GI Flashcards
N/V Gastroenteritis or Drug PATHWAY
CTZ
Receptors: Serotonin & Dopamine
N/V Gastroenteritis or Drug PATHWAY TREATMENT
Top choices:
Dopamine receptor: promethazine»_space; inexpensive, EPS SEs
Serotonin receptor: generic, still expensive
other options: antihistamines
N/V Motion Sickness PATHWAY
Vestibular pathway
Receptors: Acetylcholine-muscarinic, histamine
N/V Motion Sickness PATHWAY TREATMENT
First line:
Antihistamines»_space; sedation
Anticholinergics (antimuscarinics)»_space; CAN’T SEE, PEE, SPIT, SHIT
N/V Emotional/Anticipatory PATHWAY
Limbic system
Receptors: GABA, histamine
N/V Emotional/Anticipatory PATHWAY TREATMENT
Benzodiazepines: INC activity of GABA, an inhibitory neurotransmitter
Antihistamines: Hydroxyzine DOC for its antiemetic/sedating properties
Patient-specific treatment: PONV
5 HT3 blocker
phenothiazine
NK1 receptor blocker
Patient-specific treatment: PEDs
Phenothiazine
Antihistamine/Anticholinergic
Patient-specific treatment: PREGNANCY
Antihistamine/Anticholinergic
5 HT3 blockers: controversial
Promethazine: controversial
Patient-specific treatment: CIINV
5 HT3 blockers
NK1 receptor blockers
Cannabinoid
Benzodiazepine
Corticosteroid
Metoclopramide
Phenothiazines
Antihistamines
TREAT THE CAUSE
N/V is a SYMPTOM
most of the time, it is self-limiting = resolve on its own
newborn = congenital obstruction
infant = obstructive lesions, metabolic disease, nutrient intolerance
children/adolescents/adults = drug induced; metabolic disorders; GI disorder; Motility disorder; Acute abdomen; Infection of abdomen; CV disease; Neurological process; emotional
Phenothiazines MOA/USES
oldest
(-zine) = promethazine (phenergan) and prochlorperazine (compazine)
MOA: block dopamine in CTZ; block cholinergic, alpha1-adrenergic, histamine receptors in vomiting center
monotherapy in mild - mod nausea, or combo for severe nausea
block nausea from blood and CSF: pathogenic toxins, opiates, to much body electrolytes, partying, GI bug, trauma
Phenothiazines ADVANTAGES/DISADVANTAGES
ADVANTAGES:
inexpensive, except SR form
variety of forms
viable and practical option for LONG-TERM USE
DISADVANTAGES:
causes sedation»_space; CAUTION w/ CNS depressants
Preg C
NO anticonvulsants, Coumadin
Phenothiazines AEs
SAME AS ANTIPSYCHOTICS
Extra-pyramidal sx: tremors, tardive dyskinesia, dystonia
CONTRAINDICATED: Parkinson’s
AE: sedation, resp depression (NO children <2, elderly start low dose, resp disorders)
may suppress cough reflex
anticholinergic effects: dry mouth, dry eyes, blurred vision, urinary retention, urine color change
Antihistamines-Anticholinergics MOA/USES
MOA: block histamine and cholinergic receptors along vestibular pathway and in vomiting center
antihistamines: block H1 receptors, bind to central cholinergic receptors responsible for N/V
anticholinergics: DEC secretion of saliva and GI motility
BLOCK N/V originating from inner ear»_space; motion sickness, vertigo
motion sickness: take 30-60 min before event
patch: apply 1-2 hrs before event and may reapply q3 days
Antihistamines-Anticholinergics MEDS
dimenhydrinate (dramamine)»_space; Pre B
Diphenhydramine (benadryl)»_space; Preg B
Hydroxyzine (vistaril, atarax)
meclizine (antivert)
scopolamine
trimethobenzamide (tigan)
Antihistamines-Anticholinergics Contraindications
