CAVEATS: Is either drug better? Too little data to tell
Our conclusion is that the strengths of this meta-analysis outweigh the weaknesses, the findings across studies are consistent, and the use of smooth-muscle relaxants for this indication makes sense from a mechanistic point of view.
The quality of a meta-analysis is only as good as the quality of the included studies, and, in this case, the overall quality of studies was not uniformly high. Median Jadad score, a summary measure of study quality, was 2, and the highest score was 3 (of a maximum of 5). The most common problem was lack of blinding, which can be critical in studies with subjective outcomes such as pain. We doubt that the lack of blinding led to any significant misclassification of outcome in this study, however.
Patients either passed the stone or they didn’t, or had a surgical intervention or not. It is reassuring that, when the best quality studies (Jadad score= 3) were analyzed separately, the results were equally good.
There have not been sufficient head-to-head trials to know if one is better than the other. We prefer α-antagonists because of the lower apparent side-effect profile. Our analysis of the UHC data shows that most of the physicians who are using medical therapy are using tamsulosin primarily for this diagnosis.
The majority of the patients in the studies included in the meta-analysis had been referred to a urologist. This raises the possibility that this treatment may not be as effective in patients with less severe symptoms for whom urological consultation is not necessary.
CHALLENGES TO IMPLEMENTATION: This change should be easy to put into practice
Tamsulosin is the best studied of the drugs, but also the most expensive. Based on the estimated number need to treat (NNT) of between 3 and 4 to prevent a surgical intervention and an estimated cost of around $90 for 1 month (www. drugstore.com, February 16, 2008), tamsulosin seems like a good investment to avoid surgical intervention.
The evidence for the other α-antagonists is consistent with that of tamsulosin, but there are fewer data, so it is not clear that the other agents will work as well.
Many people with renal colic are diagnosed and treated in the emergency department; they may not see their family physician until some time after the stone is diagnosed. It is unclear what effect this delay might have on medication effectiveness.
Neither tamsulosin nor nifedipine have an FDA indication for ureterolithiasis. However, they are prescribed commonly, and most physicians are familiar with their use and adverse-effect profiles.
Drugs used in the meta-analysis studies
α-Antagonists
Tamsulosin (Flomax)
Terazosin (Hytrin)
Doxazosin (Cardura)
Calcium channel blockers
Nifedipine (Adalat, Nifedical, Procardia)
Acknowledgement
We acknowledge Sofia Medvedev, PhD of the University HealthSystem Consortium (UHC) in Oak Brook, IL for analysis of the UHC Clinical Database and the National Ambulatory Medical Care Survey data.
PURLs methodology
This study was selected and evaluated using FPIN’s Priority Updates from the Research Literature (PURL) Surveillance System methodology. The criteria and findings leading to the selection of this study as a PURL can be accessed at www.jfponline.com/purls.
