Block 3 CAS — GI Pharmacology

A comprehensive set of 52 flashcards covering key concepts in GI pharmacology.

What is the mechanism and clinical use of PPIs?

Irreversibly block H+/K+ ATPase on parietal cells; used for GERD, PUD, H. pylori therapy, Zollinger-Ellison syndrome, NSAID ulcer prophylaxis.

What are the side effects and long-term risks of PPIs?

Hypomagnesemia, B12 deficiency (long-term), increased C. diff risk, increased fracture risk, rebound acid hypersecretion.

Why is the combination of omeprazole and clopidogrel dangerous?

Omeprazole inhibits CYP2C19, reducing clopidogrel activation and increasing stent thrombosis risk.

What is the mechanism and uses of H2 blockers?

Competitively block H2 receptors on parietal cells to decrease HCl; used for GERD, PUD, nocturnal acid relief.

Why is cimetidine considered special and potentially dangerous?

Most drug-interaction prone H2 blocker; inhibits CYP450 enzymes, increases levels of warfarin, phenytoin; may cause gynecomastia.

What is the mechanism of sucralfate and its key interactions?

Binds to ulcer base forming protective barrier; requires acid to activate and reduces absorption of other drugs.

What is the mechanism and contraindication of misoprostol?

PGE1 analog decreases HCl and increases mucus; contraindicated in pregnancy due to abortifacient effects.

Which antacid causes diarrhea and which causes constipation?

Magnesium (Mg(OH)2) causes diarrhea; Aluminum (Al(OH)3) causes constipation.

What is the mechanism and side effects of metoclopramide?

D2 antagonist + 5-HT4 agonist; used for gastroparesis and GERD. Side effects include tardive dyskinesia and hyperprolactinemia.

What is the mechanism and use of ondansetron?

5-HT3 antagonist for chemotherapy-induced nausea and hyperemesis gravidarum; side effects include headache and QT prolongation.

How does erythromycin function as a prokinetic agent?

Motilin receptor agonist that stimulates gastric motility; used for gastroparesis.

What is the mechanism and contraindication of loperamide?

Peripheral mu-opioid agonist that decreases peristalsis; contraindicated in bloody diarrhea because it worsens conditions.

What is the mechanism and use of rifaximin?

Rifamycin derivative that inhibits bacterial RNA polymerase; used for traveler's diarrhea and hepatic encephalopathy.

What is the mechanism and target of lactulose?

Non-absorbable disaccharide fermented by colonic bacteria; converts NH3 to NH4+ and traps it to decrease ammonia absorption.

What role does rifaximin play in hepatic encephalopathy?

Reduces ammonia-producing bacteria in gut and is used with lactulose for recurrent hepatic encephalopathy.

What is the mechanism and use of mesalamine (5-ASA)?

Inhibits COX and LOX to decrease inflammation; used for mild-moderate ulcerative colitis.

What makes sulfasalazine unique and dangerous?

5-ASA + sulfapyridine; may cause GI upset, hemolytic anemia, and inhibit folate absorption.

What is the use of steroids in IBD and their limitations?

Used for acute flares but not for maintenance due to side effects like adrenal suppression.

What is the action of azathioprine/6-mercaptopurine in IBD?

Immunosuppressive agent used for maintenance of remission; testing TPMT enzyme activity is required before use.

What are the examples of anti-TNF biologics used in IBD?

Infliximab, adalimumab, certolizumab, golimumab; used for moderate-severe IBD and require screening for infections.

What is the mechanism and use of ursodeoxycholic acid (UDCA)?

Hydrophilic bile acid used to improve bile flow in primary biliary cholangitis.

Why are antibiotics contraindicated for EHEC O157:H7?

They can cause bacterial lysis and massive Shiga toxin release, increasing risk of hemolytic uremic syndrome.

What is the first-line treatment for C. difficile?

Oral vancomycin, as it is not absorbed and stays in the colon.

