Pain relief for Labrador

Well we have this 11 year old Labrador with an arthritic problem.

So after spending a sum of money at the Vet, we were advise to use
Rimadyl 100mg. This given as a half tablet twice a day.

Is there a good and cheaper alternative. The Rimadyl costs us 3 aussie
dollars per day.

If we don't give the dog this medication then we have hell in a way.
Excessive drinking of water takes place which can give one the idea that
this dog is a water diabetic. Never mind getting you up 3-4 times during
the night as well.

I might mention that our Lab is also epileptic, and so has her 2 pills
twice a day for that as well.

I might mention also that I saw a different Vet and he makes a compound
up for arthritis that you administer once in the evening with food that
is supposed to last for 24 hours. The tube of this stuff might last a
week, but we need to try it yet.

Human pills are cheaper at least for us; I know that our human pain
relief pills are bad news for dogs and cats.

Cheers Ezra