INTRODUCTION
As an efficacious selective serotonin reuptake inhibitor (SSRI) paroxetine is widely used for the treatment of numerous psychiatric disorders including generalized anxiety disorder, post-traumatic stress disorder, depression, obsessive-compulsive disorder and panic disorder among others.1 Among other groups of antidepressants; SSRIs, SNRIs and mirtazapine are more likely to cause hyponatremia in older adults.
Paroxetine has been shown to be more effective in the treatment of depression with least anticholinergic adverse effects compared to tricyclic antidepressants (TCA). 3 The pharmacokinetics of paroxetine differ widely among different individual groups; conclusively slower elimination has been noted in the elderly with increased plasma concentrations. It has an elimination half-life of 21 hours and a variable dosing duration that is dependent upon indication. 1
The mechanism of SSRIs which causes hyponatremia is believed to be concomitant to that of the development of syndrome of inappropriate antidiuretic hormone secretion (SIADH). The groups of population at a higher risk for developing hyponatremia with SSRIs involve the people with lower serum sodium concentrations, the elderly, female gender and reduced body weight. 4
It has been established that there is a major link between treatment with SSRIs and hospitalizations due to hyponatremia. However, this risk decreases when TCAs or mirtazapine is used. 5 Antidepressants shown not to cause hyponatremia include; amoxapine, dosulepine, doxepine, trimipramine, iproniazide. 6
Despite the effectiveness of paroxetine, a significant link to its chronic use (about 10 years) and hyponatremia has not yet been established. Studies have been conducted and have shown to indicate incidence of hyponatremia in elderly patients taking antidepressants, nevertheless; there is a lack of evidence linking the chronic use of SSRIs with hyponatremia in middle age group people.