Patient selection

Depending on the objectives of the trial and the specific treatment being evaluated, patients with either relatively homogenous conditions (e.g. painful diabetic peripheral neuropathy) or relatively heterogeneous conditions (e.g. peripheral neuropathic pain) can be studied. Careful attention must also be paid to specifying other features of the patients' pain, such as pain intensity and duration. Many studies include a minimum level of baseline pain intensity as one of the inclusion criteria in order to increase the likelihood of demonstrating a benefit of an active treatment versus placebo. Specifying too high a level of baseline pain, however, may augment responses in the placebo group by increasing regression to the mean [33]. Most recent clinical trials of treatments for chronic pain have therefore only included patients who have an average pain intensity of 4 or greater (on a 0-10 numeric rating scale) during the baseline period. The duration of time that pain has been present is also an important consideration. Typically, pain must have been present for at least 3 months to be considered chronic [2], but many studies have required a minimum pain duration of 6 months.

To eliminate patients who may have an increased risk from participating in the study and to increase the likelihood of detecting treatment benefits, clinical trials often restrict enrollment based on characteristics such as age, language, other medical conditions, known allergies, psychiatric disorders, alcohol or drug abuse, and, in women, pregnancy and the ability to conceive. Some studies have also excluded patients who have been refractory to multiple prior treatments for their chronic pain condition. Although some restrictions are necessary in defining a study sample, the use of unnecessary exclusion criteria in clinical trials reduces the generalizability of the results.

Some clinical trials are designed to exclude patients who are less likely to respond favorably to the investigational medication. Such "enriched enrollment" designs have been used to exclude patients who have done poorly with the medication during a run-in period -either because they showed a lack of benefit or because they could not tolerate its side effects - or patients who have a history of poor response to medications thought to share the same mechanism of action as the investigational treatment. Restricting the study sample to patients who are more likely to respond favorably to the study treatment can increase the likelihood that a trial will demonstrate efficacy. However, enriched enrollment designs can have important disadvantages, including limitations in the generalizability of the results because of the representativeness of the randomized sample, as well as the potential for unblinding resulting from prior experience with the medication's side effects during a run-in period. Such trial designs therefore may have greater value in establishing "proof of concept" of a potential analgesic intervention than in evaluating what the effectiveness of a treatment would be in the community.

Assessment of baseline characteristics and co-variates

There are various demographic characteristics of patients enrolled in clinical trials that must be routinely assessed, not only to accurately determine inclusion and exclusion criteria but also for use in data analyses. Depending on the condition being examined, age (e.g. in postherpetic neuralgia), sex (e.g. in fibromyalgia), and other demographic and clinical (e.g. pain duration) characteristics may be important co-variates in analyses of the data. Education, occupation, employment status, workers' compensation and other benefits, and presence of any litigation may also play a role in treatment outcome.

It is very important to record as much detail as possible regarding the patient's medical status in chronic pain clinical trials. This information should include past and present illnesses and injuries, especially any other chronic pain conditions, as well as past and present medical and nonmedical t reatments for these conditions. There is a consensus that chronic pain is a complex biopsychosocial phenomenon, and it is especially important in clinical trials to obtain information about past and present psychiatric disorders and treatments, especially mood and anxiety disorders, suicide, and substance and alcohol abuse. Such conditions may be considered exclusion criteria for a trial, and may also serve to moderate the effects of treatment [36].

Natural Pain Management

Natural Pain Management

Do You Suffer From Chronic Pain? Do You Feel Like You Might Be Addicted to Pain Killers For Life? Are You Trapped on a Merry-Go-Round of Escalating Pain Tolerance That Might Eventually Mean That No Pain Killer Treats Your Condition Anymore? Have you been prescribed pain killers with dangerous side effects?

Get My Free Ebook


Post a comment