What labs should be drawn to monitor a patient on proton pump inhibitors (PPIs)?

Laboratory Monitoring for Patients on Proton Pump Inhibitors (PPIs)

Regular laboratory monitoring is not routinely recommended for most patients on PPI therapy, but specific tests should be considered for long-term users to monitor for potential nutritional deficiencies and electrolyte abnormalities.

Recommended Laboratory Monitoring for Long-Term PPI Users

Initial Baseline Testing

• No specific baseline laboratory tests are mandated before starting PPI therapy for most patients

Monitoring for Long-Term Users (>8-12 weeks)

• Magnesium levels

  • Monitor in patients on prolonged therapy due to risk of hypomagnesemia 1, 2, 3
  • Consider checking after 3 months of continuous use 4

• Vitamin B12 levels

  • Monitor in patients on prolonged therapy, especially elderly
  • PPI-induced hypochlorhydria can reduce B12 absorption 4, 3
  • Consider checking after 3 months of continuous use 4

• Iron studies

  • Consider in patients at risk for iron deficiency
  • Gastric acid is required for optimal iron absorption 4, 3

• Calcium levels

  • Consider in patients at risk for osteoporosis
  • PPIs may affect calcium absorption 5, 3

Special Populations Requiring More Vigilant Monitoring

Post-POEM Patients

• All patients should undergo monitoring for GERD after POEM procedure
• Patients with persistent esophagitis and/or reflux-like symptoms despite PPI use should undergo additional testing 5

Patients with Pulmonary Disorders

• Patients with idiopathic pulmonary fibrosis, cystic fibrosis, or other pulmonary disorders that might require lung transplantation should have reflux monitoring with pH/impedance 5

Patients with Refractory GORD Symptoms

• After ascertaining medication compliance, further investigations may include:
  • Upper GI endoscopy
  • Ambulatory pH monitoring
  • 24-hour combined impedance–pH studies
  • Oesophageal manometry 5

Drug Interaction Considerations

Monitor for Drug Interactions

• Phenytoin: Monitor serum concentrations 6
• Digoxin: Monitor digoxin concentrations 6
• Tacrolimus: Monitor whole blood concentrations, especially in transplant patients 6
• Diazepam: Monitor for increased sedation 6

Timing of Laboratory Monitoring

• Initial monitoring: After 3 months of continuous PPI therapy 4
• For long-term users: Consider annual monitoring of vitamin B12, iron, and magnesium levels
• More frequent monitoring may be needed in high-risk patients (elderly, malnourished, or those with malabsorption disorders)

Important Caveats and Considerations

• Temporarily stop PPI treatment at least 14 days before assessing serum chromogranin A (CgA) levels, as PPIs can cause false elevations 6
• Consider stopping PPIs 14 days before secretin stimulation test to avoid false positive results suggesting gastrinoma 6
• Be aware that PPIs can cause false positive urine screening tests for THC 6
• Regular assessment of ongoing need for PPI therapy is more important than routine laboratory monitoring 4

When to Discontinue or De-escalate PPI Therapy

• Consider de-prescribing in patients without definitive indications for chronic PPI use 4
• If on twice-daily dosing, first step down to once-daily dosing for 2-4 weeks 4
• Abrupt discontinuation may lead to rebound hyperacidity; consider gradual tapering 4

Remember that while monitoring is important, the decision to continue PPI therapy should be based on a clear indication and regular reassessment of the risk-benefit profile for each individual patient.