GI drugs Flashcards
where is histamine stored from
mast cells, basophils, brain, stomach in enterochromaffin like cells
conditions that cause histamine release
tissue injury, allergic reactions, drugs, foreign substances
what type of reaction is degranulation of mast cells?
type I sensitivity
H1 receptors
throughout the body, smooth muscles, vascular, heart, CNS, endothelial cells. Increase vascular permeability and vasodilation, bronchoconstriction, itching. Symptoms are allergic: rhinitis, conjunctivitis, urticarial, bronchospasm, vasodilation, CNS: sleep/arousal, motion sickness
H2 receptors
mainly gastric parietal cells to a lesser extent vascular smooth muscle, neutrophils, CNS, heart, uterus. Gs receptors. Increased release of gastric acid, tachycardia, smooth muscle relaxation. Symptoms of GERD
H3 receptors
found in the CNS, primarily in the thalamus, caudate nucleus and cortex. Some in the small intestine and prostate. G protein coupled.
H4 receptors
recently discovered and present throughout the immune system, spleen, thymus, leukocytes, likely G protein, but mechanism is unknown.
wheal and flare
local response or wheal and flare is H1. If you were to inject histamine locally, you will see a red spot with an erythematous red base and central flare. Erythema is caused by vasodilation within a few seconds. Flare is the spread of erythema more than 1 cm beyond this site caused by dilation of vessels- itching begins here. Wheal forms within a few minutes and is localized edema a raised area due to increased capillary permeability.
allergies
vasodilation and edema lead to inflamed mucosal tissues which can cause paroxysms of sneezing, rhinorrhea, nasal obstruction, and nasal itching. The same mechanism can inflame conjunctival tissue, leading to scleral injection, watery eye drainage, and itching
uticaria
similar but present on the skin. Diagnostic criteria is itchy raised lesions that migrate.
external urticaria causes
new topical exposures, medications, foods, infections
internal urticaria causes
often the cause behind chronic urticarial no single cause could be isolated yet prolonged over six month duration of hives
what is cause of large local reaction
insect bite, sting, plant based reaction, will not migrate to hives
anaphylaxis- criteria
scheduled antihistamines are important because there is often an acute or delayed hypersensitivity reaction. Criteria is acute onset and many different things on different systems
cardiovascular symptoms of anaphylaxis
hypotension from decreased BP from H1 receptors and tachycardia- hypotension causes reflex tachycardia.
pain and itching in anaphylaxis
nerves with H1. H3 reduce the release of acetylcholine, amine, peptide transmitters in various areas of the brain and peripheral nerves
allergy induced asthma
histamine causes bronchoconstriction from H1
H1 receptor antagonists
antihistamines compete for histamine at the receptor binding site, but will not remove already bound histamine
first generation H1 blockers
for seasonal allergies, medication associated allergies, hives, itching, anaphylaxis, or vomitting. They are readily absorbed through oral mucosa administration with peak blood concentrations at 1-2 hours. They have lots of side effects. This molecule allows first generation antihistamines to cross the BBB. They have anti-cholinergic adverse effects.
ethylenediamines
significant anticholinergic side effects and sedation less GI side effects. H1 first generation blockers
diphenhydramine
helpful with allergies, anaphylaxis, hives, nausea, and sedation. Used in many over the counter sleep aids. Can cause agitation in children. It is H1 first generation blocker. ethylenediamines
dimenhydrinate
anti-emetic with strong sedation properties often used for motion sickness. This is an H1 first generation. Eryhlenediamines
alkylamines
less sedating and GI advise effects, more CNS effects- it is a first generation H1 blocker
chloropenamine
allergies and a common ingredient in OTC cold medications. Inhibits serotonin activity. It is from alkyl amine class of H1 first generation antagonists
piperazine
significant effects so used for motion sickness, nausea, vertigo. Generation 1 of H1 blockers
hydroxyzine
used for itching but for anti-anxiety- piperazine- Generation 1 of H1 blockers
meclizine
antiemetic used for vertigo- piperazine- generation 1 of H1 antagonists
cetirizine
common allergic rhinitis medication, available for over the counter and used in kids. It is piperazine generation 1 of H1 antagonist
tricyclics
related to the anti-depressants- first generation H1 blocker
promethazine
used as an anti-emetic or sedative due to an extremely strong anti-cholinergic and sedative effect. This can be used for migraines with a NSAID. cocktail with other drugs. It is a tricyclic
cyproheptadine
antihistamine and antiserotonin; helps with allergies and migraines but is mainly used for appetite stimulation. Tricyclic class
ketotifen
primarily used as an ophthalmic form for allergic conjunctivitis. it is tricyclic.
