Digoxin bioequivalence study: determination in human plasma by microparticle enzyme immunoassay

Area of Science:

• Pharmacokinetics and Bioavailability
• Analytical Chemistry
• Pharmaceutical Sciences

Background:

• Digoxin is a critical medication for managing heart conditions.
• Ensuring bioequivalence between generic and reference drug formulations is essential for patient safety and therapeutic efficacy.
• Accurate bioanalytical methods are required to assess drug absorption and bioavailability.

Purpose of the Study:

• To develop and validate a sensitive bioanalytical method for digoxin quantification using fluorescence detection.
• To evaluate the bioequivalence of a test formulation (Digox 0.25 mg tablet, Pharlab Ind. Ltd.) compared to a reference formulation (Digoxin 0.25 mg tablet, Glaxo SmithKline).

Main Methods:

• A randomized, two-period crossover study involving 30 healthy volunteers.
• Single oral dose administration of digoxin (0.25 mg) for both test and reference formulations.
• Plasma digoxin concentrations were measured over 288 hours using a microenzyme particle immunoassay with fluorescence detection.

Main Results:

• The developed bioanalytical method demonstrated specificity, sensitivity, accuracy, and precision.
• Key pharmacokinetic parameters, including AUC0-t, AUC0-inf, and Cmax, were calculated.
• The 90% confidence intervals for the ratios of the test to reference formulations fell within the acceptable bioequivalence range (80-125%).

Conclusions:

• The developed fluorescence-based method is suitable for digoxin quantification in bioequivalence studies.
• The test formulation (Digox 0.25 mg) and the reference formulation (Digoxin 0.25 mg) are bioequivalent.
• The findings support the interchangeability of the two digoxin tablet formulations.