Anti-biotics Flashcards
What antibiotic drug classes are naturally derived (5)
Penicillins Cephalosporins Macrolides Tetracyclines Aminoglycosides
What is “sensitivity”
degree to which microbial organisms are killed or their proliferation arrested by the drug
What drug class is sulfamethoxazole
sulfonamide antibiotic
What is the MOA of sulfamethoxazole
Competitive antagonist of para-aminobenzoic acid (PABA) which blocks bacterial production of folic acid
What is the MOA of Sulfamethoxazole + Trimethoprim combination drug (TMP/S)
inhibits two different step of bacterial folic acid production
What are the indications of Sulfamethoxazole + Trimethoprim combination (TMP/sulfa)
UTI, pneumocystis prophylaxis, susceptible MRSA infection
what sort of creatures are susceptible to TMP/S?
mostly microbial: Streptococcus, Staphylococcus aureus, Escherichia coli, Haemophilus influenzae, and oral anaerobes.
But also some fungi, thus use in pneumocystis prophylaxis
What is the worst reaction to TMP/S
Stevens Johnson syndrome
What are the most common reactions to TMP/S
Skin reactions like rash, photosensitivity. And of course nausea and diarrhea
What drug class are penicillins
Beta-lactam antibiotics
What is the MOA of penicillins
Bind to penicillin binding proteins (Peptoglycans) on the bacteria which inhibits the formation of peptidoglycan cross-linkage in the bacterial cell wall, which causes cytolysis and cell death.
What sort of bugs are susceptible to penicillins
mostly gram positive bugs
What type of anti-biotic causes the most severe allergic response
penicillins!
When is penicillin G indicated
for use against strep throat and some gram negs like Neisseria. Plus it is cheap!
How is the half-life of penicillin G extended
Procaine and benzathine are added to IM injection to decrease pain and increase half-life
When is amoxicillin used
it is a broad spectrum bactericidal drug used against gram pos, UTI, ENT, skin infxn. Not really for severe stuff
What is advantageous about penicillin’s range over amoxicillin’s range
penicillin can cross the BBB, and thus is used for meningitis whereas amoxicillin cannot.
how can amoxicillin’s effect be improved
By adding clavulanic acid added to prevent β lactamase inhibition. This is called Augmentin
What is augmentin’s (amoxil + calvulanic acid) MOA
binding to penicillin binding protein and inhibiting protein synthesis in the bacterial cell wall
what is the most severe common side effect of augmentin (amoxil + clavulanic acid)
The most severe cause of antibiotic induced diarrhea is pseudomembranous colitis.
How much clavulanic acid is in the 250, 500, and 750mg doses of Augmentin
The dosage applies to the amoxicillin portion only. They all contain the same amount of clavulanic acid.
What is the MOA of cephalosporins
Same as other beta-lactam antibiotics: Bind to penicillin binding proteins (Peptoglycans) on the bacteria which inhibits the formation of peptidoglycan cross-linkage in the bacterial cell wall, which causes cytolysis and cell death.
What is a first generation cephalosporin useful for
It has very good activity against gram positive, but poor gram neg coverage
What generation is cephalexin (Keflex)
1st generation cephalosporin (all 1st gen start with “ceph”)
What is the MOA of Macrolides
inhibition of bacterial protein biosynthesis by reversibly binding to the 50S subunit of the bacterial ribosome.
What is unique about the range of macrolides
Macrolides tend to accumulate within leukocytes and are therefore actually transported into the site of infection
When is use of a macrolide indicated
Infection with atypical bug (rickettsia, mycoplasma), strict penicillin allergy
What type of infections is erythromycin used for
respiratory tract infections, GC/CT, syphilis
What class of drug is erythromycin and azithromycin
macrolide antibiotic
Are macrolides bacteriostatic or bacteriocidic
Both! low doses is a static, higher doses is a cidal
What is the most common side effect of erythromycin
It is notorious for causing diarrhea and GI upset
What is notable about the dosing of azithromycin
It has a long half life (68 hrs) and can be given in a loading dose to suppose the steady state (500-1200mg)
Why is azithromycin used so often
Simple dosing schedule, wide-spectrum, and it covers atypical infections
What is the MOA of tetracyclines
It binds to the 16S part of the bacterial 30S ribosomal subunit (different part than macrolides)
What are C/I for tetracycline use
Pregnancy, infants, kids 8 or younger (15 is safer)
Why dose tetracycline stain teeth
because it is such a potent calcium binding agent, so don’t take it with dairy or calcium supplement!
Why is doxy superior to tretracycline
Better dosing schedule
What is the most common use for tetracycline
acne and rosacea, chlamydia. also lyme and rockymountain spotted fever
What is the MOA of aminoglycosides
by binding to the bacterial 30S and 50S ribosomal subunit, causing misreading of mRNA
How are aminoglycosides normally administered
By IV because they are broken down by stomach acid. also, rarely topical.
When are aminoglycosides used
Bad sick: septicemia, intra-abdominal infxn, complicated UTI, nosocomial infxn
what drug class is gentamicin (garamycin)
aminoglycoside antibiotic
What kind of bugs is gentamicin effective against
gram negatives. also, TB. topically very effective for eye infections
What are some side effects of Gentamicin
Potentially nephrotoxic and ototoxic. Permanently. So don’t give this drug unless you have to!
What is the MOA of quinolones
Inhibit bacterial DNA gyrase, thereby inhibiting DNA replication and transcription
What kind of bugs are quinolones used for
Atypical infections, and gram negative bugs
What drug class is ciprofloxacin
quinolone antibiotic
For whom is ciprofloxacin C/I
infants, children, and pregnant/lactating women, because it chelates calcium and is deposited in tissues
What is a serious side effect of ciprofloxacin
Tendonitis and achilles tendon rupture
What foods should not be taken with ciprofloxacin
dairy, since the calcium will be chelated, and caffeine, because cipro prolongs the half-life
What is a common side effect of ciprofloxacin
metallic taste in the mouth, diminished appetite, taste, and/or sense of smell
