TOWARD AN IN VITRO BIOEQUIVALENCE TEST by Jie Sheng A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Pharmaceutical Sciences) In The University of Michigan 2007 Doctoral Committee: Professor Gordon L. Amidon, Chair Professor Henry Y. Wang Associate Professor Nair Rodriguez-Hornedo Associate Professor Steven P. Schwendeman Jie Sheng © 2007 All Rights Reserved To Kurt Q. Zhu, my husband and my very best friend, and to Diana S. Zhu and Brandon D. Zhu, my lovely children. ii Acknowledgements Most of all, I thank Prof. Gordon L. Amidon, for his support, guidance, and inspiration during my graduate studies at the University of Michigan. Being his student is the best step happened in my career. I am always amazed by his vision, energy, patience and dedication to the research and his students. He trained me to grow as a scientist and as a person. I also wish to thank all of my committee members, Professors David Fleisher, Nair Rodriguez-Hornedo, Steven Schwendeman and Henry Wang, for their very insightful and constructive suggestions to my research. It took all their efforts to raise me as a professional scientist in pharmaceutical field. They all contributed significantly to development and improvement of my graduate work. Especially, Prof. Wang has also guided me in thinking of career development as if 20-year later. I felt to be his student in many ways. I thank mentors, colleagues and friends, Prof. John Yu from Ohio State University, Paul Sirois from Eli Lilly, Kurt Seefeldt, Chet Provoda, Jonathan Miller, John Chung, Chris Landoswki, Haili Ping and Yasuhiro Tsume from College of Pharmacy, for many interesting discussions throughout the graduate program. I thank L.D. and Pat for facilitating my research in the college. I also thank Iris Templin and Gail for their administrative help along the way. iii I thank Prof. David Smith for his support and guidance during the PSTP fellowship, and beyond. I thank Prof. Kyung-Dall Lee for his perspectives in teaching, science and research. Lastly, I am grateful to my husband, Kurt Zhu, for his endless love and patience. I wish that I had supported him the same way when he was in graduate school. I thank my children, Diana and Brandon, for being so close to me. iv TABLE OF CONTENTS DEDICATION…………………………………………………………………………...ii ACKNOWLEDGEMENTS…………………………………………………………….iii LIST OF TABLES……………………………………………………………………...vii LIST OF FIGURES……………………………………………………………………..ix ABSTRACT……………………………………………………………………………...xi CHAPTER I. INFLUENCE OF FASTED STATE GASTROENTEROLOGICAL FACTORS ON IN VIVO DISSOLUTION OF POORLY SOLUBLE DRUGS…………………………………………………………………...1 Introduction………………………………………………………………..1 Gastrointestinal Factors…………………………………………………...2 Motility………………………………………………………….2 pH………………………………………………………………..4 Bile Salts…………………………………………………….......4 Buffer Species…………………………………………………...6 Other Gastrointestinal Factors…………………………………..7 Effects of GI Factors on BCS II drugs…………………………………….7 Selection of Model Compounds………………………………………….11 Implications of GI Factors in Establishing Bioequivalence Dissolution Methodology……………………………………………………………..12 Summary…………………………………………………………………15 Specific Aims…………………………………………………………….16 References………………………………………………………………..21 II. PARTICLE DIFFUSIONAL LAYER THICKNESS IN A USP DISSOLUTION APPARATUS II: A COMBINED FUNCTION OF PARTICLE SIZE AND PADDLE SPEED……………………………27 Abstract…………………………………………………………………..27 Introduction………………………………………………………………28 v Theoretical Section………………………………………………………31 Experimental Section…………………………………………………….34 Results…………………………………………………………………....37 Discussion………………………………………………………………..41 Conclusions………………………………………………………………51 References………………………………………………………………..63 III. SOLUBILIZATION AND DISSOLUTION OF INSOLUBLE WEAK ACID, KETOPROFEN: EFFECTS OF PH COMBINED WITH SURFACTANT…………………………………………………………66 Abstract…………………………………………………………………..66 Introduction………………………………………………………………67 Methods………………………………………………………………….69 Results and Discussion ………………………………………………….76 Conclusions………………………………………………………………83 References………………………………………………………………..93 IV. A COMPARISON OF PHOSPHATE AND BICARBONATE BUFFERS: RELEVANCE TO IN VIVO DISSOLUTION………….96 Abstract…………………………………………………………………..96 Introduction………………………………………………………………97 Theoretical Section……………………………………………………..100 Experimental Section…………………………………………………...105 Results…………………………………………………………………..107 Discussion………………………………………………………………114 Conclusions……………………………………………………………..120 References………………………………………………………………131 V. SUMMARY……………………………………………………………134 vi LIST OF TABLES Table 1.1. Biopharmaceutical Classification System (BCS)………………………..17 Table 1.2. pH in the small intestine in healthy humans in the fasted state………….18 Table 1.3. Biopharmaceutical properties of fenofibrate, ketoprofen and indomethacin……………………………………………………………………………..19 Table 2.1. Physical characteristics of various size fractions of fenofibrate powder...52 Table 2.2. Comparison of the relationship between happ and r in: Higuchi- Hiestand’s work, Hintz-Johnson’s work and the current work in a USP dissolution apparatus II………………………………………………………………………….