antibiotics Flashcards
Penicillin G
= narrow use penicillin/beta lactam.
Route: IV or IM (poor oral bioavailability)
Use: lactamase sensitive gram -/+ cocci
(strep. pneumo, staph, neisseria, treponema, clostridium)
Beta Lactams (class of antibiotics)
Mech: irreversible inhibition of transaminase enzyme;
Structure: 2 rings, 1 = lactam
Route: oral, not topical; excreted in urine.
SE: anaphylaxis and toxicity rare, seizures @ high doses
Resistance via: penicillinase, decreased uptake
Penicillin V
= narrow spectrum penicillin/beta lactam.
Route: oral * but IV/IM if serious infection!
Use: lactamase sensitive gram +/- cocci
(strep pneumo, staph, neisseria, treponema, clostridium)
oxacillin
= beta-lactamase resistant penicillin.
Route: oral, but IV/IM if serious.
Use: penicillinase-producing Staphylococci, mixed staph/strep infections. *MRSA & enterococci = resistant
ampicillin
= extended spectrum penicillin. Route: oral, not with food Use: non-beta lactamase gram+/- bacilli (Staph, strep, E. coli, H influenzae, Salmonella, shigella) SE: rash (~common)
piperacillin
= extended spectrum penicillin,
(NOT penicillinase resistant, but not recognized by B-lactamase!)
Route: parenteral
Use: ONLY for serious G+/- (Enterococci; proteus, pseudomonas, enterobacter)
Clauvulanic acid
= beta lactamase suicide inhibitor (NOT antibiotic alone)
Route: oral
Use: w/ amoxicillin (=> “augmentin”) for beta lactamase producers
Cephalosporins (class of antibiotics)
Structure: similar to penicillins (do NOT use if penicillin anaphylaxis)
Mech: transaminase inhibitor (same as penicillin)
Route: oral/IV/IM, (not topical); Excreted w/ urine.
SE: GI, nephrotoxicity, superinfection
1st gen. cephalosporins
cephalexin (oral), cefalozin (parenteral);
Mech: inhibit cell wall synthesis
For: gram + and some community-acquired gram-; surgical prophylaxis.
*Poor CNS penetration.
SE: nephrotoxicity, allergies
2nd gen. cephalosporins
cefaclor/cefprozil (oral), cefoxitin (parenteral);
mech: inhibit cell wall synthesis
For: gram -, extended spectrum, & some oral & bowel anaerobes
SE: variable toxicity (heterogenous)
3rd gen. cephalosporins
cefpoxadime (oral), cefotaxime (parenteral);
mech: inhibit cell wall synth.
for: extended spectrum gram - (NOT for gram +)
* Good CNS penetration –> meningitis from…
pneumococci, H. influenzae, E. coli, klebsiella, pen-resistant N. gonorrhea
4th gen. cephaolsporins
cefepime (parenteral)
Mech: inhibit cell wall synth.
For: gram - and beta-lactam resistant bacteria
* good CNS penetration –> pseudomonas, enterobacteriacae
imipenem
carbapenem, w/ beta-lactam ring.
Mech: inhibit transaminase –> cell wall synth.
Route: parenteral; * good CNS penetration.
* MUST give w/ renal enzyme inhibitor, or will be hydrolyzed!
Use: only for nosocomial/mixed infections (serious!)
(wide spectrum –> Gram +, -, anaerobes, ~beta lactamase resistant) but NOT MRSA/VRSA.
SE: Seizures, nephrotoxicity, GI Sx, allergy
vancomycin
tricyclic glycoside
Mech: complex inhibition of cell wall synth., bactericidal
Route: IV, or oral if gut infection
Use: gram + cocci & bacilli (NOT gram -), MRSA, pen-resistant Strep. pneumo, coag - staph…
SE: ototoxicity & nephrotoxicity! (w/ high dose), flushing, etc.
daptomycin
(NOT a beta-lactam)
Mech: bactericidal, pokes holes in wall –> depolarize bacteria
Route: IV; renal elimination.
