Kidney stones are a common health problem that, although they can be controlled, can cause very painful pain. Now, researchers at the Massachusetts Institute of Technology have discovered a special combination of two drugs that can relax the urethra tube and make it easier for stones to pass through.
Kidney stones are crystalline substances formed in the kidneys. They usually only drain themselves, but the experience is far from pleasant – when they move through the ureter, they cause severe pain. So for the new study, scientists set out to study whether delivering muscle relaxants directly to the ureter could reduce the pain of the stones. To do this, they first tested 18 different drugs on human ureter cells grown in laboratory petri dishes and measured the effect of each drug on muscle relaxation.
After extensive searches and analysis, they found that two drugs were particularly effective: nitrobenzene (currently used to treat hypertension) and rho kinase inhibitors (for the treatment of glaucoma). And the two drugs work better together.
The scientists used the combination of the drug to test the ureter removed from the pig and found that they could reduce the number and length of contractions in the ureter. When the ureter presses toward the hard stone inside, it is these contractions that cause pain. They then tested the live pig and injected it directly into the ureter through a cystoscopy. These experiments showsimilar results, almost completely eliminating contraction.
Importantly, when the drug was given directly in this way, the researchers did not find any drugs in the pig’s blood. This means that they spend most of their time in the vicinity where they need to be targeted, which should reduce the chance of any side effects in other parts of the body.
The team says more work needs to be done to determine whether it is safe to use humans, how long muscle relaxation lasts, and how long it takes to help kidney stones pass through. In addition to kidney stones, the technique can also be used for other similar operations, such as placing stents or using endoscopes.
The study was published in the journal Nature Biomedical Engineering.