Week 2 Antiemetics & GI motility 1 of 4 Flashcards
Aspiration Occurrence in adults and children:
Adults: 1 in 8,500
<16 yrs: 1:4,400
Incidence of Aspiration undergoing elective surgery:
1: 4,500
Incidence of aspiration undergoing emergent surgery:
1: 400
What are associated with higher risk of aspiration, associated pulmonary complications, and death?
- Emergencies
2. ASA 3 or higher
Studies showed that aspiration occurs at what rates and during what?
- 1/3 during intubation
- 1/3 during extubation
- 1/3 during procedure
Role of oral antacids is to
- neutralize (remove H ions) from gastric contents
- decrease secretions of HCl into the stomach
Best example of oral antacid:
NaHCO3 (sodium bicarbonate)
-combines with HCL to produce NaCl, H2O and CO2
High pH decreases symptoms of
gastritis
Consequence of high pH
delay digestion of food
Pts with HTN and heart disease may not tolerate the sodium load associated with the chronic use of this drug:
NaHCO3 (sodium bicarb)
What can lead to acid rebound?
rapid antacid action, such that pH is raised to a neutral value
Name the drug:
- prompt neutralization of gastric acid.
- Not assoc. w/acid rebound.
- Has laxative effect.
- Systemic absorption may be sufficient to cause neurologic, neuromuscular, and CV impairment in pts with renal dysfunction.
- Renal dysfunction can also lead to metabolic alkalosis in some pts.
Magnesium Hydroxide (MOM)
Name the drug:
- can produce metabolic alkalosis w/crhonic therapy.
- symptomatic hypercalcemia may occur w/renal dx.
- may result in hypophosphatemia.
- Appendicitis has been reported d/t impact calcium carbonate fecaliths.
Calcium Carbonate
What is a fecalith?
a stone made of feces. It is a hardening of feces into lumps of varying size and may occur anywhere in the intestinal tract but is typically found in the colon.
It is also called appendicolith when it occurs in the appendix and is sometimes concomitant with appendicitis.
Name the drug:
- mix. of aluminum hydroxide, aluminum oxide, and some fixed CO2 as carbonate.
- System absorption may be high in renal dx.
- Encephalopathy in pts undergoing HD has been attributed to intoxication w/aluminum, especially in pts who ingest solutions containing citrate.
- Slows gastric emptying and causes constipation.
Aluminum Hydroxide
Name the Drug:
-Less likely to cause foreign body reaction if aspirated and mixing with gastric fluid is more complete than with particulate antacids (i.e. Tums, Rolaids)
Sodium Citrate (non particulate antacids)
Tums or Rolaids can lead to what if aspirated?
- pneumonitis
- histological changes in lungs
Dosage and admin for Sodium Citrate:
dose: 15-30 ml of 0.3 mol/liter
admin: PO, 30 mins before induction of anesthesia
Sodium Citrate is effective in increasing gastric pH in what kind of patients?
- Pregnant
- Non -pregnant
Name 5 Complications associated with Antacid Therapy:
- Chronic use symptoms
- Acid Rebound
- Milk-Alkali Syndrome
- Phosphorus Depletion
- Hypophosphatemia
Symptoms and consequences of Antacid Therapy / Chronic Use -
- alkalized gastric and urine pH resulting in bacterial overgrowth in duodenum and small intestine, and UTI.
- Increased urine pH > 24hrs after admin - leads to changes in renal elimination of drugs
Symptoms and consequences of Antacid Therapy Milik Alkali Syndrome:
- Hypercalcemia
- Increased BUN and CRT
Acid Rebound is unique to
calcium containing acids
System Alkalosis from milk alkali syndrome (marked decrease in renal fxn) is most commonly associated with
ingestion of large amounts of calcium cabronate and > 1L milk every day
Ingesting large doses of aluminum salts does what?
Binds phosphate ions in the GIT and prevents their absorption.
- can cause phosphorus depletion
Ingesting aluminum salts to induce phosphorus depletion may be helpful for what pts?
-Renal patients
b/c it can decrease their plasma phosphate concentration but renal pts may develop toxicity from the aluminum.