second generation H2 blockers
these are newer drugs are more selective for the peripheral antihistamine receptors involved in allergies os they spare many of the sedating side effects of the first generation. They are bulkier and less lipophilic so don’t cross the blood brain barrier as readily. They may also have an anti-inflammatory activity that helps in allergic asthma- may be due to H4 receptors
loratidine
the first second generation available with over the counter daily dosing. H2 second generation antagonist
azelastine
mast cell stabilizer, nasal spray and eye drop. H2 second generation antagonist
olopatadine
ophthalmic drip for allergic conjunctivitis. H2 second generation antagonist
Third generation H2 blockers
derived from second generation antihistamines.
levocetirizine
active isomer of cetirizine with fewer side effects- less drowsy. Not metabolized, so will not cute drug interactions. Helpful in asthmatics. H2 third generation antagonist
desloratidine
active metabolite of loratadine- no evidence that it is more effective. h2 third generation antagonist
fexofenadine
anti-allergy medication. H2 third generation antagonist
emesis
holdover mechanism to protect from inested toxins. It is from excessive vestibular stimulation or psychological stimuli such as fear, dread,or obnoxious stimuli like sites and odors
nucleus tractus solitaris
located in the medulla and receives input from the GI tract, vestibular system and area pastrema. Vagal afferents work here from mechanical stimulation, chemical stimulation, acetylcholine, dopamine, serotonin, histamine, neurokinins. Projects to the other medullary nuclei and coordinated vomiting response
vestibular system
CNVIII responsible for vertigo induced nausea
area postrema
next to NTS but outside the blood brain barrier in the fourth ventricle, so responds to many substances that may not cross the BBB
substance P
activates many NK1 receptors
efferents of the vomit reflex
vagus and phrenic nerves when they are stimulated, they relax the funds and body of the stomach and lower esophageal sphincter and retrograde giant contractions occur in the small intestine. Diaphragmatic and abdominal muscle contractions compress the stomach and together this produces vomiting
serotonin antagonists
these antagonize the 5HT-3 receptors on the vagal afferents in the IG tract leading to the brain. They are one of the more effective anti-emetics for chemo but good for gastroenteritis-induces nausea and emesis. Ondasetron
ondansetron
the most commonly used but still expensive can come in IV, sublingual, and oral form- serotonin antagonists- antagonize 5HT-3 receptors on the vagal afferents
substance P/Neurokinin antagonists
antagonists the the neurokinin1 receptors in the CNS inhibiting the action of substance P in the CTZ. They augment the effects of steroids and helpful for chemo and serotonin antagonists- post operative nausea. Aprepitant
aprepitant
substancep/neurokinin1 antagonist- an inhibitor or liver enzyme CYP and inducer of 29, so it decreases the clinical effect of warfarin
antidopaminergic agents
D2 dopamine receptor antagonists in the CTZ. They inhibit dopaminergic stimulation of the CTZ. Anti-psychotics doses for nausea are 1/3 of dose required for psychosis. Used for nausea from drugs and surgery. Metoclopramide, phenothiazine, procholrperzane
metoclopramide
at higher doses, acts as 5HT-3 receptor antagonist. It increases the tone of the gastroesophageal sphincter and enhances gastric emptying and small intestine motility. This allows to work well as a pro kinetic gastroperesis. It can cause diarrhea, it is contraindicated if there is obstruction because it can cause perforation. Extrapyramidal symptoms like dystonia, akthesia, tradeoff dyskinesia, neurologic malignant syndrome, fever, rigidity, mental status change, rhabdo. Pre-treat with migraine cocktail. sedation, depression, increased prolactin, and increased QT interval. Anti-dopanergic
phenothiazine- procholrperzane
possesses anti-muscarinic activity so its is helpful with vestibular disorders. Often used as migraine abortifactant. anti-dopaminergic
butyrophenones
haloperidol, antidopaminergic. same side effects as metoclopramide
scopolamine
antimuscarinic that works on the vestibular system via M1 receptors. Muscarinic receptors are involved in the visceral afferent input from the gut to vomiting center and in the tract that CNVIII takes from the labryinth to the CTZ via the vestibular nucleus. Great for motion sickness. Anticholinergic side effects: dry mouth, blurred vision, drowsiness, available orally, trandsermally, parentally
H1 antihistamines
first generation anti-histamines so they easily cross into the CNS. These CNS effects help the motion sickness/vestibular nausea but can cause sedation and muscarinic receptor blocking: dimeydridate, meclizine, promethazine
promethazine
blocks 5HT-3 commonly used in pregnancy, used for refractory hiccups
corticosteroids
not approved for nausea/vomiting but commonly used for chemo induced vomiting both alone, they work bettie in combination with other anti-emetics: methylpredisolone, dexamethasone
methylprednisolone
IV formulation for corticosteroids. Can be used for chemo induced vomiting alone or in other combinations
dexamethasone
longer lasting steroid- oral and IV- chemo induced vomiting alone or in combination
benzodiazepines
these have no intrinsic anti-emetic properties but will sometime help with amnesia during emetogenic period or anticipatory nausea can cause sedatiion and amnesia of vertiginous episodes, so can cause sedation and amnesia of vertiginous episodes so may be paired with meclizine: lorazepam and diazapam
lorazapam
benzo for chemo during or before
diazepam
longer acting- bento for chemo during or before anticipatory nausea
cannabinoids
synthetic derivatives of tetrahydrocannabinol or THC. Unclear mechanism of action- possible inhibition of cortical activity and anyphylaxis. Helpful wit chemo induced vomiting if given prior to chemo. Uncertain about potential for abuse adverse effects: dry mouth, sedation, vertigo, ataxia. In elderly it can cause delirium, disorientation, hallucinations: dronabinol
dronabinol
cannabinoid that is helpful if used before chemo. Uncertain abuse potential.
