Among drugs which cause weight gain, the tricyclic antidepressant medications are a drug class producing persistent andproblematic bodyweight gaininmanytreated patients. Major depressive illness is often associated with reductions in appetiteandbodyweight,andtreatmentwith antidepressants effectively restores mood,appetite andweight. However, afrequent complaint of patients treated with tricyclic drugs is of excessive and unwanted weight gain, oftentimes resulting in medication noncompliance. The incidence of weight gain during acuteandchronic treatmentwith different, frequently prescribed antidepressant drugs will be reviewed, as will the possible mechanisms by which such drugs alter caloric intake and expenditure, contributing to drug-induced weight gain.
Key words: antidepressants, ingestive behavior, obesity, depressionTricyclic Antidepressants and Weight Gain: Defining the Problem Change in body weight is a frequent symptom of major depression, likely secondary to alterations in appetite. Patientstypicallylose weight (12,13,15), althoughsomedo gain weight during a depressive episode (12,17,18). As a pharmacologic treatment, the tricyclic antidepressants remain, even after almost 40 years, the first choice of medication for the treatment of severe major depression throughout the world (16). Althoughvery effective agents for restoration of normal mood, there are numerous side effects associated with this drug treatment, particularly unwanted and excessive weight gain. Previously, weight gain during antidepressant treatment had been interpreted as a positive sign of improvement, so prevalent and predictable was the effect. Such weight gain is of concern to both patient and clinician, as this is the reason often cited for medication non-compliance. Over the past 15 years, severalnewer medications of a different drug class, the selective serotonin reuptake inhibitors (SSRk), have become available. These drugs are effective as antidepressants, without the side effect of weight The use of two frequently prescribed tricyclic drugs, amitriptyline (4,8,10,14) and imipramine (1,4,5) havemost often been associated with increasing body weight during treatment (Table 1). Moreover, withinthe tricyclic drug class, amitriptyline appears to promote weight gain to a much greater degreethanthe others (Table 1). In contrast, zimelidine, (which is no longer prescribed but belongs in the category of selective serotonin reuptake inhibitors) did not promote weight gain. Importantly, in our own studies, no relationship between clinical response and weight gain was observed (4,5,10). In fact, weight change during drug treatment was not negatively correlated with that occurring at disease onset; that is, weight gain was not simply areflection of weight lost during the depressive episode. These results suggest that drug-induced changes in weight likely result from a pharmacologic action of the drug independent of its effect on mood. The mechanism(s) by which tricyclic antidepressants promote weight gain are not well understood and can r...