Nearly Half of Patients Misuse Their Pain Meds

Adherence to prescribed medication regimens is essential for effectively treating chronic pain conditions. However, a new study reports that therapeutic nonadherence, or “medical misuse,” of analgesics is common, with underuse more prevalent than overuse or abuse.

Researchers at a single multidisciplinary pain treatment center in Belgium assessed adherence to prescribed analgesic regimens in 281 patient during a 19-week period [Broekmans et al. 2010]. On self-reported measures nearly half (48%) of the patients were nonadherent, with 34% of them admitting underuse and 14% overuse of their prescribed medications. Overall, older patients were significantly more adherent, although age-group differences were not vast; the mean age in adherent patients was 54 years compared with 47 to 49 years in nonadherent patients. Underuse was significantly associated with taking non-prescribed analgesic agents as a form of supplemental self-medication. Overuse was significantly influenced by tobacco smoking, being prescribed opioid analgesics, and regimens requiring a higher number of medication doses per day. The researchers conclude that therapeutic nonadherence, especially underuse of medication, occurs frequently among patients with chronic nonmalignant pain; however, prospective research is needed to learn about the impact of such misuse on clinical outcomes.

FURTHER ANALYSIS: This was an observational study of European patients predominantly suffering from back pain (n=91), neuropathic pain (n=60), and fibromyalgia (n=42); persons with cancer-related pain were excluded. Patients overusing or underusing their medication only once were considered to be nonadherent, although the researchers claimed an alternate analysis using less stringent adherence criteria produced equivalent results (69% of under-users were doing so daily, as were 54% of over-users). Either over- or underuse might be considered as “medical misuse” of analgesics, since patients did not appear to be abusing or diverting the medications for nonmedical purposes. While 25% of participants admitted taking a non-prescribed analgesic agent, none of them claimed to have used illegal drugs (albeit, 13 patients acknowledged smoking cannabis occasionally, which may have been for analgesic effect). However, patients might be reluctant to admit illicit drug use, resulting in underreporting, and self-reports were not cross-checked via urine drug testing.

Tobacco smoking was found to be a significant predictor of medication overuse, which the researchers suggest might be a marker of patients’ lower priority on health and, thereby, less attention to therapeutic compliance. Others have proposed smoking as a surrogate marker for substance-use problems [see blogpost 1/22/10], but one study found smoking as a trigger for headaches [see blogpost 8/4/09] and recently reported research demonstrated a modest association of smoking and pain prevalence [Shiri et al. 2010]. Further research is needed to clarify the role of tobacco smoking in affecting patient compliance and response to analgesic therapy. Along with that, another interesting finding was that opioid analgesics prescribed on a frequent dosing schedule incurred overuse, which suggests that long-acting opioids allowing less frequent dosing may be important in facilitating adherence.

There are several limitations of the investigation by Broekmans and colleagues: 1) the clinical impact of nonadherence on pain relief and other factors could not be established, 2) the patients recruited for study were from a tertiary care (pain specialist) center, so the results cannot be generalized to other settings, 3) pain medications — whether opioid, nonopioid, or atypical analgesics (eg, antidepressants, anticonvulsants) as considered in this study — represent only one component of chronic noncancer pain therapy, 4) it is unknown whether the results of this study would apply to non-European patient populations. Of interest, a lack of health insurance covering medications might be an expected factor in noncompliance; however, for unexplained reasons, adherent patients were significantly less likely to have such compensation than either over- or under-users.

Certainly, therapeutic noncompliance is a problem throughout medical practice, particularly for chronic conditions requiring sometimes complex daily medication regimens. For example, it was long ago recognized that from >50% to >70% of patients with diabetes, hypertension, or asthma are noncompliant with their medication regimens and, consequently, from 30% to 80% experience exacerbations of their illnesses [O’Brien and McLellan 1996]. Therefore, the observations of this study in patients with chronic pain — 48% not strictly compliant — are not surprising. Given that pain medication underuse seems to be an even more prevalent problem than overuse, which might incur treatment failure, it is important not only to inform patients about the possible harms of taking too much medication but that analgesics must be taken regularly at the doses prescribed for desired pain relief. Further research is needed to define risk-factor profiles of over- versus under-users, which may lead to more effective adherence-enhancing interventions.

REFERENCES:
> Broekmans S, Dobbels F, Milisen K, et al. Pharmacologic pain treatment in a multidisciplinary pain center: Do patients adhere to the prescription of the physician? Clin J Pain. 2010;26:81–86 [abstract].
> O'Brien CP, McLellan AT. (1996) Myths about the treatment of addiction. Lancet. 1996;347:237-240 [article here]. Additional references in: McLellan AT, Lewis D, O’Brien CP, et al. Is Drug Dependence a Chronic Medical Illness. 2009 [document here].
> Shiri R, Karppinen J, Leino-Arjas P, et al. The association between smoking and low back pain: a meta-analysis. Am J Med. 2010;123(1):87.e7-35 [abstract].