Pharmacology - Jacobs Cards Flashcards
Clostridium difficile (C. diff.) secretes toxin A, which has what type of enzyme activity?
Glycosyltransferase (adds a surar onto Rho signaling protein, compromising intestinal barrier)
What toxin does Clostridium perfringens secrete that causes GI symptoms (diarrhea)?
Clostridium perfringens enterotoxin (CPE)
Is Borrelia burgdorferi (Lyme disease) a rod, sphere, or spirochete?
Spirochete
Is Treponema pallidum (syphilis) a rod, sphere, or spirochete?
Spirochete
How do tetracyclines work?
Inhibit protein synthesis (30S)
How do aminoglycosides work?
Inhibit protein synthesis (30S)
How do macrolides work?
Inhibit protein synthesis (50S)
How does clindamycin work?
Inhibits protein synthesis (50S)
How does linezolid work?
Inhibits protein synthesis (50S)
How does lefamulin work?
Inhibits protein synthesis (50S)
How do fluoroquinolones work?
Inhibit bacterial topoisomerases (DNA Gyrase and Topoisomerase IV)
How does sulfamethoxazole work?
Antifolate (Inhibits dihydropteroate synthetase, DHPS)
How does trimethoprim work?
Antifolate (inhibits dihydrofolate reductase, DHFR)
What is the generic name for the fixed 1:5 combination of trimethoprim (TMP) and sulfamethoxazole (SMZ)?
co-trimoxazole
What is the brand name for co-trimoxazole?
Bactrim
Why are sulfamethoxazole and trimethoprim used together (as co-trimoxazole)?
They are synergistic.
What type of fetal defect can occur if pregnant women take co-trimoxazole (TMP-SMZ)?
Neural tube defects
Why can co-trimoxazole cause hyperkalemia?
Trimethoprim resmbles the K+ sparing diuretic, triamterene (aldosterone antagonist)
How does polymyxin B work?
Forms holes in bacterial membranes
How does metronidazole work?
Bacterial enzymes use it to generate reactive oxygen species.
How does nitrofurantoin work?
Bacterial enzymes use it to generate reactive oxygen species.
How does vancomycin work?
Inhibits cell wall biosynthesis
How does bacitracin work?
Inhibits cell wall biosynthesis
Define the abbreviation VRE
Vancomycin-Resistant Enterococci
Define the abbreviation MRSA
Methicillin-Resistant Staphylococcus aureus
Why do penicillins (e.g. ampicillin) improve Gram POS coverage for aminoglycosides (e.g. gentimicin)?
Penicillins weaken the cell wall, which allows penetration of aminoglycosides
Which antibiotic class binds to negatively-charged phospholipids in the proximal tubule, and its high concentration there causes tubular necrosis (renal damage)?
Aminoglycosides
What antibiotic complexes with uromodulin in renal casts in thick ascending limb?
Vancomycin
What renal enzyme converts imipenem to a toxic metabolite that causes kidney damage?
DHP-1 (dihydropyrimidinase-1)
WHat DHP-1 inhibitor is co-administered with imipenem, to prevent renal injury?
Cilastatin
What is the main step in bacterial cell wall synthesis that penicillins inhibit?
Transpeptidase reaction
What is the main step in bacterial cell wall synthesis that vancomycin inhibits?
Transglycosylase reaction
What is the step in bacterial cell wall biosynthesis that bacitracin inhibits?
Phosphatase (dephosphorylation of C55-isoprenyl pyrophosphate)
Are antistaphylococcal penicillins effective against MRSA?
No
Renal transporter that secretes penicillin into tubular lumen.
Organic anion transporter (OAT)
Why does probenecid increase the half-life of penicillins?
Probenecid inhibits organic anion transporter (OAT)
Define the abbreviation KPC
Klebsiella pneumoniae carbapenemase
What drug classes does KPC cleave?
Penicillins, Cephalosporins, Carbapenems, and Monobactams (aztreonam)
What drug classes do metallo-beta-lactamases cleave?
Penicillins, Cephalosporins, Carbapenems, and Monobactams (aztreonam)
Define the abbreviation NDM-1
New Delhi Metallo-beta-lactamase 1
What drug classes to extended-spectrum beta lactamases cleave?
