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Chapter 16 Cholinesterase Inhibitors

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Other Gastrointestinal Drugs
Antiemetics
Given tosuppress nausea and vomitingEmetic responseComplexreflexafter activatingvomiting centerinmedullaoblongataSeveral types of receptorsinvolved in emetic responseSerotonin, glucocorticoids,substance P, neurokinin1,dopamine, acetylcholine, and histamineMany antiemetics interact with one or more of the receptors
Antiemetics
Serotonin receptor antagonistsGranisetron, dolasetron, palonosetronOndansetron (Zofran)First approved forchemotherapy-induced nausea and vomiting (CINV)Blocks type 3 serotonin receptors on afferent vagal nerveMore effective when used withdexamethasone(these drugs together are first-line for many highlyemetogenicchemotherapy regimens)
Antiemetics
GlucocorticoidsUnknown mechanism of action (MOA) as antiemeticMethylprednisolone (Solu-Medrol)Dexamethasone (Decadron)Commonly used to suppress CINV, but this is not an FDA-approved applicationEffective alone and in combination with antiemetics
Antiemetics
Substance P/neurokinin1antagonistsAprepitant (Emend)Blocks neurokinin1-type receptors (for substance P) in the chemoreceptor trigger zone (CTZ)Prevents postoperative nausea/vomiting and CINVProlonged duration of action (delayed CINV and acute)- for DELAYED nausea and vomitingAdverse effectsDrug interaction
Antiemetics
BenzodiazepinesLorazepam (Ativan)Used in combination regimens to suppress CINVThree primary benefitsSedationSuppression ofanticipatory emesisProduction of anterograde amnesia
Antiemetics
Dopamine antagonistsPhenothiazines(prochlorperazine,promethazine)Blockdopamine2receptors in CTZSurgery, cancer, chemotherapy, and toxinsSide effectsExtrapyramidal reactionsAnticholinergic effectsHypotension and sedation
Antiemetics
ButyrophenonesHaloperidol (Haldol) anddroperidol (Inapsine)Block dopamine2receptors in CTZPostoperative nausea/vomiting, chemotherapy emesis, radiation therapy, and toxinsSide effectsSimilar to phenothiazinesMay cause prolonged QT and fatal dysrhythmiasElectrocardiographic monitoring needed
Antiemetics
Metoclopramide(Reglan)Blocks dopamine receptors in CTZPostoperative nausea/vomiting, anticancer drug, opioids, toxins, radiation therapy
Cannabinoids
Dronabinol(Marinol) andnabilone(Cesamet)Related to marijuanaCINVMOA with emesis unclearPotential for abuse andpsychotomimeticeffects (caution in patients with history of psychotic or anxiety disorders
Management ofChemotherapy-Induced Nausea and Vomiting
Three types of emesisAnticipatoryOccurs before drugs are givenAcuteOnset within minutes to a few hoursDelayedOnset 1 day or longer after drug received
Management of Chemotherapy-Induced Nausea and Vomiting
Antiemetics aremore effective in preventing CINV than suppressing CINV in progressGivebefore chemotherapy drugsMonotherapy and combination therapy may be needed
Drugs for Motion Sickness
ScopolamineMuscarinic antagonistSide effectsDry mouthBlurred visionDrowsiness
Drugs for Motion Sickness
AntihistaminesDimenhydrinate (Dramamine), meclizine (Antivert), cyclizine (Marezine)Considered anticholinergics—block receptors for acetylcholine and histamineSide effectsSedation (H1-receptor blocking)Dry mouth, blurred vision, urinary retention, constipation (muscarinic receptor blocking)
Diarrhea
Characterized bystools of excessive volume and fluidity and increased frequencyof defecationSymptom of GI diseaseCausesInfection, maldigestion, inflammation, functional disordersof the bowelComplicationsDehydration and electrolyte depletion
Diarrhea
ManagementDiagnosisand treatment ofunderlying diseaseReplacement of lost water and saltsRelief of crampingReducing passage of unformed stoolsTwo major groups of antidiarrhealsSpecific antidiarrheal drugsNonspecific antidiarrheal drugs
Nonspecific Antidiarrheal Agents
OpioidsMost effectiveantidiarrhealagentsMany do not cross the blood-brain barrier likeopioidsgiven for painMany are not water-soluble and can’tbe injectedActivate opioid receptors in GI tractDecrease intestinal motilitySlow intestinal transitAllow more fluid to be absorbedDecrease secretion of fluid into small intestine and increase absorption of fluid and saltDiphenoxylate (Lomotil) and loperamide (Imodium)

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Chapter 16 Cholinesterase Inhibitors