The regulation of serum sodium after replacing carbamazepine with oxcarbazepine.
OBJECTIVE
To evaluate changes in serum electrolyte balance and underlying regulatory mechanisms in 10 male patients with epilepsy 2 and 6 months after replacing long-term carbamazepine (CBZ) monotherapy with oxcarbazepine (OCBZ) monotherapy. Arginine vasopressin (AVP) is thought to be most important underlying mechanism of CBZ-related hyponatremia via direct or kidney tubular mechanisms. Furthermore, AVP is as well hormonally regulated by the renin-angiotensin-aldosterone system and atrial natriuretic peptide (ANP).


METHODS
The medication of the patients was changed from CBZ to OCBZ. Serum electrolytes, creatinine, albumin, aldosterone, and the N-terminal fragment of ANP (NT-proANP) concentrations were measured before and 2 and 6 months after the change in the medication.


RESULTS
The mean serum sodium level diminished after the medication was changed. Serum sodium levels decreased below the reference range in two (20%) patients during OCBZ medication. Serum sodium levels decreased altogether in four patients, and remained unaltered in six patients. Serum aldosterone levels increased in the six patients whose serum sodium concentrations did not decrease, but no increase was found in the patients with decreased sodium levels during OCBZ medication. Serum NT-proANP levels decreased in all patients.


CONCLUSIONS
Serum sodium levels decrease after replacing CBZ with OCBZ. The low serum NT-proANP concentrations appear to reflect the decreased serum sodium levels, but a compensatory aldosterone response may prevent the development of hyponatremia in some patients during OCBZ medication.
Isojärvi
J I
JI
Department of Neurology, University of Oulu, FIN-90220 Oulu, Finland.
Huuskonen
U E
UE
Pakarinen
A J
AJ
Vuolteenaho
O
O
Myllylä
V V
VV
D000328:Adult; D000450:Aldosterone / Q000097:blood / Q000502:physiology; D000927:Anticonvulsants / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D002220:Carbamazepine / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives / Q000627:therapeutic use*; D003404:Creatinine / Q000097:blood; D004827:Epilepsy / Q000097:blood* / Q000188:drug therapy*; D006801:Humans; D007010:Hyponatremia / Q000097:blood / Q000139:chemically induced; D008297:Male; D020097:Natriuretic Peptide, Brain; D009419:Nerve Tissue Proteins / Q000097:blood / Q000502:physiology; D000078330:Oxcarbazepine; D010446:Peptide Fragments / Q000097:blood / Q000502:physiology; D011188:Potassium / Q000097:blood; D011446:Prospective Studies; D012709:Serum Albumin / Q000032:analysis; D012964:Sodium / Q000097:blood*; D014882:Water-Electrolyte Balance / Q000502:physiology
D000927:Anticonvulsants; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D012709:Serum Albumin; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain; D002220:Carbamazepine; D000450:Aldosterone; D012964:Sodium; D003404:Creatinine; D011188:Potassium; D000078330:Oxcarbazepine