Polypharmacy in Treating Chronic Pain

Las Vegas—Until recently, patients with chronic pain were treated in similar ways despite differences in their characteristics or conditions. Now rather than using a medication such as morphine for any type of pain, providers are using various treatments for different pain mechanisms and utilizing multimodal therapies and combination pharmacotherapies. Kathryn L. Hahn, PharmD, DAAPM, CPE, affiliate faculty, Oregon State University College of Pharmacy, and pharmacy manager, Bi-Mart Corp, Springfield, Oregon, discussed the topic at the AAPM in a session titled Using Rational Polypharmacy to Optimize Chronic Pain Management. She defined polypharmacy as using multiple medications to treat the same condition, using multiple drugs from the same class, and using multiple drugs with the same or similar mechanisms of action to treat different conditions. In rational polypharmacy, patients take several medications to achieve pain relief with minimal toxicity.

According to Dr. Hahn, some of the goals of rational polypharmacy in pain management include using lower doses of ≥1 drugs to minimize adverse effects, increasing adherence, maintaining the analgesic efficacy to prevent pain, increasing the efficacy using ≥2 drugs with different mechanisms of action, targeting different but associated symptoms, and targeting different locations of the disease process. There are several treatment options to manage pain. Simple analgesics include acetaminophen, salicylates, and nonsteroidal anti-inflammatory drugs. Opioid analgesics include as-needed administration of short-acting opioids, patient-controlled analgesia, and regularly scheduled administration of long-acting opioids. Adjuvant analgesics include antidepressants, anticonvulsants, topical products, muscle relaxants, and sleeping agents. Dr. Hahn said there are 2 main barriers to rational polypharmacy: drug–drug interactions and drug–disease interactions. Although prescription opioid misuse, abuse, and addiction receive much public attention, Dr. Hahn said there are more prevalent and controllable problems concerning interactions between opioids and other medications than there are in determining people’s risk for misuse, abuse, and addiction. “It’s much more simple to prevent a drug–drug interaction than decide who’s at risk for misuse or abuse,” Dr. Hahn said.

Most patients taking opioids also are prescribed ≥1 adjunctive medications, according to studies that Dr. Hahn mentioned; 1 survey indicated 78% of patients with chronic pain take over-the-counter drugs. She said a potential major problem is that patients may use multiple prescribers who are unaware of all of the medications prescribed. For instance, Dr. Hahn said patients who are taking opioids and coadministered cytochrome P450 (CYP450) metabolized drugs can have an increase or decrease in metabolism, leading to higher or lower than expected drug levels that inhibit or induce the intended effect. Dr. Hahn discussed several strategies to minimize the risks of drug–drug interactions. Providers should be aware of other medications that are metabolized via the CYP450 enzyme system and may interact with opioid analgesics. They should also ask patients at every visit about the medications they are taking and detail the drugs and doses. In addition, patients should be told of any potential adverse effects associated with the medications.

If possible, Dr. Hahn said patients should be prescribed drugs that are metabolized via other pathways or by multiple CYP450 enzymes. “We need to be aware of how to increase efficacy and decrease risk,” Dr. Hahn said. “Everything today is about risk mitigation.” Drug–disease interactions are also common. Dr. Hahn defined the interaction as the impact of ≥1 drugs on a preexisting medical condition, disease state, or pathological process. For instance, a prolonged QT interval can put patients at risk for arrhythmia, which can lead to syncope, ventricular fibrillation, or death.