06 Factors Affecting Medication Selection, Mechanisms of Action, and Treatment of GI Infections Flashcards
What factors influence the selection of medications for GI infections?
Factors likely include the causative organism, infection severity, patient age, pregnancy status, comorbidities, resistance patterns, and drug-specific characteristics (e.g., toxicity and contraindications).
How do beta-lactam antibiotics work, and how can resistance develop?
They inhibit bacterial cell wall synthesis by blocking transpeptidases. Resistance arises from penicillinase production or altered target enzymes.
What is the mechanism of vancomycin, and what causes resistance?
Vancomycin inhibits cell wall synthesis by binding to D-Ala-D-Ala, blocking trans-glycosylation. Resistance occurs via target site modification, e.g., D-Ala to D-lactate.
What is the mechanism of fluoroquinolones, and what are their key uses?
They inhibit bacterial DNA replication by targeting DNA gyrase and topoisomerase IV. Used for Shigella, Salmonella, E. coli, and Campylobacter.
What are key adverse effects of fluoroquinolones?
Tendonitis, tendon rupture; contraindicated in pregnancy and children.
What adverse effects are associated with aminoglycosides?
Nephrotoxicity, ototoxicity, and neuromuscular blockade.
What is a unique side effect of clindamycin?
Pseudomembranous colitis.
What is the mechanism of metronidazole, and what infections does it treat?
It disrupts DNA in anaerobes. Treats amebiasis, giardiasis, trichomoniasis, and H. pylori.
What are the advantages of tinidazole over metronidazole?
Longer acting and better tolerated.
How does albendazole work, and what infections does it treat?
Inhibits microtubule synthesis, impairing glucose uptake in helminths. Treats ascariasis, hookworm, pinworm, hydatid disease, and cysticercosis.
What is the mechanism of praziquantel?
Increases calcium permeability in helminths, causing paralysis. Treats schistosomiasis and tapeworm infections.
What is the first step in managing acute diarrhea?
Oral rehydration solution (ORS) to restore fluid balance using sodium-glucose transport.
When is empiric antibiotic therapy for diarrhea recommended?
For severe cases, invasive bacterial infections, elderly patients, or specific pathogens (e.g., shigellosis, C. difficile).
What are the risks of inappropriate antibiotic use in diarrhea?
Resistance, gut flora imbalance, prolonged illness, C. difficile infection, and hemolytic-uremic syndrome (HUS).
What is the mechanism and use of rifaximin?
Inhibits bacterial RNA synthesis. Used for IBS-D, traveler’s diarrhea, and hepatic encephalopathy.
