Page 76 - BSAVA Guide to Pain Management in Small Animal Practice

5 | Pharmacological treatment of pain

VetBooks.ir opioid sparing e ect Romundstad et al., 4; NSAIDs, or those prone to this problem. This
may be prevented by the administration of
aldron et al., 1 .
famotidine or omeprazole to reduce gastric
Data are lacking in dogs about the analgesic
e ects of glucocorticoids and, despite acid production u anich, 1 . See
dexamethasone being licensed as an anti- ‘Serotonin toxicity’.)
in ammatory but not for perioperative In humans, tramadol is metabolized to an
analgesia , only the clinical e cacy of active metabolite (O-desmethyl tramadol or
prednoleucotropin (PLT) has been documented . is a high a nity P agonist and is
(McKellar et al., 1991 . times as potent as tramadol. ogs produce
he e cacy and tolerability of PL , a only small amounts of ODM and lack of this
combination of cinchophen and prednisolone, is metabolite may explain the variations in e cacy
also con rmed anecdotally and by direct reported in this species. Indeed, a signi cant
clinical experience. Cinchophen is an NSAID, proportion of dogs may not respond at all.
with a non speci c C inhibiting e ect. PL is Analgesia associated with tramadol in dogs
licensed for the treatment of osteoarthritis in may be primarily due to its serotonin and
dogs, and it is contraindicated in pregnancy, noradrenaline reuptake inhibition. Cats produce
severe renal disease, congestive heart failure, more active metabolites and analgesia is likely
hepatitis, and concurrent diuretic therapy. It due to opioid receptor agonism, and opioid-
should not be used with other steroids and related adverse e ects may occur. In cats, the
NSAI s. Side e ects of PL are those typical of duration of action is longer, so that twice daily
steroids and NSAIDs, and include polyuria/ dosing is appropriate (Pypendop and Ilkiw,
polydypsia/polyphagia, fat redistribution, 8 . ramadol used alone is not suitable for
immunosuppression, and gastrointestinal upset. treating severe pain (Benitez et al., 1 , but it
The manufacturer’s indications state that an may be useful in combination with NSAIDs.
initial 14 day treatment period should be Tramadol has become popular as it can be
followed by a 14 day treatment free interval, given orally at home by the owners. It is useful
before continuing with further treatment. The when NSAIDs are contraindicated (e.g. if the
e uivalent of . 6 mg kg of prednisolone patient is receiving corticosteroids), or if
should be administered twice daily with food. outpatients require analgesia in addition to that
The dose should be tapered at the end of a provided by NSAIDs. The usual recommended
treatment period, as for steroid therapy. dose is mg kg twice cats or three times
(dogs) daily by mouth.
Tramadol Sustained release tramadol tablets are
Tramadol is a MOP agonist with weak receptor available for human use; however, these are
unsuitable for dogs due to poor absorption and
a nity. It also inhibits serotonin and short duration of action iorgi et al., 1 . heir
noradrenaline reuptake by spinal cord use has not been investigated in cats.
neurones, providing analgesia by
enhancement of descending antinociceptive
pathways at the spinal level. It is metabolized Serotonin toxicity
in the liver with several active metabolites Serotonin toxicity may occur if drugs
potentially being produced and excreted in that increase serotonin concentrations
urine. In humans, tramadol can lower the are overdosed or administered together.
seizure threshold and, while this has not been Reported veterinary cases have been due
investigated in veterinary patients, it may be to overdose, rather than drug combinations.
wise to avoid tramadol in animals with a history Examples include St John’s wort, foods
of seizures. There is some evidence in humans containing high levels of tryptophan (e.g.
and dogs that tramadol or other serotonin cheese), tramadol, pethidine, fentanyl,
reuptake inhibitors can increase the risk of chlorpheniramine, selective serotonin
gastro-duodenal ulceration in patients taking

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