pregnancy induced emesis
easting modification, and other pharmacologic means are attempted prior to medications for morning sickness and treating any contributing symptoms like GERD: pyridine, antihistamines, domapine antagonists, sertonin antagonists
pyroxidine
combined with doxylamine for pregnancy
antihistamines in pregnancy
diphenhydramine, dimenhydramine, and mecxline
motion sickness drugs
scopolamine, preomethazine, prochlorperzine, meclizine, lorazapam, diazepam
postoperative vomiting
scopolamine, metclopramide, prochloperazine, ondansteron, promethazine
drug induced vomiting
prochlorperazine, metoglopramide, ondansteron
cytotoxic drug induced vomiting
procholorperazine, metocholpramide, dropabinol, nabilone, ondansterone, solumedroel, lorazapeam,
pregnancy induced vomiting
promethazine, metoclopramide, procholperazine, pydridozine, doxylamine, diphenhyrdramine, meclizine
GERD and Peptic Ulcer Disease-treatment goals
relieve pain, promote healing, prevent recurrence, prevent complications, (hemorrhage, obstruction, perforation)
vagus nerve in relation to upper Gi
releases acetylcholine which binds to M3 receptors to power the proton pump. Releases gastrin releasing peptide, which activates G cells enterochromaffin like cells to release histamine
histmaine for upper GI
it directly activated the proton pump and the ECL/histamine action is the primary way that gastrin causes increased gastric acidity. Gastrin directly binds to parietal cells to release gastric acid
H. pylori
it is responsible for a majority of peptic ulcer disease and almost all duodenal ulcers. The organism attacks the epithelial cells and releases enzymes that damage mucosal cells induces inflammation and tissue destruction. Eradication of h.pylori heals most peptic ulcers and significantly reduces recurrence rate for gastric and duodenal ulcers, so exclusion of H.pylori and treatment if needed is crucial to PUD treatment
h.pylori treatment- triple therapy
triple therapy- PPI+two of the following (clarithromycin/amoxicillin, metronidazole, tinidazole, tetracycline) Used to be standard therapy- rabeprazole and amoxicillin for five days followed by rabeprozole, clarithro, metronidazole,tinidazole for another five days
h.pylori treatment- quadruple therapy
PPI+clarithromycin, amoxicillin/metronidazole+bismuth. If cannot tolerate, PPI, H2 blockers_antibiotics for at lest four weeks can be used but its less effective
H2 blockers
reversible block of histamine H2 receptors leading to decreased hydrogen ion secretin by parietal cells. Sometimes used for allergic reaction to provide some excess histamine antagonism. Good for dyspepsia and GERD. These really help with nighttime secretion but only offer moderate relief during meal time surge. They decrease pepsin. the half life is typical for needing twice a day dosing: Randitine, famotidine, cimetidine, nizatidine
cimetidine
anti-androgenic side effects: impotence, gynecomastia, galactorrha, CYP inhibitor, so can have medication side effects- H2 blocker
randitine, famotidine, cimetidine, nizatidine
H2 blockers used for reversible histamine blocking of H2 so can reduce parietal acid secretion.
