Reactions 864 - 11 Aug 2001

SCarbamazepine/levomepromazine

Syndrome of inappropriate antidiuretic hormonesecretion leading to hyponatraemia: case report

Syndrome of inappropriate antidiuretic hormone secretion(SIADH) leading to severe hyponatraemia occurred in a40-year-old man receiving treatment with levomepromazineand carbamazepine [duration of treatment not stated] after hevomited and drank a large quantity of water.

The man had a history of cerebral palsy, mental retardationand absence epilepsy and his treatment regimen consisted ofcarbamazepine 500 mg/day, levomepromazine 185 mg/day,biperiden, phenytoin, clonazepam and haloperidol. 30minutes after he had vomited and then consumedapproximately 6L of water over a 2-hour period, heexperienced 6 grand mal seizures. He was hospitalised 7 hourslater in an unresponsive state. Significant laboratoryparameters included serum sodium level 98 mEq/L, serumosmolality 213 mOsm/kg of water, serum cortisol level 30.1µg/dl (normal 2.7–15.5), urinary sodium level 47 mEq/L andurinary osmolality 398 mOsm/kg of water. He was diagnosedwith hypotonic hyponatraemia with concentrated urine due todrug-induced SIADH, vomiting and excessive waterconsumption. He experienced another 4 grand mal seizuresafter admission to hospital.

The man was treated with IV sodium chloride andfurosemide. Ten hours after admission his seizures stoppedand 6 hours later, his serum sodium level was 107 mEq/l. Hewas then given a weaker solution of IV sodium chloride and at30 hours postadmission, his serum sodium level had increasedto 117 mEq/L. He recovered with no further neurologicaleffects.

Author comment: ‘We should be aware that severehyponatremia may develop in patients treated with drugswhich can induce SIADH when further impairment of renalwater excretion or excessive water intake occursconcomitantly.’Matsumura M, et al. Severe hyponatremia in a patient treated withlevomepromazine and carbamazepine. Internal Medicine 40: 459, May 2001 -Japan 807206270

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Reactions 11 Aug 2001 No. 8640114-9954/10/0864-0001/$14.95 Adis © 2010 Springer International Publishing AG. All rights reserved