What are the recommended dosages and indications for adjuvant drugs in the treatment of pain in dogs and cats?

The adjuvant drugs listed in Table 16 are recommended for use in combination with opioids, NSAIDs, and local anesthetics, or as substitutes when there is a contraindication for one of the previous classes of analgesics.
Amantadine is effective in dogs with refractory OA to treatment and should be administered with NSAIDs or other analgesics. Doses of up to 14 mg/kg have been reported in combination with meloxicam in a dog with neuropathic pain.
Amitriptyline should not be administered concomitantly with other serotonergic drugs and has an unpleasant taste, which may not be an option if administration becomes stressful or forced.
Gabapentin should be administered in combination with opioids and can cause sedation and ataxia. It is effective in chronic pain in dogs and cats, and in reducing stress related to transport and veterinary visits in cats.
Pregabalin can be administered once 1 hour before intervertebral disc surgery followed by administration every 8 hours for 5 days after surgery in dogs. It can also be used to reduce stress related to transport in cats.
Ketamine is used for preoperative pain in dogs and cats and is administered as a bolus before surgery followed by a CRI for up to 72 hours.
Tramadol is used for preoperative pain in cats and can be administered orally, intravenously, or intramuscularly. It should not be administered concomitantly with other serotonergic drugs.
Glucocorticosteroids are best indicated for the treatment of allergic and autoimmune disorders and specific inflammatory conditions. They have anti-inflammatory properties that can provide pain relief.
Anesthetics inhalants do not have antinociceptive properties and simply block pain perception during general anesthesia.
Maropitant is an NK-1 receptor antagonist used to treat and prevent emesis. It can reduce the requirements for inhalant anesthetics after IV administration in dogs and cats.
Acepromazine is a tranquilizer that does not have analgesic properties. It is widely used in the perioperative period and can cause clinically significant hypotension at high doses or in hypovolemic animals.
Physical rehabilitation involves the clinical evaluation and treatment of musculoskeletal and neurological deficiencies in intra-articular, capsular, ligamentous, muscular, myofascial, and central and peripheral neural tissues.