Management of Opioid Induced Hyperalgesia – The Impact on Workers’ Compensation Claims
The impact of opioid use in workers’ compensation claims has been widely researched and the shocking results continue to reveal that opioid use remains a very significant concern for workers’ compensation carriers. As evidenced by the NCCI Workers’ Compensation Prescription Drug Study: 2013 Update, the average narcotic cost per claim continued to increase as did the average number of narcotic prescriptions per claim. According to statistics cited by the National Safety Council, claims costs for injured workers prescribed even one opioid medication were four times higher than claims where no opioid medications were prescribed.
Continued use of increasing dosages of opioid medications can lead to many physical and psychological issues, including a phenomenon known as opioid induced hyperalgesia.
What is opioid induced hyperalgesia?
Opioid Induced Hyperalgesia (OIH) is a paradoxical sensitization to pain in patients with chronic opioid use. OIH is typically suspected when there is an increase in perceived pain with the increase in opioid use. A key element to note is that pain from OIH does not necessarily originate from the source of injury or disease. It presents as a generalized, diffuse and ill-defined pain unresponsive to increasing opiate doses. There’s no standardized formula for diagnosing OIH as the exact mechanism for its development is still unknown. The prevailing thought is that there is an imbalance between the antinociceptive and pronociceptive pathways. Eisenberg et al., suggested six clinical criteria to consider when diagnosing OIH.
Table 1 Suggested Criteria for Diagnosing OIH
- Increased pain intensity while chronic opioid treatment
- No disease progression
- No evidence of withdrawal
- No evidence of tolerance
- Decreased pain intensity due to reduction in opioid dose
- No evidence of addiction
OIH is not to be confused with tolerance or withdrawal though some of the symptoms are similar. Symptoms like allodyna (pain from stimuli which does not ordinarily cause pain) and hyperalgesia are common to tolerance, withdrawal and OIH leading to confusion. Tolerance is defined as the decreasing efficacy of a drug over time. Pain from tolerance improves as opiate doses are increased while increasing opiate dosage has no effect in OIH.OIH or Tolerance
Treatment of OIH and opioid switching
Managing OIH can be challenging as well as time consuming. One rule of thought is to wean patients completely off opioids. It is important to set the right expectation with patients when embarking on this path as weaning could exacerbate pain and cause mild withdrawal symptoms. Weaning in conjunction with an interdisciplinary Functional Restoration Program, can result in improved outcomes. As concluded in a study performed by Townsend, et al, patients on chronic opioid therapy who chose to participate in a Functional Restoration Program incorporating opioid withdrawal, experienced a significant and lasting decrease in pain and an improvement in daily function.
A more common management option is rotating opioids or opioid switching. One cost effective alternative researched involved the use of methadone. Rotating to methadone, which is significantly less expensive than most narcotic pain medications, can improve OIH as demonstrated by Chu et al. Methadone (Average Wholesale Price of $0.14 to $0.26 per pill) is dramatically less expensive than typical opioids utilized for chronic pain such as OxyContin (Average Wholesale Price of $3.35 to $18.72 per pill), Opana ER (Average Wholesale Price of $2.26 to $14.49), hydromorphone ER (Average Wholesale Price of $13.53 to $54.15 per pill) or morphine sulfate ER (Average Wholesale Price of $1.05 to $18.38). Although studies of patients addicted to methadone have shown that methadone can worsen OIH. NMDA receptor antagonists are a class of anesthetics that work to inhibit the action of the N-methyl-D-aspartate receptor. These class of meds have been demonstrated to be effective options for opioid switching in the management of OIH. Methadone has mild NMDA antagonist properties which could explain why it works. Dextromethorphan, a cough suppressant, is an NMDA antagonist and has been shown to be effective when combined with morphine. Buprenorphine has also shown promise in the treatment of hyperalgesia. Other agents like pregabalin, gabapentin, propranolol, propofol and cox-2 inhibitors have been shown to have some degree of success in treating OIH though the evidence is mixed.
Though OIH is not widely recognized by clinicians due to the lack of criteria for separating it from withdrawal or tolerance resulting in a conclusive diagnosis, it is, however, a phenomenon seen more and more in practice due to the increasing use opioids. As a result, further research is needed to better understand this phenomenon and provide more effective recommendations to clinicians for diagnosis and treatment.
With respect to OIH in workers’ compensation patients, claims management personnel should continue to monitor claims for signs of escalating narcotic use with little symptom reduction or improvement in function. Early intervention can be the key to preventing and treating OIH.