Use: gram + skin/soft tissue infections
(MRSA, streptococci, enterococci; NOT VRSA)
SE: muscle pain, elevated creatinine
Tobramycin
bactericidal aminoglycoside,
Mech: mis-incorporates AAs –> block bacterial protein synth.
Route: IM/slow IV, topical (burns) or oral for gut inf.;
- renal excretion;
Use: tenacious aerobic gram - (E coli, Klebsiella, Psuedomonas)
* NOT for anaerobes.
SE: Low therapeutic index! => ototoxicity, nephrotoxicity, contraindicated in pregnancy (crosses placenta).
Doxycycline
bacteristatic (non-beta lactam),
Mech: blocks bacterial protein synth via ribosome
Route: parenteral, topical. Hepatic clearance (???)
Use: Rocky mtn spotted fever, mycoplasma, chlamydia
SE: pseudomembranous colitis, GI irritation, photo-sensivity, many DDIs!
Drug-drug interactions of doxycycline:
- Barbiturates, Phenyltoin: induce metabolism of doxycycline
- -> lower serum [ ]
- may decrease Oral Contraceptive efficacy
- increase anti-coag. effect of Warfarin (!)
Erythromycin
bacteriostatic macrolide
Mech: protein synth inhibition via ribosome
Route: oral or IV, ~no CNS distribution; excreted w/ bile.
Use: gram - & + aerobes; (esp. if penicillin allergy!)
- also anaerobes: Mycoplasma pneumo, Bordatella pertussis, Legionella, Corynebacter diptheriae
SE: very safe. may inhibit cytP450 –> lower warfarin, etc. tx
may antagonize other anti-microbials!
clindamycin
bacteriostatic,
Mech: blocks ribosome
Route: oral, IM, IV, topical; Not to CNS; hepatic metabolism.
Use: bacteroides (intra-abdominal inf/abscess),
- serious gram+ if penicillin allergy.
SE: diarrhea/pseudomemb. colitis, rash, crosses placenta
Linezolid
synthetic anti-microbial
Mech: block protein synth.
Route: oral; hepatic metabolism
Use: MRSA/MSSA, vanc-res. enterococcus, pen-res. S. pneumo
SE: diarrhea, headache, vomiting; rarely thrombocytopenia
sulfamethoxasole
bacteriostatic, selectively toxic to bacteria (folate-synthesizers)
Mech: inhibit folate synth. (PABA structural analog)
Route: oral, gets to CNS; hepatic metab. & renal excretion
* must Lower dose if renal insufficiency*
Use: UTI, acute otitis media, bronchitis exacerbation
always w/ trimethoprim
SE: crystalizes if dehydrated, acute hemolytic anemia if G6P def., aplastic anemia, crosses placenta & milk…
sulfamethoxazole drug-drug interactions
increases activity of:
- anti-coagulants
- anti-convulsants
trimethoprim
Mech: blocks DNA synth & cell prolif. by decrease thymine (inhibits dihydrosulfate reductase)
Route: oral; hepatic metab, renal excretion.
Use: UTIs (E coli, enterobacter, etc.)
* always w/ sulfamethoxasole*
SE: skin rxn, thrombocytopenia if already folate-def., renal impairment if already renal disease
Ciprofloxacin
quinolone.
Mech: inhibits bacterial gyrase & topoisomerase –> DNA damage
Route: oral, varied metabolism/clearance.
Use: UTI, (not a 1st line drug), resp. infections
SE: rare…tendon rupture, seizures if take w/ NSAIDs
metronidazole
Mech: damages cell macromolecs (ie: DNA)
* prodrug selectively activated in protozoa
Route: oral; hepatic metab/clearance
Use: anaerobes, parasites
SE: dry mouth, CNS effects… do NOT take w/ EtOH!
