What are the medication options for treating eating disorders in an 18‑year‑old patient?

Medication Options for Eating Disorders in an 18-Year-Old

Psychotherapy is the cornerstone of eating disorder treatment at age 18, with medication serving as an adjunct only for specific disorders: fluoxetine 60 mg daily for bulimia nervosa and lisdexamfetamine for binge-eating disorder, while no medications are approved or recommended for anorexia nervosa. 1

Treatment Algorithm by Eating Disorder Type

Anorexia Nervosa

• No pharmacological treatment is recommended or FDA-approved for anorexia nervosa 1, 2
• At age 18 (emerging adult), family-based treatment should be the first-line intervention if a caregiver is involved, focusing on normalizing eating behaviors and restoring weight 1
• If living independently, eating disorder-focused psychotherapy is the primary treatment, addressing fear of weight gain and body image disturbance 1
• Olanzapine shows promise in research for promoting weight gain in outpatients with anorexia nervosa, but it remains off-label and is not guideline-recommended 3, 4

Bulimia Nervosa

The American Psychiatric Association recommends treating adults with bulimia nervosa with eating disorder-focused cognitive-behavioral therapy combined with fluoxetine 60 mg daily, prescribed either initially or if there is minimal response to psychotherapy alone by 6 weeks of treatment 1

• Fluoxetine is the only FDA-approved medication for bulimia nervosa 5, 6, 2
• The therapeutic dose is specifically 60 mg daily, which is higher than typical antidepressant dosing 1, 5
• This medication reduces binge-eating and purging episodes even in patients without comorbid depression 2
• For an 18-year-old with an involved caregiver, family-based treatment may be considered as an alternative psychotherapy approach 1

Binge-Eating Disorder

Adults with binge-eating disorder should receive eating disorder-focused cognitive-behavioral therapy or interpersonal therapy; those who prefer medication or have not responded to psychotherapy alone should be treated with either an antidepressant or lisdexamfetamine 1, 7

Lisdexamfetamine (First-Line Medication Option)

• FDA-approved specifically for moderate to severe binge-eating disorder in adults 8, 6, 2
• Dosing protocol: Start at 30 mg once daily in the morning, titrate in 20 mg increments at weekly intervals to target dose of 50-70 mg daily (maximum 70 mg) 8
• Demonstrates medium effect size (Hedges g = 0.57) in reducing binge frequency 2
• Critical contraindications: history of drug abuse, uncontrolled hypertension, cardiovascular disease, hyperthyroidism, glaucoma, anxiety, or recent MAOI use 8
• Black box warning: High potential for abuse, misuse, and addiction; requires careful patient selection and monitoring 8

Antidepressant Options (Alternative)

• SSRIs, particularly fluoxetine, reduce binge frequency with small effect size (standardized mean difference = -0.29) 2, 3
• Other antidepressants including mirtazapine may be considered off-label 3
• Avoid bupropion as bulimia nervosa and binge-eating disorder are contraindications due to seizure risk 1, 3

Critical Assessment Requirements Before Medication Initiation

Mandatory Medical Workup

• Complete blood count and comprehensive metabolic panel including electrolytes, liver enzymes, and renal function to identify hypokalemia, hyponatremia, or other abnormalities 1
• Electrocardiogram in all patients with restrictive eating or severe purging behaviors to assess for QTc prolongation, which predicts sudden cardiac death risk 1
• Vital signs including orthostatic pulse and blood pressure to detect cardiovascular instability 1
• Height, weight, and BMI documentation 1

Psychiatric Comorbidity Screening

• Screen for depression, anxiety, obsessive-compulsive disorder, and suicidality at every visit, as 25% of anorexia nervosa deaths result from suicide 1, 9
• Assess for substance use disorders, as these affect medication selection and safety 1, 3

Common Pitfalls to Avoid

• Never use appetite suppressants or weight-loss medications (phentermine, orlistat, GLP-1 agonists) in eating disorder patients, as these are contraindicated and potentially harmful 1
• Do not prescribe bupropion or naltrexone/bupropion combination to patients with bulimia nervosa or binge-eating disorder due to significantly increased seizure risk 1, 3
• Avoid monotherapy with medication alone for any eating disorder; psychotherapy must be the foundation of treatment 1, 7
• Do not delay psychiatric referral for coordination of multidisciplinary care incorporating medical, psychiatric, psychological, and nutritional expertise 1, 7
• Never assume normal laboratory values exclude serious illness, as approximately 60% of anorexia nervosa patients show normal routine testing despite severe malnutrition 7

Medication Considerations for Comorbid Conditions

Depression

• SSRIs (particularly fluoxetine) or mirtazapine are appropriate first-line options 3
• Avoid bupropion in patients with any purging behaviors 3

Anxiety

• Acute anxiety may warrant short-term benzodiazepine treatment with lorazepam 3
• SSRIs provide longer-term anxiety management 3

Treatment Monitoring and Duration

• Reassess treatment response at 6 weeks for bulimia nervosa patients on fluoxetine; if minimal response, optimize psychotherapy or adjust medication 1
• Evaluate lisdexamfetamine response at 12 weeks at maximum tolerated dose; discontinue if insufficient benefit 8
• Monitor QTc intervals serially in patients with ongoing restrictive eating or severe purging 1, 7
• Periodically reevaluate long-term medication usefulness, as extended treatment efficacy beyond initial trial periods is not well-established 5, 2