Ranirestat is primarily used in the treatment of diabetic neuropathy, a common complication of diabetes that affects the nerves. It works by inhibiting the enzyme aldose reductase, which plays a key role in the pathway that leads to nerve damage in diabetic patients. By blocking this enzyme, ranirestat helps to reduce the accumulation of sorbitol in nerve cells, thereby alleviating symptoms such as pain, numbness, and tingling in the extremities. This makes it a valuable therapeutic option for improving the quality of life for individuals suffering from diabetic neuropathy.