Recently, my 11months son has been detected with high level of blood sodium 169. Further, it has been diagnosed as Diabetic insipidus and said to treat it on priority. With this, the doctors have started the medication (in ICU) assuming it as central diabetic insipidus. As the drugs have not responded, they changed the drug (hydrochlorothiazide) and conformed it as Nephrogenic diabetic insipidus. Now, the blood sodium level is around 140 and they said to continue the tablet regularly (with periodic monitoring).
My question is, contiuing the tablet lifelong is the only medication or is there any other treatment to make it all right at once. In case of, continuous usage of hydrochlorothiazide, what would be the side effects?

Expecting your answers.