……53 Table 2.3. Particle sizes and Re: comparison of fenofibrate powder dissolution in a USP dissolution apparatus II and previous studies using the function form of Eq 2……54 Table 3.1. Equilibrium solubility (mg/mL r S.D.) of ketoprofen at various pH and SLS concentrations………………………………………………………………………85 Table 3.2. Solubilization power (CSN) of various pH and SLS concentrations on ketoprofen………………………………………………………………………………..86 Table 3.3. The intrinsic dissolution rate ( J /Z 1/ 2 , ×10421/21/2mg / cm / s / radr S . D .) of ketoprofen at various pH and SLS concentrations……………………………………………………………………………87 Table 4.1. Commonly used pharmaceutical dissolution media/buffers for simulating upper small intestine……………………………………………………………………121 Table 4.2. Parameters used in theoretical analysis…………………………………122 Table 4.3. Intrinsic flux of ketoprofen in the phosphate and in the bicarbonate buffer systems, experimental and theoretical results…………………………………………..123 Table 4.4. Intrinsic flux ratios of indomethacin in the phosphate versus in the bicarbonates, experimental and theoretical results……………………………………..124 vii Table 4.5. Intrinsic dissolution rates of ketoprofen in 50mM pH 6.8 phosphate and bicarbonate buffers……………………………………………………………………..125 Table 4.6-1. Drug flux ratio in USP 50 mM phosphate and 15mM bicarbonate buffers: the impact of drug solubility and drug diffusion coefficient (drug pKa = 3)…………..126 Table 4.6-2. Drug flux ratio in USP 50 mM phosphate and 15 mM bicarbonate buffers: the impact of drug solubility and drug diffusion coefficient (drug pKa = 5)…………..126 Table 4.7-1. Drug flux ratio in USP 50 mM phosphate and 15 mM bicarbonate buffers: the impact of drug pKa and drug diffusion coefficient (drug solubility = 1×10-8 M)….127 Table 4.7-2. Drug flux ratio in USP 50mM phosphate and 15 mM bicarbonate buffers: the impact of drug pKa and drug diffusion coefficient (drug solubility = 1×10-3 M)…..127 Table 4.8. Phosphate buffer as an equivalent substitute for 15 mM bicarbonate buffer……………………………………………………………………………………128 Table 4.9. pKa values, maximum dose, and salt forms of some BCS II weak acids.................................................................................................................................129 viii LIST OF FIGURES Figure 1.1. The chemical structures of fenofibrate, ketoprofen and indomethacin……………………………………………………………………………..20 Figure 2.1a. DSC thermograms of the jet-milled fenofibrate…………………………..55 Figure 2.1b. DSC thermograms of fenofibrate “as received” from Sigma……………..55 Figure 2.2. PXRD patterns of fenofibrate “as received” and jet-milled……………...56 Figure 2.3. Particle size distribution of fenofibrate powders………………………...57 Figure 2.4. SEM picture of a typical fenofibrate powder (63-75Pm)………………..58 Figure 2.5. Dissolution profiles of various size fractions of fenofibrate powder at 50 rpm and 100 rpm. (Error bars represent the standard deviation of a mean of three experiments.)…………………………………………………………………………….59 Figure 2.6. Bifunctional analysis of the dependence of diffusional layer thickness happ on particle sizes under different hydrodynamics in a USP dissolution apparatus II (n = 3)……………………………………………………………………………………….60 Figure 2.7. Dependence of happ on square root of particle sizes under different hydrodynamics in a USP dissolution apparatus II (n = 3)………………………………61 Figure 2.8. Dimensionless analysis of the dependence of diffusional layer thickness happ on particle sizes and hydrodynamics in a USP dissolution apparatus II (n = 3)…..62 Figure 3.1. Chemical Structure of ketoprofen………………………………………88 Figure 3.2. Total solubility as function of pH and SLS…………………………….90 Figure 3.3. Intrinsic dissolution curves of ketoprofen at various SLS concentrations pH 4.0 buffers…………………………………………………………………………..91 Figure 3.4. The intrinsic dissolution rate as function of pH and SLS………………92 ix Figure 4.1. Dependence of drug flux ratio in the USP 50 mM phosphate buffer versus 15 mM bicarbonate buffer on drug pKa and solubility…………………………………130 x ABSTRACT TOWARD AN IN VITRO BIOEQUIVALENCE TEST by Jie Sheng Chair: Gordon L. Amidon Oral absorption of Biopharmaceutics Classification System (BCS) II drugs is limited by in vivo dissolution. The current pharmacopeial in vitro dissolution methodologies are designed for quality control, and do not reflect in vivo performance criteria. This project is an investigation into the key in vitro dissolution parameters: hydrodynamics, pH, surfactants/bile