I wondered the same thing about dog glucosamine vs human, I had a client who suggested the human version. I asked 2 different pharmacists, they told me that no you should never give any animal human supplements because:
1. they will only retain 5% of the glucosamine because ours is processed differently
2. they cannot digest the plastic coating around the glucosamine itself and it hurts the stomach lining of the animal and that can lead to complications.
3. you need ALOT more of a human pill vs a dog pill.
4. it's just bad.... anything that is made for humans should not be given to animals unless expressly recommended by your vet.
I spend 100$ (plus tax) every 3 months for my dog's glucosamine pills, she is currently on Novo-Flex 900mg tablet, she gets 2 per day (she's a king shepherd 112 pounds) thats about 33$ per month. As long as I can afford to spoil her, keep her at 100% health, idc what it costs, she will get what she needs, 33 bucks a month is chump change to the love I get back from her lol, neurotic though she may be XD