Unit 2- Antiemetics Flashcards
Emesis Trigger Centers
Vomiting center, chemoreceptor trigger zone, cerebral cortex, and vestibular apparatus
Vomiting Center
Located in medulla oblongata and receives input from CTZ, vestibular disturbance, higher cortical centers, and peripheral sensory
CTZ Receptors
5-HT3, D2, opioid R, NK1, CB1
Pharynx and GI Receptors
5-HT3, 5-HT4, D2
Vestibular Receptors
H1, Ach M3/5
Histamine receptor
H1
Serotonin Receptor
5-HT3
Substance P Receptor
NK1
GABA Receptor
GABA A and GABA B
Acetylcholine Receptor
M1
Dopamine Receptor
D2
Endorphin Receptors
opioid receptors and CB1
Therapeutic Emetics
Apomorphine, hydrogen peroxide, xylazine, medetomidine, midazolam/hydromorphone
Dog CTZ Receptors
Increase D2 receptors make emesis stimulation more successful, increased H1 receptors
Cat CTZ Receptors
Decreased D2 receptors, increased sensitivity to α2 receptors
Apomorphine
Dopamine agonist, antagonist to serotonin and adrenergic receptors, more successful in dogs, may have opioid like effects
Apomorphine Administration
IV reaches CTZ before crossing BBB to reach emesis center that prevents emesis
Apomorphine Sedative Reversal
Opioid antagonists like naloxone
Apomorphine Emesis Reversal
Dopaminergic antagonist like Acepromazine
Cat Emetics
α2-agonists: xylazine and medetomidine/dexmedetomidine that are highly lipophilic and directly reach receptors in the brain and GI
Xylazine
α2 antagonist, common in cats, not reliable in dogs, use lower doses than for sedation
Serotonin 5-HT3 Antagonists
Ondansetron and granisetron, block 5-HT3 in VC and CTZ for chemotherapy nausea
Serotonin 5-HT3 Antagonist Adverse Effects
Headache, dizziness, itching, constipation, ECG abnormalities
Prokinetic D2 Antagonists
Metoclopramide, domperidone
Neuroleptic D2 Antagonists
Chlorpromazine and Droperidol
D2 Antagonists
Block D2 and serotonin receptors in CTZ, used for vomiting of non-specific cause
D2 Antagonist Adverse Effects
Dyskinesia, sedation, postural hypotension, extrapyramidal symptoms
Substance P Antagonists
Aprepitant, Cerenia, binds neurokinin 1 receptor in VC to treat motion sickness, chemotherapy vomiting, post-op vomiting
Substance P Antagonist Adverse Effects
Dyskinesia, sedation, dizziness, hiccup, hypotension
Antihistamines
Diphenhydramine and dimenhydrinate, block histamine at H1 receptor and Ach at M1 receptor for motion sickness and morning sickness
Antihistamine Adverse Effects
Sedation, hypotension, confusion, dry mouth, dilated pupils, urinary retention, constipation
Anticholinergics
Hyoscine Butylbromide, Dicyclomine block Ach at M1 receptor in motion sickness and morning sickness
Anticholinergic Adverse Effects
Tachycardia, blurred vision, dry mouth, constipation, urinary retention
Benzidiazepines
Lorazepam, diazepam, Midazolam enhance GABA effects, used as psychotropic, calms the brain, and prevents anticipatory vomiting
Benzodiazepine Adverse Effects
Sedation, dry mouth, dizziness, paradoxical agitation
Corticosteroids
Dexamethasone, methylprednisolone used in chemotherapy-induced comitign
Corticosteroid Adverse Effects
Hyperglycemia, hypertension, osteoporosis, insomnia, intraocular pressure, infection susceptibility, increased appetite, obesity
Cannabinoids
Nabilone and Dronabinol used in anticancer-induced vomiting
Cannabinoid Adverse Effects
Euphoria, dysphoria, sedation, agitation, hallucination, restlessness, insomnia, irritability, tachycardia, and palpitation
Post Operative Vomiting Drugs
Dopamine antagonists, 5HT3 antagonists, and NK1 antagonists acting on CTZ
Cytotoxic Drug Induced Vomiting Drugs
5-HT3 antagonists, NK1 antagonists, D2 antagonists, Cannabinoids, and Glucocorticoids acting on CTZ
Motion Sickness Drugs
Muscarinic antagonists and antihistamines acting on H1 and M1-M3 receptors in vestibular system
