Economic Implications of Potential Drug–Drug Interactions in Chronic Pain Patients

Robert Taylor Jr; Joseph V Pergolizzi Jr; R Amy Puenpatom; Kent H Summers


Expert Rev Pharmacoeconomics Outcomes Res. 2013;13(6):725-734. 

In This Article


Based on these studies, polypharmacy is a problem for patients with chronic OA and cLBP pain and may be the main driver between DDEs and higher costs, especially for younger patients (Table 3). Polypharmacy, taking multiple concurrent agents, exposes patients to the potential risk of DDI. After the first prescription drug, every additional agent the patient takes has been shown to increase his/her risk for a DDE.[13] Among older and younger OA patients in this study who took an index opioid, the risk of DDE occurrence increased by 138% with each additional prescription dispensed. The rate of DDE in OA patients varied depending on how many drugs the patient took in the baseline period (6-month period prior to index date), such that 14.5% of those taking no prescription drugs during baseline experienced a DDE during the 30-day study period compared with 61.2% of those taking four or more prescription drugs during the 6-month baseline. This is a significant risk considering many chronic pain patients who are most likely on more than one medication due to comorbidities, and thus it is important for physicians and pharmacists to be aware of a patient's current medications.

The literature on polypharmacy tends to focus on geriatric patients, because older patients have more ailments and consequently take more medications.[38,39] Less frequently discussed is polypharmacy in younger patients. In these retrospective database studies of OA and cLBP chronic pain patients, there was no marked distinctions in prevalence or economic outcomes between the younger and older patient cohorts. In fact, younger OA and cLBP patients had significantly higher total medical payments (medical plus prescription drugs) with DDE than without DDE mainly due to differences in prescription costs (Table 3). Therefore, it may be useful to regard polypharmacy as more than just a geriatric problem and to recognize its implications in the burgeoning and heterogeneous chronic pain populations. This trend in younger adults is not restricted to chronic pain patients. Current studies have pointed to an uptrend in the use of multiple medications in children, especially in children and young adults with psychiatric disorders[40,41] and in hospitalized children.[42] Many of these medications, especially benzodiazepines used for psychiatric disorders are metabolized through the CYP450 system and may increase the risk of a potential DDI when combined with certain opioids.[43] Thus, when accounting for children and the geriatric population, the prevalence of DDIs and their associated financial impact may be greater than is currently appreciated, possibly because polypharmacy is more widespread than many clinicians may realize.

Polypharmacy may also occur with the taking of over-the-counter (OTC) drugs and supplements, herbal products, teas or foods. Senior citizens who take at least one prescription drug take at least one OTC drug and 52% take at least one supplement.[44] Younger patients also consume OTC products, vitamins and supplements and their use of these products have been in an uptrend during recent years.[45–47] For that reason, these studies may sometimes include patients in the non-DDE group when, in fact, they do experience a DDE with an OTC product, supplement or food. If such an unidentified DDE leads to adverse event, health care utilization and associated payments, the estimates in these studies between the DDE and non-DDE patients may be biased. For that reason, the results of these studies must be viewed as a conservative estimate of the financial impact of DDEs.