Why should fluoroquinolones not be used for Campylobacter infections?

Increasing resistance; azithromycin is preferred as first-line treatment.

When should antibiotics be used for non-typhoidal Salmonella?

When patients are immunocompromised, bacteremic, or in cases of infants, elderly, or sickle cell disease.

What happens when metronidazole is combined with alcohol?

Disulfiram-like reaction causing nausea, vomiting, flushing due to accumulation of acetaldehyde.

What are the GI uses and warnings of fluoroquinolones?

Used for Salmonella, Shigella, and traveler's diarrhea; warnings include QT prolongation and potential tendon damage.

What is ceftriaxone's association with biliary sludge?

Ceftriaxone can precipitate in bile, causing biliary sludge, especially in children on prolonged therapy.

What GI organisms does metronidazole cover?

C. difficile, Bacteroides fragilis, Giardia, and amoebic infections.

What is the mechanism of fluconazole and its primary uses?

Inhibits ergosterol synthesis and is used for Candida esophagitis and oropharyngeal candidiasis.

What are the key facts about nystatin?

Binds ergosterol to form pores; too toxic for systemic use, only for oral/esophageal candidiasis.

What is a unique side effect of voriconazole?

Visual disturbances, including photopsia and altered color vision.

What is the mechanism and use of echinocandins?

Inhibit fungal cell wall synthesis; used for systemic Candida infections.

What spectrum of infections does amphotericin B treat?

Broad spectrum including Candida, Aspergillus, and Cryptococcus; used for severe systemic fungal infections.

What is the mechanism of acyclovir?

Activated by viral thymidine kinase; inhibits viral DNA polymerase, used for HSV esophagitis.

What is ganciclovir primarily used for and its major toxicity?

Used for CMV colitis/esophagitis; major toxicity includes myelosuppression.

When is foscarnet used?

For CMV and HSV resistant to ganciclovir/acyclovir; associated with nephrotoxicity and electrolyte disturbances.

What is metronidazole’s role in treating parasitic infections?

First-line treatment for Giardia and Entamoeba histolytica; must follow with paromomycin.

What does paromomycin treat?

Used for E. histolytica cyst eradication and is safe in pregnancy.

What does albendazole treat and its contraindication?

Broad-spectrum antihelminthic for various parasites; teratogenic and contraindicated in pregnancy.

What is the mechanism of ivermectin?

Enhances GABA transmission to cause paralysis in parasites; used for Strongyloides and scabies.

What parasites are treated with praziquantel?

First-line for trematodes and cestodes, except in ocular cysticercosis.

What is nitazoxanide's mechanism and unique side effect?

Inhibits anaerobic metabolism; causes harmless yellow-green urine.

What is TMP-SMX's role in treating parasitic infections?

First-line for Cyclospora and Isospora; can cause hemolytic anemia in G6PD deficiency.

Why should antibiotics be avoided in EHEC?

They can cause Shiga toxin release which increases the risk of HUS.

Why shouldn't loperamide be given for bloody diarrhea?

May worsen conditions by prolonging toxin exposure in the gut.

Why are PPIs a problem with itraconazole?

PPIs raise gastric pH, hindering itraconazole absorption which leads to treatment failure.

Why must albendazole be given before aspirating an Echinococcus cyst?

To pre-treat for anaphylaxis risk from ruptured cyst fluid.

What can happen if steroids are given without ruling out Strongyloides infection?

May lead to hyperinfection syndrome and life-threatening complications.

What issue arises with pip-tazo and galactomannan assays?

Can cause false-positive results for Aspergillus, misleading diagnosis.

Why should ganciclovir and zidovudine be avoided together?

Both cause myelosuppression, leading to severe leukopenia and thrombocytopenia.

What is the alternative for treating pinworms in pregnancy?

Use pyrantel pamoate, as albendazole and mebendazole are teratogenic.