Antidepressant-Induced Weight Gain and Metabolic Management

Practice flashcards covering the epidemiology, mechanisms, risk stratification, and mitigation strategies for antidepressant-induced weight gain based on clinical notes.

Antidepressant-Induced Weight Gain Prevalence

A side effect affecting between $40\text{--}65\%$ of patients taking antidepressants.

High-Risk Antidepressant Agents

Medications consistently associated with significant weight gain, specifically mirtazapine, paroxetine, and tricyclic antidepressants (TCAs) like amitriptyline and nortriptyline.

Low-Risk/Weight-Favorable Agents

Antidepressants associated with weight loss or neutrality, such as bupropion, fluoxetine, vortioxetine, vilazodone, and trazodone.

Intervention Threshold (4 Weeks)

A weight change of $\ge 5\%$ at $4$ weeks, which serves as a predictor of the long-term weight trajectory and should prompt clinical intervention.

FDA Clinically Relevant Weight Gain

An increase of $\ge 7\%$ of baseline body weight.

Histamine H1 Receptor Antagonism

A mechanism strongly correlated with increased appetite, reduced satiety, and increased carbohydrate cravings; notable in TCAs and mirtazapine.

Muscarinic Receptor Antagonism (M3)

Blockade associated with increased appetite and impaired insulin-secretory response to hyperglycemia; observed in paroxetine and TCAs.

5-HT2C Downregulation

A chronic effect occurring after $6\text{--}12$ months of treatment where desensitized serotonin receptors lead to a loss of satiety signaling and increased carbohydrate cravings.

Anorexigenic Effect (Acute 5-HT2C)

The short-term stimulation of 5-HT2C receptors on proopiomelanocortin (POMC) neurons in the hypothalamus, which enhances satiety and reduces food intake.

$\beta_3$-adrenoceptors

Receptors in adipose tissue through which noradrenergic effects promote weight neutrality by converting fat into heat and energy.

Dopaminergic Influence on Weight

Dopamine enhances satiety and energy expenditure by activating the hypothalamic melanocortin system; medications like bupropion (NDRI) utilize this pathway.

Mirtazapine Mechanism

Potent dual antagonism of histamine H1 and serotonin 5-HT2C receptors, along with 5-HT2A blockade leading to excessive NPY release and disinhibition of orexigenic signaling.

Paroxetine (Risk Level)

The SSRI with the highest weight-gain potential, linked to H1 and anticholinergic burden along with 5-HT2C downregulation.

Amitriptyline (Weight Profile)

A TCA associated with a mean gain of $+1.52\,kg$ in short-term and $+2.24\,kg$ in long-term treatment, often leading to progressive weight gain.

Phenelzine (Metabolic Effect)

An irreversible MAOI that alters adipocyte differentiation and is associated with a mean gain of $+9.1\,kg$ at $6$ months.

Escitalopram vs. Sertraline

Escitalopram shows a distinctly higher weight gain profile compared to sertraline, possibly due to greater serotonin transporter binding affinity.

Sertraline Biphasic Pattern

Initial weight-neutrality or slight loss ($\sim -0.87\,kg$) followed by long-term moderate weight gain due to eventual 5-HT2C receptor downregulation.

Vortioxetine (Long-term Data)

A multimodal agent showing low incidence of gain, with mean changes of $+0.7\,kg$ to $+0.8\,kg$ in open-label extensions.

Desvenlafaxine

A weight-favorable SNRI option showing clinically minimal weight reduction in short-term trials and no significant long-term changes.

CYP2C19 Poor Metabolizers

A specific genetic risk factor identifying patients at higher risk for weight gain on citalopram and escitalopram.

Metformin (Adjunctive Dose)

The most widely used pharmacological adjunct for treating psychotropic-related gain, typically dosed at $500\text{--}2500\,mg/day$.

Liraglutide (Dosing)

A GLP-1 receptor agonist titrated from $0.6\,mg$ SC daily to $3.0\,mg$ as indicated for obesity and tolerated.

Naltrexone/bupropion Titration

Combination therapy titrated from $8/90\,mg$ daily to $32/360\,mg/day$ over $4$ weeks to promote weight loss in overweight patients with MDD.