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Pharm-Fluroquinolones & PCNs & Ceph


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Mechanism of Fluoquinoles?
G-: Inhibit DNA Gyrases (topoisomerase II in mammals). It cuts & reanneals DNA to get rid of supercoils.

G+: Inhibits Topoisomerase IV – involved in separation of daughter cells
Cipro HC Otic
Class: Fluroquinolones
Ciprofloxacin plus hydrocortisone, used for Otis Media
Which 3 Fluoroquinolones has an ophtlamic use?
Which Fluoroquinolone is used for community-acquired pneumonia & chronic bronchitis?
Which fluorquinolone is used only for UTIs?
Which fluroquinoline is used for both UTIs and Lower RTIs?
What are 3 fluorquinolones with no special characteristics?
Which fluoroquinolone has the best G- activity?
Which Fluoroquinolon is a good choice against anaerobes?
Which bacteria is a common cause of peritonitis in a perforated colon? What is used to treat it?
Bacteroides fagilis (G- rod)
Use ampicillin + Sulbactam or Piperacillin + Taxobactam

Another common peritonitis pathogen: P. aeruginosa
What does Sulbactam do?
It's a beta-lactamase inhibitor, can used in association with penicillin n increase G- spectrum
What was Piperacillin designed for?
For Tx of "stubborn" pseudomonas infections
Side effects of Fluoquinolones
NVD are always SE with antibiotics, but esp. with this class.
Cardiotoxicity/Increased QT interval - not for cardiac conduction pts
Arthopathy - damage to growing cartilage in kids
Tendon rupture (shoulder, hands)
CNS stimulation - convulsions/pyschoses
Major "Side effect" infection caused by fluoroquinoles?
C. difficile diarrhea & pseudomembanous colitis due to killing normal flora that keeps it in check in the gut. 2 toxins produced. Plaques on mucosa form "pseudomembrane."
Treatment for pseudomembranous colitis?
1st choice: Metronidazole (usually for protozoa). Mech: forms reactive anion that damages DNA of C. difficile

2nd choice: Vancomycin
What's the general structure of Penicillin and what determines the different properties of Rx in the class?
Made of a thiazolidine ring + a beta-lactam ring with side chains that give the different drugs their properties.
What's the mechanism of Penicillins?
Treat mostly G+, but some G- too.

Penicilin permanently inhibits transpeptidase, inhibiting synthesis of cell wall (can't x link because can't remove terminal D-alanine), making it easily lysed. Therefore penicillin is cidal.
What is the main mechanism of bacterial resistance to PCNs?
Beta-lactamases break the b-lactam ring of PCM, making the molecule non-functional
aka benzyl PCM
Given IV or IM, not acid stable for PO use
Three forms:
Aqueous - IM/IV with Na or K salt (Na an issue with CHF)
Procaine - IM, depot slows absorption, numbs site - can cause allergy (ester)
Benzathine - IM, longest acting
Dosing for PCN G?
Expressed in "units" where 1 unit - 0.6 ug. 1 million units=600 mg.

Example: for Syphillis, tx 2.4 mil units IM single dose
Acid stable PCN for oral use, dosed in mg. Given 1 hr a.c. or p.c.
Alternative treatment for Syphillis with PCN allergy?
doxycycline or tetracycline PO
ceftriazone IV/IM (3rd gen cephlosporin)
a.c. stands for?
antes cibos - before meal
post cibos - after meal

(think AM and PM)
The 3 penicillinase-resistant PCNs?
Dicloxacillin - PO
Oxacillin - PO or injectable
Nafcillin - injectable

Cleared by both biliary & renal excretion, good in liver or kidney disease
MRSA - what does it stand for?
Methicillin Resistant Staph Aureus. Refers to bacteria that are resistant to the 3 Penicillinase-resistant PCNs (also called Beta-lactamase resistant PCNs). Methicillin discontinued, name stuck
Also known as extended spectrum PCNs
Similiar spectrum as PCN but with greater G- coverage. Susceptible to PCNases.
Describe the 2 Aminiopenicillins
Ampicillin - PO or IV

Amoxicillin - PO
With Clavulanate (b-lactase inhibitor)= Augmentin
Not used for peritonitis - no IV use
Organisms causing most Otitis media? Tx?
Strep. pneumonia (G+) = 50%
H. influenzae (G-) = 25%

If antibiotics used in last month, use Augmentin rather than Amoxicillin

In kids, use pediazole (sulfsozizole + erythomycin)
Use for Aminopenicillins?
Ampicillin + sulbactam for peritonitis due to b. fragilis

