1 - Antibiotics Flashcards
Intro
-inhibition of protein synthesis
Bacteria = 70S ribosomes (50S + 30S)
30S = aminoglycosides and tetracyclines (buy AT 30)
50S = Chlorampenicol, macrolides (Erythro, azithrom clarithro), clinda/Lincomycin (CEL at 50)
Penicillins: Amoxicillin, Dicloxacillin
- adverse reactions
- cross-sensitivity
1:HS rxns
-T1: anaphylaxis, urticaria (IgE-mediated rxns)
-T4: contact derm
Others: render oral contraceptives ineffective, Stevens-Johnson syndrome (amoxi)
Pens + Cephs have beta-lactam ring
-C = 6-member ring
-P = 5-member ring
If pt is allergic to PCN, theres ~1% risk will also be allergic to 1st gen cephs (rx with caution)
Both: contraindicated in pts with IgE-mediated T1 HS (urticaria, anaphylaxis)
Sulfonamides: Sulfisoxazole, Sulfacetamide, Sulfamethoxazole, Sulfadiazine
- opthalmic indications/adverse effects
- systemic indications/adverse effects
Ophthalmic
- use: topical ophth rarely used (previously rxd for bleph and conj-itis)
- SE: burning, stinging, contact derm, local photosensitization (sunburn on eyelid margins)
Systemic
-use: sulfadiazine + pyrimethamine tx’s toxoplasmosis
—Bactrim = sulfamethoxazole + trimethoprim
-SE:
—kernicterus in infants (bilirubin accum in brain) = contraindicated in pregnancy
—may induce myopic shift (think sulfa, CAIs, pilo)
—Stevens-Johnson syndrome
Trimethoprim, Pyrimethamine
- clinical indications
- adverse effects
Topical ophth trimethoprim: gram(+) and (-) infections
- not effective against pseudomonas
- available in combo with polymyxin B = Polytrim (bacterial conj-itis, esp kids)
Pyrimethamine: oral for ocular toxoplasmosis (with sulfadiazine (di and py for toxo))
Oral trimethoprim can cause bone marrow suppression (Treats Marrow Poorly) -> aplastic anemia (recall chloramphenicol also), leukopenia, granulocytopenia
Pyrimethamine can have similar toxicity
Tetracyclines: Tetracycline, Doxycycline, Minocycline
- MOA
- clinical indications
Protein synthesis inhibitor - binds to 30S subunit and prevents access for aminoacyl tRNA, bacteriostatic
Doxy:
-meibomianitis, acne rosacea: alters configuration of oil glands, decr release of irritating free FAs
-chlamydial ocular infections (trachoma, adult inclusion)
-RCE: decr risk of recurrences (inhibits MMPs)
Mino:
-RXd in low doses for long-term management of acne vulgaris
Cephalosporins: Cephalexin, Ceftriaxone
- MOA
- clinical indications (lexin vs triaxone)
Cell wall inhibitor - blocks mortar/glue (transpeptidase)
All have good gram(+)
1st gen (cephalexin): commonly used for skin infections, which are primarily caused by gram(+) (think staph)
-includes dacryoadenitis/cystitis, preseptal
3rd gen (ceftriaxone): also has gram(-) coverage, esp used against gonorrhea (gram neg diplococci) as IM injection
-IV cef is the TOC for gonococcal conj-itis + orbital cellulitis (H. flu)
Aminoglycosides: Tobramycin, Gentamicin
- MOA
- clinical indications
Protein synthesis inhibitor - binds to 30S
Effective against gram(+) and (-), with better (-) coverage
Used to be first-line against ocular bacterial infections before fluoros
Tobra: avail in topical gtt and ung form
Both: available in fortified concentrations
-RXd with fortified cefazolin for tx of sight-threatening corneal ulcers
Macrolides: Erythro/Azithro/Clarithromycin
- MOA
- clinical indications
Protein synthesis inhibitor - binds to 50S subunit
Oral azithro: safe in pregnancy, chlamydial infections (trachoma, adult inclusion), convenient single 1g dose, take on empty stomach
Topical ophthalmic azithro (Azasite): bacterial conj-itis and blepharitis, dose BID x 2days, then QD x 5days (recall: preserved with BAK = no CLS during tx)
Topical opthalmic erythro: uncommonly rxd due to poor resistance, used for prophylaxis, dosed at night, also prophylaxis of gonococcal opthalmia neonatorum (recall: used in place of silver nitrate; ophth neo usually chlamydial)
Oral clarithro: respiratory infections
Cephalosporins: Cephalexin, Ceftriaxone
- adverse effects
- coverage of cephs by generations
HS rxns
May destroy normal microflora -> alters absorption of vit K -> excessive thinning of blood in pts taking warfarin (K-antagonist)
-recall K is needed for “klotting”
1st: (+)
2nd: (+), some (-)
3rd/4th: (+) and (-)
Bacitracin
- MOA
- clinical indications
- combos
Cell wall synth inhibitor - blocks bricks (peptidoglycan) from growing cell wall
Gram(+) only, ung only, blepharitis (staph)
