E-drug: Cyclosporin eye drops (cont'd)
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A more basic question to how to formulate cyclosporin eyedrops,
is: what is the evidence that topical cyclosporin has clinically useful
activity in local immune-mediated inflammatory conditions in the
eye? Does this large and poorly soluble agent penetrate the cornea
at rates high enough to establish useful concentrations in the
aqueous humor and various internal eye structures?
But, if I had to make such a formulation, I'd try using 1.8 megarads
of gamma ray sterilization. Conventional pharmaceutical practice
is to use 2.5 megarads, but for a topical agent I think that the lower
dose would be satisfactory. One should, however, look for
radiation-induced breakdown products of a complex molecule like
cyclosporin A. Another approach is to try 0.25 micron filtering,
though I don't know how well olive oil will pass thru such filters.
John Urquhart MD, FRCP(Edin)
Prof. of Pharmaco-epidemiology
Maastricht University
Maastricht, NL
US office: 975 Hamilton Ave
Palo Alto, CA 94301, USA
internet: urquhart@netcom.com
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