Penicillins and Cephalosporins
Is ceftolozane/tazobactam effective against KPC-producing Gram NEG pathogens?
No
Does the beta-lactamase inhibitor tazobactam inhibit penicillinases and ESBLs?
Yes
Does tazobactam inhibit NDM-1
No, there are no beta lactamase inhibitors that cover NDM-1 (yet)
If ceftazidime/avibactam effective against KPC-producing Gram NEG pathogens?
Yes (but there is emerging resistance)
What is the % cross-reactivity in hypersensitivity cases between penicillins and cephalsporins?
About 10%
Which carbapenem has the best CNS access (e.g. for treating Pseudomonas or Neisseria)?
Meropenem
Are carbapenems effective against CRE?
No, CRE is Carbapenem-Resistant Enterobacteriaceae
Are carbapenems effective against ESBL-producing Gram NEG bacteria?
Yes, ESBLs cleave penicillins, cephalosporins, and monobactams (aztreonam), but not carbapenems.
Do carbapenems cover B. fragilis?
Yes
Does piperacillin-tazobactam (Zosyn) cover B. fragilis?
Yes
Is meropenem/vaborbactam (Vabomere) effective against NDM-1?
No, there are no clinically useful metallo-beta-lactamase inhibitors available (yet)
Is aztreonam a beta lactam?
No, it is a monobactam. It is rarely cross-reactive in patients that are hypersensitive to penicillins.
Is aztreonam broad-spectrum against Gram NEG or Gram POS?
Aztreonam is broad spectrum against Gram NEG bacteria; except: ESBL, KPC, and metallo-beta lactamase strains (e.g. NDM-1)
Are beta lactamase inhibitors (e.g. tazobactam) competitive or irreversible?
Competitive
What drug class does cefotetan belong to?
Cefamycins (but it is often classified as a Cephalosporin)
Is aztreonam effective against Pseudomonas?
Yes. Used against drug-resistant strains, and for pnenumonia prophylaxis in cystic fibrosis patients.
What IV antibiotic can cause red man syndrome (red, itchy skin caused by histamine release) if infused too quickly?
Vancomycin
Is vancomycin broad spectrum against Gram POS or Gram NEG bacteria?
Gram POS (Strep, Staph, and Enterococci, except VRE)
How is vancomycin administered for intestinal C. difficile-associated diarrhea (CDAD)?
Orally
How is vancomycin administered for systemic infections?
Intravenous
How is vancomycin eliminated?
Renally, as unchanged drug (caution: vancomycin accumulates in patients with renal failure!)
Is vancomycin effective against MRSA?
Yes
Name two organs that vancomycin is toxic to.
Ears (ototoxic) and kidneys (nephrotoxic)
How is bacitracin administered?
Topically
Is bacitracin a peptide or a small molecule drug?
Peptide
Why does bacitracin have a high incidence of contact dermatitis?
It is a peptide and elicits an immune response.
Does topical bacitracin give coverage against Gram POS or Gram NEG bacteria?
Gram POS
Name the aminoglycosides
amikacin gentamicin neomycin streptomycin tobramycin
Name the tetracyclines
doxycycline minocycline tetracycline demeclocycline (other broader-spectrum ones not listed)
Name the macrolides
azithromycin clarithromycin erythromycin fidaxomicin
Name the carbepenems
doripenem ertapenem imipenem/cilastatin meropenem
Name the aminopenicillins
amoxicillin ampicillin
Name the natural penicillins
Penicllin G Penicillin V
Name the beta lactamase inhibitors
Except for clavulanate, they end in -bactam:clavulanate sulbactam tazobactam avibactam relebactam vaborbactam
How is aztreonam administered?
Intravenously, except for Psudomonas prophylaxis in cystic fibrosis.
What pathogen are cefamicins (cefotetan) active against that cephalosporins are not?
Bacteroides fragilis (anaerobe)
What pathogen is the second-generation cephalosporins (e.g. cefuroxime) active against that the first-generation (e.g. cefazolin) is not?
