An Interview with Thomas E. Quinn, MSN, RN, AOCN
|This month PainEDU interviews Thomas Quinn, an oncology nurse at Massachusetts General Hospital in Boston with 25 years experience in a variety of treatment settings. Tom has been teaching about pain in a variety of forums to patients, community groups, and health professionals of all disciplines. He discusses various considerations of opioid rotation, including aspects of the clinical decision making process.
What are some common clinical situations when a clinician might want to consider opioid rotation?
Thomas E. Quinn, MSN, RN, AOCN: There are several reasons to consider changing a patient from one opioid to another. This process is often called "opioid rotation" but "opioid switching" might be more descriptive. To my knowledge there have been no extensive studies of the practice, so we donít know much about prevalence, but one can extrapolate from the literature both therapeutic and situational reasons. Therapeutic reasons include the development of unacceptable side effects with or without adequate analgesia; true allergy to the current opioid, which is quite rare; or a current regimen that isnít working, that is, does not provide sufficient analgesia despite dose escalation. Situational reasons include limitations in available drug formulations; patient difficulty in adhering to the prescribed regimen; and non-clinical factors such as reimbursement issues, difficulty obtaining a particular drug, or the medication is not on formulary.
EC: What do you mean by formulation limitations?
TQ: Here are a couple of examples. If you need to change the route and the current drug is not available via the desired route, you will need to change the drug. If the patient is taking a combination product such as hydrocodone with acetaminophen and the dose needs to be increased beyond the point where acetaminophen toxicity needs to be considered, the drug will need to be changed.
EC: When might it be inappropriate to rotate a patient?
TQ: Many patients and some clinicians reach the erroneous conclusion that an allergy is present because of nausea and vomiting or some other side effect. The opioid should be changed only if the side effect has been treated appropriately. Most patients will develop tolerance to the side effects (with the exception of constipation) within a few days, even without treatment. Sometimes both patients and clinicians jump to the conclusion that a particular opioid "doesnít work". There is no standard dose that works for every patient: opioid therapy must be individually titrated to patient need. In almost every case either the dose has not been sufficiently escalated or the dosing interval is too long. Careful assessment and dose adjustment should be initiated before deciding that this is the rare patient in whom a particular drug is not metabolized. Sometimes a clinician has a "favorite opioid" with which they are familiar and comfortable. It would not be appropriate to change to the favorite drug in the absence of evidence that there is a problem with the current regimen for this patient. Similarly, changing a drug on the basis of demographics rather than clinical response is inappropriate. For example, an elderly patient who is doing fine on morphine should not be changed to hydromorphone because of the theoretical higher risk of metabolite accumulation in elders.
EC: What are some of the issues a clinician must resolve when deciding whether to rotate a patient from one opioid to another?
TQ: Are side effects truly intractable? Has there been sufficient dose and interval adjustment to be sure that the current agent isnít working? Has the assessment determined whether a neuropathic component to the pain is present? Adding an adjuvant co-analgesic rather than switching opioids may be the more appropriate clinical response. Is patient/family ability to adhere to the regimen a factor that needs to be considered from either an educational or clinical support perspective? What post-rotation monitoring/follow-up will be available? Has expert consultation been considered?
EC: Please discuss a few of the factors a clinician should consider during the opioid rotation decision-making process.
TQ: A thorough assessment is the key to proper management. If the prescribed therapy isnít getting the expected results, reassessment must look for medical and psychosocial factors that impact the treatment decision. Some important questions might include: Are side/toxic effects likely to be related to poor elimination? An agent less likely to accumulate toxic metabolites should be considered. Are other clinicians caring for this patient adequately informed of and in support of the change? Has the patient/family been involved in the discussion? What is the patientís previous history with the proposed new agent? If there is a true allergy, is the new agent in a different opioid subclass? Are there pharmacokinetic issues, such as CYP system metabolism, that need to be taken into consideration, especially regarding concurrent medications? What post-rotation monitoring/follow-up will be available? Has expert consultation been considered?
EC: In selecting an equianalgesic calculator, are there any issues that clinicians should be aware of?
TQ: There are several equianalgesic tables available, and a few desktop or PDA calculators. There is no standard for determining equianalgesic values between opioids, so different tables and calculators may use different conversion factors. For this reason, it is very important that all clinicians caring for the patient (including those in the pharmacy) should use the same calculator. It is prudent to have a second clinician independently check calculations. It is a good idea to check the sourceóare references or some other evidence base cited? Just because a drug is included in the calculator, doesnít mean it is a good choice. Select the drug based on patient and drug characteristics, then go to the calculator to determine the safe starting dose of the new drug. Equianalgesic doses are mostly based on limited research. At best they are approximations. By its nature, a calculator cannot take into consideration individual patient characteristics, or common variations in pharmacokinetics. For all of these reasons the safe starting dose is the calculated equianalgesic dose minus some significant factor, usually defined as 25-50% of the calculated dose. Most tables and calculators grossly underestimate the potency of methadone. Other opioids in the calculator are assumed to have a potency in a fixed ratio with the other opioids. There is no fixed ratio between methadone and other opioids. The safest approach would be to remove methadone from the equianalgesic calculator and use a dedicated evidence-based conversion method.
In terms of characteristics of an electronic calculator, there are a number of factors to consider. Are most of your clinical tools on a desktop or handheld platform? Look for a calculator that fits your style. If you need both, try to get them from the same source, so that the reference tables are the same. If a trial version is available, get it. Youíll want to test drive to determine ease of use and real world clinical utility. If you are in a group practice or institution, try to get your colleagues to adopt the same product. Consistent use of the same tools facilitates both patient safety and clinical efficacy. Many patients are on more than one opioid, such as a fentanyl patch supplemented by oral morphine for breakthrough pain. Try to get a calculator that can simultaneously convert two or more opioids.
EC: What do you think is the most common misconception about opioid rotation? Why do you think that is?
TQ: I think there are three common barriers/misconceptions: I donít think the term "opioid rotation" is widely recognized among non-specialists. It is not as descriptive as "opioid switching". I think most clinicians are unaware of the significant differences, especially potency differences, between opioids. There has been a well-documented deficit regarding pain management in the basic education of physicians, nurses, and pharmacists that is only now being addressed. Fortunately, there are a great many resources available to clinicians, but we are all limited by ďnot knowing what we donít know. Many clinicians looking at an opioid equianalgesic table or calculator will assume that this is an easy "cookbook" method for dose calculation. Doing the calculation is just one step in a complex process.