General Considerations in the Use of Adjuvant Analgesics

Chapter 21


General Considerations in the Use of Adjuvant Analgesics



THE use of adjuvant analgesics in the management of pain is a “labor intensive” endeavor that includes careful patient selection, evaluating and selecting the best agent and dosing regimen, assessing response to treatment, and adjusting therapy to achieve the greatest benefit. All these activities are predicated on a systematic assessment of the patient, both initially and throughout the course of therapy. Over time, changes in pain, adverse effects, or any concerns regarding quality of life may lead to modifications in therapeutic approaches to managing pain.


Few studies actually capture the frequency with which adjuvant therapy is used. In one study on the use of treatment modalities, 723 community residents with moderate to severe pain were surveyed about their use of analgesics (Vallerand, Fouladbakhsh, Templin, 2005). Approximately 75% reported taking nonopioids, 15% reported taking opioids, and 11.6% reported taking adjuvant analgesics. Of concern, fully 28% were taking drugs for pain but had not informed their primary care providers. This finding underscores the importance of patient education about the need for communication with the health care provider who prescribes their analgesics. The safe prescription of the adjuvant analgesics depends on accurate information about all the drugs taken by the patient (see the discussion of patient education at the end of Section V).



Drug Selection


The selection of a specific adjuvant analgesic is usually based on the nature and characteristics of pain and the presence of other symptoms and co-morbidities. For example, an early trial of an analgesic antidepressant is justified by the existence of a co-morbid depression, which would be considered a separate target for this therapy.


Drug selection also may be influenced by the results of specific studies and accumulated clinical experience. For example, there are both controlled trials and several decades of experience suggesting the efficacy of carbamazepine in trigeminal neuralgia, and patients with this disorder often are offered a trial of this drug first. Similarly, patients with fibromyalgia usually are considered for a trial of the drugs that have been studied and are now approved for this condition, such as pregabalin and duloxetine.


In most circumstances, both the existing data and experience are insufficient to narrow the choice of drug substantially. Many options exist, and drug selection is based on guidelines or other factors; if one drug fails to provide adequate pain relief, others may be tried. In short, most of the therapeutic process involving the adjuvant analgesics follows an “informed trial-and-error” strategy in which drugs are offered in sequential trials based on the current evidence base, clinical experience, and other factors, such as age, co-existing medical conditions, prior response to a particular drug, issues with convenience and adherence to therapy, cost and availability of agents, and access to care and follow-up treatment. Decisions should be thoughtfully determined by an examination of the potential benefits and risks associated with therapy (Gatchel, Okifuji, 2006).


Cost comparison research is largely lacking, and the complex issue of cost-effectiveness usually ends with a decision influenced by the need for out-of-pocket expenses (a so-called cost-minimization strategy). A more sophisticated analysis involves assessment of pain intensity and distress, drug options, dosing regimen, likelihood of adherence, ancillary costs (e.g., other medications needed to control the adverse effects of the analgesics), and third-party payer influence (Gore, Sadosky, Tai, et al., 2007; O’Connor, Noyes, Holloway, 2007; Tarride, Gordon, Vera-Llonch, et al., 2006). The limited information about these factors at the start of therapy typically results in a prediction about overall costs that is highly tentative. An excellent cost analysis of the effect of pregabalin in the treatment of radiculopathy in the primary care setting found that pregablin alone or as an add-on therapy at doses within the recommended range significantly reduced pain, which translated into meaningful reductions in the use of both health care and non–health care resources (Saldana, Navarro, Perez, et al., 2010). The increases in drug cost were offset by a significant decrease in the costs associated with other components of health care, such as complementary tests, medical visits, and nondrug therapies.


Patient preference also is critical to consider in drug selection. Patients may express preferences that are idiosyncratic (e.g., knowledge of a family member who experienced benefit or adverse effects from a drug) or informed by factors that may influence their ability to tolerate a drug or adhere to therapy. Collaborative decision making around the use of therapeutic options for pain relief increases the likelihood that the patient will be adherent with the treatment plan (Manias, Williams, 2008).



Dosing


The adjuvant analgesics are heterogeneous, and dosing regimens vary. A few of the drugs are available as parenteral formulations, which can be used in monitored environments and administered at full doses promptly (e.g., a relatively large, intravenous [IV] loading dose of a corticosteroid, lidocaine, or valproate in the management of severe neuropathic pain).


In the more common scenario of oral drug administration in the ambulatory setting, low initial doses and gradual dose escalation may avoid early adverse effects or allow tolerance or adjustment to the adverse effects. In medically ill patients, this precaution is especially appropriate when adjuvant analgesics are initiated. When low doses and gradual titration to therapeutic effects are employed, it is easier to optimize therapy and balance pain relief with adverse effects. In some cases, patients must be forewarned that onset of analgesia with adjuvant drugs is likely to be delayed. Otherwise, patients may become discouraged and stop taking the drug.



Variability in Response


There is considerable variability among individuals in their response to adjuvant analgesics, including agents within the same class. While specific patient characteristics (e.g., advanced age, co-existing organ dysfunction or failure, and inherent differences in the ways patients metabolize and respond to drugs) may increase the likelihood of some common adverse effects, it is nonetheless true that neither beneficial nor unfavorable effects from any specific medication can be reliably predicted. The potential utility of adjuvant analgesics may only be established through repeated trial and error, allowing sufficient time to determine whether an adjuvant agent is likely to reduce pain.


The existence of significant intraindividual variation in the response to the large group of adjuvant analgesics must be explained to patients. If a treatment regimen is not successful, it is also critical that patients are aware of other options that can be tried. Frustration with the delay in finding an effective drug and the time required with each drug to explore the dose range should be acknowledged, but patients also should be encouraged to hold on to hope that a useful therapy will be found.

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Related posts:

  1. Perioperative Nonopioid Use
  2. Other Challenges in Pain Assessment
  3. Intravenous Patient-Controlled Analgesia
  4. Switching to Another Opioid or Route of Administration

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Jun 24, 2016 | Posted by in PHARMACY | Comments Off on General Considerations in the Use of Adjuvant Analgesics

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