Haemophilus influenzae
Which cephalosporin is active against MRSA?
ceftaroline (advanced gen cephalosporin - sometimes called fifth gen)
What cephalosporins that are active against Pseudomonas?
Ceftazidime (3rd gen) and Cefipime (4th gen) note: Cefipime/Avibactam and Ceftolozane/Tazobactam also cover Pseudomonas.
Is ceftriaxone active against gonorrhea (Neisseria gonorrhea)?
Yes. But gonorrhea is often concomitant with Chlamydia, so doxycycline or azithromycin is usually added for coverage.
Is ceftriaxone effective against Chlamydia?
No. If ceftriaxone is used for a mixed STD, you should add azithromycin or doxycycline to cover Chlamydia.
What can happen if too much penicillin is given intrathecally for a CNS infection (e.g. mixing up doses)?
Seizures
Does vancomycin have a broad or narrow therapeutic window?
Narrow (therapeutic index is small, risk of toxicity if levels not monitored)
Name two classes of antibiotics that cause photosensitivity.
Tetracyclines and Fluoroquinolones
What class of antibiotics deposit in bone, and can stain developing teeth in children?
Tetracyclines
Name two antibiotic classes that bind to multivalent cations - avoid taking with dairy, antacids, or supplements containing Ca2+, Mg2+, Al3+, or Fe3+.
Tetracyclines and Fluoroquinolones
What effect do multivalent cations (calcium, iron, aluminum, magnesium) have on tetracyclines and fluoroquinolones?
If taken together, they inhibit oral absorption of the antibiotic (wait 2 hours).
What oral tetracycline is taken for acne vulgaris?
Sarecycline
Are aminoglycosides more effective against Gram POS or Gram NEG pathogens?
Gram NEG (aerobes)
Why are aminoglycosides not effective (when used alone) against Gram POS organisms?
They cannot penetrate the thick cell wall.
Are aminoglycosides positively or negatively charged?
Positively charged
Name two drug classes that have a post-antibiotic effect (PAE) - continue inhibiting bacterial growth after levels drop.
Aminoglycosides and Fluoroquinolones
Name two drug classes that are most effective when high peak concentrations are reached (PK index: PEAK/MIC)
Aminoglycosides and Fluoroquinolones
Are aminoglycosides orally bioavailable?
No, if treating a systemic infection, you need to inject them.
Which macrolide is not absorbed in the GI tract?
Fidaxomycin - taken orall for C. diff.
Are macrolides effective against Gram POS pathogens?
Not reliably - there is a lot of Strep. resistance (note: azithromycin may fail treating some URIs due to Strep. pneumo. resistance).
Are macrolides effective against Enterobacteriaceae (e.g. E. coli, Klebsiella pneumoniae)?
Not against most. Azithromycin is effective against Shigella and Salmonella, but not others).
List drug regimens for H. pylori.
Triple therapy: clarithromycin + amoxicillin (or metronidazole) +PPI Quadruple therapy: bismuth subsalicylate + tetracycline + metronidazole + PPI
What antibiotic causes inducible drug resistance in some bacteria, evaluated by a D-test in labs?
Clindamycin
What class of antibiotics is useful at inhibiting bacterial toxin production (e.g. necrotizing fasciitis)?
Protein synthesis inhibitors (clindamycin or linezolid are most effective)
Is linezolid orally bioavailable?
Yes, linezolid has excellent oral bioavailability.
What is lefamulin indicated for?
Community acquired pneumonias (CAP) - broad spectrum for pneumonia pathogens but NOT MRSA
What class of antibiotics can cause achilles tendonitis (and possible tear)?
Fluoroquinolones
What is the drug of choice in treating syphilis (Treponema pallidum)?
Penicillin G (Bicillin L-A) - 3 injections (1 per week)
Brand name for ceftriaxone
Rocephin
Are macrolides effective against Psudomonas?
No.
Are macrolides effective against Clostridium difficile?
Only fidaxomycin (Dificid) - active against C. diff.
Are macrolides effective against Bacteroides fragilis?
No.
Is clindamycin effective against Bacteroides fragilis?
Yes.
What antibiotic is also a monoamine oxidase inhibitor (MAOI)?
Linezolid