The nonsteroidal antiinflammatory drug (NSAID) salsalate while approved for use in humans is not approved for use in dogs. I could locate no literature pertaining to its adverse effect profile in dogs nor its use in general. Aspirin is a similar NSAID and can administered at a dose of 10 mg/lb with food twice daily. For a better overview, please see my synopsis of how you might approach Pepper's osteoarthritis:
We use a multimodal approach to osteoarthritis in our dogs - dietary management, nonsteroidal antiinflammatory pain relief, neutraceuticals, life-style changes and stem cell therapy. When used concomitantly these approaches should synergize and provide the best control of symptoms. For example, Pepper might show considerable improvement if you add fish oil to her diet. The omega-3 fatty acids in fish oil are anti-inflammatory. I use the cost-effective generic human fish oils and dose them at 20 mg/lb daily of the EPA in the fish oil. You'll find the amount of EPA on the label of your fish oil product. If not, you should be able to find that information on the manufacturer’s website.
Avoid flax oil because it is poorly bioavailable to dogs. They can't metabolize it properly.
If you prefer, there are diets that are extremely high in omega-3 fatty acids. Hill's Prescription Diet j/d is one such diet.
Many vets feel that injections of Adequan (polysulfated glycosaminoglycan) work better than oral neutraceuticals such as glucosamine/chondroiton sulfate or the over the counter Cosequin or prescription Dasequin (please see here: http://www.amazon.com/Nutramax-Cosequin-PLUS-Chewable-Tablets/dp/B003ULL1NQ/ref=sr_1_1?s=pet-supplies&ie=UTF8&qid=1432474254&sr=1-1&keywords=cosequin). Adequan is injected into Pepper weekly for a number of weeks at her vet's discretion. You can read more about Adequan here: http://www.adequancanine.us/
Regenerative stem cell therapy has come into its own and is now available for addressing osteoarthritis in dogs . Please see Vet-Stem's website here for more information:***@******.*** The regenerative stem cells are created from Pepper's fat cells and are capable of differentiating into a variety of tissue types including tendon, ligament, bone, cartilage, and muscle and have been proven to reduce pain and inflammation. I understand, however, that you may not want such an invasive procedure for Pepper.
We have to suspect that just as in people, osteoarthritis in dogs is painful. If a prescription nonsteroidal antiinflammatory drug (NSAID) such as carprofen or meloxicam isn't sufficient for controlling pain, please consider adding a well-tolerated narcotic such as tramadol to these therapies mentioned above. All of these drugs are available from Pepper's vet. Aspirin dosed at 10 mg/lb with food every 12 hours can be helpful in a pinch. Acetaminophen is OK at 7 mg/lb thrice daily but isn’t antiinflammatory as is aspirin.
Weight reduction is essential. The less weight Pepper's joints need to carry, the better.
Please respond with further questions or concerns if you wish.