SIADH and Risperidone

[wolfvgang22]

I have an outpatient over 60 with schizophrenia who has had suspected SIADH associated with Risperidone. Polydipsia is not present. Hyponatremia improved with reduction in Risperidone from 5mg daily to 2mg daily, but unfortunately paranoid delusions and auditory hallucinations that were controlled on 5mg returned. Does anyone have experience with SIADH and atypical antipsychotics? A review of the literature has not been helpful so far in differentiating one atypical antipsychotic with another.

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[icysky]

Just an intern but I did see a few of these presentations on the floor. Usually the patients were elderly and on multiple psych meds like SSRIs and not just antipsychotics. We consulted psych and they usually did a wash out of meds and then admitted them inpatient then did med changes. Can’t tell you what they did though, sorry.

 

[clozareal]

Did you get serum (low) and urine (high) osmolality and urine sodium (high)? I would also get serum creatinine to rule out renal insufficiency and TSH to rule out bad hypothyroidism as a cause of low serum osmolality.

How fast did you reduce the risperidone? Sometimes rebound psychosis can happen if you decrease it too fast. If it was quick, then maybe go back up and then titrate slower while at the same time recommending fluid restriction if the hyponatremia isn't too bad?