Hi X,
You are right-giving 4 mls would be tough.  Melatonin comes in 1 mg and 3
mg tablets, and they are OTC.  Most stores (GNC, Wal-Mart, etc) carry the
tablet form.  You can crush the 1 mg tablet and mix with a small amount of
Ferrretone or food to give once a day, or use the 3mg tablet to mix with
ferrettone or food (A/D, baby food) for a 3 day supply.  I would recommend
the 1 mg tab, so you are giving the right amount per day.  On the other
hand if you have 3+ ferrets that you will be medicating then the 3mg
tablet is a little better cost wise.
 
Again I suggest giving it 8-9 hours after sunrise to help mimic
fall/winter photoperiods.
 
Hope to post more info on the injectable mink implant soon.
 
Hope that helps,
Jerry Murray, DVM
[Posted in FML issue 3669]