Lysodren was been pretty well abandoned years ago in favor of more
effective approaches which are better suited to the type of adrenal
disease ferrets get (which isn't Cushings).  See these vet posts and
article, and certainly with a little searching you will find more:
 
http://miamiferret.org/fhc/murray.htm
http://listserv.cuny.edu/Scripts/wa.exe?A2=ind9605&L=ferret-search&P=R24306
http://listserv.cuny.edu/Scripts/wa.exe?A2=ind0101&L=ferret-search&P=R21160
http://fhl.sonic-weasel.org/browse.php?msg=YG7815
http://fhl.sonic-weasel.org/browse.php?msg=YG3473
http://fhl.sonic-weasel.org/browse.php?msg=YG1137
http://fhl.sonic-weasel.org/browse.php?msg=YG1127
http://fhl.sonic-weasel.org/browse.php?msg=SG3059
http://fhl.sonic-weasel.org/browse.php?msg=YG11338
http://fhl.sonic-weasel.org/browse.php?msg=YG1952
http://fhl.sonic-weasel.org/browse.php?msg=YG1928
[Posted in FML issue 4363]