Antihistamines: CAUTION asthma, glaucoma, GI/GU obstruction
NO LACTATION
Anticholinergics: CAUTION: glaucoma, bladder neck obstruction, GI obstruction
Antihistamines-Anticholinergics AEs
Antihistamines: sedation, drowsiness, confusion
Anticholinergics: CAN’T SEE, PEE, SPIT, SHIT
mydriasis, blurred vision, urinary retention, dry mouth, constipation
Benzodiazepines MOA/USES
MOA: blocks signals from limbic system from reaching vomiting center
usually used in combo w/ other agents for CINV
USES: N/V and provide an anxiolytic and amnesic effect
most beneficial w/ anticipatory N/V
Benzodiazepines DOC/Contraindications/AEs
DOC: Lorazepam
Preg D
CONTRAINDICATIONS: hepatic/renal failure
AE: CNS depression, paradoxical CNS stimulation
**MONITOR LFTs before dosing
Serotonin Receptor Blockers MOA/USES
MOA: block 5HT3 receptors (many in GI tract)
USES: initially for CINV, but expanded to radiation induced N/V and PONV
Serotonin Receptor Blockers AEs
oral administration encouraged
Preg B
AE: few
HA, fatigue, dizziness, constipation, pruritis, fever
Cannabinoids
MOA: unknown
does NOT involve CTZ
AE: sedation, ataxia, dysphonia, may develop tolerance to most AEs w/ repeated dosing, but NOT antiemetic effect
Appetite stimulant»_space; the munchies
Cannabinoids Routes PROBLEMS
Smoking: works like PCA, risk of high THC levels producing AEs
Vaporizing: patient control intake, risk HIGH initial blood levels, NOT easily nebulized, coughing/irritation
oral: predictable onset, absorption rate variable, first-pass effect; difficult to titrate optimum dose
sublingual: patient controlled, rapid onset, less AEs, ONLY IN UK
NK1 Receptor Antagonists
newest
aprepitant (emend)
Crosses BBB to occupy NK1 receptors
MOA: inhibit substance P from binding to NK1 receptor = no N/V
augment activity of 5HT3 receptor blockers
NK1 Receptor Antagonists AEs
AE: fatigue, dizziness, hiccups, **elevated LFTs
CYP3A4 inducer
**can cause life threatening reactions when combined w/ certain drugs
N/V Other Meds
Metoclopramide: A Prokinetic
Corticosteroids: used for CINV
MOA: unknown
BEWARE GI irritation, Hyperglycemia
AE: steroid psychosis, HA, insomnia, glucose intolerance»_space; long-term use
Antacids: coat the stomach or neutralize acid
GERD Patho
relaxed LES or cardiac sphincter allows contents to be splashed into esophagus
ACID burns esophageal tissue
GERD Causes
GERD Risk Factors
GERD Diagnostic criteria
PUD Patho
supply and demand: supply of gastric assaults > gastric defenses
types: duodenal and gastric ulcers
PUD Causes
Duodenal:
1st: H. pylori
2nd: NSAIDs
Gastric: H. pylori
INC acid and pepsin secretion, NSAIDs, impaired mucosal protection, pyloric stenosis, chronic gastritis
PUD Risk Factors
smoking
NSAIDs
ETOH
H. pylori
PUD Diagnostic criteria
H2 Receptor Antagonists MOA/USES
“-idine”
ranitidine, famotidine
MOA: reduce HCl secretion by blocking one of the triggers of H+ production
USES:
self-tx heartburn
NO first-line tx GERD
Used as maintenance after PPI for GERD
Used in PUD for continued acid suppression after ulcer healed
H2 Receptor Antagonists Contraindications
CAUTION: elderly, renal patients = CNS effects
H2 Receptor Antagonists AEs
antiandrogen (gynecomastia, impotence)
CNS: confusion, agitation, psychosis, depression, disorientation