Symptoms and consequences of Antacid Therapy Phosphorus depletion:
- Osteomalacia
- Osteoporosis
- Fractures
If aluminum containing antacids are given chronically, what should we consider supplementing?
phosphate
Gastric alkalization increases gastric emptying resulting in
faster delivery of drugs into the small intestines
Aluminum hydroxide accelerated absorption and increases bioavailabilty of:
Diazepam
*MOA is unknown!
Antacids decrease bioavailability of oral cimetidine by
~ 15%
The capacity of some drugs to form complexes with antacids may decrease
their bioavailabilty
Antacids containing aluminum and a lesser extent calcium or magnesium interfere with absorption of:
- tetracyclines and possible
- digoxin
from the gi tract
What interferes with absorption of tetracyclines and possible digoxin from gi tract
Antacids containing aluminum and a lesser extent calcium or magnesium
Examples of 1st Gen H1-Receptor Antagonists
First generation:
- Chlorpheniramie
- Cyproheptadine
- Diphenhydramine
- Hydroxyzine
Examples of 2nd Gen. H1-Receptor antagonists
Second Generation:
- Loratadine
- Acrivastine
- Azelastine
“LAA” say LAA because you’re not sedated! :D
Histamine Receptor Antagonists 1st generation
- tend to produce sedation
- activate muscarinic, cholinergic, 5-hydroxytryptamine (serotonin), or Alpha-adrenergic receptors
Second Gen. H1 - Histamine Receptor Antagonists Pharmacokinetics
- low water solubility
- not available for parenteral use
H1-Receptor antagonists Clinical Uses:
- most widely used of all medications
- Prevent allergic rhinoconjunctivitis (sneezing, nasal/ocular itching, rhinorrhea, tearing, etc.)
- Less effective for nasal congestion characteristic of a delayed allergic reaction
- may provide some protection against bronchospasm (induced by histamine, exercise, cold dry air)
- admin w/Epi in the tx of acute anaphylaxis
- pruritus
- uricaria
- angioedema
- prophyactically for anaphylactoid reactions to radiocontrast dyes
- Little benefit in the tx of upper RTI
- no beneift in mgmt of otitis media
First Generation H1-Receptor antagonists SE’s
-Tachycardia
-QTc interval prolongation
CNS effects
-somnolence
-slowed reaction time
-cognitive impairment
Muscarinic /anticholinergic effects:
- dry mouth
- blurred vision
- urinary retention
- impotence
Examples of H2 Receptor Antagonists:
- Cimetidine
- Famotidine
- Nizatidine
- Ranitidine
H2 Receptor Antagonists MOA:
competitively and selectively inhibit the binding of Histamine to H2 Receptors
-thereby decreasing the intracellular concentration of cAMP and the subsequent secretion of hydrogen ions by parietal cells.
H2 Receptor Antagonist potency of inhibition of secretion of gastric ions
(least to most)
Varies from 20-50 fold:
Cimetidine least potent and famotidine the most potent
H2 Receptor Antagonists Clinical Uses:
- tx duodenal ulcer disease
- chemoprophylaxis (to increase GI pH prior to induction)
- decrease risk of acid pneumonitis if inhalation of gastric fluid were to occur in pre-op period
- decrease gastric fluid volume
H2 Receptor Antagonists Drug Interactions:
-most common with Cimetidine
principal type of interaction with Cimetidine is impairment of the hepatic metabolism of another drug bc of the binding of cimetidine to the heme portion of the cytochrome p450 oxidase system.
- Retards metabolism of propranolol, diazepam
- may slow metabolism of Lidocaine
H2 Receptor Antagonists SE’s:
Interaction with cerebral H2 receptors
- H/a
- Somnolence
- confusion
Interaction with Cardiac H2 receptors
- bradycardia
- HB
- Hypotension
Hyperprolactinemia Acute pancreatitis Increased Hepatic transaminase levels Alcohol dehydrogenase dehydration Thrombocytopenia Agranulocytosis Interstitial nephritis Interference w/drug metabolism by Cytochrome P450
In some patients with refractory urticaria, concurrent treatment with an H2-receptor antagonist (cimetidine, ranitidine) may enhance
relief of pruritus.
H2 receptors account for what % of all histamine receptors in the vasculature?
10-15%