Pharmacology Flashcards
MOA for Bacitracin
inhibits transfer of transpeptidase into growing bacterial cell wall
Drugs that inhibit protein synthesis by binding to 30S subunits
Aminoglycosides
Tetracyclines
Drugs that inhibit bacterial protein synthesis by binding to the 50S subunit
Chloramphenicol, macrolides, clindamycin
Drugs that inhibit folic acid synthesis
Sulfonamides
Trimethoprim and pyrimethamine
MOA for fluoroquinolones
inhibits DNA gyrase and topoisomerase IV
Side effects of oral antibiotics
GI effects (nausea, vomiting, bloating, decreased appetite, diarrhea)
MOA of penicillins and cephalsporins
inhibit cell wall synthesis by inhibiting transpeptidase
Bacitracin only effective against which bacteria & how would you prescribe it?
gram + , QD - TID for blepharitis
amoxicillin
- MOA inhibits transpeptidase
- better gram (-) coverage
- NOT resistant to penicillinase
What does dicloxacillin and augmentin treat?
hordeola, preseptal cellulitis
Which drugs are penicillinase resistant?
- oxacillin
- dicloxacillin
- cloxacillin
How is Augmentin prescribed?
500 mg , 875 mg, 1,000 mg tabs BID x 1 week
Dicloxacillin
- best for methicillin-sensitive staph aureus (MSSA)
- NOT effective for staphylococcal strain (MRSA)
Adverse effects for penicillin
- urticaria & anaphylaxis (IgE mediated type 1 reaction) to contact dermatitis (type 4)
- render oral contraceptives ineffective
- Stevens-Johnson syndrome in pts taking amoxicillin
Why are patients usually allergic to both cephalosporins & penicillins?
They both have beta-lactam ring
Cephalosporin - 6 ring
Penicillin - 5 ring
1% risk that the pt is allergic to BOTH
Contraindicated in pt with hx of IgE type 1 hypersensitivity rxn (urticaria & anaphylaxis)
Cephalosporins MOA
Inhibit transpeptidase
what is cephalexin used to tx for?
skin infections caused by gram + bacteria - dacryadenitis, dacryocystitis, and preseptal cellulitis - SHOULD NOT BE USED IN ISOLATION W/ MRSA
Dosage for cephalexin
250-500mg BID to QID for the tx of dacryocystitis, dacryadenitis, & preseptal cellulitis
What is ceftriaxone used to tx?
tx gonorrhea conjunctivitis & orbital cellulitis
Ceftriaxone dosage for gonococcal conjunctivitis corneal involving and noninvolving
Involving - IV every 12-24 hours for 3 days
Non-involving - single 1 gram IM injection
Ceftriaxone dosage for orbital cellulitis
1 gram IV qday x 1 week
Adverse effects for cephalosporins
destroy normal micrflora - alters absorption of vitamin K causing “thinning” of blood in pts taking warfarin (Vit K antagonist)
Gram coverage for cephalpsporins
1st gen: gram (+)
2nd gen: gram: some(-) & (+)
3rd gen: gram (-) & (+)
Gram coverage for aminoglycosides
gram + and -, better gram - coverage
List Aminoglycosides & MOA
TobraGent30
Gentamycin
Tobramycin
Inhibit binding of 30s ribosomal subunit
What is tobradex used to tx?
inflammation w/ bacterial infection (staph marginal keratitis, corneal infiltrates)
List Tetracyclines
Tetracycline
Doxycyline
Minocycline
Contraindications for tetracylcines
pt with renal failure, children & pregnant pt
MOA of tetracyclines
Binds to 30S subunit
What does mincocyline tx? dosage?
low doses & long term tx of acne vulgaris
What is doxycycline used to tx?
- meibomianitis
- Acne rosacea
- Chlamydial conjunctivitis
- RCE
How long does epithelial basement membrane and hemidesmosomes formation take to heal?
approx 2 months
SE for tetracyclines
Pseudotumor cerebri, bone growth retardation, discoloration of teeth
SE for tetracyclines
Pseudotumor cerebri, bone growth retardation, discoloration of teeth
Minocycline SE
blue sclera & pigmented cyst on the conjunctiva
Which drugs block protein synthesis at the 50S ribosomal subunit?`
Chloramphenicol, macrolides (erythromycin, azithromycin) , lincomycin, & clindamycin
MOA for chloramphenicol
inhibits bacterial protein synthesis by binding to 50S ribosomal subunit
- effective against gram (+) and gram (-) bacteria
- ointment or topical ophthalmic solution
Adverse effects for chloramphenicol?
Topical ophthalmic use has caused fatal aplastic anemia
Extended therapy may result in optic neuritis
Macrolides MOA
(erythromycin/azithromycin)
- inhibits bacterial protein synthesis by binding to 50S ribosomal subunit
Macrolides are usually prescribed for what?
