EVALUATION OF THE OFWL IRON CHELATOR DEFERIPRONE iNÏTHE WHITE LEGHORN CHICKEN AND DOMESTIC PIGEON A Thesis Presented to The Faculty of Graduate Studies of The University of Guelph by DOUGLAS P. WXITESIDE In partial FuIfilment of requirements for the degree of Doctor of Veterinary Science August, 200 1 O Douglas P. Whiteside, 2001 National Library Bibliothèque nationale of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. rue Wellington Ottawa ON KIA ON4 Ottawa ON KIA ON4 Canada Canada Your RIe Vorre réMmce Our 6Ie Mfr8référence The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, han, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in rnicroform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni Ia thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. EVALUATION OF THE OFML IRON CHELATOR DEFERIPRONE IN THE WHITE LEGHORN CHICKEN AND THE DOMESTIC PIGEON Douglas P. Whiteside Advisor: University of Guelph, 2001 I.K. Barker Iron storage disease is a significant concern for avian coI1ections in zoos and in certain species of pet birds. In this thesis, the clinical applicability of the oral iron chelator defenprone to treat iron overload was evaluated in avian species. After inducing experimental hemosiderosis in two avian models, the White Leghorn chicken and the domestic pigeon, a combined pharmacokinetic and clinical trial was carried out. Deferiprone is rapidly absorbed from the avian gastrointestinal tract, with peak plasma concentrations of the dmg in iron-loaded chickens (48.65 t 13.75 pg/mL) and pigeons (22.23 t 13.75 ug/mL) reached approximately one hour after administration of an oral dose of 5Omgkg. The dmg has a large apparent volume of distribution in the chicken and the pigeon, and the elimination half-life of approximately three hours in both species is longer than in studied marnmals. As measured by hepatic iron concentrations at the end of the snidy, deferiprone eliminated experimentally-induced hemosiderosis in a 30 day treatment period. Administration of the dmg Ieads to a dose-dependent increase in iron excretion in both species of birds. Potential complications associated with deferiprone therapy in birds are zinc deficiency and weight loss, and possible mortality, especially as iron stores are depleted. Deferiprone is a promising orally active iron cheIator for the treatment of iron overload in birds. Further clinical studies in affected species are needed to determine the most effective way to use this dmg while rninimizing the side effects associated with its administration. ACKNOWLEDGMENTS This project was made possible through the support and aid of many people. I would like to first extend thanks to my research advisory cornmittee, Ian Barker, Kay Mehen, Peter Codon and Robert Jacobs. Their insightfd contributions and editorial comrnents greatIy improved the quality of this thesis. The pharmacokinetic component of this project would not have been possible without the generous involvement of Michael Spino and Apotex Inc. 1 am indebted to Ange10 Tesoro at the Faculty of Pharmacy, University of Toronto, for his expertise in performing high performance liquid chromatography for determination of plasma deferiprone concentrations. 1 particularly would like to thank Michael Spino and Fernando Tncta of Apotex Inc., and Jake Theissen and Ange10 Tesoro of the Faculty of Pharmacy, University of Toronto, for their support and refkeshing enthusiasm for the project, and for inspiring many inteIIectua1 discussions about rny research. Apotex Inc. generously supp lied the deferiprone for the project. Many thanks to the veterinary technicians and externship students at the Toronto Zoo's Anima1 Health Center who assisted me with the project, and to the keepers at the Animal Health Center for their assistance with animal husbandry. Am Bell of the Arkell Research Station, University of Guelph generousIy provided the chickens and their food for the study. Bruce Hunter was very supportive of the pr~ject.Trudy Davis energetically executed the administrative details of my graduate program. William Sears provided statistical guidance. Nick Shrier of the Animal Health Laboratory, University of Guelph was instrumental in the determination of hepatic and excreta iron concentrations. 1 am especially appreciative of the support of my advisors, lan Barker and Kay Mehren. Both have been patient and supportive fnends, allowing me the fieedorn to learn from my mistakes, and providing invaluable insight and guidance when it was most needed. Many thanks to lan for sharing his infinite knowledge with me, and for teaching me histopathology. 