Antibiotics

Slackers Facts by Mike Ori

Disclaimer

The information represents my understanding only so errors and omissions are probably rampant. It has not been vetted or reviewed by faculty. The source is our class notes.

The document can mostly be used forward and backward. I tried to mark questionable stuff with (?).

If you want it to look pretty, steal some crayons and go to town.

Finally…

If you’re a gunner, buck up and do your own work.

What are the types of beta lactam antibiotics

PenicillinsCephalosporinsCarbapenemsMonobactams

Name the classes of penicillins

StandardAntistaphylococcal

AminoAntipseudomonal

What are the anti-staph penicillins and their routes

Nafcillin - IVDicloxacillin - PO

What are the standard penicillins and routes

Penicillin V – POPenicillin G - IV

Which bacteria are exquisitely sensitive to standard penicillins

Group A strep (pyogenes)

Amino penicillins names and routes

Ampicillin – PO,IVAmoxicillin – PO

What is typically coadministered with the aminopenicillins

Beta lactamase inhibitorsAmoxicillin – clavulanate

Ampicillin - sulbactam

What is the CSF action of aminopenicillins

Can reach CSF if the meninges are inflamed

What side effect can happen when giving aminopenicillins to pt with infectious

mononucleosis, chronic lymphocitic leukemia, allopurinol

RashLowest incidence with allopurinol, others are

very high.

Cephalosporins names, generation, routes, and gram positive/negative effectiveness

Generation Route Positive Negative

Cefazolin 1 IM, IV +++ +

Cephalexin 1 PO

None tested 2 ++ ++

Ceftriaxone 3 IM, IV ++ +++

Ceftazidime 3 IM, IV

Cefepime 4 IM, IV +++ +++

Susceptibility by generation. General trend is down with gram positives and up with gram negatives.

Which generation reaches effective levels in the CSF

Third gen

Your patient has an allergy to penicillin G can you administer cephalosporins

Maybe. Contraindicated if the pt experienced an IgE mediated rash. Caution with other

penicillin type reaction.

Carbapenems names, routes, and spectrum

Imipenem, IVBroadest range of all available antibiotics.

Excellent penetration through porins into gram negative periplasmic space

What is cilastin

A drug coadministered with imipenem to inhibit kidney ezymes that breakdown imipenem into

nephrotoxic metabolites

Imipenem ADR

Seizures

Monbactam names, routes, spectrum

Aztreonam, IVgram negatives including P aeruginosa.

Ineffective against gram positives or anaerobes

Glycopeptides name, route, spectrum

Vancomycin, IV, Gram positives only

Vanco has poor oral availability so why do the dosing instructions include oral

administration?

Vanco is useful for treatment of gram positive anaerobic infections of the GI tract such as C.

difficile infections.

Describe the ADR from rapid infusion of vancomycin

Rapid infusion results in histamine release that cause flushing of the skin of the neck and

upper trunk that can result in hypotension. AKA red man or red neck syndome

List the protein inhibitory antibiotic classes and their action

Aminoglycosides – 30sMacrolides – 50s

Lincosamides – 50sTetracyclines – 30s

Chloramphenicol – 50sStreptogramins – 50s

Oxazolidinones – ribosome assembly

Aminoglycoside names, routes, spectrum

Gentamicin, IVTobramycin, IV

Both are effective against aerobic gram negative and mycobacterium

Aminoglycoside toxicity characteristics

Nephrotoxic and ototoxic above an patient variable threshold in time dependent manner

Aminoglycoside dosing characteristics

Concentration dependent killing with significant post antibiotic effect allows for once daily

dosing.

Note: This contrasts to most others that are both time and concentration dependent.

Why are aminoglycosides ineffective against anaerobic bacteria?

Entry into the cell is mediated by oxygen dependent transport.

Aminoglycoside resistance basis

Transferase enzymes inactive them. Unlike penicillins, there are variations in the

resistance enzymes.

Aminoglycoside toxic trough threshold

Trough concentrations above 2 mcg/mL are predictive of toxicity

Macrolide names, route

Azithromycin, PO (Z pack), IV

Azithromycin indications

Treatment of out of hospital community acquired respiratory infection and in hospital

pneumonia in combination.STD’s

Macrolide CSF penetration characteristics

Poor

Azithromycin volume of distribution

Extremely high volume of distribution with tissue concentration 10-100x plasma.

Azithromycin half life

2-4 days

Primary azithromycin caution

Caution in PT with prolonged QT interval due to risk of torsades des pointes

Lincosamides name, route, spectrum

Clindamycin, PO,IV, strep, staph, anaerobes

Clindamycin indications

Anaerobes above the diaphragm

Clindamycin associated disease

C-diff enteritis

Tetracycline name, route, spectrum

Doxycycline, PO, IV, Chlamydia, mycoplasma, spirochetes

Tetracyclines contraindication

Children and pregnant or breastfeeding women due to staining of developing teeth

Tetracycline food cautions

Do not take with meals, supplements, or vitamins due to cation chelation

Your PT is a lifeguard with chlamydia, should you prescribe doxycycline?

No, photosensitivity is a common side effect.

Chloramphenicol indication and route

Given IV as second line therapy for CSF infections

What is the basis of chloramphenicol’s black box warning

Causes dose dependent myelosuppression that can lead to aplastic anemia.

Fluroquniolones names, route, spectrum

CiprofloxacinLevofloxacinMoxifloxacin

Excellent oral availability. IV forms exist.Active against gram negative bacilli

Fluroquniolones CSF therapeutic role

Unknown. Not recommended for meningitis.

What are common ADR to fluoroquinolones

CNS: hallucinations, delerium, seizuresBone: Cartilage damage, tendonitis

Pregnancy class C

Ok Smarty, what is pregnancy class C

C = don’t give it to them cause it jacks up animal fetuses and the IRB won’t give you the go

ahead to test it on humans.

What are the respiratory fluoroquinolones?

LevifloxacinMoxifloxacin

Fluoroquniolones food cautions

Do not take with meals, supplements, vitamins as chelation occurs.

Metronidazole route and spectrum

Obligate anaerobes, PO and IV

Metronidazole function

Creates reactive intermediates and free radicals that damage cellular components.

Your patient has an anaerobic bacterial infection. He has a small firm micronodular

liver. What are the issues for metronidazole?

Hepatic metabolism with renal excretion. Disulfiram like effects with alcohol use.

Rifmycin antibiotic mechanism

Inhibits RNA polymerase

Rifampin metabolism

Hepatic. Induces microsomal system which increases metabolism of other drugs.

Sulfonamide action

Inhibits PABA conversion to dihydrofolate by dihydropteroate synthetase

Trimethoprim action

Inhibits DHF conversion to THF by DHR reductase

What is TMP-SMX and why is it given?

TMP = trimethoprimSMX = sulfamethoxazole (a sulfonamide)

Given in combination to increase their effectiveness by 20-100 times over SMX alone.

TMP-SMX indication

UTI and pneumocystis jiroveci pneumonia

Your patient complains of a rash after starting UTI treatment. What did you prescribe. Are

you worried about the rash?

You prescribed TMP-SMX. You would be very worried about this rash and would advise your

PT to stop taking the drug immediately.

Your patient does not stop taking the drug even though you called back later and re-iterated

the importance. A few days later you receive a courtesy call from an ER doc advising you that they are admitting your pt. What is a

potential admitting diagnosis?

Stevens-Johnson syndrome or toxic epidermal necrolysis.

Which of the drugs (TMP/SMX) most likely caused the reaction and what is its general

class.

Sulfamethoxazole. It is a sulfa drug.