An 83-year-old woman with no known drug allergies or toxic habits.
Relevant personal history included hypertension and osteoporosis treated with amyloid in combination with hydrochlorothiazide and alendronate, respectively.
She was admitted to our hospital due to deterioration of her general condition, anorexia and progressive consciousness that began four days after her home, in which she suffered a fracture of the sacral slope and a fall of both.
During the physical examination, it was observed that the patient was afflicted with cutaneous manifestations.
The most characteristic laboratory findings were serum sodium levels 108 mEq/L (severe hyponatremia) that led to admission.
The first step was to suspend the diuretic treatment that the patient was taking at her home (self-medication and hydrochlorothiazide), without obtaining any change in sodium levels.
SIADH was suspected and treated with usual treatments to correct this alteration 4,5,6, starting with water restriction and isotonic saline.
Since no response was obtained, this treatment was stopped and tolvaptan was prescribed.
Treatment was initiated with 15 mg every 24 hours.
On the second day of treatment the patient developed renal failure and oliguria.
Because anuria is one of the contraindications for tolvaptan7, physicians decided to increase the dosing interval to 48 hours instead of stopping treatment.
This regimen was maintained for 15 days and because sodium levels decreased rather than increased, it returned to the initial 15 mg daily regimen.
The necessary tests were carried out to detect the possible cause of SIADH and to avoid any attributable cause it was decided to maintain long-term treatment for hyponatremia.
During conservative treatment with vasopressin receptors, serum sodium remained at mean levels of 129.67 mEq/L [127-132 mEq/L].
Based on this consideration and the literature review by the prescribing physician, the prescriber decided to discontinue tolvaptan treatment (the patient received a total of 14 doses of tolvaptan in 23 days) to request urea.
Acofarma®) with the appropriate dose for the patient (15 gr every 12 hours) to the mental health unit of our dementia service.
With this treatment a slight increase in serum sodium levels was observed, reaching a mean level of 134.25 mEq/L [132-136 mEq/L].
During admission, the patient received a total of 30 doses of urea for 15 days.
Upon stabilizing the sodium levels and improving the patient's symptoms, it was decided to discharge him maintaining the SIADH treatment with the dose of 15 g of urea every 12 hours in an indefinite manner, disagreeable in 50 ml.
This would be prepared and dispensed in the patient's reference pharmacy.
1.
Comment/discussion
In our clinical case, the use of urea as an alternative to tolvaptan in SIADH was an effective alternative, since it allowed obtaining the same result as tolvaptan in stabilizing serum sodium.
Furthermore, taking into account the direct cost of one dose of tolvaptan (66.92 euro) and urea (0.15 euro), it is also an efficient option, since with urea the cost is markedly lower.
The case described here presents urea as an alternative treatment with similar benefit and more economical than is currently used as a reference.
However, urea presents certain characteristics, such as the need for two daily doses and its bad organoleptic characteristics.
Tolvaptan, on the contrary, does not have these features.
The use of urea in the chronic treatment of SIADH of unknown origin could be an efficient alternative for this pathology.
