2018 Volume 34 Issue 4 Pages 467-470
A 79–year–old man with Parkinson's disease was admitted to our hospital for drug adjustment. He had been on medication for the disease for 8 years. He showed worsening orthostatic hypotension. Droxidopa was increased from 300 to 900mg/day, and pramipexole was decreased from 2.25 to 1.5mg/day. He subsequently showed improved orthostatic hypotension. However, he developed worsening hyponatremia (126mEq/L) after drug adjustment. He received a diagnosis of syndrome of inappropriate secretion of anti–diuretic hormone (SIADH) due to the low serum osmolarity, high urine osmolarity, and high level of ADH. He showed no improvement of hyponatremia on water intake restriction. Pramipexole 1.5mg/day was changed to rotigotine 13.5mg/day because of the diagnosis of pramipexole–induced SIADH. Thereafter hyponatremia improved and did not recur. Pramipexole–induced SIADH is rare ; however, we must be careful to avoid hyponatremia when pramipexole is administered to Parkinson's disease patients.