Polysporin = bacitracin(+) + polymyxin B(-) Neosporin = polysporin + neomycin
Trimethoprim, Pyrimethamine
-MOA
Interfere with bacterial DNA - inhibit dihydrofolate reductase (DHF red)
-enzyme that converts DHF acid to tetrahydrofolic acid (THF) in the second step of folic acid synth
Sulfonamides: Sulfisoxazole, Sulfacetamide, Sulfamethoxazole, Sulfadiazine
-MOA
Interfere with bacterial DNA - inhibit dihydropteroate synthase (DHD synth)
- enzyme that converts PABA to dihydrofolic acid (DHF) in the first step of folic acid synth
- bacteriostatic
- gram(+) and (-)
Tetracyclines: Tetracycline, Doxycycline, Minocycline
- pharmacokinetics
- adverse effects
Absorbed in GI tract: impaired by cations in dairy, antacids, iron-containing compounds
Excreted via kidneys: contraindicated with renal failure
*Exception: doxycyline can be taken with food, is eliminated in fecal matter
Contraindications: pregnancy, children
SE: pseudotumor cerebri, slows bone growth, teeth discoloration
Minocycline = blue sclera, pigmented cysts on conj (think a minnow, but actually a big BLUE shark that comes and bites you)
Pregnancy and drugs
“FAT PAC: she’s not fat, she’s just pac-ing a baby”
Avoid FAT, give PAC
Fluoros (bones), Aminoglycos (nephro/ototox), Tets
Pcns, Azithro*, Cephs
*safest
Fluoroquinolones
- adverse effects
- ages approved for
Oral fluoroquinoLONES hurt the BONES
- can cause tendonitis, damage to cartilage formation, inhibition of bone growth
- contraindicated in pregnancy, children, adolescents (<18)
All topical ophth fluoros EXCEPT LEVO are approved for use in pts 1 year and older
Lincomycin, Clindamycin
- MOA
- clinical indications
Protein synthesis inhibitor - REVERSIBLY bind to 50S subunit
MRSA! (also anaerobic infxns)
MRSA drugs
“Bacteria Can’t Decide”
Bactrim (trimethoprim-sulfamethoxazole)
Clindamycin
Doxycyline
Intro
-interfering with bacterial DNA
Folic acid - necessary for DNA synth, unlike humans (dietary) bacteria must produce their own, sulfonadmides (synthase) + trimethoprim/pyrimethamine (reductase)
Gyrase + topoisomerase 4 - enzymes utilized for bacterial DNA synth, fluoros
Penicillins: Amoxicillin, Dicloxacillin
- MOA
- clinical indications (A vs D)
- pregnancy?
Cell wall synth inhibitor - blocks mortar/glue (transpeptidase)
All have good gram(+)
A: better gram(-) than D
-NOT resistant to PCNase: combined with clavulonic acid = Augmentin
D: resistant to PCNase = DOC for MSSA (tho ineffective against MRSA)
RX’d to combat bacterial infections of lids: hordeola, preseptal (Staph. Aureus infections)
Generally very safe in all trimesters of pregnancy
Intro
-inhibition of cell wall synthesis
Bacteria have cell walls not present in human cells
Peptidoglycans = “bricks”, provide structural integrity, bacitracin
Transpeptidase = “mortar”, cross-linking of peptidoglycans, pens + cephs
Stevens-Johnson syndrome
- what
- medications associated with
Fever, lesions on skin/mucous membranes -> sloughing of skin over 10% or less of the body surface area
-conj lesions (85% pts)
Sulfonamides (incl bactrim), amoxicillin, allopurinol
Drugs to take on empty stomach
PAT
Pcn, Azithro, Tets
Aminoglycosides: Tobramycin, Gentamicin
- combos
- adverse effects
TobraDex = tobramycin 0.3% + dexamethasone 0.1% (strong steroid)
-RXd for inflammatory ocular condns with assoc bacterial infection (e.g. staph marginal keratitis (immune system rxn, not active infection), corneal infiltrates)
Topicals are notorious for SPK (ocular surf dz) and delayed corneal re-epitheliazation
Fluoroquinolones
-name and differentiate drugs in 2nd, 3rd, 4th generations
All gram (-), as incr generations incr gram(+)
2nd (-): cipro, ofloxacin (think 2 = CO-op or CO2)
3rd (-,+): levofloxacin (3-Leaf clover)
4th (-,+): gati, moxi, besifloxacin (GuMBy)
Chloramphenicol
- MOA
- clinical indications
- adverse effects
Protein synthesis inhibitor - binds to 50S subunit
Effective against gram(+) and (-)
“Dinosaur” = never used anymore
Topical use has caused fatal APLASTIC ANEMIA (only topical that causes)
Extended therapy may result in OPTIC NEURITIS
Fluoroquinolones
- MOA
- clinical indications
Inhibit DNA synth - inhibit DNA gyrase AND topoisomerase IV
Topical ophth: cls-related corneal ulcers, corneal abrasions, bacterial conj-itis (think ant seg infxn, esp cornea)
Systemic:
- cipro: rxd for gram(-) urinary/GI infections
- moxi: pneumonia, sinusitis, intra-abdominal/skin infxns
