Thermodynamic Equivalence to Demonstrate Bioequivalence
The 1980s saw emergence of generic drugs in the US that has saved hundreds of billions of dollars to patients and improved accessibility to drugs. The statute that created this abbreviated pathway for approval of generic drugs stated that therapeutic equivalence means same concentration of active drug at the site of action, an evaluation that was neither possible nor practical. So, the FDA recommended using blood level studies as a surrogate test demonstrating bioequivalence.