons. Switching opioids can result in better analgesia, fewer side effects, and improved quality of life.

Opioid calculators included in this review suggest conversion ratios from the standard of morphine to the selected opioid. Controversy has vexed the process of opioid rotation, due to the flawed evidence base yielding a conversion ratio. Pharmaceutical safety studies of healthy participants receiving single doses of opioids were the basis for some ratios. While not realistic for people with serious illness, some websites will still only quote these ratios (e.g., this one by Global RxPh). In 2009, several articles suggested that clinician inexperience with rotation and unsafe protocols for rotation to methadone may have contributed to the increasing opioid harms in the United States.

Two open access 2018 articles1,2 summarize the 20+ years of attempts to establish equianalgesic conversion ratios in patients with cancer and other illnesses. Reference 2 is the best article for clinical insights.

Opioid rotation is a necessary skill for palliative care providers with access to affordable multiple opioids, and it makes sense that opioid calculator apps would exist. To my surprise, I found that many have disappeared. Here is what I did find.

Most-used calculators
are not useful for PC

One of the two most popular medical calculators, MDCalc Medical Calculator (you need to sign up to use it) has a calculator for determining the morphine milligram equivalent (MME) in order to comply with the U.S. Centers for Disease Control and Prevention (CDC) guidelines for chronic nonmalignant pain. The app cautions that it is not be used at end of life, for malignant pain, or for opioid rotation. MDCalc can be useful for other medical calculations, but enormous file sizes [iPhone (190 MB) and on Google (57 MB)] make it too large for many phones. Calculate by QxMD, the other popular medical calculator app, has nothing for pain, chronic pain, palliative care, or cancer pain.

A direct search for “opioid calculator” led me to the Opioid Calculator app by the Faculty of Pain Medicine of the Australian and New Zealand College of Anaesthetists. On Google Play it looks like it might be for opioid rotation as demo screens are titled “equianalgesic dose.” The app does say that it is a tool for the calculation of MME, but it does not say if it is indicated for use in nonmalignant chronic pain, and does not apply specifically to palliative care. If the MME is more than 100 mg, the screen becomes an alarming scarlet color. It is not appropriate for people with advanced illness and could reduce confidence in using opioids.

My guess is that other opioid calculators were likely withdrawn due to liability concerns. The current ones have become a daily MME calculator aimed at curbing the dose of opioids used in chronic noncancer pain.

Drawbacks to app
for opioid rotation

eOpioid was the one app solely intended for opioid rotation. Developed by SentientWare in 2009, its last update was five years ago. It allows conversion from one opioid to another and one route to another, but it is intended for the advanced user who can set their own conversion ratios and their own adjustment for cross-tolerance. The instructions are long, detailed, and in my opinion increase the complexity of opioid rotation. In short, this app may be useful for palliative care physicians who can spend the time to learn how to use it safely and don’t mind paying $6.99, but dangerous for any physician not familiar with opioid rotation.

In conclusion, since every phone has a calculator and clinical palliative care sources provide conversion ratios, one can calculate a starting dose for the new opioid without an app. After all, an app cannot provide the clinical judgment and close follow-up that is necessary for safe and effective rotation.

References

1. Schuster M, Bayer O, Heid F, Laufenberg-Feldmann R. Opioid Rotation in Cancer Pain Treatment — A Systematic Review. Dtsch Arztebl Int 2018; 115(9): 135-42.

2. Treillet E, Laurent S, Hadjiat Y. Practical Management of Opioid Rotation and Equianalgesia. J Pain Res 2018; 11: 2587-2601.


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