PHARM250 Gastrointestinal System Cheat Sheet by kjaniskevich

Osmotic agents
glycerin (suppo­sit­ory), lactulose, polyet­hylene glycol (PEG) 3350, magnesium citrate, sodium phosphate, magnesium hydroxide (milk of magnesia), sorbitol

Contain poorly absorbed ions or molecules that create an osmotic gradient to retain water within the intestinal lumen – the ↑ pressure on the intestinal wall induces gastric motility
Used for bowel evacua­tions before procedures (if high, frequent dosing) or for daily mainte­nan­ce/­pre­vention (if low, daily dosing)
BM within 30 mins (high, frequent doses) -> 3 days (low daily doses)

Stool softeners
Docusate sodium or docusate calcium

Act as a surfactant → better mixing of aqueous and fatty substances to soften the fecal mass
A preven­tative measure rather than a “rescue”
Sometimes added to other laxatives (for the “gentle” touch)
Most recent evidence suggests not better than placebo
What to expect: BM in 1 - 5 days

Suppos­itories & Enemas
Mineral oil retention enema, Phosphate enema, Tap water enemaMicrolax® Enema (sodium citrate, sodium laurel sulfoa­cetate)

For acute relief or bowel prep for procedure
Not for management of chronic consti­pation
Presence of object in rectum stimulates defecation reflex
This is in addition to any benefits provided by specific ingredient (i.e. glycerin – osmotic; mineral oil – lubricant)
Patient should try to retain (hold in) product as long as possible (generally a few minutes)
What to Expect: Cleansing of bowel within 1 hour; if no BM – call physician Not pleasant, therefore not the preferred route

Adsorbant agents
attapu­lgite (Kaope­ctate®, Fowler’s®)

Adsorbs fluid in intestine, reducing stool liquidity
May give some relief, very safe (can use in kids)

Antise­cretory agents
bismuth subsal­icylate (Pepto­-Bi­smol®)

Stimulates absorption of fluid and electr­olytes across intestinal wall; also bacter­icidal (e. coli)and anti-i­nfl­amm­atory
Not for children (related to ASA  Reye’s)
Good option for travel­ler’s diarrhea

Slows intestinal motility by stimul­ating opioid receptor, which reduces fecal volume and increases viscosity
Very high first-pass effect and poor penetr­ation of blood-­brain barrier
No dependence or tolerance with long-term use
Also useful for radio- or chemo-­induced diarrhea

Osmotic Agents

nausea, abdominal bloating, cramping, diarrhea, flatul­ence, skin rashes­/hives

Stool softeners

bloating, abdominal discom­fort, flatulence

Suppos­itories & Enemas

discom­fort, bloating, cramping, allergic reactions

Dimenh­ydr­inate (Gravol®)

drowsiness + antich­oli­nergic effects

Domper­idone

headache, menstrual irregu­lar­ities, dry mouth, diarrhea, abdominal discomfort

H2-Ant­ago­nists

headache, dizziness, drowsiness Difficult to differ­entiate between heartburn symptoms and some adverse effects (nausea, vomiting, consti­pation, diarrhea)
Very rare – reduction in RBC, WBC, and platelets; bradyc­ardia, allergic reactions
Because of reduction in acidity, it can potent­ially interact with absorption of drugs or vitamins (like B12) that need an acidic enviro­nment to absorb
Separate as much as possible, while also unders­tanding that we want prolonged reduction in acidity

Sucralfate

consti­pation or diarrhea, nausea, headache, indige­stion, dry mouth
Bezoars have been reported in people treated with sucralfate (most had comorb­idities that contri­buted such as low gastric motility)
May increase blood glucose due to high carboh­ydrate content

Misopr­ostol

headache, abdominal cramps, diarrhea, vaginal bleeding, uterine cramping

Immuno­-su­ppr­essants
Methot­rexate (MTX)

ulcerative stomat­itis, leukop­enia, nausea, abdominal distress, malaise, fatigue, chills & fever, dizziness, decreased resistance to infection

Local anesth­etics (dibuc­aine, pramoxine)

Use > 7 days: possible CNS effects (restl­ess­ness, excite­ment, nervou­sness, parest­hesias, dizziness, tinnitus, blurred vision, nausea and vomiting, muscle twitching and tremors, convul­sions) and cardio­vas­cular effects (hypot­ension, bradyc­ardia)

