Pharm Antimicrobials Flashcards
Drug groups
- cell wall inhibitors
- protein synthesis inhibitors
- bacterial DNA interference
CW: pens, cephs, bacitracin
PS: aminoglycosides & tetracyclines (30S), chloramphenicol, macrolides, & clindamycin (50S)
DNA: sulfonamides, TMP, & pyrimethamine (folic acid), fluoroquinolones (DNA gyrase and topo IV)
For most class of oral antibiotics, __ effects are common and should be kept in mind when prescribing/educating
GI - nausea, vomiting, bloating, decr appetite, diarrhea
Cell wall inhibitors
- building blocks of cell walls
- glue/mortar that holds blocks together
- drugs that work on each
Peptidoglycan
Transpeptidase
Pep-can = bacitracin Transpep = pens, cephs
Bacitracin
- MOA
- clinical indications
- dosing
Inhibits transfer of peptidoglycans (mucopeptides) into the growing cell wall
ONLY gram(+) Blepharitis
Ung only
QD to TID
What components make up
- Polysporin
- Neosporin
P: Bacitracin (+) and Polymyxin B (-)
N: Polysporin and neomycinq
Penicillins
- drug names (2)
- MOA
- clinical indications
Amoxicillin (Principen)
Dicloxacillin (Dynapen)
Inhibits transpeptidase (glue/mortar)
A&D both have good gram (+)
A has better gram (-); combined with clav acid to become resistant to pcnase (Augmentin)
D is resistant to penicillinase (as is oxacillin, cloxacillin)
-DOC for methicillin-sensitive staph infections (esp MSSA), however is NOT EFFECTIVE AGAINST MRSA
A&D: combat bacterial infections of the eyelid (e.g. hordeola, preseptal cell) that are most often caused by S. aureus
Pencillins
- dosing
- adverse effects
- pregnancy
Augmentin: 500, 875, or 1000mg tablets BID x 1 week
Dicloxacillin: 250mg QID x 1 week
Hypersensitivity rxns: urticaria & anaphylaxis (IgE type 1), contact derm (type 4)
Stevens-Johnson syndrome from amoxicillin
Generally very safe in all trimesters
Penicillin and Cephalosporin cross-sensitivity
Both have beta-lactam rings
- P = 5-member
- C = 6
(+)PCN allergy = 1% chance also allergic to 1st gen cephs
Both contraindicated in pts with hx of IgE type 1 HSRxn (urticaria, anaphylaxis)
Cephalosporins
- drug names (2)
- MOA
- clinical indications & dosing
Cephalexin (Keflex)
Ceftriaxone (Rocephin)
Inhibits transpeptidase (glue/mortar)
All have good gram (+)
3rd and 4th gen have better gram (-) coverage
Cephalexin (Keflex): 1st gen; commonly rx’d for skin infxn - dacryoadenitis, dacryocystitis, preseptal; do not use in isolation for MRSA suspect; 250-500mg BID to QID
Cephtriaxone (Rocephin): 3rd gen; intravenous ceftriaxone is the TOC for gonococcal conjunctivitis and orbital cellulitis
Gono conjitis: if cornea-involving 1g IV every 12-24hrs with varying duration (usually 3-5 days); if not involving cornea single 1g IM injection
Orbital: 1g IV QD x 1 week
Cephalosporins
-adverse rxns
Hypersensitivity
May destroy the normal intestinal microflora, altering absorption of vit K = excessive thinning of the blood in pts taking warfarin (vit K antag)
Aminoglycosides
- drug names (2)
- MOA
- clinical indications & dosing
- adverse effects
Gentamicin (Garamycin)
Tobramycin (Tobrex)
Bind to 30S to inhibit protein synthesis
Effective against gram (+) and (-), with better (-)
Previously used 1st line against ocular bact infxns (now use fluoros)
T: available in topical ophthalmic and ung form
G&T: available in fortified concentrations and rx’d with fortified cefazolin (1st gen) for sight-threatening corneal ulcers
SPK, delayed corneal re-epithelialization
TobraDex
- components
- clinical indications
Tobramycin 0.3% (30S/aminoglycoside)
Dexamethasone 0.1%
QID for inflammatory conditions with associated bacterial infxn: staph marginal keratitis, corneal infiltrates
Tetracyclines
- drug names (3)
- MOA
Tetracycline
Doxycycline
Minocycline
Bind to 30S to inhibit protein synthesis & prevent access of aminoacyl tRNA
Bacteriostatic
Tetracyclines
-clinical indications & dosing
Minocycline: low dose for long-term mx of acne vulgaris
Doxycycline: alters the configuration of oil glands & decr the release of irritating free fatty acids
