Interfere with peptidoglycan synthesis of susceptible bacteria gram negative are resistant

Antibiotics Flashcards by Andrew Spilker

What is in contrast to the proven benefit of Abx prophylaxis for surgical procedures?

Misuse of Abx in the general population.

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What percent of all Abx prescriptions are written for what kind of diagnosis(es)?

21%
* URI
* Bronchitis

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Regarding SCIP, what do the first three measures dictate for Abx?

Prophylactic Abx given within 1 hr of incision
Abx selection for surgical pts
Abx discontinued within 24hrs after surgery (48hrs for Cardiac surgery)

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The use of Abx prophylaxis in surgery considers what?

Risk-to-Benefit ratio

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What is the most frequent complication from prophylactic abx?

Pseudomembranous enterocolitis

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What is the most frequently selected prophylactic abx? Why?

Cephalosporins
* Wide therapeutic index
* Low S/E incidence

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What kind of Penicillin-allergy reaction(s) would cephalosporin administration be considered not safe?

IgE mediated (Anaphylaxis, urticaria, Bronchospasm)
Exfoliative dermatitis

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A pt has a exfoliative/IgE mediated to penicillin, what abx may be indicated?

B-lactam abx
Clindamycin
Vancomycin

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Dosing for Cefazolin & Redosing interval?

2gm <120kg

3gm >120kg
* 4 hrs

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Dosing for Ciprofloxacin & Redosing interval?

400mg
* N/A

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Dosing for Clindamycin & Redosing interval?

900mg
* 6 hrs

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Adult/Pediatric dosing for Gentamicin & Redose interval?

5mg/kg for Adults
2.5mg/kg Pediatrics

N/A redose

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Adult/Pediatric dosing for Metrondiazole & Redose interval?

500 mg for Adults
15 mg/kg Pediatrics

N/A redose

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Adult/Pediatric dosing for Vancomycin & Redose interval?

15 mg/kg for Adults
15 mg/kg Pediatrics

N/A redose

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80% of Nosocomial infections occur where?

Urinary Tract
Respiratory
Bloodstream

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What medical device is the most common cause of bacteremia/fungemia in hospitalized patients?

IV access catheters

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Where do the organisms infecting IV catheters come from, example of two?

Skin flora
* S. aureus
* S. epidermidis

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What Abx is selected for IV infection, why?

Vancomycin
* High incidence of MRSA or MRS epidermidis

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What is a concern when any drug is administered in early pregnancy?

Teratogenicity

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Which antibiotics are generally considered to be safe in pregnancy?

penicillins
cephalosporins
erythromycin base

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Which antibiotics maybe require dose adjustment in the elderly?

aminoglycosides
vancomycin

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Penicillin’s MoA?

Interfere with peptidoglycan synthesis of susceptible bacteria
gram negative are resistant

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Penicillins are the drugs of choice for the treatment of:

streptococcal, pneumococcal, meningococcal infections
gas gangrene
rheumatic fever

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Penicillin excretion

renal excretion is rapid
(60-90% of IM dose excreted in 1 hour)

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which PCN has the highest incidence of skin rash? when does it present?

Ampicillin (9%) - appears 7-10 days after inititation of therapy

Amoxicillin vs ampicillin duration

amoxicillin is better absorbed from GI tract, present in circulation **twice** as long as ampicillin

Carbenicillin's effect on coagulation?

Interferes w/ platelet aggregation -> Prolonged Bleeding time * Does not affect platelet count

What are the beta lactamase inhibitors? What do they do?

* clavulanic acid, sulbactam, tazobactam * bind irreversibly to beta lactamase enzymes produced by bacteria, inactivate them, make the bacteria sesntive to beta-lactamase susceptible penicillins

Majority of allergic reactions to cephalosporins are what? when do they occur?

cutaneous manifestations occuring 24 hours after exposure

How frequent are cross-reactivity reactions between Penicillins & Cephalosporins? What results from this frequency?

**Very Infrequent** * Often used as alternatives in pts w/ penicillin allergies

What structure of penicillin is indicated in cross-reactivity reactions? How frequent are these reactions?

Î²-lactam ring * Actual cross-reactivity is **Rare**

What kind of surgeries are First gen. cephalosporins frequently used as prophylaxis? | 5

* CV * Orthopedic * Biliary * Pelvic * Intraabdominal

What characteristic do all generations of cephalosporins share?

All can: * Penetrate joints * Cross the placenta

Advantage of Cefazolin vs. Cephalothin?

Same abx spectrum but: * Higher blood levels * Due to slower renal elimination

Which Abx is viewed as the drug of choice for surgical prophylaxis?

Cefazolin

What advantage do third generation Cephalosporins have over the others?

Resist hydrolysis by the Î²-lactamases of many G- bacilli

Which cephalosporin has the longest half-life amongst its generation and what bacteria is it highly effective against?

Ceftriaxone (3rd gen.) * G- Bacilli

What bacteria is Gentamicin active against? What is a toxic serum level?

