Evaluation of stability using one versus three tubes for each quality control concentration in matrix-based bioanalysis

Aim: Contract research organizations and pharmaceutical firms have performed stability testing using one of two methods: storing in the freezer a single tube of matrix for each quality control concentration (Method 1), followed by aliquoting and analysis; and storing three tubes for each quality control concentration, followed by analysis (Method 2). This research project was conducted to determine if there were detectable differences between Method 1 and Method 2. Methodology: Five model drugs were selected: teriflunomide (stable compound) and acetyl salicylic acid, simvastatin, tenofovir alafenamide and valganciclovir (stability concerns). Samples were stored at -80°C for 1, 3 and 12 months and then analyzed. Samples were also placed at different locations within the freezer. Results: For the drugs tested, the results suggest that there is no significant difference in the outcome of stability testing, regardless whether Method 1 or Method 2 was followed.