Letter: Diuretics during lithium therapy

Lithium side effects and toxicity: prevalence and management strategies

Despite its virtually universal acceptance as the gold standard in treating bipolar disorder, prescription rates for lithium have been decreasing recently. Although this observation is multifactorial, one obvious potential contributor is the side effect and toxicity burden associated with lithium. Additionally, side effect concerns assuredly play some role in lithium nonadherence. This paper summarizes the knowledge base on side effects and toxicity and suggests optimal management of these problems. Thirst and excessive urination, nausea and diarrhea and tremor are rather common side effects that are typically no more than annoying even though they are rather prevalent. A simple set of management strategies that involve the timing of the lithium dose, minimizing lithium levels within the therapeutic range and, in some situations, the prescription of side effect antidotes will minimize the side effect burden for patients. In contrast, weight gain and cognitive impairment from lithium tend to be more distressing to patients, more difficult to manage and more likely to be associated with lithium nonadherence. Lithium has adverse effects on the kidneys, thyroid gland and parathyroid glands, necessitating monitoring of these organ functions through periodic blood tests. In most cases, lithium-associated renal effects are relatively mild. A small but measurable percentage of lithium-treated patients will show progressive renal impairment. Infrequently, lithium will need to be discontinued because of the progressive renal insufficiency. Lithium-induced hypothyroidism is relatively common but easily diagnosed and treated. Hyperparathyroidism from lithium is a relatively more recently recognized phenomenon.

Assessment and treatment of bipolar disorder in the elderly

The aetiology of late-onset bipolar disorder is heterogeneous because the disease is more likely to have a secondary (i.e. a medical disorder or medication-induced) cause in older than in younger patients. Elderly patients with bipolar disorder typically require lithium dosages that are 25 to 50% lower than those used in younger individuals. Information on the use of valproic acid (sodium valproate) in elderly patients with bipolar disorder is limited but encouraging. In contrast, there is virtually no information regarding the use of carbamazepine or other drugs in this patient group. Electroconvulsive therapy is well tolerated by older people and can be useful for these patients.

Effect of chronic oral furosemide administration on the 24-hour cycle of lithium clearance and electrolyte excretion in humans

The effect of chronic furosemide treatment on the circadian cycle of lithium clearance (CLLi) and electrolyte excretion has been examined in 8 young, male volunteers, by performing two 24 h clearance experiments, before and after one week of treatment with furosemide 80 mg once daily. After 8 days on furosemide there was a significant decrease in creatinine clearance (-21%), plasma Na (-8.4 mM) and plasma K (-0.58 mM). At that time, however, there were no changes in 24 h-values of CLLi or Na excretion, although the magnitude of the circadian variation in CLLi and other renal parameters was increased. Both CLLi and CLNa were increased in the first 3 h following furosemide administration and thereafter they fell below the control level in the remaining hours of the experiment. From the absolute and fractional changes in CLLi it is suggested that compensatory Na conservation in response to chronic furosemide treatment occurs between doses, and that it involves decreased output from the proximal tubules combined with increased fractional Na reabsorption in the distal nephron.

Frusemide: a safe diuretic during lithium therapy?

This paper reports the effect of frusemide given in therapeutic doses for hypertension in patients receiving prophylactic lithium for affective disorders. It was found that frusemide had no significant effect on plasma lithium concentration in these patients who were studied over a 12-week period. It was concluded that frusemide is a safe diuretic to administer to patients receiving lithium therapy.

Lithium's effects on the kidney

Although lithium was known to cause changes in renal physiology, it was considered safe until reports in late 1977 suggested that it may induce chronic irreversible nephropathy. Later reports documented similar lesions in non-lithium-treated patients with affective disturbances. Thus, the data are inconclusive. Concern for the kidney during lithium therapy is now greater than it was originally, but confidence in lithium's safety is higher than it has been for the past four years. Physician appreciation of the foregoing factors, careful patient selection, and informed consent are important in lithium therapy. An understanding of lithium use in patients in a low-sodium state or on diuretic therapy and avoidance and treatment of lithium intoxication are advocated. Good prelithium workups and closer monitoring of patients on long-term lithium therapy are recommended.