Cilastatin is primarily used in clinical medicine to enhance the effectiveness of the antibiotic imipenem. It works by inhibiting the enzyme dehydropeptidase in the kidneys, which would otherwise break down imipenem before it can exert its full antibacterial effect. By blocking this degradation, cilastatin prolongs the active life of imipenem in the body, allowing for lower doses and reduced risk of kidney toxicity. It is not used as a standalone antimicrobial agent but is always co-administered with imipenem in the treatment of severe infections such as those in the abdomen, lungs, urinary tract, and bloodstream, especially when caused by multidrug-resistant bacteria. Its role is purely protective and supportive, ensuring that imipenem reaches its target sites in sufficient concentrations to be effective.