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Exogenous and endogenous drug delivery to the bovine eye

Punch, Peter Ivan Percy (1984) Exogenous and endogenous drug delivery to the bovine eye. PhD thesis, Murdoch University.

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Abstract

Traditional methods for the treatment of infectious bovine keratoconjunctivitis (IBK) have principally involved the topical application of antibacterial drops and ointments. Repeated application of these preparations are necessary to maintain therapeutic drug concentrations in the eye. It has been previously suggested that the requirement for repeated applications of topical drugs to cattle affected with IBK was the major reason for cattle owners failing to treat infected cattle.

Two methods of treatment which would require the handling of infected animals on only one occasion and which could be administered by lay personnel were investigated. The first method was the investigation of chemically modified collagen and gelatin as possible biodegradable matrices for the sustained delivery of gentamicin to the bovine eye. Chemical modification procedures used included the solubilisation of collagen by succinylation and crosslinking collagen and gelatin by the addition of formaldehyde. Solubility of the collagen and gelatin was examined in normal saline and an artificial tear solution. None of these procedures resulted in a matrix which would provide an adequate drug delivery polymer due to poor control of the drug release rate and poor mechanical properties. Investigation of model plastic ring shaped inserts failed to find a method for fitting an insert which would be retained in the eyes of all cattle, but it was confirmed that the material the insert was made from must by sufficiently rigid to retain its shape and yet elastic enough to conform to the shape of the conjunctival sac. From these experiments it was concluded that the design of an antibiotic impregnated biodegradable ocular insert for use in cattle eyes using modified collagen or gelatin was not practical and that insoluble inserts would offer considerable advantages over soluble inserts. Insoluble inserts would provide better retention of the devices and greater control of the drug release rate.

The second method investigated was the systemic administration of antibiotics to determine if concentrations of antibiotic in tears adequate to inhibit Moraxella bovis, the principle aetiological agent of IBK, could be achieved. Lipophilic antibiotics were detected in tears in concentrations which should inhibit the growth of M. bovis. The difference between lipophilic and non-lipophilic drugs was probably due to failure by the non-lipophilic antibiotics to equilibrate across the plasma: tear membrane prior to the secretion of the tears. These results may be of considerable importance for the treatment of IBK.

Item Type: Thesis (PhD)
Murdoch Affiliation: School of Veterinary Studies
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: repository@murdoch.edu.au. Thank you.
Supervisor(s): Slatter, Douglas, Costa, Nick and Wilcox, Graham
URI: http://researchrepository.murdoch.edu.au/id/eprint/53397
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