Amoxicillin for Otitis media and dental procedure prophylaxis

Either: URTIs from Strep pyogenes/pneumonias (G+) or H. flu (G-), Sinusitis from Strep peumonia, H. flu or Moraxella catarrhalis

Either Amol
Antipseudomonas PCNs?
Still susceptible to b-lactamases
Good against some psudomonas (modest vs P. aerugiosa) and some resistant Proteus

Ticarcillia - IV
Piperacillin - IV
Side effects of PCNs?
-Hypersensitivity (allergy). Rashes, fever, bronchospasms, serum sicknes, Stevens-Johnson syndrome, anaphylaxis

-Superinfection - normal flora can't keep pathogen in check
-Increase seizure risk if penetrates BBB (such as with low renal fcn)
Penicilin metabolite is:
Penicilloic acid
Another name for PCNases?
How do B-lactam antibiotics work and what are examples?
Inhibit transpeptidase
PCNs, Cephalosporins, Carbapenems
Structure & Mech of Cephalosporins?
Similar to PCN but instead of Thiazolanine ring, has a dihydrothiazine ring. Again the side chain determines character. Same mechanism – inhibit transpeptidase.
What is the advantage of Cephalosporins over PCNs?
Resist many b-lactamases but not all
How many 1st generation Cephlosporins? What are they?
What bacteria are covered?
Just two:
G+ plus these G-: Proteus mirabilis, E.coli, Klebsiella pneumonia (PEcK)
What can 2nd generation Cephlosporins cover?
Les G+ than 1st gen & more G-: HNPEcK - adds H. flu & Neisseria (meningitidis & gonorrhoeae)
What's the Cephlosporin that doesn't start with Cef? Brand name? Route? What generation of Cephlosporin?
Leorcarfef - Lorabid
Oral BID (thus the "bid" in name)
2nd generation
List 2nd gen Cephlosporins
Cephamycins (ie Cefoxitin for B. fragilis)
Coverage of 3rd Generation of Cepholosproins compared to early generations?
Much less G+ but much more G-
List some 3rd generation cephlosporins
Ceftriaxone - use, route, CI
USE: Meningitis from Strp pneum & N mening & for Gonorrhoeae
IV/IM - easily displaces bilirubin from albumin
Don't use in infants ,3mon (risk of kernicterus) unless as single dose for gonorrhea conjuct.
Cefotaxime - use, route
Also good for meningitis (like ceftriaxone). Coveres Bacteroides. IV/IM
Special characteristic of Cefdinir?
A 3rd gen cephlosporin that binds Fe - reddens feces, esp in infants on high Fe formula
Name 2 4th generation Cephalosporins
Characteristeics of Cefepime
Route: IV/IM
Use: G- rods resistant to 3rd gen, good CNS penetration
SE: myclonus, disorientation, EEG changes and higher risk in epileptics
Side effects of Cephalosporins?
For all of them: Hypersensitivity (allergic rxn)
Coagulation abnormalities with Cemetazole, cefoperazone, cefotetan & ceftriaxone
Carbapenems: coverage? Mech?
Broadest spectrum B-lacm, G+ and G-, includes anaerobes & some MRSA. Reserved for resistant infrections
Name 3 Carbapenems
Imipenem - always with Cilastatin, IV/IM
Meropenem - IV
Ertapenem - qd
Use of Carbapenems?
For resistant infections of
-Lower Resp tract
-Intra-abdom, gyn, bacterial septicemia
-Bone, joint, skin infections
Vancomycin - use, route
For MRSA or MSSA + PCN allergy, or food poisoning for B. cereus

Esp. used for pseudomembranous colitis
Mechanism for Vancomycin
Binds to d-alanine terminus so can’t X-link peptidoglycan (PCN can’t x-link because the enzyme is knocked out)
Side Effect of Vancomycin
Red man/ Red neck syndrom after rapid IV --> flushing of upper body/neck, hypotension, tachycardia & shock.

Cause: Histamine release from mast cells & basophils
Fosomycin - mechanism?
Inhibits enolpyruvate transferase – which catalyzes PEP to UDP-N-aceytlglucosamine (which goes to form the Park Peptide) for making peptidoglycan. So: no cell wall synthesis
Use of Fosomycin?
UTIs from E. coli and Enterococcus faecalis in women
Use, route & SE of Daptomycin?
IV, lipopeptide, for skin infections from G+ & MRSA
SE: Increase creatin kinase
Bacitracin characteristics & use?
Cidal vs. various G+ cocci & bacilli
USE: topical for minor cuts/scrapes, opthalmic ointment (DOC is bacitracin + polymyxin B, an OTC)
Bacitracin mechanism? SE?
Binds to pyrolphosphate so lipid carrier can’t carry NAG/NAM outside for cell wall synthesis


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