BERKELEY, CA (UroToday.com) - Results from this systematic review demonstrate evidence for a higher stone expulsion rate and a reduced time to stone expulsion using α-blocker or calcium channel blockers compared to a standard therapy or placebo control group. Of nine α-blocker trials investigating stone expulsion with mean stone sizes <5 mm, only four studies demonstrated a significantly higher expulsion rate in the treatment group. In contrast, regarding α-blocker trials with stone sizes ≥5 mm, 19 of 20 studies demonstrated a significant benefit in stone expulsion rates mirrored by an increase of the ARR from 0.15 to 0.31. Results might indicate that with decreasing stone size, an additional benefit for medical expulsive therapy is less likely because of the high spontaneous expulsion rate.

Most studies were predominantly small, conducted in single institutions. The vast majority of randomised studies incorporated into the present systematic review is not blinded, with an inadequately or unclear allocation concealment leading to a tendency towards overestimating the effectiveness of treatment effects.

Heterogeneity within selected studies complicates integration. Clinical heterogeneity was expected, including trials using different drugs with the same class effect, different doses, or different formulations. Additional factors possibly increasing heterogeneity between studies were the difference in time intervals from a colic episode to initiation of Medical Expulsive Therapy (MET), the combination of blinded and nonblinded trials, insufficient or unclear allocation concealment, different durations of MET, and different follow-up periods defining treatment success or failure.

Moderate heterogeneity was detected, questioning whether it is appropriate to pool the results. However, excluding two studies in with unusually low stone expulsion rates in the control group or excluding one study with excellent overall stone-free rates after SWL eliminated heterogeneity while maintaining RRs.

The adjunctive usage of various medications for MET theoretically could have an influential effect on treatment outcomes in either overestimation or underestimation of treatment effects. The treatment effect of tamsulosin or nifedipine could be overestimated because of a suspected synergistic effect of corticosteroids on stone expulsion. However, standard treatments were accepted as control groups because an influential effect on stone expulsion for neither regimen has been demonstrated so far.

Although the level of evidence for MET is high, the lack of multicentre, randomised, placebo-controlled studies with larger numbers of patients possibly results in an enhancement of the expulsive properties of the tested drugs. Therefore, high-quality trials are needed to confirm the results obtained in this systematic review.