Today's Veterinary Practice

JAN-FEB 2016

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tvpjournal.com | January/February 2016 | Today's VeTerinary PracTice elemenTs oF oncology Peer reviewed 49 16 to 24 treatments, with fractions of 2 to 3 gy, yielding a total dose of 48 to 60 gy. Levels of Pain a general understanding of the type of pain induced by defnitive radiation treatment is important; Table 2 (page 53) lists some common tumors treated with defnitive radiation therapy and expected levels of pain associated with treatment. in general, defnitive treatment of deep-seated tumors, such as brain tumors, is associated with few painful side effects, whereas treatment of superfcial tumors, such as those occurring on the skin or oral mucosa, is expected to elicit painful acute side effects. This difference in pain occurs because treatment of deeper tumors deposits most of the radiation energy in deeper tissues, such as the brain, while tissues and organs with more sensitive pain receptors, such as skin, are spared from a signifcant dose of radiation (paradoxically, the brain itself lacks pain receptors). 9 The sensation of a headache or fatigue has been reported in humans with brain tumors, and the same sensation may occur in animals. This sensation is thought to be infammatory—a result of perilesional edema and potential stretching of the meninges due to the space-occupying mass. 10 Acute Effects The target of radiation-induced damage is the dna of rapidly proliferating cells, and the most signifcant side effects of radiation therapy are desquamation of the skin, mucositis, and keratoconjunctivitis sicca of the ocular adnexa. These side effects generally occur in treated areas around a cutaneous, oral, or nasal tumor. acute side effects result from depletion of stem Recently, a veterinary product with a higher concentration of buprenorphine (1.8 mg/ mL; Simbadol, zoetisus.com) and a highly concentrated transdermal fentanyl liquid (50 mg/mL; Recuvyra, elancovet.com) have become available for treating pain in pets. Although these new, long duration, highly concentrated narcotics show promise, they must be administered and handled under the direct supervision of a veterinarian due to the potential for abuse and safety concerns. Concentrated Buprenorphine Oral transmucosal (OTM) buprenorphine at a dose of 80 to 120 mcg/kg (highly concentrated preparations, such as Simbadol, may make OTM administration more practical) is effective for analgesic durations of 12 to 24 hours in dogs and cats. 6-7 We advise against sending this drug home with clients due to abuse concerns unless no other options are available for adequate pain control. transdermal fentanyl Transdermal fentanyl liquid is a new method for treating acute pain in dogs (the product is not approved for use in cats and should not be used due to safety concerns). Its advantages include: • efficacy: Appears to reach bloodstream within 30 minutes of application, attain therapeutic plasma concentrations within 2 to 4 hours of administration, and maintain therapeutic effect for 4 days • Safety: See below • economy: Less expensive than fentanyl patches and injectable fentanyl • Convenience of administration: One transdermal application provides 4 days of analgesia. The side effects of transdermal fentanyl liquid are similar to those of injectable fentanyl, including anorexia, sedation, hypothermia, and dysphoria. Our clinical experience suggests that respiratory depression and bradycardia are less frequent than with injectable fentanyl. Remember that once transdermal fentanyl liquid has been applied, its activity cannot be halted unless it is antagonized partially or completely using butorphanol or naloxone, respectively. To minimize risks when using transdermal fentanyl liquid as a premedication, other tranquilizers and sedatives should be avoided or administered at lower doses. Transdermal fentanyl liquid also has a propofol and inhalant sparing effect 8 that should be considered during anesthesia induction and maintenance. For debilitated dogs, ½ to ¾ of the labelled dose may be applied rather than the full dose (2.7 mg/kg). Other opioids may be added if pain is under controlled. Hospital personnel and owners should be aware of the site of administration of transdermal fentanyl and avoid direct contact with it for 72 hours after application. Any contact with bare skin should be avoided and hand washing should be implemented should anyone touch the area of application before 72 hours. new opioids for Pain Control in Cancer Patients

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