What Doesn't Work for Renal Colic

Written by Thomas Davis

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Neither IV magnesium nor intranasal desmopressin provided any additional pain relief when used as an adjunct to NSAIDs for renal colic.

Why does this matter?
Ureteral stones hurt. They irritate the ureter and cause increased ureteral pressure that leads to prostaglandin release. Prostaglandin increases renal perfusion and subsequently increases urine production, further raising ureteral pressure. NSAIDs break this cycle by inhibiting prostaglandin production, which may be why NSAIDs are so effective in renal colic. What if this cycle can be blocked at a different point by using an antidiuretic such as desmopressin? Or what if the pain pathway can be blocked at other sites, such as at the NMDA receptor using magnesium, which has been shown to be beneficial in peri-operative pain.

“Doctor, now which medicine goes up the butt, up the nose, and in the IV?”
The first double-blind RCT compared intranasal desmopressin (40 mcg) to placebo. All 124 patients in the study received standard care, which in this Iranian study was indomethacin 100mg via rectal suppository. Renal colic was diagnosed using clinician judgment, which severely limits the study.  Using a visual analog pain scale, both arms of the study found significantly reduced pain (p < 0.001) but no difference between treatment arms (p = 0.35). Additionally, there was no significant difference in need for morphine for rescue analgesia.

The second double-blind RCT was also an Iranian study that evaluated the efficacy of magnesium 50mg/kg IV as an adjunct therapy to ketorolac 30mg IV in 87 patients. All patients had renal colic diagnosed using CT or ultrasound. Similar to the aforementioned study, both treatment arms had a significant reduction in pain at 30 minutes using a visual analog scale. However, there was no statistical difference in pain between the two arms (p = 0.23).

Sources

Reviewed by Clay Smith

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