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My DEMS I > Lower GI Pharm > Flashcards

Lower GI Pharm Flashcards

1
Q

Ondansetron

Granisetron

A

Serotonin recep (5HT3) antagonists

  • good absorption from GI
  • hepatic CYP metabolism

SE: well tolerate, occasionally GI upset (diarrhea, constip), headaches

  • *greatest efficacy of anti-emetic classes
  • prevention/tx of chemo induced n/v
  • post op
  • n/v assoc w/ post op use of opioid analgesics
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2
Q

Metoclopramide, Prochlorperazine

A

D2 antagonists
(Metoclopramide also blocks 5HT3)

Droperidol: D2 antag too

  • SE: extrapyramidal sx
  • restlessness, fatigue, drowsiness, diarrhea

Metoclopramide: for n/v w/ chemo

Prochlorperazine: less effective against emetic stimuli in gut (med by 5HT3 recep); BUT M, H1 block increases utility in nausea w/ motion sickness; blocking alpha1 receptors increases potential for hypotension

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3
Q

Meclizine, Promethazine, diphenhydramine (dimenhydrinate)

A

Antihistamines

First gen agents:

  • good CNS penetration
  • additional muscarinic receptor blocking actions

mostly motion sickness and post op emesis

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4
Q

Scopolamine

A

Anticholinergic agent

mostly: prevent/treat motion sickness
some effect: post op n/v

Transdermal
DOA: 72 h

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5
Q

Dexamethasone

A

anti-emetic

decreases PG synthesis

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6
Q

PRN anti-emetics

A

lorazepam
prochlorperazine plus diphenhydramine
metoclopramide plus diphenhydramine

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7
Q

For high level acute vomiting

A

mod to high: granisetron + dex

mild: ondansetron + dex

Low: dexamethasone

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8
Q

N/v of pregnancy

A

(not assoc w/ increased fetal risk)

First line:
pyridoxine (B6) + H1 antagonist (doxylamine)

No improvement: D2 antag (prochlorperazine) or metoclopramide (2nd line bc movement disorders)

If dehydrated+ hospitilization: 5HT3 antag (ondansetron) but increases QT!!

Glucocorticoids (methylprednisolone) reserved for refractory n/v (2nd tri)

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9
Q

1st line agent for nausea of morning sickness

A

Pyridoxine (Vit B6)

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10
Q

used transdermally for motion sickness

A

scopolamine (muscarinic antag)

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11
Q

OTC agent for motion sickness with antimuscarinic ADRs

A

dimenhydrinate (1st gen antihistamine)

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12
Q

Used for gastroparesis, risk of EPSE

A

metoclopramide (D2 antag)

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13
Q

Most efficacious for n/v of chemo & opioids

A

ondansetron (5HT3 antag)

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14
Q

Drug induced constipation

A

Antimuscarinic agents:
Antispasmodic agents, overactive bladder agents

Drugs with antimuscarinic side effects:
1st generation antihistamines
Tricyclic antidepressants
Typical antipsychotic agents (esp low potency)

Antacids
Calcium carbonate
Aluminum

Calcium channel blockers (esp. verapamil)

Opioid analgesics

5HT3 antagonists

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15
Q

Meds to treat constipation: first recommendation

A

Fiber/bulk forming: Psyllium

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16
Q

Fiber/bulk forming agents

A

psyllium

Approximates physiological mechanism (facilitates passage-stimulates peristalsis via H20 absorption –> bulk expansion)

Effective in 12-24 hrs to 3 days - take with fluids

May combine and interact with other drugs (digoxin / salicylates), so space dosing

17
Q

Saline (osmotic) cathartics

A

added to fiber as SECOND step to treat constipation

  • non-absorbable ions–> osmotic retention of intestinal water–> increased peristalsis
  • also used in purging doses for food/drug poisoning

Milk of magnesia (Mg(OH)2), magnesium citrate:
for mild to moderate constipation; Avoid in renal dysfunction

Phosphate enemas: reserved for fecal impaction

Polyethylene glycol – electrolyte solutions (PEGs)
High vol soln: bowel cleansing bf procedure; has Na/K salts to prevent net transfer of electrolytes
smaller vol soln: hard to treat constip; daily for electrolyte depletion