Chlamydial infections (trachoma, AIC) b.c of its convenient 1 gram dose - take on an empty stomach or azithromycin can be rx as 4 250 mg capsules or as 2 500mg capsules
Z-Pak six 250mg capsules; 2 capsules are taken on the first day, then one capsule is taken each day for the remaining 4 days
Tri-Pak = 3 500mg capsules
Topical azithromycin (azasite): indicated for tx of bacterial conjunctivitis and blepharitis - a novel drug delivery system allows for prolonged drug contact time
Blepharitis = BID x 2 days, then QDay thereafter until sx resolve (often several months)
The recommended dosing for bacterial conjunctivitis is BID x 2 days, then QDay for 5 days
ERYTHROMYCIN
uncommonly prescribed for active bacterial infection due to poor resistance profile, Rx for prophylaxis of gonococcal opthalmia neonatorum
ORAL CLARITHROMYCIN prescribed for respiratory infections
Azasite contains which preservative?
BAK - pts who wear CL are advised to discontinue CL wear during tx
Lincomycin, clindamycin (Cleocin) MOA
inhibit bacterial protein synthesis by reversibly binding to 50S ribosubunit
Lincomycin and clindamycin are used to tx what?``
MRSA (Methicillin resistant staph aureus) and anaerobic infections `
What is recommended for the treatment of MRSA
“Bacteria Cant Decide”
Bactrim (trimethoprim & sulfmethoxazole)
Clindamycin
Doxcycyline
Antibiotics that interfere with Bacterial DNA
Sulfonamides: Sulfisoxazole (Gantrisin), sulfacetamide (sulamyd), sulfamethoxazole (Gatanol), sulfadizine)
Trimethoprim (Primsol), pyrimethamine (Daraprim)
Sulfonamides MOA
- Inhibit dihydropteroate synthase (enzyme that converts PABA to dihydrofolic acid) as the first step of folic acid synthesis
- these drugs are bacteriostatic agents that are prescribed to tx gram (+) and gram (-)
What are sulfonamides used to tx?
- Topical sulfisoxazole and sulfacetamide: prescribed for bleph and conjunctivitis but now RARELY used
Sulfa topical side effects?
Most common side effects of ophthalmic administration include burning, stinging, contact dermatitis, and local photosensitization
tx for toxoplasmosis
sulfadiazine is prescribed with pyrimethamine to treat toxoplasmosis
Bactrim is a combination of which to medications?
sulfamethoxazole and trimethprim
Oral sulfonamides side effects
can cause kernicterus in infants due to bilirubin accumulation within the brain (contraindicated during pregnancy); may induce myopic shift, in pt’s refractive error
Topical + oral sulfonamides can cause SJS
What is Stevens-Johnson syndrome?
disease characterized by fever and lesions on the skin and mucous membranes that result in sloughing of the skin over 10% or less of the body surface area
Can cause conjunctival lesions in 85% of pts - ranging from mild conjunctival injection to sever conjunctival scarring
Commonly associated with meds (sulfonamides, including bactrim, amoxicillin, allopurinol) and infections
Trimethoprim MOA
inhibit dihydrofolate reductase - an enzyme that converts dihydrofolic acid to tetrahydrofolic acid in the second step of folic acid synthesis
Topical opthalmic trimethoprim
effective against gram + & - infections, but not effective against Pseudomonas
It is available in combination with polymyxin B (strong gram -) agent
Pyrimethamine can be given orally for ocular toxoplasmosis infections
What does the Ocular TRUST study state?
trimethoprim & tobramycin (to a lesser extent) are the most potent topical ophthalmic antibiotics against MRSA; other studies have shown besifloxacin and vancomycin are also effective against MRSA
Polytrim is dosage
QID for 5-7 days for bacterial conjunctivitis
adverse effects of trimethoprim
bone marrow suppression, apalstic anemia, leukopenia, granulocytopenia. Pyrimethamine can have similar toxicity
“Trimethoprim = TMP = TREATS MARROW POORLY”
DNA gyrase and topoisomerase blocers
fluroquinolones
2nd gen: ciprofloxacin (Coloxan, cipro), ofloxacin (oculoflox)
3rd gen: levofloxacin (Quixin)
4th gen: gatifloxacin (zymar), moxifloxacin (vigamox, avelox), besifloxacin (besivance)
Fluoroquinoles MOA
inhibit bacterial DNA by inhibiting DNA gyrase and topoisomerase IV
Fluoroquinolones are used to treat which conditions?
CL related corneal ulcers, corneal abrasions, and bacterial conjunctivitis
Dosage of fluroquinolones for infectious corneal ulcers
Q15 mins for 1 hr, then Q1H tehreafter with daily follow up
Fluoroquinoles dosage for corneal abrasions
corneal abrasions and corneal erosions: most often QID for prophylaxis
Ciprofloxacin can treat which conditions?
prescribed for gram (-) urinary & GI infections
Moxifloxacin
approved for tx of penumonia, sinusitis, intra-abdominal and skin infections
Side effects for fluoroquinolones
“fluroquinoLONES can hurt the attachment to your BONES”
tendintis, contraindicated in pregnancy, children, and adolescents below the age of 18 due to damage in cartilage formation and inhibition of bone growth
3rd and 4th gen fluoroquinolones have been formulated to improve effectiveness against gram __
+