1 wodd also like to thank Graham Crawshaw and Dale Smith for their support during rny residency. 1 have been able to share the experience of the graduate progam with several intellectual and dedicated colleagues whom 1 consider close friends. Finally, 1 would like to acknowledge Kestra Self, and rny farnily for their unconditional love and support. Many thanks to Kestra for her patience. and for providing unrelentinj persona1 support and assistance when it was needed most. Thanks to rny mom who has always been my pilla- of support and encouragement, inspiring me to pursue my goals and drearns, to my brother Rob, who has always been my closest fiend, and always motivates me to think beyond traditional boundaries, and to Bill for his support. The Toronto Zoo Foundation and the Pet Trust Fund at the Ontario Veterinary College generously fùnded this research project. I am also grateful to the Toronto Zoo Foundation for funding my residency. DECLARATION OF WORK PERFORIMED 1 declare that, with the exception of the technical analyses listed below, al1 of the work reported in this thesis was performed by me. Plasma analysis for deferiprone using high performance liquid chrornatogaphy was performed by Ange10 Tesoro at the Faculty of Pharmacy, University of Toronto (Toronto, Ontario), in consultation with Dr. Jake Theissen and Dr. Michael Spino (Apotex Inc., Weston, Ontario). The template for pharmacokinetic calculations was also developed at the Faculty of Phmacy, University of Toronto. Al1 hematology, Siochemical, trace rnineral, and plasma iron assay analyses, and hepatic and excreta iron concentration determinations were camied out at the Animal Health Laboratory, University of Guelph (Guelph, Ontario). The Histotechnology division of the Animal Health Laboratory performed the histological staining of tissue sections. Al1 statistical analyses were psrforrned in consultation with William Sears at the Ontario Veterinary College, University of Guelph (Guelph, Ontario). LIST OF TABLES Table Page Comparison of pharmacokinetic parameters afier oral administration of a single dose of defenprone to iron-loaded and control White Leghom chickens. Comparison of pharmacokinetic parameters after oral or intravenous administration of a single dose of deferiprone to control White Leghorn chickens. Comparison of pharmacokinetic parameters after oraI administration of a single dose of deferiprone to iron-loaded and control domestic pigeons. Comparison of pharmacokinetic parameters after oral or intravenous administration of a single dose of deferiprone to non-iron-loaded control domestic pigeons. Comparison of p harmacokinetic parameters after administration of a single dose of deferiprone on Day 1 and Day 30 to iron-loaded domestic pigeons. Mean weekly change in absolute and percentage bodyweight in iron- loaded and deferiprone treated, iron-loaded and control White Leghom chickens and domestic pigeons. Mean plasma zinc levels in iron-loaded and deferiprone treated, iron- loaded and control White Leghom chickens and domestic pigeons. Plasma iron, total iron-binding capacity, unbound iron-binding capacity and transferrin saturation in iron-loaded and deferiprone treated, iron-loaded and non-iron-Ioaded control White Leghorn chickens and domestic pigeons. 90 Companson of mean hepatic iron concentrations in iron-loaded and deferiprone treated, iron-loaded and non-iron-loaded control White Leghorn chickens and domestic pigeons. 9 1 Summary of histological grading of Perl's Prussian blue stained tissues in the three treatment groups- iron-loaded and deferiprone treated, iron-loaded and non-iron loaded White Leghom chickens. 4-5b Summary of histological grading of Perl's Pmssian blue stained tissues in the three treatrnent groups- iron-loaded and defenprone treated, iron-loaded and non-iron loaded domestic pigeons. 94 LIST OF J?IGUFWS Figure Page Structural formula of defenprone Mean plasma concentrations versus time (0-6 hours) highlighting the absorption and early distribution of defenprone in iron-loaded and control White Leghorn chickens afler a single oral dose. Mean plasma concentraiions versus time (0-24 hours) in iron-loaded and control White Leghorn chickens after a single oral dose of deferiprone. Mean plasma concentrations versus time (0-6 hours) afier