Antibiotics I

Penicillins and Cephalosporins

--Indication for bactericidal antiobiotics: Endocarditis, Meningitis, Neutropenic patients

--Bactericidals: Vancomycin, Fluoroquinolones, Penicillin, Aminoglycoside, Cephalosporin, Metronidazole

--Bacteriostatics: Erythromycin, Clindamycin, Sulfamethoxazole, Trimethoprim, Tetracycline, Chloramphenicol

--Penicillin G can be used for beta-hemolytic strep (tx strep throat) and syphilis

--Beta-lactamse stable penicillins (methicillin, nafcillin, dicloxacillin) is used for Staph aureus; not active again gram negatives, and Enterococcus and Listeria

--Aminopenicillins. AmOxicillin > ampicillin absorption. Broad spectrum gram neg and gram positive coverage for non-penicillinase bacteria. Crosses BBB.

--Antipseudomonals. Ticarcillin, Carbenacillin, Piperacillin.

--Side effects: Allergic (rash; methicillin -- interstitial nephritis)

--beta-lactamase inhibitors: expand spectrum to many penicillinase-positive bacteria. example: clavulanic acid

--Cephalosporins: similar pharm to penicillins. more heavily protein bound, cross BBB better; liver can deacylate (deactivate some); some are excreted in bile, can form stones

--Cefazolin (1st gen) -- Staph, mixed Staph and beta-hemolytic Strep infections

--Cefoxitin (2nd gen) -- Bacteroides, mixed anaerobic infections

--Third generation: cross BBB, can treat meningitis (but not Listeria; treat pneumococcus

--Cefepime (4th gen) developed to be active against AmpC beta-lactamases (produced by Enterobacter, Serratia, Citrobacter etc). AmpC beta-lactamases also resistant to beta-lactamase inhibitors

--Dose: 4x MIC

Carbapenems

--Renally excreted

--Can cause seizures at high doses since CROSSES BBB; need to adjust dose for renal status

--Imipenem requires cilastatin since renally metabolized; meropenem does not

--Ertapenem. Pro: once a day, since protein bound. Con: not active against Pseudomonas.

Monobactams

--Useful for gram - bacteria

--Bacteria do not induce beta-lactamases against it. Resistance sometimes if constitutive expression of beta-lactamase.

--Not cross-allergenic with penicillins/cephalosporins. Can be used in people allergic to those drugs.

Vancomycin

--Not renally excreted or absorbed (like inulin)

--Some dose-dependent toxicity; adjust also for kidney status

--Nephrotoxicity, Otoxocity, Thrombophlebitis (NOT); Red Man syndrome (pretreat with antihistamines, slow infusion rate; not an allergy)

--Orally for C. difficiles (not absorbed)

--Can't use IM -- toxic to tissue (similar to chemos)

--IV use for staph (esp MRSA), strep, including enterococcus (except VRE a growing problem)

--Dalbavancin: Long half-life, low volume of distribution