18
Q

Lactulose

A

saline (osmotic) cathartic

dissacharide metab by colonic bacteria to low MW acids–> osmotic diarrhea–> increased peristalsis

alternative for acute constipation– useful in elderly

19
Q

Stimulant – Irritant Laxatives

A

**if fiber/saline fail
Bisacodyl
Senna
Castor Oil

20
Q

Bisacodyl

A

stimulant/irritant laxative

increases peristaltic activity via local irritation (PG-NO)–> accum water and elec–> increased motility

active in 6-10 h po or 15-60 min pr

effective, could have dangerous SE: electrolyte/fluid deficiencies, severe cramping

Most widely abused class but safe for chronic use in recommended doses

interindividual variation

21
Q

Castor Oil

A

Stim/irritant lax

  • has triglyceride that is hydrolyzed in the gut to ricinoleic acid
  • acts in SI–> stim fluid/elec secretion and speed intestinal transit

-Castor bean has ricin, toxic glycoprotein

22
Q

Docusate

A

Stool-Wetting agent and emollient

“Colace”

surfactant that acts as stool-softener (facilitates admixture of aqueous and fatty substances)

Role is prevention - used in patients with CV disease / hernia / postpartum patients

Often in combination with stimulant laxative when initiating opioid analgesic therapy

23
Q

Lubricant (mineral oil, olive oil)

A

Stool-Wetting agent and emollient

coats fecal contents

caution in very young/elderly – potential for aspiration into lungs

24
Q

Peripherally acting opioid antagonists for opioid induced constipation

A

-failed laxative therapy

Methylnaltrexone:
given SC, doesn’t cross BBB, expensive!!!

Naloxegol

  • oral derivative of naloxone
  • first pass metab is high
  • 10$/d
25
Q

Drug induced diarrhea (for reference)

A

Antibiotics (esp. broader spectrum agents): super infection

Colchicine (anti-inflammatory agent for gout)

Digoxin: parasympathomimetic action

Magnesium Antacids: osmotic laxative action

Misoprostol: prostaglandin analog stimulates intestinal musculature

Muscarinic Agonists: increased parasympathetic tone

Reserpine: sympatholytic agent allows parasympathetic dominance in GI tract

SSRIs: elevated synaptic 5HT levels stimulates GI motility

26
Q

Loperamide

A

Opioid receptor agonist affecting intestinal motility (mu), intestinal secretion (delta), and absorption (mu and delta)

Anti-secretory activity against cholera toxin

Effective against traveler’s diarrhea, alone or with antibiotics - discontinue if no improvement in 48 hours

Side effects:
Low addiction liability for acute use due to low water solubility (difficult to dissolve and then inject)

Few adverse effects but overdosage can cause CNS depression (esp. in children) and paralytic ileus

27
Q

Polycarophil

A

safe and effective (marked capacity to bind free fecal water)

Useful in diarrhea (absorbs 60X weight in H2O) AND constipation (prevents fecal desiccation)

28
Q

Adsorbents

A

Kaolin, pectin, attapulgite, charcoal, bismuth subsalicylate

  • adsorb “toxins” causing diarrhea
  • mild to moderate diarrhea
  • only small effect on fluid volume excreted

***Avoid bismuth subslicylate in kids

29
Q

Probiotics

A

-commonly Lactobacillus species

Suppress growth of pathogenic organisms  restore normal flora  possible role in antibiotic-associated, viral, or Traveler’s diarrhea

30
Q

low dose TCADs and others for IBS

A

TCADs:relieve abd pain in IBS

diarrhea: loperamide
constipation: osmotic laxatives

Antispasmodics: dicyclomine, hyoscyamine

constipation: Tegaserod (severe)
severe diarrhea: Alosetron

31
Q

Alosetron

A

serotonin 5HT3 Antagonist

  • reduces pain, inhibits colonic motility
  • P450 metab

Use:
severe IBS in women w/ diarrhea (restricted due to risk of ischemic colitis)

Adverse rxn: CONSTIPATION (30%)

32
Q

Tegaserod

A

Serotonin 5HT4 AGONIST

–> peristaltic reflex–> gastric emptying and intestinal motility

low oral avail (bf meals)
renal excretion, hepatic metab

Use:
women under 55: IBS pts with constipation

Adverse rxn: diarrhea (early, resolves)
-linked w/ heart attacks, strokes, unstable angina–> restricted use.

My DEMS I (26 decks)

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