What is the best course of treatment for a patient with cyclical vomiting, hypokalemia, and swollen parotid glands, with a low Body Mass Index (BMI) and suspected bulimia nervosa?

Treatment of Suspected Bulimia Nervosa with Severe Medical Complications

This patient requires immediate medical stabilization for life-threatening hypokalemia and malnutrition, followed by concurrent initiation of fluoxetine 60 mg daily and eating disorder-focused psychotherapy, with mandatory multidisciplinary coordination among medical, psychiatric, and nutritional specialists. 1, 2

Immediate Medical Assessment and Stabilization (First Priority)

The clinical presentation—BMI 16, chronic hypokalemia despite replacement, cyclical vomiting, and parotid enlargement—strongly suggests bulimia nervosa with severe purging behaviors. 1, 3, 4 This constellation requires urgent evaluation before any other intervention:

Critical Initial Workup

• Obtain comprehensive metabolic panel immediately to quantify the severity of hypokalemia and assess for hypochloremic metabolic alkalosis from chronic vomiting 1, 5
• Perform electrocardiogram urgently to evaluate for QTc prolongation, as severe hypokalemia (particularly <2.5 mmol/L) can cause life-threatening arrhythmias and sudden cardiac death 6, 7
• Check complete blood count to detect anemia and leukopenia associated with severe malnutrition 1, 5
• Measure vital signs including orthostatic pulse and blood pressure, as significant orthostatic changes indicate cardiovascular instability requiring hospitalization 1, 5

Key Clinical Pitfall

Patients with chronic purging behaviors adapt to severe hypokalemia and may appear asymptomatic despite dangerously low potassium levels (as low as 1.6-2.8 mmol/L). 6, 8 Do not be falsely reassured by the absence of physical symptoms—the risk of sudden cardiac death remains high. 7 One case series documented QTc normalization taking 10 days despite aggressive potassium replacement, even after vomiting ceased. 6

Electrolyte Replacement Strategy

• Administer intravenous potassium cautiously (approximately 2346 mg/day in severe cases), along with magnesium (72 mg/day), calcium (80 mg/day), and phosphorus (769 mg/day) 6
• Monitor ECG continuously during initial stabilization, as normalization of cardiac function lags behind weight recovery 6
• Avoid aggressive hyperalimentation initially to prevent refeeding complications; use slightly above minimum energy requirements 6

Pharmacologic Treatment (Concurrent with Medical Stabilization)

Initiate fluoxetine 60 mg daily as soon as medical stability permits. 2, 9 This is the only FDA-approved medication for bulimia nervosa and is statistically superior to placebo in reducing binge-eating and purging frequency. 2, 9

Dosing Algorithm

• Start at 60 mg daily administered in the morning (not the standard 20 mg antidepressant dose) 2, 9
• For some patients, titrate up to 60 mg over several days if tolerability is a concern 9
• Do not use standard antidepressant doses (20 mg)—only 60 mg has proven efficacy for bulimia nervosa 2, 9

Alternative if Fluoxetine Intolerance

If the patient cannot tolerate fluoxetine, switch to sertraline 100 mg daily or citalopram (particularly if prominent depressive symptoms are present). 2 Continue cognitive-behavioral therapy regardless of medication choice. 2

Psychiatric and Behavioral Treatment (Essential Component)

Refer immediately for eating disorder-focused psychotherapy, as psychiatric treatment is essential to address the underlying disorder driving purging behaviors. 1, 2, 5

Psychotherapy Approach

• Implement cognitive-behavioral therapy (CBT) focused on normalizing eating behaviors and addressing body image disturbance 2, 5
• CBT should be initiated alongside fluoxetine, or if there is minimal response to psychotherapy alone by 6 weeks of treatment 2
• For younger patients or those with family involvement, consider family-based treatment 2

Treatment Goals by Phase

The American Gastroenterological Association framework for cyclic vomiting syndrome is relevant here, though this patient's vomiting is behaviorally driven: 1

• Prodromal phase: Educate patient to recognize early warning signs and seek intervention
• Emetic phase: Terminate episodes through behavioral strategies and medical support
• Inter-episodic phase: Prevent recurrence through ongoing therapy and medication

Nutritional Rehabilitation

Establish goal weight based on age, height, and premorbid weight (current BMI 16 indicates severe malnutrition). 1 For a growing young adult, reevaluate goal weight at 3-6 month intervals. 1

• Medical stabilization and nutritional rehabilitation are the most crucial determinants of short- and intermediate-term outcomes 1
• Coordinate with a registered dietitian experienced in eating disorders 1, 2

Addressing Parotid Enlargement

The bilateral parotid swelling (sialadenosis) is a direct consequence of chronic vomiting and typically resolves with cessation of purging behaviors. 3, 4

• Reassure the patient that parotid enlargement is usually transient and will improve with treatment adherence 4
• Surgical intervention (superficial parotidectomy) is rarely required and should only be considered if swelling persists after sustained recovery and causes significant distress 3
• B-scan ultrasonography can assess the nature of enlargement if diagnosis is uncertain 4
• Hyperamylasemia commonly occurs in bulimic patients and may help confirm the diagnosis 4

Ongoing Monitoring Protocol

Monitor weight and vital signs at each visit, with particular attention to orthostatic changes. 1, 5

Follow-up Schedule

• Assess response to treatment every 6-12 weeks by quantifying reduction in binge-eating and purging frequency 1, 2
• Repeat comprehensive metabolic panel regularly until electrolytes stabilize 5
• Continue fluoxetine 60 mg daily for at least 52 weeks if the patient responds during the acute treatment phase, as maintenance treatment has demonstrated benefit 9

Predictors of Better Outcome

• Higher baseline BMI and lower baseline binging/purging frequency predict better response 1
• Better treatment adherence (measured by therapy attendance and medication compliance) correlates with improved outcomes 1
• Reduction in purging behavior at 3 months predicts abstinence at 1 year 1

Multidisciplinary Coordination (Mandatory)

All eating disorder treatment requires coordination among medical, psychiatric, psychological, and nutritional expertise. 2 This patient's severe medical complications make solo management inappropriate and potentially dangerous.

• Establish clear communication channels between primary care, psychiatry, and nutrition 2
• Consider hospitalization if orthostatic instability, severe electrolyte abnormalities, or suicidal ideation are present 1
• Screen for comorbid psychiatric diagnoses (depression, anxiety, obsessive-compulsive disorder) which may require additional treatment 1