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24 Cards in this Set
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species capable of vomiting
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carnivores/omnivores
primates swine some birds reptiles |
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species not capable of vomiting
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horses
ruminants rodents guinea pigs rabbits |
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vomit reflex
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vomiting center of brain; ultimately initiated by vomiting center through direct or indirect stimulation
afferent pathways to vomiting center GIT - stimulation of afferent nerves in stomach and intestines by irritation, inflammation, distension pharyngeal - direct stimulation of glossopharyngeal n. intracranial - trauma, intracranial pressure, psychogenic vestibular - motion sickness, vestibulitis humoral - blood-borne drugs/toxins stimulation of CRTZ |
afferent pathways to vomiting center
GIT - stimulation of afferent nerves in stomach and intestines by irritation, inflammation, distension pharyngeal - direct stimulation of glossopharyngeal n. intracranial - trauma, intracranial pressure, psychogenic vestibular - motion sickness, vestibulitis humoral - blood-borne drugs/toxins stimulation of CRTZ |
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neurotransmitters
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vomiting center - serotonin (5HT), norepinephrine, dopamine (DA2), substance P (SP) - neurokinin receptors (NK-1)
CRTZ - dopamine (DA), 5HT, acetylcholine (muscarinic), NE, SP |
vestibular system - Ach, histamine (dogs)
GIT - 5HT |
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species differences in neurotransmitters
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cats more susceptible to alpha-2 (xylazine) induced vomiting
dogs - histamine, vestibular, not cats dogs > DA induced vomiting (apomorphine) |
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vomiting is a symptom, not a disease. rule out...
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parasitic, gastritis, enteritis, gastric dilation-volvulus, GI obstruction, drug/toxin induced, motion sickness, renal failure, liver failure, ileus
regurgitation dysphagia |
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phenothiazines
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broad spectrum (WRT diseases)
DA(2) antagonists other effects - alpha-1 antagonists, antihistamines (H1), antimuscarinics drugs - chlorpromazine, acepromazine, promethazine, prochlorperazine primarily eliminated by hepatic metabolism potentiate other sedatives epinephrine reversal due to alpha-1 blockade precautions include dehydration (alpha-1 antagonist) |
AE
sedation decreased seizure threshold hypotension extrapyramidal signs?? |
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antimuscarinic drugs
(muscarinic receptor antagonists) |
indication - motion sickness, hypermotile diarrhea
pharmacokinetics? no information available drugs - aminopentamide, atropine, scopolamine, isopropamide |
AE
xerostomia decreased stomach emptying ileus urine retention, constipation increase intraocular pressure excitement in cats |
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antihistamines
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inverse agonists: H1 receptor - stabilizes receptor in an inactive state
efficacy dogs>cats (motion sickness) most also produce mild antimuscarinic effects hepatic metabolism drugs - diphenhydramine, dimenhdrinate, promethazine, phenothiazine |
AE
sedation excitement (cats) antimuscarinic |
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metaclopramide
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broad spectrum antiemetic - DA2 antagonist, prokinetic (stomach, small intestine), 5HT3 antagonist (increase doses)
increases prolactin release (see domperidone); increase aldosterone release (Na, H2O retention); ~50% PO bioavailability (dogs); hepatic metabolism; prokinetic effects (proposed mechanisms) - increased Ach release? increased sensitivity Ach receptors? antagonize inhibitory effect of dopamine (DA2)? increase gastric emptying; increase tone of gastroesophageal sphincter; increase duodenal motility |
AE
excitement/behavior changes exacerbation of seizures abdominal pain/colic, GIT reupture (obstruction and foreign bodies are contraindications) extrapyramidal signs?? involuntary muscle movements - chronic use aldosterone release - peripheral edema, congestive heart failure prolactin release - lactation |
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serotonin antagonists
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5HT3 antagonists
inhibits vagal afferent from intestines - also some (less) activity at CRTZ, vomiting center high efficacy antiemetic (GI causes of vomiting) minimal DA, Ach, GI prokinetic effects |
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ondansetron
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5HT3 antagonist
