A client has been on carbamazepine for 6 weeks. The nurse re… | MyMerci
Medical EmergenciesPA
Question
A client has been on carbamazepine for 6 weeks. The nurse reviews labs and notes serum sodium 126 mEq/L. What is the priority nursing action?
1Discontinue the medication immediately without contacting the provider
2Encourage 3 liters of free water intake to dilute the medication
3Administer a hypotonic saline infusion
4Withhold the next dose and notify the provider — carbamazepine-induced SIADH should be evaluated✓ Correct answer
Explanation
Correct (1): Carbamazepine can cause SIADH (syndrome of inappropriate antidiuretic hormone) — water retention and dilutional hyponatremia. At Na 126 with neurologic symptoms, hold the dose and notify the provider for evaluation (further fluid restriction, possible drug change, careful sodium correction). (2) More free water worsens hyponatremia. (3) Hypotonic fluid worsens it further. (4) Abrupt discontinuation requires provider order to avoid seizure rebound.
In-depth explanation
Memory Tip Carbamazepine = "Crystals lock in water" → SIADH·hyponatremia. CPG Check baseline and periodic sodium during carbamazepine therapy; risk highest in elderly and women.
Clinical scenario
Scenario 58-year-old male on carbamazepine 400 mg PO BID × 6 weeks reports headache, mild confusion, and decreased urine output. Serum sodium 126 mEq/L (low).
Key concepts
SIADH — Excess ADH secretion causing water retention, dilutional hyponatremia, and concentrated urine despite low serum osmolality.
Dilutional hyponatremia — Low serum sodium from water excess rather than sodium loss; treatment is fluid restriction.
Carbamazepine adverse effects — SIADH, agranulocytosis, hepatotoxicity, SJS, and CYP3A4 autoinduction — all require monitoring.