I am glad my vet figured it all out for me and recommended Glycoflex - much easier! She prefers Glycoflex because it contains perna mussel.
My vet is big on holistic supplements and has a book that she looks up dosages by weight, recommended uses, etc. She wrote everything down on paper, how much Lady should get of each everyday, including MSM and vitiman C so I could choose which Glycoflex formula was best.
I think a lot depends on the stage of arthritis. Lady has very bad arthritis so my vet wanted her to get MSM everyday for inflamation. You might not need anti-inflamatories in a young dog with, say, borderlines knees that you are trying to avoid surgery with. An older dog like Maxi would probably need MSM which Syn-Flex doesn't appear to have, but you could add that separately.
Here's some more information:
Perna Canaliculus Mussel
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The perna canaliculus mussel is a frequent source of glucosamines in joint supplement products including the popular line of glyco-flex products for dogs, cats & horses. The perna mussel comes from New Zealand and is a natural source of glucosamines, glycosaminoglycans and omega-3 fatty acids. Other names for the perna mussel or perna rich supplements include green lipped mussel, seatone, or greenshell mussel. Perna mussel has been successful in managing degenerative joint diseases and arthritis in both human and people. It also is reported to improve mobility and reduce the pain, swelling, and inflammation associated with arthritis. The perna mussel is often used as a dietary supplement to help with issues related not only arthritis, but also, asthma, menstrual pain, multiple sclerosis and skin problems as well. Although generally beneficial and safe, some side effects are possible including allergic reactions, fluid retention, skin rash and upset stomach. In addition, perna mussel supplements should not be given to people or animals with allergies to fish or shellfish.
Dog Joint Supplements With Perna: Glyco-Flex Glyco-C-Mine Synovi Resources ArthiSoothe
MSM - Methylsulfonylmethane
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MSM is a commonly used acronym for methylsulfonylmethane, a naturally occurring source of sulfur and an ingredient often featured in joint supplement products. Methylsulfonylmethane (MSM) contains sulfur in a form the body can readily use. Sulfur is necessary for the production of collagen, glucosamine, chondroitin and certain anti-oxidants - all of which are vital to healthy cartilage and overall joint health. MSM is believed by some to have multiple health benefits including anti-inflammatory, detoxifying and healing properties. MSM is also claimed to help with blood circulation, muscle cramps, energy, alertness, food allergies and free radicals. One advantage to MSM is that it provides the vital sulfur ingredient without having a "sulfuric" taste or smell.