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

Effect of an increase in brain serotonin on the osmoregulatory response to a hypo- or hyperosmotic load in Wistar and vasopressin-deficient Brattleboro rats

Serotonin and its receptor agonists stimulate the release of arginine vasopressin (AVP) into peripheral blood under intraventricular injection. To test the hypothesis that brain serotonin can modulate the development of natural osmoregulatory responses, the effect of an increase in endogenous brain serotonin on the response to an intragastric hypo- or hyperosmotic loading was studied in Wistar and AVP-deficient Brattleboro rats. 5-Hydroxytryptophan (5-HTP), the rate-limiting serotonin biosynthesis precursor known to increase the brain level of serotonin, was injected intraperitoneally (5 mg/100 g body weight). The renal functional parameters (glomerular filtration rate [GFR], free water reabsorption, and urine flow rate) were monitored during the 4 h after intragastric infusion of water or a 2% NaCl solution (5% of body weight). Plasma AVP was measured by radioimmunoassay. In Wistar rats, intraperitoneal injection of 5-HTP at the same time as water loading prevented the development of the renal diuretic response: there was no increase in urine flow rate and GFR, and free water reabsorption remained at the high level. In AVP-deficient Brattleboro rats, unlike Wistar rats, 5-HTP treatment was without effect on the renal function parameters. In Wistar rats, injection of 5-HTP at the peak of water diuresis produced an abrogation of the diuretic response to water loading due to the increase in free water reabsorption. Plasma AVP increased from 1.2 +/- 0.4 to 4.2 +/- 1.6 pg/ml (n = 8 in each group, p < 0.01). Hyperosmotic treatment of Wistar rats with a 2% NaCl solution stimulated AVP secretion compared to baseline (from 3.2 +/- 0.1, n = 7 to 5.6 +/- 0.9, n = 7, p < 0.01), and the saluretic response developed on the background of high free water reabsorption. When injected concomitantly with NaCl solution, 5-HTP revealed no additive effect on plasma AVP and on free water reabsorption. We conclude that the 5-HTP-caused increase in brain serotonin contributed significantly to the dynamics of changes in the osmoregulatory response to the hypo-osmotic challenge due to stimulation of AVP secretion. 5-HTP had no additive effect on the osmoregulatory response to hyperosmotic loading. Peripherally injected 5-HTP had no effect on the renal function, being absent in AVP-deficient Brattleboro rats.

A review on hyponatremia associated with SSRIs, reboxetine and venlafaxine

Hyponatremia, defined as serum sodium below 135 mmol/l, is a potentially life-threatening condition and was shown to be more frequent in elderly and psychiatric patients. In the last years numerous case reports on SSRI- and venlafaxine-induced hyponatremia were published indicating a higher incidence than previously thought. Only few studies have been performed and the incidence reported varies widely from 4.6/1000 people to 25%. It is still unclear if any single SSRI shows a higher incidence of hyponatremia than the others. Some data suggest that venlafaxine may have a stronger association to hyponatremia than SSRIs. Risk factors include age, female sex, low body mass index, severe physical illness, history of former hyponatremia and co-medications known to induce hyponatremia, especially thiazide diuretics. Symptoms of hyponatremia are usually neuropsychiatric (e.g. restlessness, lethargy, cognitive impairment), and any worsening in psychiatric symptoms in patients with a corresponding risk-profile receiving SSRIs or venlafaxine should give cause to check serum electrolytes. Usually SSRI-induced hyponatremia occurs within approximately 30 days and is reported to improve after withdrawal of the drug. Further controlled studies to confirm the true incidence of hyponatremia due to SSRI or venlafaxine and to define predictors more precisely are needed.

Hyponatraemia associated with psychotropic medications. A review of the literature and spontaneous reports

Psychotropic medication-induced hyponatraemia is an uncommon but important clinical problem with potential serious consequences if not recognised and treated early. Several risk factors have been associated with the development of hyponatraemia. This article reviews reported cases of hyponatraemia associated with the use of psychotropic medications and evaluates possible risk factors and causes. The data were sourced by a search of Medline for reports of hyponatraemia associated with the use of psychotropic medication between January 1966 and December 2000 and a search of US Food and Drug Administration (FDA) spontaneous reporting system database between January 1966 and December 1999. All the reports were included in this review. In the case reports the following data were assessed: age, gender, daily dosage, days to onset, days to recovery, medical condition, concurrent medications. Several risk factors were identified: advanced age, female gender, use of other medications, medical comorbidity. The risk of hyponatraemia was found to be higher during the first 2 weeks of treatment. Administration of the dosage of the drug was not found to be related to the development of hyponatraemia. Hyponatraemia can cause confusion, agitation and lethargy. Any change in the course of illness should alert the physician to the possibility of hyponatraemia.

Drug and ECT treatment of depression in the elderly, 1996-2001: a literature review

A computer-based literature search of all antidepressant and electroconvulsive therapy (ECT) treatment studies published between 1995 and September 2001 was conducted. In addition, a review of published chapters, review articles, and metaanalyses was also conducted. Articles were categorized into those reporting comparative studies, those in which the therapeutic agent was not compared with another, articles about ECT, and review articles. These recent publications support the conclusions from prior reviews that antidepressants and ECT are effective and safe treatments for depressed elderly patients. Differences in efficacy and side effects appear to be slight among the various types of antidepressants. Research studies of depressed elderly increased markedly since 1995 compared with all previous years although more studies are still necessary.