PPI
these block the protein pump directly by forming a covalent disulfide bond. Better for nocturnal symptoms. These are delayed release so easier for adherence. Once a day dosing can make this easier. Some people are rapid metabolizers so have failure without increasing the dose
indications for PPI
first line for PUD because it blocks everything happening upstream so good acid suppression, NSAID gastritis, gastronomes, part of treatment for Pylori, stress ulcer prophylaxis
adverse effects of PPI
decreased acidic environment can lead to increased risk of diff, patient in the ICU are increased risk of nosocomial pneumonia, decreased absorption of food bound materials. This can lead to increased risk of osteoporosis with chronic use, hypo magnesia, iron deficiency
PPI drugs
omeprazole, esomprazole, lansonprazole, pantropazole
octreotide
somatistatin analog- great for gastronomes will inhibit the release of gastrin and histamine by ECL. Helps with diarrhea in VIPomas and carcinoid tumors can used for esophageal varies acutely in the ICU, for chronic use it should be subcutaneous
misprostol
prostaglandin E1 agonist that inhibits gastric acid secretion of mucus and bicarbonate by epithelial cells. Can be used for PUD and prevention of gastric ulcers in long term NSAIDs. Must be four times daily so not very well tolerated also causes diarrhea and cramping. Cytoprotective
sulcradate
viscous polymer or sucrose octasulfate and aluminum hydroxie. usually is a suspension. Can coat the stomach adhering to ulcers and it inhibits pepsin-catalyzed hydrolysis or mucosal proteins. It also impedes absorption of other drugs
calcium carbonate
constipation very large doses can lead to rebound acid secretion
aluminum hydroxide
constipation
magnesium hydroxide
diarrhea from the magnesium often aluminum magnesium combination controls the GI side effects like Mylanta
Milk Alkalai
increased milk ingestion or overuse of antacids causing increased calcium, alkalosis, hypophophatemia, and mild acute kidney injury
IBS
can be constipation or diarrhea predominant and sometimes alternating. Many patients have chronic and idiopathic constipation. Most drugs are orally administered
acute constipation
can be from trauma, surgery, pain medications, hypthyrodism
chronic constipation cause
its from lasting changes
non-pharmacologic treatment for constipation
should be first-line. Fruits, whole grains, vegetables, adequate hydration, and regular exercise.
biggest issue with laxatives
electrolyte derangement are the biggest issue they alter the water in the colon, so it messes with the ion concentrations of the body
bulk forming laxatives
resembles dietary fiber, absorbs and retains water in the intestinal lumen to increase the mass. This causes mechanical distention of the intestinal wall which stimulates peristalsis. They need to be taken with a full glass of water for the appropriate hydration of the fiber. These come in pills, powders. there are some in other forms. They are some side effects but are fool proof. The worst that usually happens is gas or bloating. If a great deal of bulk forming laxatives are used without enough water, it can cause an impaction can also be used for diarrhea: psyllium, calcium polycarbophil, wheat dextrin, methyl cellulose
psyllium, calcium polycarbophil, wheat dextrin, methyl cellulose
bulk forming laxatives
osmotic laxatives
These work by increasing moisture and causing intestinal distention to facilitate peristalsis. Polyethylene glycol, laceless, magnesium agents
polyethylene glycol
PEG- tasteless, odorless, liquidform. Usually bowel preparation prior to colonoscopy. Can cause some nausea, bloating, and cramping
lactulose
an osmotic agent to help with constipation. its other indication is hepatic encephalopathy in cirrhotics. It is coverted in the colonic bacteria. Can cause bloating and flatulence
magnesium agents
can cause hypermagnesiumia in renal failure patients. Magnesium oxide or magnesium citrate
magnesium oxide
milk of magnesia- poorly absorbed salt that becomes osmotic. Sometimes given for chronic hypomasgnesia can cause diarrhea
enemas
will have osmotic agents, soap suds, SMOG, sodium phosphate. There is somewhat of a risk of electrolyte derangement with repeated saline enemas. Enemas can come in over the counter, small, plastic bottles, hanging to gravity attached that goes up there
glycerine suppositories
tend to be used for infants with constipation
docusate
surfactant lacatives- stool softeners because they actually incorporate water into the fatty intestinal issue and make the stool softer and help lubricate the intestinal lumen. Occasional absorption issues or rashes
stimulants for laxatives
composed of natural or synthetic compounds that alter the fluid secretion to stimulate peristalsis. the amount of peristalsis generated can cause cramping, electrolyte, abnormalities, gastric, rectal irritation. Senna, bisacodyl
Senna
stimulant laxatives, it is used for natural combines with decussate in the formulation called D. Started to prevent opioid, overuse of this can cause melanosis coli
bisacodyl
this is the other stimulant laxative. synthetic or suppository
prokinetics
serotonin is the big player in treating motility issues. It is produced and released by enterochromaffin cells in the gut where it activates 5HT3 and HT4 receptors on cholinergic neurons and enhance peristalsis. Drugs that activated 5HT receptors increase motility and have been used in treating constipation. 5HT3 are used for diarrhea
metoclopramide
prokinetic- dopamine antagonist that prevents relaxation of the GI smooth muscle. It generated increased tone in the esophagus and stomach creating propulsion machine. It helps with gastroparesis by accelearing gastric emptying. It is sometimes used for GERD, refractor constipation due to decreased motility and emesis