Glossary of Pharm - Gastrointestinal drugs

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What are the functions of the colon?
- absorption of WATER
- absorption of ELECTROLYTES (not nutrients...that occurs in small intestine)

What are some alterations in absorption in the colon?
- delay in transport through intestine --> dehydrated hard stool
- insufficient fluid absorbed --> watery stool
- frequency of stool elimination is variable

What is the role of fiber?
- absorbs water so stool remains soft
- can be digested by colonic bacteria --> contributes to mass
How much fiber should we consume each day?
20-35 grams/day
What is the role of water when there is adequate intake?
- some water is absorbed to blood stream from the bowel
- some water contributes to stool softness
What is the role of water when there is insufficient intake?
- bowel retains water --> hard stool
How much water should we consume per day?
6-8 glasses (8oz. each)
What is constipation?
difficult, incomplete, or infrequent evacuation of dry hardened feces from the bowels

***determined by altered consistency more than frequency!!

What are some causes of constipation?
1. excessive ALCOHOL consumption (dehydrates), intake of WHITE FLOUR, DAIRY products, & CHOCOLATE (similar action of opioids --> decreases peristalsis)
2. Aging (slows fecal transit time & elderly people generally exercise less)
3. Drugs that reduce intestinal motility

What are the effects of laxatives?
Used to ease or stimulate defecation:
- SOFTENS stool
- increases stool VOLUME
- ACCELERATES fecal passage through the intestine
- facilitates evacuation from the rectum

When should mild laxatives be taken?
- true diagnosis of constipation
- if defecation causes hemorrhoids & bleeding
- for prevention of impaction for bedridden/paralyzed patients
- correcting constipation associated with PREGNANCY or DRUGS
- loss of abdominal or perineal muscle tone in the elderly
- if straining; can increase myocardial demand (valsalva maneuver)

When should CATHARTIC laxatives be taken?
- removal of poisons
- treatments/procedure preparation:
- stool sample
- pre-op bowel cleanse
- cleansing for bowel xray

What are some contraindications of laxative use?
- acute surgical abdomen:
- post-op pain
- inflammation
- no bowel sounds
- fecal impaction or obstruction (perforation)
- abdominal pain, cramps, nausea (symptoms of appendicitis, diverticulitis, ulcerative colitis)
- habitual use

What are the classifications of laxatives?
1. Bulk forming - Psyllium (Metamucil)
2. Surfactant - Docusate (Colace)
3. Stimulant - Bisacodyl (Dulcolax)
4. Osmotic - Milk of Magnesium (MOM)
5. Miscellaneous:
- Mineral oil
- Lactulose
- Glycerin suppository

What is the use, MOA, & adverse effects of MINERAL OIL as a laxative?
Use: for fecal impaction (by enema)
MOA: lubrication from indigestible oils
Adverse Effects:
-systemic intake - fat deposits on liver
- excess - decreases fat soluble vitamins

What is the use, MOA, & adverse effects of LACTULOSE as a laxative?
Use: if unresponsive to other forms of bulk forming laxatives
MOA: bulk forming from mild OSMOTIC action (1-3 days)
Adverse Effects: flatulence (gas) & cramping

What is the use, MOA, & adverse effects of GLYCERIN SUPPOSITORY as a laxative?
Use: children (mild & effective) - 30 mins onset
MOA: osmotic agent that softens & lubricates stool
Adverse Effects: None

What are the causes and effects of laxative abuse?
Misconceptions & marketing --> cleanse or empty the bowel --> over-emptying takes 2-5 DAYS to replenish --> takes another dose & empties again --> DECREASED REFLEXES for defecating --> DEHYDRATION & ELECTROLYTE IMBALANCE
What are non-drug methods for treating & preventing constipation?
- increase activity
- increase fluid intake
- Increase finer (fruits, veg, bran)
- Heed urge
- allow time

Other nursing implications regarding constipation include:
- assess abdominal distension
- listen to bowel sounds
- take note of bowel patterns
- sudden changes or undiagnosed pain could be serious
- discontinue laxatives if diarrhea results
- patient should drink plenty of fluids
- educate patient regarding frequency & consistency
- normal frequency: 3 per day - one a week
- expect results of laxatives within 2-3 days (depending)

What is diarrhea?
excessive volume, fluidity, and frequency of bowel movements
What are the causes of diarrhea?
- infection
- maldigestion
- inflammation
- medication side effects (antibiotics)
- substances (ex. lactose)
- disorders (IBS, chron's disease or ulcerative colitis)

What is the pathophysiology of diarrhea?
1. Nonabsorbable substance (some sugars) --> draws excess H20 into intestine --> diarrhea
2. Bacteria --> increases secretion of mucosal fluids and electrolytes --> diarrhea
3. Disrupted digestion (ex. surgical shortening) --> increased motility --> diarrhea

What are some goals regarding diarrhea management?
- diagnose & treat underlying disorder
- replace fluids/electrolytes
- provide relief of cramping
- reduce unformed stool

What are some nursing considerations (assessment) prior to treating diarrhea?
- assess hydration, serum electrolytes, hepatic & renal function (before giving meds)
- contraindications for anti-diarrheals:
- pregnancy & lactation
- severe dehydration
- electrolyte imbalance
- liver, renal disorders
- glaucoma (increases intraoccular pressure)
- Down's syndrome (low muscle tone in intestine - do not treat for diarrhea)

What causes indirect emetic (vomiting) Response?
Signals from STOMACH or DRUGS cause INDIRECT stimulation of vomiting center (1st sends signal to CTZ (chemo-receptor trigger zone)
What causes direct emetic (vomiting) response?
Signals from BRAIN, SENSES, INNER EAR --> DIRECT stimulation of vomiting center
What chemical mediators bind with receptors and result in emesis (vomiting)?
1. 5HT - serotonin
2. DA - dopamine
3. M - Muscarinic cholinergic
4. H1 - Histamine1

*cholinergic means releasing or responding to acetylcholine

What 4 receptors are involved in the emesis (vomiting) response?
1. 5HT - serotonin
2. DA - dopamine
3. M - Muscarinic cholinergic
4. H1 - Histamine1

*cholinergic means releasing or responding to acetylcholine

What receptors are located in the cerebellum and are signalled by the inner ear to cause emesis?
- H1 = histamine1
- M = muscarinic
What receptors are located within the CTZ (chemo-receptor trigger zone) and are signalled by the stomach/small intestine or drugs (opioids, chemotherapy)?
5HT - serotonin
DA - dopamine
M - muscarinic

What types of laxatives involve osmosis?
- stimulants (draws water into bowel)
- lactulose (also bulk forming)
- glycerin (also a lubricant)

What are the effects of surfactant laxatives?
breaks up stool and allows water in
What are the effects of stimulant laxatives?
osmotic action that draws water into the bowel
When should a fleet enema or soap suds enema be used?
For GI surgery:
- perianal
- perineal areas
- GI tract

*should not be used routinely!

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