hematologic: rare, but need to monitor
drowsiness, dizziness, N/V/D, constipation
**may raise LFTs, d/c if it does
H2 Receptor Antagonists Interactions
Antacids DEC absorption
uses CYP450 pathway: cimetidine
PPI MOA/USES
MOA: inhibit H/K/ATPase pump, blocking the final step in H+ secretion
PPI Contraindications
Contra: hypersensitivity
CAUTION: hepatic dysfunction, elderly
PPI AEs
Common: dizziness, drowsiness, abd pain, constipation, diarrhea, flatulence
long-term = nutrient deficiencies, INC risk c diff, INC hip fracture, gastric CA
PPI Interactions
Food DEC absorption
Antacids
MOA: neutralize acid
CAUTION: renal issues or hypercalcemic state (renal calculi)
Drug absorption effect: give other agent first, take antacid 2 hrs later
Be careful of Na content
Sucralfate
alkaline aluminum salt
MOA: binds to necrotic tissue at ulcer site; protective barrier to acid, pepsin, bile salts
USES: duodenal ulcers NOT from H. pylori
stress ulcer prophylaxis
PREGNANCY SAFE
EMPTY STOMACH
AVOID ANTACIDS
AE: constipation
may DEC absorption of drugs = separate dosing by 2 hrs
Misoprostol
inhibit gastric secretion by inhibiting histamine-stimulated cycle
Mod DEC in pepsin concentration
produces UTERINE CONTRACTIONS
NO PREGNANCY
CAUTION: renal impairment, >65 yo
AE: diarrhea
GERD algorithm
PUD algorithm
H. Pylori MULTI-TREATMENT
First-line:
1) PPI, amoxicillin, clarithromycin
2) PPI, clarithromycin, metronidazole
Second-line:
1) PPI, amoxicillin, clarithromycin, tinidazole
2) bismuth subsalicylate, metronidazole, tetracycline, PPI
Salvage tx only: PPI, amoxicillin, levofloxacin
Diarrhea PATHO
Osmotic: pulls water into intestine (lactose intolerance, high sugar intake, poorly absorbed salts)
Secretory: Cl secretion, disrupt NaCl reuptake (cholera, celiac disease, crohn’s, bacterial endotoxins)
Exudative: inflammation of mucosa (enteritis, colitis, inflammatory conditions)
Altered Intestinal Motility: INC motility = DEC reabsorption (bowel resection, vagotomy, meds)
Diarrhea CAUSES
infections
medications
disease states
Diarrhea Diagnostic
INC in frequency of loose, watery stools over a period of 24-48 hrs
Constipation CAUSES
diet
lifestyle
meds
disease
Bulk forming laxatives
fiber lax
preferred agents for constipation relief
pull water into stool to swell and INC stool bulk
bulk stimulates movement of intestines
NO tx opioid induced constipation
Can be used as antidiarrheal
work in 12-24 hrs
Bulk forming laxatives CONTRAINDICATIONS
esophageal strictures
GI ulcerations
GI stenosis
GI obstruction
CAUTION: DM (carb content from fiber)
Bulk forming laxatives AEs/INTERACTIONS
AE:
INC flatulence
INC bloating
abd fullness, cramping
N/V w/ excess use
INTERACTIONS:
contains aspartame
AVOID gluten intolerance
quinolones or TCN = absorption blocking
Hyperosmotic laxatives
INC osmotic pressure = stimulates intestinal motility
does not degrade colonic bacteria so less bloating
supp for promotes rectal stimulation
Hyperosmotic laxatives CONTRAINDICATIONS
lactulose:
CAUTION DM
Appendicitis, acute abd, fecal impaction, intestinal obstruction
long-term use causes dependence
not useful: IBS, severe bloating or fullness
Hyperosmotic laxatives AE
glycerin: safest; may cause rectal irritation
GI upset
Diarrhea
nausea
cramps
bloating
Saline laxatives
