Chapter 19 The Prevention and Management of Pain in Canine Patients 489postherpetic neuralgia, with a superior
kinetic profile to gabapentin (does not
require dose escalations). Its utility in dogs
remains unknown but it would be expected
to have a similar, if not more predictable,
effect to gabapentin. A pharmacokinetic‐
based dose has been proposed for dogs
(Salazar et al., 2009). It is an FDA controlled
(and rather expensive) drug and a generic
version will not be available until after 2018.
● Topiramate (Topamax®) is an anticonvul-
sant drug in common use for chronic
migraine headaches in humans, and with
evidence of efficacy for other chronic pain
conditions such as lower back pain
(Muehlbacher et al., 2006). Studies have
established the pharmacokinetics in dogs
and one study looked at its use in a canine
neuropathic pain disease; improvement
was shown but was less effective and had
more adverse effects than gabapentin
(Plessas et al., 2015).
● Ziconotide (Prialt ®) is a voltage‐gated cal-
cium channel blocker that was designed for
intrathecal use only. It represents a new
class of drug and therapeutic intervention
for long‐standing severe neuropathic pain
in humans (Schmidtko et al., 2010).
Amantadine
Amantadine is an antiviral compound with
weak dopaminergic effects, and is reported to
exert an analgesic effect through NMDA recep-
tor antagonism (Plumb, 2011). It is the only
drug shown to be an effective adjunct to
NSAIDs in canine OA, with improved pain
scores when the NSAID was combined with
amantadine, versus NSAIDs alone (Lascelles
et al., 2007). Toxicity and kinetic studies have
been performed in humans (Vernier et al., 1969),
but not in dogs.
Tips for use
The customary dose in dogs is 3–5 mg/kg s.i.d.,
but pharmacokinetics suggest a b.i.d. schedule
as more rational (Moore, 2016). Agitation, trem-
ors, and diarrhea are adverse effects reported
anecdotally.
Other drugs in class
● Orphenadrine, an anti‐Parkinson’s
NMDA‐R antagonist blocks voltage‐gated
sodium channels in the dorsal root ganglion
and has demonstrated analgesic action in
chronic pain states (Desaphy et al., 2009).
Experience in animals is limited.
See Figure 19.3 for cautions regarding possible
monoamine drug interactions.Tricyclic antidepressantsTricyclic antidepressants (TCAs) exert their
analgesic activity by blocking norepinephrine
and serotonin (5‐HT) reuptake in the dorsal
horn, allowing these inhibitory neurotransmit-
ters to exert a prolonged and more pronounced
effect. Since clinical depression is also partially
mediated through norepinephrine and seroto-
nin, patients may enjoy the benefit of TCAs
from these coexisting mechanisms. Additional
effects include interaction with NMDA activity
and sodium channel blockade. As a class,
TCAs are a first‐line medication for neuro-
pathic pain in humans (Finnerup et al., 2005).
Amitriptyline is the most commonly used TCA
in humans, primarily for diabetic neuropathy
(Longmire et al., 2006), and is used in animals
primarily for chronic feline interstitial cystitis
(Chew et al., 1998). The pharmacokinetics of
amitryptiline have been evaluated in dogs
(Norkus et al., 2015), and there is one published
report of its use in a case of neuropathic pain
(Cashmore et al., 2009). In humans, despite the
efficacy of TCAs in treating neuropathic pain,
the adverse effect profile often limits its use.
Anecdotally in dogs, suggested doses of up to
3–4 mg/kg b.i.d. seem to be well tolerated
(KuKanich, 2013).Other drugs in class
● Cyclobenzaprine (Flexeril®) is a muscle
relaxant with a chemical structure similar to
TCAs, and is used in humans for fibromyal-
gia and pain associated with muscle spasm
and myofascial trigger points.See Figure 19.3 for cautions regarding possible
serotoninergic drug interactions.