How do you manage polyuria and polydipsia from lithium?

My first step is to confirm that the symptoms, including polydipsia and polyuria, are due to NDI and not other reasons. Other potential causes that should be excluded are:

• Psychogenic polydipsia
• other substance-induced, such as caffeine, diuretics
• primary DM
• pituitary related
• CKD

Lowering the dose might help, if possible, by discontinuing Li. If not possible, adjunctive medications to help with this SE are used.

I have also found that switching the Li immediate release to extended release has helped, such that patients do not have to wake up at night to urinate. These cases are not Li-induced NDI, but simply have polyuria due to Li.

Amiloride 5 mg will do the trick for most patients. Make sure you are around 0.75, using IR Li, all at night.