- meibomianitis: 50 or 100mg BID x 4-8 weeks (or until symptom relief) then QD 3-6mo
- acne rosacea: 100mg BID until symptoms relief (2-6 weeks) then taper to 100 QD for several weeks; some pts require long-term tx with Periostat = low-dose 20mg tablet; Metronidazole (MetroGel) topical gel 1% can be used for pts with chronic acne rosacea
- chlamydia conjitis:
- RCEs:
Tetracyclines
- pharmacokinetics
- adverse effects
Absorption in the GI tract is impaired by cations in dairy, antacids, and iron-containing compounds
Primary route of excretion is kidney - contraindicated in renal failure
Doxycycline is an exception: can be taken with food, is eliminated in fecal matter, is safe for renal failure
Contraindicated in pregnancy and children
Pseudotumor cerebri, bone growth retardation, discoloring teeth
Minocyline: blue sclera, pigmented cysts on conj
Chloramphenicol
- brand name
- MOA
- adverse effects
Chloroptic
Bind to 50S to inhibit protein synthesis
Effective against gram (+) and (-)
Topical use has caused fatal aplastic anemia
Extended tx can cause optic neuritis
Macrolides
- drug names
- MOA
Erythromycin
Azithromycin (Zithromax, Azasite)
Clarithromycin (Biaxin)
Bind to 50S to inhibit protein synthesis
Macrolide clinical indications & dosing
Oral azithro (Zithromax): chlamydial infxns (trachoma, adult inclusion) = single 1g, taken on empty stomach
- also available in Z-pak: six 250mg (2 capsule day 1, 1 capsule remaining 4 days)
- Tri-pak: three 500mg
Topical ophthalmic azithro (Azasite): bacterial conjitis and blepharitis
- conjitis: BID x 2 days, then DQ x 5 days
- bleph: BID x 2 days, then QD until symptom relief (often several months)
- preserved with BAK, d/c CLS wear during use
Topical ophthalmic erythro ung: prophylaxis (gonococcal ophthalmia neonatorum in place of silver nitrate); not usually used for active infxns due to poor resistance profile; dosed at night
Oral clarithro: respiratory infxns
Lincomycin, Clindamycin
- brand name
- MOA
- clinical indications
C: Cleocin
Reversibly binds to 50S inhibiting protein synthesis
MRSA and anaerobic infxns
Antibiotics used for MRSA
“Bacteria Can’t Decide”
Bactrim (TMP-SMX)
Clindamycin
Doxycycline
Sulfonamides
- drug names (4)
- MOA
Sulfisoxazole (Gantrisin)
Sulfacetamide (Sulamyd)
Sulfamethoxazole (Gantanol)
Sulfadiazine (Microsulfan)
Inhibit dihydropteroate synthase (enzyme that converts PABA to dihydrofolic acid for the 1st step in folic acid synth)
Bacteriostatic
Gram (+) and (-)
Sulfonamides
- ophthalmic indications & adverse effects
- systemic indications & adverse effects
Ophthalmic:
- topical sulfisoxazole and sulfacetamide were commonly used for bleph/conjitis, but are now rarely used
- most common SE: burning, stinging, contact derm, photosensitization (sunburn on the eyelid margin)
Systemic:
- sulfadiazine + pyrimethamine = tx toxoplasmosis
- sulfamethoxazole + trimethoprim = Bactrim
- SE: orals can cause kernicterus in infants due to bilirubin accumulation in the brain (contraindicated during pregnancy); may induce a myopic shift; topical ophthalmics and orals may cause Stevens-Johnson syndrome
What is Stevens-Johnson syndrome
Fever, lesions on skin/mucus membranes -> sloughing over 10% or less of the body surface area, conj lesions (85%)
Most commonly assoc with medications (sulfonamids (incl bactrim), amoxicillin, allopurinol) and infections
Trimethoprim, Pyrimethamine
- brand names
- MOA
- clinical indications
- adverse effects
Trimethoprim (Primsol)
Pyrimethamine (Daraprim)
Inhibit dihydrofolate reductase (enzymes that converts dihydrofolic acid into tetrahydrofolic acid in 2nd step of folic acid synth)
Idications
- Topical ophthalmic trimethoprim: effective against gram (+) and (-), but not pseudomonas; available with poly b as Polytrim
- Oral pyrimethamine: ocular toxoplasmosis infections
SE:
- Oral TMP: bone marrow suppression (Treats Marrow Poorly) -> aplastic anemia, leukopenia, granulocytopenia
- Pyrimethamine can have similar toxicity
