Passing kidney stones could become faster and less painful with a new two-drug combination that’s delivered directly to the source of the discomfort, say researchers from the Massachusetts Institute of Technology and Massachusetts General Hospital. 

When kidney stones are passed on their own, their movement through the ureter (the tube that connects the kidneys to the bladder) can be excruciating. In a new study in pigs, two commonly used drugs injected into the ureter helped relax the organ and reduce the frequency and length of painful contractions during the stone-passing process, reported senior author Michael Cima, Ph.D., of MIT. 

One of the drugs is nifedipine, a calcium channel blocker used to treat high blood pressure, while the other is known as a ROCK (rho kinase) inhibitor, typically used to treat glaucoma. 

The treatment could also make it easier and less painful to insert stents into the ureter, Cima and colleagues theorize. This is sometimes done after a kidney stone is passed, to prevent the tube from collapsing.

“If you look at how kidney stones are treated today, it hasn’t really changed since about 1980, and there’s a pretty substantial amount of evidence that the drugs given don’t work very well,” said lead author Christopher Lee, Ph.D. “The volume of how many people this could potentially help is really exciting.”

The researchers have launched a startup company, Fluidity Medicine, with the goal of  testing the treatment in human patients.

Currently, kidney stones that can’t or won’t come out on their own may be broken up using ultrasound therapy, or surgically removed. Certain types of stones can be dissolved using alkaline citrate salts, sodium bicarbonate or the gout medication allopurinol, according to the National Center for Biotechnology Information.

The research was published in the journal Nature Biomedical Engineering.