Paroxetine-induced SIADH

Selective Serotonin Reuptake Inhibitor-Induced Hyponatremia and the Plastic Surgery Patient

Cosmetic plastic surgery procedures continue to increase in frequency, and a greater number of them now occur outside of an acute-care hospital setting. In addition, antidepressant use is also rising, with a greater number of patients taking selective serotonin reuptake inhibitors to aid in a variety of mood and anxiety disorders. Americans spend more than $86 billion each year on antidepressants, as 34 million people in the United States are taking at least one of these medications. Many side effects of selective serotonin reuptake inhibitors are well known and not clinically relevant to practicing surgeons. Hyponatremia, however, is a well-documented side effect of these medications that has received relatively little attention in the surgical literature. Postoperative hyponatremia results because of a decrease of antidiuretic hormone suppression that occurs with selective serotonin reuptake inhibitor administration. Here, the authors first review the literature reporting hyponatremia with selective serotonin reuptake inhibitor use. The authors then present two cases of severe postoperative hyponatremia after plastic surgery operations. The authors propose that patients using selective serotonin reuptake inhibitors, especially elderly patients and those undergoing procedures with expected large fluid shifts, should be tested preoperatively and postoperatively for serum sodium levels so that a diagnosis of hyponatremia may be made early and treated before a catastrophic event.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

[Paroxetine-induced hyponatremia in an elderly man due to the syndrome of inappropriate secretion of antidiuretic hormone]

We report an 82-year old man prescribed paroxetine who had hyponatremia and in whom the syndrome of inappropriate secretion of antidiuretic hormone was diagnosed. He had taken sulpiride for depressed mental status. However, he showed parkinsonism, which was an adverse effect from the treatment of sulpiride. Therefore sulpiride was changed to selective serotonin reuptake inhibitor, paroxetine 10mg daily. His depressed mental status deteriorated after paroxetine treatment started. His depression had not lessened after 12 days, and the dosage was increased to 20mg daily. On the 15th day after starting paroxetine, routine laboratory tests showed that his serum sodium level was 126 mEq/l. We recognized that his confusion and loss of appetite were symptoms of hyponatremia, rather than of worsening depression. Laboratory data revealed hyponatremia, low serum osmolarity (242 mOsm/kg) with a relatively high level of serum antidiuretic hormone, and concentrated urine (439 mOsm/kg). We diagnosed the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), associated with paroxetine. The dosage of paroxetine was reduced gradually and the serum sodium level returned to normal on day 2 after medication ceased completely. Paroxetine produces fewer adverse effects than other types of antidepressants. However, its use can be associated with inappropriate secretion of antidiuretic hormone in the body and may lead to SIADH, which is characterized by hyponatremia, a potentially fatal condition that is typically asymptomatic until it becomes severe. SIADH is more likely in some populations, including the elderly. Serum sodium levels should be monitored closely, especially in elderly patients.

Hyponatremia associated with selective serotonin-reuptake inhibitors in older adults

OBJECTIVE

To review the incidence, risk factors, mechanism, times of onset and resolution, and treatment of hyponatremia associated with selective serotonin-reuptake inhibitors (SSRIs).

DATA SOURCES

An English-language literature search was conducted using MEDLINE (1966-December 2005) using the search terms selective serotonin-reuptake inhibitor, hyponatremia, syndrome of inappropriate secretion of antidiuretic hormone, citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, and sertraline. Additional references were identified by reviewing bibliographies of articles retrieved.

STUDY SELECTION AND DATA EXTRACTION

Relevant data were extracted from published reports, letters, and studies of humans with hyponatremia and/or syndrome of inappropriate secretion of antidiuretic hormone (SIADH) secondary to SSRIs. All articles identified from data sources were reviewed for relevant information. Applicable information was included in this review.

DATA SYNTHESIS

Numerous case reports, observational studies, and case-controlled studies, as well as one prospective clinical trial, have reported hyponatremia associated with SSRI use, with the incidence varying from 0.5% to 32%. Risk factors for the development of hyponatremia with SSRIs include older age, female gender, concomitant use of diuretics, low body weight, and lower baseline serum sodium concentration. In published reports, hyponatremia developed within the first few weeks of treatment and resolved within 2 weeks after therapy was discontinued. The mechanism by which SSRIs cause hyponatremia is thought to be secondary to development of SIADH. Treatment of isovolemia hypotonic hyponatremia associated with SSRI use includes water restriction and mild diuresis with a loop diuretic. More severe cases may be treated with higher doses of loop diuretics and hypertonic saline. There have been few reports of rechallenge with the same or another SSRI or substitution of another agent from a different therapeutic class. In some, but not all, cases hyponatremia recurred.

