Thanks for the clarification. . .I was thinking that Crispin's first liver enzyme elevation was before the melatonin.
From what I have read, Melatonin causes no hepatopathy in dogs or cats and there have been "no reported side effects in ferrets". I have read about it's use as adjunctive treatment for adrenal disease in ferrets (I personally have not had a ferret patient with adrenal disease. . .yet), but know that oral melatonin or an implant is used.
There's a vet tech. on this site that saw our conversation and thought that this handout would be helpful. I think you may have read this but will pass it along anyway. We all work together here! http://www.lafebervet.com/downloads/education/Adrenocortical_Disease_in_the_Ferret.pdf
I've also researched S-Utensil Methionine or SAMe which we do use to support and heal the liver. I cannot find any contraindication for use with so there should be no problem using these together.
Since Crispin's liver enzyme is still really barely elevated even after 2 years on the melatonin, I doubt that giving the melatonin is causing any problem. I would think that if the melatonin was cause a hepatopathy that more and more liver cells would be affected and his ALT would be elevating.
So, these are my thoughts now: I would continue the melatonin. I would also recommend that when you can you have the abdominal ultrasound done to evaluate all of Crispin's abdominal organs but mostly to look at his liver and gall bladder, pancreas and adrenal glands. I would also say that using the SAMe may be helpful to Crispin.
One question I have since looking at the briefs about melatonin again: What dose are you giving him? If it is 1ml, then what is the concentration of the liquid you are using? Or are you giving him 1mg?