The Problem with Trying to Study Drug Treatment for Back PainGetting a handle on what kind of pain medications work best for back pain is not an easy task. There are just so many variables to consider and compare. Does the patient have back and leg pain or just back pain? Does the patient take the prescribed drug for four weeks? Six weeks? Longer?
Researchers try to look at all the studies and combine results for a better understanding of effects. But according to pain research done in Europe, the design of each study isn't similar enough to really allow such a meta-analysis. For example, sometimes patients are given drug combinations rather than a single drug. The dosage might be increased until it reaches a point where it's effective and the side effects are tolerable or patients may be given the same dose from day one.
There are other confounding factors. Patients may stop taking the drug and withdraw from the study for any number of reasons. It could be they experienced no pain relief or there might have been unpleasant side effects, so the patient(s) quit taking the medication.
When the patient stops taking the drug but remains in the study, it is referred to as discontinuation. When the patient stops taking the drug and no longer participates in follow-up, the missing data falls under the category of withdrawal.
Classic studies include patients who are really receiving the medication while others get a placebo (sugar pill with no active ingredients). A review of the results of classic design trials showed a range of discontinuations or withdrawals that were similar between active medication and placebo groups. And there is evidence that some people keep taking the drug and staying in the studies even though they didn't get a useful level of pain relief.
Once the data is all collected, the way in which it is analyzed is important. Lack of proper statistical analysis can result in poor-quality information that can't be used in combination with other studies. The way patient outcomes are defined from study to study can be a real challenge. Some researchers use 30 per cent reduction in pain as the success point. This is not a standard cut-off value, so again, not all studies can be compared because of differences like this.
In general, research to study pain relieving medications given for more than six weeks as the primary treatment for chronic low back pain is very limited. Good research design, valid trials, and successfully capturing the effects of each drug treatment are all problem areas in this type of research. Studies that only report that the drug worked but nothing else make it difficult to compare between this drug and that drug.
The authors of this research review offer several suggestions for improving research in the area of pain relievers for chronic low back pain. They make these suggestions after reviewing all the trials reported and carefully studying 14 randomised double-blind trials of good quality. Patients were all followed for at least six weeks. Medications included common narcotics and antidepressants used in pain control.
First, the diagnosis for each patient must be clear and reported consistently. This is crucial when including patients who have back pain only versus back and leg pain because the two groups may respond differently to the treatment under study.
Next, the way success is reported must be consistent across all studies. Is 30 per cent pain reduction enough to be considered successful? More? Less? A standard cut-off point would make it possible to compare the results of one study to another.
And finally, assessment of pain reduction should include how the change in pain has affected the patients. Questionnaires should be completed before and after treatment in order to assess the effect of pain (and then pain relief) on return-to-work, quality of life, and function in daily activities. Other areas of study could also be included such as how much the treatment costs and which method is most cost-effective.
R. Andrew Moore, et al. Chronic Low Back Pain Analgesic Studies -- A Methodological Minefield. In PAIN. June 2010. Vol. 149. No. 3. Pp. 431-434.
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