title: Quality by design in formulation and process development for a freeze-dried, small molecule parenteral product: a case study.
abstract: A case study has been developed to illustrate one way of incorporating a Quality by Design approach into formulation and process development for a small molecule, freeze-dried parenteral product. Sodium ethacrynate was chosen as the model compound. Principal degradation products of sodium ethacrynate result from hydrolysis of the unsaturated ketone in aqueous solution, and dimer formation from a Diels-Alder condensation in the freeze-dried solid state. When the drug crystallizes in a frozen solution, the eutectic melting temperature is above -5°C. Crystallization in the frozen system is affected by pH in the range of pH 6-8 and buffer concentration in the range of 5-50 mM, where higher pH and lower buffer concentration favor crystallization. Physical state of the drug is critical to solid state stability, given the relative instability of amorphous drug. Stability was shown to vary considerably over the ranges of pH and buffer concentration examined, and vial-to-vial variability in degree of crystallinity is a potential concern. The formulation design space was constructed in terms of pH and drug concentration, and assuming a constant 5 mM concentration of buffer. The process design space is constructed to take into account limitations on the process imposed by the product and by equipment capability.
authors.affiliation: Purdue University, West Lafayette, IN, USA.
authors.forename: Linas N
authors.initials: LN
authors.lastname: Mockus
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Paul
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Pease
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Harper
authors.forename: Prabir K
authors.initials: PK
authors.lastname: Basu
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Oslos
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Sacha
authors.forename: Wei Y
authors.initials: WY
authors.lastname: Kuu
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Hardwick
authors.forename: Jacquelyn J
authors.initials: JJ
authors.lastname: Karty
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Pikal
authors.forename: Eun
authors.initials: E
authors.lastname: Hee
authors.forename: Mansoor A
authors.initials: MA
authors.lastname: Khan
authors.forename: Steven L
authors.initials: SL
authors.lastname: Nail
mesh_terms: D002021:Buffers; D002626:Chemistry, Pharmaceutical; D003460:Crystallization; D015195:Drug Design; D004355:Drug Stability; D004976:Ethacrynic Acid / Q000737:chemistry*; D005612:Freeze Drying; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D044366:Transition Temperature
chemical_list: D002021:Buffers; D004976:Ethacrynic Acid