Duralactin or Microlactin alone?

One of my cats has had respiratory issues(upper and lower: mild asthma, URIs, allergies) most of his life(he's a 15 year old former feral).  He had a recent URI flareup and I reordered his lysine/dmg treats along with duralactin(the lysine/microlactin/omega liquid combo) and the Duralactin capsules that are simply Microlactin.  I considered ordering "people" Microlactin but could not find much information/reviews indicating it's efficacy.  We had it at the vitamin store I worked at but it was very expensive, sold poorly, was marketed for joint inflammation alone, and I can't recall any positive reviews on it.  Has anyone had any experience with it?  I thought it was time to try something new and if anything it could at least help with his arthritis. 

I wouldn't give anything that I didn't trust completely.  You seem to have a poor opinion of the Microlactin. Go with your instincts.