hepatic metabolism dogs - short T 1/2 (30 min), poor PO %F (<10%), duration of effect 6-8 hrs indications - gastroenteritis, chemotherapy induced vomiting, parvoviral gastroenteritis generic available, cheap |
AE (human)
headaches, dizziness, constipation more AE may be noted due to increasing use in vet med |
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maropitant
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NK-1 antagonist (CRTZ, vomiting center)
high efficacy - motion sickness, cemotherapy, GI dogs T 1/2 ~6hrs, only antiemetic with SID, PO%F ~30% (low but can overcome with higher doses) hepatic metabolism - dose dependent, saturable, recommended short term administration cats ~15hr T1/2, 100% SC F, 50% PO F vet label |
AE - pain/swelling on injection
diarrhea lethargy/depression/weakness ataxia, sedation, anaphylaxis bone marrow suppression in dogs <11 weeks prolonged QT interval precautions - underlying cardiac dz (safety untested, Ca and K channel blocker, diltiazem, amlodipine, sotalol, other antiarrhythmic drugs (atenolol, quinidine, etc., doxorubicin), reported AE (potentially cardiac - collapse, weakness, arrhythmias, bradycardia, syncope, unconsciousness, pulmonary edema, heart disorder, cardiac arrest likely drug-drug interactions (undocumented) w/phenobarbital (increased maropitant elimination), and ketoconazole/itraconazole/cimetidine/fluoxetine/paroxetine/quinidine (decreased maropitant elimination) use cautiously with liver disease, saturable metabolism in healthy livers, probably more pronounced in liver dz |
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other antiemetics
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dexamethasone - chemotherapy
butorphanol, tentanyl - chemotherapy |
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motion sickness
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dogs - antihistamines, phenothiazines, maropitant
cats - phenothiazines, maropitant |
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drug induced vomiting
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maropitant, metoclopramide, phenothiazines
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GI disease
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5HT3 antagonists (high efficacy)
phenothiazines (high efficacy) metoclopramide maropitant avoid antimuscarinics |
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phenothiazines AE
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AE
sedation decreased seizure threshold hypotension extrapyramidal signs?? |
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antimuscarinics AE
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AE
xerostomia decreased stomach emptying ileus urine retention, constipation increase intraocular pressure excitement in cats |
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antihistamines AE
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AE
sedation excitement (cats) antimuscarinic |
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metaclopromide AE
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AE
excitement/behavior changes exacerbation of seizures abdominal pain/colic, GIT reupture (obstruction and foreign bodies are contraindications) extrapyramidal signs?? involuntary muscle movements - chronic use aldosterone release - peripheral edema, congestive heart failure prolactin release - lactation |
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metaclopromide use
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use - antiemetic, stimulate upper GIT motility (anecdotal - gastroparesis, regurgitation, gastric dilatation and volvulus (GDV)), increase rumen contractions, tx functional pyloric obstruction, decrease postoperative ileus in horse (rare use due to AE)
essentially o effects on large intestine |
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ondanestron AE
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AE (human)
headaches, dizziness, constipation more AE may be noted due to increasing use in vet med |
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maropitant AE
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AE - pain/swelling on injection; diarrhea; lethargy/depression/weakness; ataxia, sedation, anaphylaxis
bone marrow suppression in dogs <11 weeks; prolonged QT interval; precautions - underlying cardiac dz (safety untested, Ca and K channel blocker, diltiazem, amlodipine, sotalol, other antiarrhythmic drugs (atenolol, quinidine, etc., doxorubicin), reported AE (potentially cardiac - collapse, weakness, arrhythmias, bradycardia, syncope, unconsciousness, pulmonary edema, heart disorder, cardiac arrest likely drug-drug interactions (undocumented) w/phenobarbital (increased maropitant elimination), and ketoconazole/itraconazole/cimetidine/fluoxetine/paroxetine/quinidine (decreased maropitant elimination); use cautiously with liver disease, saturable metabolism in healthy livers, probably more pronounced in liver dz |
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