draw water into intestine via osmosis = INC intraluminal pressure = INC motility
similar to hyperosmotic lax
used as pre-procedure PREP
Saline laxatives CONTRAINDICATIONS/AE
Contraindications:
low salt diet
renal disease = hypoK, hyperMg, hypoCa, hyperNa
CAUTION ELDERLY
AE: dehydration
Saline laxatives INTERACTIONS
separate administration from:
Azoles
antifungals
quinolones
TCN
Stimulant laxatives
bisacodyl, senna, castor oil
INC peristalsis of intestine, promote fluid accumulation
AVOID long-term tx
work 6-10 hrs after oral administration; 15-120 min after rectal administration
Stimulant laxatives CONTRAINDICATIONS
acute abdomen
fecal impaction
intestinal obstruction
may cause exacerbation of hemorrhoids or rectal fissures
Stimulant laxatives AEs
N/V
abd cramping
laxative dependence
Surfactant laxatives (stool softeners)
docusate sodium
docusate calcium
DEC surface tension of liq contents of bowel
Incorporates more liq into stool forming a softer mass
LOC to prevent straining
PREVENT CONSTIPATION – NO TX
combo w/ fiber products
Surfactant laxatives CONTRAINDICATIONS/INTERACTIONS
NO contraindications
useful in those on restricted Na diets
interaction w/ mineral oil–INC absorption which INC risk for liver toxicity
Surfactant laxatives AEs
well-tolerated
stomach upset
mild cramping
diarrhea
throat irritation
PEARL: can be used to soften cerumen before irrigation
CONSTIPATION TREATMENT
TLCs
First-line: bulk-forming lax
Second-line: MOM
Third-line: stimulant (high abuse potential; mineral oil)
Antimotility Agents
Loperamide
Diphenoxylate w/ atropine
Derivative of OPIATES
Slows GI motility by effecting intestinal musculature
INC transit time = INC absorption
Antimotility agents CONTRAINDICATIONS/AEs/INTERACTIONS
Contraindications: exacerbate infectious diarrhea by DEC expulsion of infecting organism
AE: Abd discomfort, constipation, dry mouth
NO CHILDREN <4
Atropine SE
INTERACTIONS: diphenoxylate = CNS depression
Loperamide - HIGH first pass effect = CAUTION LIVER FAILURE
Atypical antidiarrheals
antisecretory, antimicrobial, adsorbent properties
TX: traveler’s diarrhea
contains salicylate: CAUTION ASA sensitivity or treatment
NO CHILDREN = Reye’s syndrome
AE: black stools, black tongue, tinnitus
Adsorbents
(Kaolin, pectin, attapulgite)
Donnagel, Kaopectate)
Adsorb water and solidify stools
given after each BM until diarrhea resolved
AE: constipation, feeling of fullness, upset stomach, bloating, flatulence
relatively safe
interactions: may adsorb nutrients and meds
Absorbents
polycarbophil (fibercon, fiberall)
absorbs water from GI tract
AE: constipation, feeling of fullness, upset stomach, bloating, flatulence
relatively safe
interactions: may adsorb nutrients and meds
Diarrhea TREATMENT
TLCs: diet (low fiber, lactose free, gluten free, BRAT)
First-line: LOPERAMIDE
Second-line: Adsorbent or bismuth subsalicylate; do NOT use bismuth w/ flu in <18yr
Third-line: diphenoxylate w/ atropine
Anthelmintic (PINWORMS)
Pyrantel pamoate
Reece’s pinworm medicine OTC
KILLS ADULT WORM ONLY, DOSE REPEATED (for eggs)
NO PREGNANT
AE: rash, HA, dizziness, sleepiness, N/V
May take w/ food
Anthelmintic (PINWORMS)
Mebendazole
RX needed = KILLS ADULT WORMS
Preg C
AE: angioedema, fever, dizziness, HA, rash, abd pain, N/V/D
tablet can be crushed and mixed w/ food