CONCLUSIONS

Practitioners should be on the alert for this potentially life-threatening adverse event, especially in older adults with other risk factors for developing hyponatremia.

Hyponatraemia and selective serotonin re-uptake inhibitors in elderly patients

Hyponatraemia (serum sodium arbitrarily defined as less than 135 mmol/L) is an increasingly recognised adverse effect of selective serotonin re-uptake inhibitors (SSRIs). Its precise prevalence and incidence in the elderly are hard to determine because of confounding factors including other prescribed medications and medical conditions. Although hyponatraemia has been reported with all SSRIs and venlafaxine, most studies are small, retrospective, limited by confounding variables or are individual case reports. The risk of developing hyponatraemia while on an SSRI seems to increase with age, female, sex, previous history of hyponatraemia and the concomitant use of other medications known to include hyponatraemia. The sodium concentrations of most patients with SSRI associated hyponatraemia return to normal within days to weeks of SSRI withdrawal. A few cases of SSRI rechallenge indicate that hyponatraemia may sometimes be a transient effect with tolerance developing over time. There is an urgent need for controlled, rigorous studies to confirm the extent of the association between SSRIs and hyponatraemia. Older drugs such as tricyclic antidepressants also need systematic study. It remains quite unclear whether any specific SSRI or venlafaxine has a stronger association with hyponatraemia than any other antidepressant drug.

Effect of paroxetine on plasma vasopressin and water load testing in elderly individuals

Hyponatremia sometimes occurs in elderly depressed patients treated wtih a serotonin reuptake inhibitor (SRI). The cause of the hyponatremia is not yet understood. The objective of this study was to determine the effects of paroxetine, an SRI, on osmoregulated release of vasopressin (also termed antidiuretic hormone) in elderly depressed patients with normal serum sodium. Four women and one man ages 61 to 74 years with a major depressive disorder were administered a water load after they had been treated with a therapeutic dose of paroxetine for 3 to 11 months. Three healthy elderly subjects not receiving paroxetine served as controls. Both the patients and the control subjects excreted > 90% of the ingested water and lowered urine osmolality to < 100 mosmol/kg. We conclude that long-term treatment with paroxetine alone does not appear to affect the ability to excrete a water load or appropriately dilute the urine during a water load (both indices of vasopressin function) in a small group of elderly patients without other risk factors for the development of hyponatremia.

Selective serotonin reuptake inhibitors and hyponatraemia: review and proposed mechanisms in the elderly

The association between selective serotonin reuptake inhibitors (SSRIs) and hyponatraemia has been well documented, the elderly appearing to be at greatest risk. An analysis of data of hyponatraemia in the elderly using SSRIs from all published cases and from the Committee on Safety of Medicines found that the mean time to detection was about 3 weeks after commencing SSRIs. A wide range of time to detection (1-253 days) and non-specific symptoms suggest hyponatraemia is detected by chance rather than being specifically looked for. In the elderly there are physiological changes, a high prevalence of medical illnesses and concomitant drug use, which may precipitate hyponatraemia. Together with a risk of altered water regulation in psychiatric illness this may account for the particular susceptibility of the elderly to hyponatraemia whilst using SSRIs.

Hyponatraemia associated with the use of selective serotonin re-uptake inhibitors

OBJECTIVE

The aim of this study is to examine the frequency and severity of hyponatraemia in a psychogeriatric inpatient population taking selective serotonin re-uptake inhibitors (SSRIs).

METHOD

Casenotes for 1 year were reviewed and 53 patients with 55 admissions were identified. Eighteen were treated with fluoxetine and 37 with paroxetine. Five (28%) of the patients on fluoxetine and eight (22%) on paroxetine were, or became, hyponatraemic.

RESULTS

The SSRI was discontinued in two symptomatic patients. Serum sodium returned to normal in nine patients maintained on the SSRI. Two patients maintained on an SSRI remained hyponatraemic but asymptomatic.

CONCLUSIONS

Hyponatraemia may be a relatively common early asymptomatic side effect of SSRIs, especially in older women. Serum sodium should be measured before commencing an SSRI and monitored during the first month. Any patient who exhibits symptoms of hyponatraemia, or whose depression apparently worsens, while on an SSRI must have their serum sodium measured. Discontinuation of the SSRI may be avoidable if serum sodium levels can be closely monitored.