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Pharmacology
Chapter 14 Drugs Used to Relieve Pain & Inflammation
Question | Answer |
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Explain the anatomy & physiology associated with pain production & relief. | Pain is an unpleasant sensory/emotional experience associated with tissue damage. Pain starts in the terminal ends of sensory nerve fibers called nociceptors. It is activated through chemical, mechanical or thermal stimulation. |
List the four steps in the production of pain sensation. | Transduction-nociceptors create impulses; transmission--impulses transmitted to CNS; modulation--suppression or amplification of impulses (sent to cerebral cortex); perception--impulses processed & recognition= pain perception. |
What are the two types of fiber systems that transmit pain impulses? | Type A delta fibers--sharp, localized pain; Type C unmyelinated fibers--dull, poorly localized pain (humans). |
Discuss the difference between physiologic and pathologic pain. | Physiologic--alerts the animal to potential danger & avoid further tissue damage. Pathologic--results from tissue/nerve damage; three classes: visceral-hollow abdominal organs; somatic-musculoskeletal system; neuropathic-injury of peripheral or CNS |
Describe the concepts of preemptive & multimodal pain therapy. | Preemptive--anticipate pain & provide medication to prevent it; multimodal--use of multiple products in coordination to provide most pain management possible w/ comfort of patient in mind. |
List the physical signs associated with the expression of pain in animals. | increased heart rate; increased respiratory rate; mydriasis; salivation; vocalization; changes in facial expression; aggression; guarding the site; restlessness; unresponsiveness; failure to groom; abnormal gait; abnormal stance. |
Describe the mechanism of action of NSAIDs. | Inhibit the enzyme cyclooxygenase (COX), of which there are two forms: COX 1 (constituted form)--modulates renal blood flow & synthesis of GI mucosa; COX 2 (induced form)--promotes formation of prostaglandin from arachidonic acid. |
Which NSAIDs are thought to produce fewer GI side effects? | those that inhibit COX-2. |
List the different types of NSAIDs. | salicylates; pyrazolone derivatives; flunixin meglumine; dimethyl sulfate (DMSO); buscopan compositum; acetaminophen; propionic acid derivatives. |
Which NSAID has limited use in veterinary medicine & why? | acetaminophen; it is discouraged due to the risk of potential toxicity. |
Describe the uses for salicylates. | mild to moderate pain (arthritis, hip displasia); post-adulticide treatment for heartworm disease; analgesia/anti-pyrexia; cats w/ cardiomyopathy; endotoxic shock. |
Explain the uses of pyrazolone derivatives for pain management. | Analgesia (mild to moderate pain); anti-inflammatory action; anti-pyrexia. |
When is the use of flunixin meglumine appropriate for pain management? | For use in horses/cattle for analgesia; anti-pyrexia; anti-inflammatory effects. |
Describe the uses for dimethyl sulfate (DMSO). | Topical for acute swelling in dogs & horses; IV adjunct to intestinal surgery; cerebral edema or spinal cord injury (IV); perivascular injection of chemotherapeutic agents (topical). |
When is buscopan compositum used for pain? | In horses, for abdominal pain associated w/ colic. |
List some propionic acid derivatives and their uses. | carprofen--degenerative joint disease; post-operative pain. naproxen--pain, inflammation, lameness (from myositis in horses); soft tissue diseases (horses). Etodolac & deracoxib--osteoarthritis in dogs. Firocoxib--osteoarthritis in dogs & horses |
What are potential adverse side effects of NSAIDs? | GI ulcers; GI bleeding; hepatotoxicity; nephrotoxicity; inhibition of cartilage metabolism; bone marrow suppression; bleeding tendencies from reduced platelet aggregation. |
Describe how antihistamines work. | They prevent histamine from combining with tissue receptors or by displacing histamine from receptor sites. |
What is the difference between H1 histamine receptors and H2 histamine receptors? | H1--affect progression of allergic response; may contribute to motions sickness & nausea. H2--cause increased flow of hydrochloric acid by GI mucosa; blockers reduce secretion and can be used to treat GI irritation/ulcers. |
List the indications for muscle relaxants. | Acute inflammatory & traumatic conditions of muscles and the spasms that may result. |
Describe the two categories of corticosteroids & their effects. | mineralcorticoids--regulate electrolyte & water balance in body; glucocorticoids--exert anti-inflammatory and immunosuppressive effects; influence metabolism of carbohydrate, fat & protein. |
Describe the hypothalamic-pituitary-adrenal axis, which controls the release of corticosteroids in the body. | Feedback mechanism related to cortisol level in blood. Hypothalamus sends CRF to anterior pituitary when level low; pituitary releases ACTH into blood, carried to adrenal cortex; adrenal gland releases cortisol. High level inhibits release of CRF. |
List indications for the use of corticosteroids. | allergic reactions/conditions; inflammatory conditions; shock/toxemia; laminitis; conjunctivitis/uveitis; Addison's disease; autoimmune disease; lymphocytic neoplasms. |
Describe short- and long-term side effects of corticosteroid use. | Short--polyuria, polydipsia, depressed healing, polyphagia & weight gain, hyperadrenocorticism, GI ulcers, abnormal behavior. Long--osteoporosis; hypoadrenocorticism; thinning of skin & muscle wasting. |
What is the mechanism of action of local anesthetic agents? | Prevent the generation and conduction of nerve impulses into peripheral nerves. |
List indications for local anesthetic agents. | General anesthesia not available or too dangerous; small laceration; diagnose lameness in horses; prevent straining during replacement of prolapsed uterus; place endotracheal tube in cats |