Is lithium induced weight gain a dose-dependant side effect?

Fråga: Is lithium induced weight gain a dose-dependant side effect?

Sammanfattning: The mechanisms underlying lithium-induced weight gain are poorly understood and there is only anecdotal evidence that the weight increase is a dose-dependant adverse effect.

Svar: Weight gain increases the risk of lithium regimen noncompliance, and it has been cited as one of the primary reasons patients stop taking the drug (1).

The effects of lithium on body weight have been summarised in a recent review article (2). In two placebo-controlled randomised trials, lithium treatment for one year caused significant increases in body weight. In one of these (n=21), the mean weight gain in lithium treated patients was four kg, compared to one kg in the placebo group. In the second study (n=90), a weight gain of more than 5 percent from baseline was seen in 13 percent of the lithium treated patients, compared to 7 percent of those receiving placebo. Still larger weight increases were observed in eight un-controlled lithium studies with follow-up times of one to 17 years (2).

The mechanisms underlying lithium-induced weight gain are poorly understood. Proposed mechanisms include appetite-stimulating actions in the hypothalamus, insulin-like effects leading to increased glucose absorption into adipocytes, water retention and increased intake of carbohydrate-rich beverages due to lithium-induced thirst. Furthermore, a high comorbidity with mood disorders and obesity/eating disorders complicate the task of understanding lithium´s effects on the body weight (1,2,3).

The only published data allegedly speaking in favour of lithium-induced weight gain being a dose-dependant side effect is an open-label study in ten patients (4). Following a lithium dose reduction resulting in a mean plasma concentration of 0.7 mmol/L, weight loss was noted in one of the ten patients and a lithium-induced oedema resolved in another. Obviously, this study had not enough power to differentiate between actual dose-reduction effects and chance findings.