Lithium can cause a variety of side effects.The ones that are specific to the kidneys are Nephrogenic Diabetes insipidus. It is a problem related to ADH receptor resistance with normal ADH levels and is characterized by polyuria,polydipsia with a high serum osmolality and decreased Urine osmolality. One of the explanations for lithium to cause nephrogenic Diabetes insipidus is due to its ability to inhibit the Epithelial Sodium channels present in the Collecting Ducts of the Nephrons.
This toxicity of lithium can be managed with hydration that is First line. Drugs that increase lithium levels in the blood should be avoided such as Thiazides,calcium channel blockers and NSAIDs. Thiazides are used to treat NDI but need to be avoided if the NDI is due to lithium,hence,hydration is the first line treatment.