An 18‑year‑old female on fluoxetine (Prozac) presents with elevated alkaline phosphatase, elevated aspartate aminotransferase, elevated alanine aminotransferase, fever, lymphocytosis, negative mononucleosis test, and normal renal function; what is the appropriate management?

Immediately Discontinue Fluoxetine and Initiate Close Monitoring for Drug-Induced Liver Injury

This patient's presentation is highly concerning for fluoxetine-induced hepatotoxicity and requires immediate drug discontinuation, close monitoring, and comprehensive workup for alternative etiologies. The combination of significantly elevated transaminases (AST 190, ALT 171), elevated alkaline phosphatase (215), fever, and lymphocytosis in an 18-year-old on Prozac strongly suggests drug-induced liver injury (DILI), particularly given the acute symptomatic presentation 1, 2.

Immediate Management Steps

Stop fluoxetine immediately. The patient meets criteria for drug interruption based on multiple guideline thresholds: ALT >3× upper limit of normal (ULN) with symptoms (fever, feeling unwell) warrants immediate drug cessation 3, 4. The FDA label for Prozac specifically warns that drug-induced hepatitis is suspected when ALT is ≥3× ULN in the presence of hepatitis symptoms, and hepatotoxic drugs should be stopped immediately 5, 2.

Repeat liver function tests within 48-72 hours to assess trajectory. Obtain ALT, AST, alkaline phosphatase, total and direct bilirubin, and INR 6, 4. This rapid reassessment is critical to determine if liver injury is progressing or stabilizing after drug withdrawal 3, 7.

Differential Diagnosis Workup

While fluoxetine-induced hepatotoxicity is the leading diagnosis, exclude other causes of acute hepatitis systematically 1, 5:

• Viral hepatitis panel: Hepatitis A, B, C, Epstein-Barr virus (EBV), cytomegalovirus (CMV), and herpes simplex virus given the fever and lymphocytosis 1, 5. The negative monospot does not exclude EBV entirely, as serologic testing (IgM anti-VCA) is more definitive 1.

• Autoimmune hepatitis: Check antinuclear antibodies (ANA), anti-smooth muscle antibodies (ASMA), anti-liver kidney microsomal antibodies (anti-LKM), and immunoglobulin G levels 1, 8. Autoimmune hepatitis can present acutely with fever and lymphocytosis in young women, and drug-induced autoimmune hepatitis has been reported with various medications 1.

• Other drug exposures: Acetaminophen level, review of all medications including over-the-counter drugs, herbal supplements, and dietary supplements 5, 7.

• Wilson disease screening: Serum ceruloplasmin and 24-hour urinary copper, particularly important in this age group 9, 8.

• Biliary obstruction: Right upper quadrant ultrasound to evaluate biliary tree and liver parenchyma 9.

Pattern Recognition

The hepatocellular pattern of injury (transaminases elevated more than alkaline phosphatase) with fever and systemic symptoms is consistent with fluoxetine-induced acute hepatitis 10, 11. Fluoxetine hepatotoxicity, though uncommon (asymptomatic elevations in 0.5% of patients), can present as acute hepatitis with significant transaminase elevations 10. Recent animal studies demonstrate that fluoxetine significantly raises ALT and alkaline phosphatase, with more severe effects in males 11.

The lymphocytosis may represent either a drug hypersensitivity reaction or viral infection, making the viral workup particularly important 1.

Monitoring Protocol

Follow liver function tests closely until normalization or return to baseline 3, 6:

• Repeat LFTs every 48-72 hours initially if values are stable or improving 6, 4
• If ALT/AST continue rising or bilirubin doubles, consider hospitalization and hepatology consultation 7, 4
• Monitor for signs of hepatic decompensation: coagulopathy (INR), encephalopathy, ascites 1, 12

Do not rechallenge with fluoxetine. Per FDA guidance and consensus recommendations, fluoxetine should not be restarted in patients who have had signs or symptoms consistent with hepatic injury with ALT >3× ULN unless another explanation definitively accounts for the liver injury 6, 2. Given the symptomatic presentation with fever, rechallenge is contraindicated 6.

Critical Thresholds for Escalation

Urgent hepatology referral is indicated if 1, 4:

• ALT/AST continue to rise despite drug discontinuation
• Total bilirubin rises to ≥2× ULN or direct bilirubin doubles from baseline 7, 4
• INR increases to >1.5 4
• Development of hepatic encephalopathy, ascites, or other signs of liver failure 1

Alternative Antidepressant Selection

Once liver injury resolves, select an alternative antidepressant from a different class to avoid cross-reactivity 3. Consider agents with lower hepatotoxicity risk and avoid other SSRIs initially given the class effect potential 2. Consultation with psychiatry for medication selection is appropriate once the acute liver injury has resolved 1.

Key Pitfalls to Avoid

• Do not attribute elevated transaminases solely to viral infection without excluding DILI, as fluoxetine can cause acute hepatitis that mimics viral hepatitis 10
• Do not continue fluoxetine while "monitoring" – the drug must be stopped immediately when hepatotoxicity criteria are met 5, 2
• Do not assume negative monospot excludes all viral causes – obtain comprehensive viral serologies 1
• Do not overlook autoimmune hepatitis, which can be drug-triggered and presents similarly in young women 1