Enzymatic Stability of Alteplase Solution for Injection: Effect of Various Methods of Thawing Frozen Solutions

ObjectiveTo modify and evaluate an established chromogenic assay protocol for measuring plasminogen activator inhibitor type-1 (PAI-1) activity to measure tissue plasminogen activator (tPA) activity and compare the enzymatic activity of alteplase as a function of the conditions under which it is thawed.MethodsA 50 mg vial of alteplase was reconstituted with sterile water to make a 1 mg/mL stock solution (nominal concentration). Plastic syringes were loaded with 0.5 mL of alteplase stock solution and stored at −20°C. After 8 days, samples were thawed by 3 methods – via body temperature (37°C), room temperature (20°C), or in a refrigerator (2°C). Thaw times were recorded. The thawed solutions, along with a freshly prepared alteplase solution, were assayed using the modified protocol of the Spectrolyse PAI-1 kit to determine residual tPA enzyme activity.ResultsValidation of the modified protocol for the Spectrolyse PAI-1 kit used to measure tPA activity produced a linear response with coefficients of determi...