Prescr­iption product specif­ically for nausea and vomiting during pregnancy
Mechanism of action largely unknown
Doxylamine = antihi­sta­mine; pyridoxine = vitamin B6
Safe for baby
Used when concerned about proper nutrition
Effect ~ 8 hours after dose

Mechanism of action: serotonin receptor antagonist in chemor­eceptor trigger zone and along GI tract (CTZ)
Primary use: chemot­herapy induced nausea & vomiting
Occasi­onally used in severe nausea & vomiting in pregnancy (concerned about baby nutrition)

Most effective if taken regularly (every day) to consis­tently reduce acid and allow lesion to heal
Can also be used as needed (PRN) for heartburn by anyone
Very safe, Smoking decreases the effect­iveness of H2-ant­ago­nists (encourage smoking cessation)

Have a longer onset of action than H2-ant­ago­nists (don’t work as quickly) – would not be effective to use PRN (as needed) for heartburn

Must be specific for h. pylori – breath tests confirm presence
We attempt to completely eradicate the bacteria, due to extremely high rate of recurrence
Eradic­ation of h. pylori allows ulcers to heal more rapidly and remain in remission longer, often perman­ently
Otherwise, organism may survive for life
We always give at least 2 antibi­otics to:
Increase effect­iveness of therapy
Reduce chance of resistance
Also give with H2-ant­agonist or a PPI to allow for healing

Neutralize acid that is already present – do NOT have an effect on future acid secretion – supportive role only
Most approp­riately used as needed (PRN)
Very safe and can be used for long periods of time (years) with few conseq­uences – Tums® are also used as a calcium supple­ment! – but long term use for recurring heartburn indicates underlying problem
Can interfere with absorption of many medica­tions – separate by 2 hours

Aminos­ali­cylates
5-amin­osa­licylic acid (5-ASA), sulfas­ala­zine, mesalamine

Anti-i­nfl­amm­atories (a GI topical effect)
Inhibit production of inflam­matory mediators prosta­gla­ndins and leukot­rienes
For mild symptoms, would not treat an exacer­bation
Used to lengthen times between exacer­bations
Can be given orally (formu­lated for minimal systemic absorp­tion) or rectally (if lesions are more present in lower tract) – all work topically

A unique cortic­ost­eroid used specif­ically for IBD
Encaps­ulated to avoid signif­icant absorption in stomach or duodenum, then released slowly in lower tract
In direct (topical) contact with lesions (ulcers)
Any absorption that does occur is almost entirely removed by first-pass metabolism
Avoids most long-term cortic­ost­eroid adverse effects (would still monitor)

Folate antago­nist, interf­ering with DNA synthesis, repair, and cellular replic­ation – most active against rapidly dividing cells
Used in many auto-i­mmune diseases (rheum­atoid arthritis, IBD)
Due to the mechanism of action, we must replace folic acid that is being inhibited

tumour necrosis factor (TNF)-α inhibitor (a cell signaling protein involved in inflam­mation and immune response)

Abdominal pain or discomfort with altered bowel habits which occur over a period of at least 3 months
“Altered bowel habits” = bloating, cramping, mucous in stool, consti­pation, diarrhea

Calcium channel blockers (CCB)
pinaverium

very specific for GI smooth muscle, reduces muscle contra­ctions by inhibiting calcium influx (hypot­ens­ion!)

Antide­pre­ssants
TCAs & SSRIs

address neurol­ogical connection (serotonin receptors in CNS and GI) and overlap of neurol­ogical conditions with IBS
_{55% patients given TCA or SSRI saw benefit compared to} 35% placebo

Acute or chronic inflam­mation of the pancreas (very painful)
Usually caused by gallst­ones, heavy alcohol use, or cystic fibrosis (CF)

Commonly seen with consti­pation, diarrhea, pregnancy, advancing age and possibly physical exertion
Symptom relief only – no meds are curative
Products can provide short-term relief of pain, burning, itch, discomfort and irritation while swelling subsides and healing occurs

Cortic­ost­eroids
hydroc­ort­isone

to reduce itch and inflam­mation
Safe if < 14 days of continued use

Anti-i­nfe­ctives
framycetin

if concerned about infection

Vasoco­nst­rictors
phenyl­ephrine

to relieve inflam­mation and limit bleeding; short term only