Bioavailability of digoxin tablets in patients with gastrointestinal dysfunction

Area of Science:

• Gastroenterology
• Pharmacokinetics
• Drug Absorption

Background:

• Gastrointestinal disorders can affect drug absorption.
• Digoxin is a commonly prescribed medication with a narrow therapeutic index.
• Understanding digoxin bioavailability in various GI conditions is crucial for patient management.

Purpose of the Study:

• To assess digoxin bioavailability in patients with diverse gastrointestinal disorders.
• To identify factors influencing digoxin absorption in these patients.
• To determine the impact of specific gastrointestinal surgeries on digoxin bioavailability.

Main Methods:

• Administered single 0.5 mg oral doses of digoxin tablets to 47 patients.
• Measured area under the serum concentration-time curve (AUC) to assess bioavailability.
• Correlated digoxin bioavailability with various clinical parameters including xylose absorption and fecal fat.

Main Results:

• Normal digoxin absorption was observed in most patients with ileal resection, sprue, and other GI disorders, even with steatorrhea.
• Impaired digoxin bioavailability was noted in 5 of 9 patients following jejunoileal bypass.
• A strong correlation was found between remaining jejunal length and digoxin AUC (r = 0.86).

Conclusions:

• The upper small intestine is the primary site for digoxin absorption.
• The ileum can compensate for jejunal dysfunction or bypass.
• Jejunoileal bypass significantly impacts digoxin bioavailability, highlighting the importance of monitoring drug levels in these patients.