* P. aeruginosa * G- Bacilla * > 9 mcg/mL serum = toxic

What use is common with Neomycin?

Topically on: * Skin * Cornea * Mucous membranes PO does not undergo systemic absoprtion and is used for GI surgery to reduce flora and as adjunt to therapy of hepatic coma

Which drugs are Aminoglycosides?

* Streptomycin * Gentamicin * Neomycin

Common side-effects of Aminoglycosides?

* **Ototoxicity** * **Nephrotoxicity** * **Skeletal Muscle Weakness**

What drugs accentuate the ototoxic effects of Aminoglycosides?

* Furosemide * Mannitol * Other Diuretics

How does ototoxicity occur from Aminoglycosides?

Drug-induced destruction of vestibular/cochlear sensory hairs * with chronic therapy/elderly pts w/ decreased renal function

Common presentation of aminoglycoside associated nephrotoxicity? Reversible?

* Inability to concentrate urine * Proteinuria * RBC casts Reversible if drug is discontinued

Most nephrotoxic aminoglycoside?

Neomycin

How does skeletal muscle weakness occur from aminoglycosides?

* Inhibt prejunctional release of Ach * Decrease postsynaptic Ach sensitivity

How do you treat aminoglycoside related skeletal muscle weakness?

IV calcium

Which drugs are Macrolides?

* Erythromycin * Azithromycin * Clindamycin

Erythromycin spectrum of activity?

Most G+ bacteria

What drugs are ideal for those who cannot tolerate Penicillins or Cephalosporins?

Clinda or Erythromycin

Consequential side effect of Erythromycin?

Prolongs QTc (repolarization) -> TDP

How does Azithromycin compare to Erythromycin?

* Similar Abx spectrum * Prolonged elimination half-life (68hrs) permits once/day dosing x 5 days (Z-pack)

How does Clindamycin compare to Erythromycin?

* Similar Abx spectrum * More active against anaerobes

Side effects of Clindamycin?

* Severe pseudomembranous colitis * Pre/post-junctional effects @ neuromuscular junction that cannot be antagonized by IV calcium or anticholinesterase drugs * Large doses -> profound NMB in absence of ND-NMBs/Succinylcholine recovery

Class and MoA of Vancomycin?

Bactericidal Glycopeptide * impairs cell wall synthesis of G+ bacteria

What bolded reason is Vanco utilized for?

Administered IV for treatment of: * Staphylcoccal * Streptococcal * Enterococcal endocarditis In pts w/ Penicillin/Cephalosporin allergy

Oral adminstration of Vanco is used for? Why?

* Staphylococcal enterocolitis * Abx-associated Pseudomembranous enterocolitis Poorly absorbed for GI tract

Drug of choice for MRSA?

Vancomycin

Recommended infusion rate of Vancomycin? Why?

10-15 mg/kg over 60 min * Minimize histamine release -> HoTN

When should prophylactic Vanco be given?

2 hrs prior to surgery

Vancomycin elimination

90% recovered unchanged in urine

What can rapid infusion (<30 min) of Vanco cause?

Infusions <30 min -> HoTN & Cardiac Arrest

Vanco associated histamine release is characterized as what?

Red man Syndrome * HoTN * Facial/Truncal erythema

What drugs/doses may be given to prevent histamine side effects w/ Rapid Vanco administration (1gm over 10 min)?

Oral H1 (Benedryl 1mg/kg) & H2 (Cimentidine 4mg/kg) antagonists given 1 hr prior to induction

Vancomycin plasma concentrations >30mcg/mL are associated with what effect?

Ototoxicity

Bacitracins common for what application

Topical - optho or derm from gram +

Metrondiazole is (bactericidal or bacteriostatic) effective against what species?

* Clostridium * Anaerobic G- Bacilli

Metronidazole is useful in treating:

* CNS, Bone, Joint infections * Abdominal/Pelvic sepsis * Endocarditis

Metronidazole is a useful prophylaxis for what kind of surgeries?

Elective colorectal surgery

Metronidazole S/E

* Dry mouth * Metallic Taste * Nausea * Given w/ Etoh -> disulfiram-like reaction

Fluoroquinolones abx spectrum?

* Broad spectrum * Bactericidal against G- bacilli

Fluoroquinolones are clinically useful in treating what kind of infections?

GI/GU infections

Fluoroquinolones are associated with what effect(s)?

* **Tendonitis** * **Tendon Rupture**

What Abx are Fluoroquinolones?

* Ciprofloxacin * Moxifloxacin

What infections is Ciprofloxacin *highly* effective in treating?

* Urinary/Genital tract infections * Prostatitis * GI infections

Why is Moxifloxacin only recommended when less toxic options aren't available? | 8

* Peripheral neuropathy * SIADH (Syndrome of inappropriate secretion of ADH) * Tendonitis * Acute Liver Failure * QTc prolongation * Toxic epidermal necrolysis (TEN) * Psychotic reactions * SJS (Steven-johnson syndrome)