What tests are recommended for patients taking Cymbalta (duloxetine)?

Recommended Testing for Patients Taking Cymbalta (Duloxetine)

Before starting duloxetine, obtain baseline liver function tests (ALT, AST, GGT, alkaline phosphatase, bilirubin) and assess renal function (creatinine, eGFR), as duloxetine is contraindicated in patients with substantial alcohol use or chronic liver disease and requires dose adjustment in renal insufficiency. 1, 2

Pre-Treatment Baseline Testing

Essential Laboratory Tests

• Liver function panel: Measure ALT, AST, GGT, alkaline phosphatase, and total bilirubin before initiating therapy 1, 3
• Renal function: Obtain serum creatinine and calculate eGFR, as duloxetine requires caution in renal insufficiency 2
• Blood pressure measurement: Establish baseline BP, as duloxetine can cause modest elevations in systolic and diastolic blood pressure 2, 1

Risk-Specific Baseline Testing

• For patients with diabetes: Check HbA1c and fasting glucose if prescribing for diabetic peripheral neuropathy 4, 2
• For elderly patients or those at fall risk: Document baseline orthostatic vital signs (BP and pulse supine and standing after 1-3 minutes), as duloxetine increases fall risk through orthostatic hypotension 1
• For patients on anticoagulants or NSAIDs: Consider baseline CBC to establish platelet count, as duloxetine increases bleeding risk when combined with these medications 1

Monitoring During Treatment

First Month of Therapy

• Liver enzymes at 2-4 weeks: Recheck ALT and AST, as asymptomatic elevations occur in approximately 27% of patients in the first month, though clinically significant elevations requiring discontinuation are rare (1.8%) 3
• Blood pressure weekly for first 4 weeks: Monitor for hypertensive effects, particularly in patients on doses above 60 mg daily or those taking concomitant antihypertensives 1
• Orthostatic vital signs at each visit: Assess for symptomatic orthostatic hypotension, especially during dose titration, as syncope and falls tend to occur within the first week but can happen at any time 1

Ongoing Monitoring Schedule

• Liver function tests every 6 months: Continue monitoring ALT, AST, and bilirubin, as abnormalities persist in approximately 23% of patients at 6 months 3
• Blood pressure at each visit: Document BP at every clinical encounter, as duloxetine can cause sustained elevations 2, 1
• Annual comprehensive assessment: For patients on long-term therapy, obtain annual liver panel, renal function, and BP measurement 2

Special Population Considerations

Pediatric Patients (7-17 years)

• Height and weight at baseline and regularly thereafter: Monitor growth parameters, as duloxetine causes mean weight decrease of 0.1 kg at 10 weeks (versus 0.9 kg gain with placebo), with 16% experiencing clinically significant weight loss (≥3.5%) 1
• Height percentile tracking: Document height at each visit, as mean decrease of 1% in height percentile was observed over 9 months (2% decrease in ages 7-11,0.3% increase in ages 12-17) 1

Patients with Diabetes

• HbA1c every 3 months initially, then every 6 months: Monitor glycemic control when treating diabetic peripheral neuropathy 4
• Annual comprehensive diabetic assessment: Include urine albumin-creatinine ratio and eGFR as part of standard diabetes care 4

Patients on Concomitant Medications

• For CYP1A2 inhibitors (e.g., fluvoxamine, ciprofloxacin): Avoid combination or monitor closely for duloxetine toxicity, as these potent inhibitors significantly increase duloxetine levels 1, 5
• For drugs metabolized by CYP2D6 with narrow therapeutic index: Monitor drug levels or clinical effects, as duloxetine is a moderate CYP2D6 inhibitor 1, 5

Critical Safety Monitoring

Signs Requiring Immediate Testing or Discontinuation

• Jaundice, dark urine, or right upper quadrant pain: Obtain urgent liver panel and discontinue duloxetine if ALT/AST exceed 3-4 times upper limit of normal 1, 3
• Blisters, peeling rash, or mucosal erosions: Discontinue immediately, as Stevens-Johnson syndrome has been reported at rates exceeding general population incidence 1
• Recurrent falls or syncope: Reassess orthostatic vital signs and consider dose reduction or discontinuation 1
• Signs of serotonin syndrome: Monitor for mental status changes, autonomic instability, neuromuscular symptoms, or GI symptoms, particularly when combining with other serotonergic drugs 1

Common Pitfalls to Avoid

• Do not assume normal baseline liver function eliminates monitoring need: Asymptomatic liver enzyme elevations develop during treatment in over one-quarter of patients 3
• Do not overlook orthostatic vital signs in elderly patients: Fall risk increases steadily with age and is proportional to the degree of orthostatic BP decrease 1
• Do not prescribe duloxetine without assessing alcohol use: The drug is contraindicated in patients with substantial alcohol consumption due to hepatotoxicity risk 1
• Do not combine with MAOIs or start within 5 days of MAOI discontinuation: This combination is contraindicated due to serotonin syndrome risk 1