Chapter 19 The Prevention and Management of Pain in Canine Patients 495and gabapentin/pregabelin. These papers are
drawn mainly from trials involving diabetic
neuropathy and post‐herpetic neuralgia, leav-
ing the relevance in animals uncertain.
(1) Pain‐modifying analgesic drugs:
(a) Gabapentin or pregabelin
(b) TCAs, e.g., amitriptyline
(c) Amantadine
(d) ± Tramadol
(e) New drugs to consider:
(i) duloxetine, venlafaxine
(ii) tapentadol
(f) Acetaminophen + hydrocodone or
codeine (breakthrough pain only).
(2) NSAIDs
(3) Weight optimization.
Cancer pain
Osteosarcoma, and any cancer metastatic to
bone, is one of the most painful chronic pain
conditions a dog may encounter. This is due to
a combination of unique factors including
upregulation of COX enzymes, osteoclast‐
induced necrosis, lymphatic obstruction, and
bioactive, pro‐inflammatory cytokines that sus-
tain and enhance the nociceptive pathways in
ways distinct from other sorts of chronic
inflammatory conditions. When clients have
opted for palliative care, it is likely that the
patient’s pain will be the terminal event. For
this reason, it is warranted to access the entire
pain‐modulating arsenal. The prospect of
drug–ADE interaction exists, but since the risk
of undermanaging the disease’s pain is death
(euthanasia), aggressive multimodal polyphar-
macy pain management is warranted. The
International Veterinary Academy of Pain
Management (IVAPM) adopted a position/
consensus statement supporting the primacy of
wise, rational use of pain management medica-
tions over the hypothetical fear of ADE in pal-
liative care situations.
A recent review in human literature using a
number needed to treat : number needed to
harm ratio (NNT:NNH) cited gabapentin, pre-
gabelin, and strong opioids as the most effec-
tive and best‐tolerated drugs in cancer‐related
pain, while amitriptyline, tramadol, and
NSAIDs elicited more minor effects or an unfa-
vorable safety profile (Tassinari et al., 2011).
(1) NSAIDs: The antineoplastic effects of cer-
tain NSAIDs in humans (Gupta & Dubois,
2001) and in dogs (Knapp et al., 1994) have
been well established and appear to be
mediated through the upregulation of the
COX2 enzymes in some neoplasms of
these species (Mohammed et al., 2004).
(2) Opioids: Fentanyl (Duragesic®) and
buprenorphine (e.g., BuTrans®) patches
are labeled precisely for use in cancer
breakthrough pain in humans. In dogs one
must be mindful that the veterinarian
could be liable if a human was exposed to
the drug during its use for the canine
patient. While the long‐term use of oral
opioids in animals is currently limited,
they would be indicated in this patient
population.
(3) Pain‐modifying analgesic drugs:
(a) Gabapentin or pregabelin
(b) TCAs, e.g., amitriptyline
(c) Acetaminophen ± hydrocodone or
codeine
(d) Amantadine: though not studied in
humans for cancer pain, its NMDA‐R
antagonist activity makes its consid-
eration worthy
(e) ± Tramadol
(f) Additional drugs to consider:
(i) duloxetine, venlafaxine
(ii) tapentadol
(iii) mexilitine—for chemotherapy‐
induced neuropathic pain.
(4) Bisphosphonates: Compounds that may
palliatively alleviate osteosarcoma‐related
pain by decreasing osteoclast activity, with
pamidronate in most common use for
dogs (Fan et al., 2005). Intravenous infu-
sions are administered in patients not
undergoing amputation and chemother-
apy. Anecdotally, 60% of dogs will be
responsive within a week, and in about
half of those the effect will be durable (i.e.,
>4 months). It appears to be most effective
when administered as part of multimodal
therapy (Lorimier, L. P., personal commu-
nication). Nephrotoxicosis is reported to
be a limiting adverse effect.
(5) Lidoderm® patch: Used with anecdotal
success and considered safe due to very
little systemic absorption. However, the
patch must be secured properly to prevent
ingestion.