sentences:  Glucose concentrations are often elevated in diabetics and aldose reductase has long been believed to be responsible for diabetic complications involving a number of organs.Many aldose reductase inhibitors have been developed as drug candidates but virtually all have failed although some such as epalrestat are commercially available in several countries.Additional reductase inhibitors such as ranirestat, ponalrestat, rinalrestat, risarestat, sorbinil, and berberine are currently in clinical trials.