MEDICATIONS COMMONLY ADMINISTERED IN THE OLDER ADULT POPULATION
There is an abundance of medication that is commonly prescribed in the older population. Many of the medications that are used have a signihcant list of side effects, which are often treated with the addition of other medications. This may lead to a prescribing cascade and increasing polypharmacy [30,31]. In the following section, we will provide a general overview of the medications associated with the highest risk of adverse events. For ease of reference, the common “offenders” are placed in table format at the conclusion of this section.
The variety of commonly used pain medications ranges from topical analgesics to intravenous opioids. Here, we discuss the most commonly used oral medications. We focus initially on medications used to treat nociceptive pain (i.e., pain originating from bones, organs, or other tissues), then review medications for neuropathic pain.
Acetaminophen, which is available as an over-the-counter medication, is a hrst-line medication for pain relief for many acute and chronic conditions such as osteoarthritis [31,32]. Due to the potentially hazardous effects on the liver, the U.S. Food and Drug Administration (FDA) now restricts the amount that can be combined with other medications to 325 mg since, the maximal recommended daily dose is not to exceed 3 g a day [32-34]. Greater restrictions are usually placed on patients taking the blood thinning medication, warfarin, to 2 g per day or those with alcohol consumption greater than two drinks per day .
NSAIDs are not only widely prescribed but are also easily accessible over the counter. These medications are a very broad class (i.e., COX-1 vs. COX-2 inhibitors) and are commonly used in the treatment of acute and chronic pain. The most common complications are gastrointestinal bleeding, kidney injury, cardiovascular disease, and hematologic problems  and the FDA recommends against the chronic use of NSAIDs in the older adult due to these risks [36-38,93,94].
The use of opioids for the management of chronic pain in the older adult has surged over the last couple of decades . Although the American Geriatric Society (AGS) cautiously recommends opioid therapy in the older adult population with persistent moderate to severe pain, there is little evidence in the literature showing efficacy of opioids in the management of chronic pain [40,41]. The rate of overdose from opioids has risen drastically over the last decade, primarily due to the increase in prescribing practices of opioids for the treatment of chronic pain [39,42]. In the older adult population, the use of opioids caries up to an eightfold increase in the risk of respiratory depression, falls, and fractures . Mild side effects in this class of medications also include nausea, vomiting, somnolence, constipation, altered liver metabolism, and hypogonadism . Opioids are commonly prescribed in combination with acetaminophen. Many over-the- counter medications also contain acetaminophen, which can lead to unintended excessive use of this medications.
Tramadol has become a more commonly prescribed pain medication due to its action as a weak mu-opioid receptor agonist with serotonergic and noradrenergic properties. The increased risk of serotonin syndrome and lowering of the seizure threshold are the major side effects, with nausea being a common clinical side effect associated with tramadol. Because tramadol is only a weak opioid receptor agonist, there is a lower risk of tolerance, dependence, and respiratory depression .
The treatment of neuropathic pain (i.e., pain involving the central or peripheral nervous system) in the older adult involves only a few hrst-line agents. Gabapentin and Pregabalin work in the central nervous system on voltage-dependent calcium channels and are commonly used to treat pain associated with diabetic neuropathy, postherpetic neuralgia, hbromyalgia, and poststroke and spinal cord injury dysesthesia. Common side effects include edema, somnolence, dizziness, and abnormal thinking [45,46]. Both of these medications are excreted by the kidneys and require adjustments in dosing in patients with chronic renal insufficiency.
Serotonin and norepinephrine reuptake inhibitors (SNRIs) (e.g., duloxetine, venlafaxine, and mirtazapine) are a newer class of medications that are more commonly used for the treatment of depression . More recent studies have shown some efficacy in the treatment of chronic pain with neuropathic properties with these agents [48,95]. The side effects of these medications are discussed with the antidepressant medications later in this section. Opioids can be effective agents for neuropathic pain and are discussed elsewhere.