45-46_Penicillins, Beta Lactams

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Used as solution to short 1/2 of penicilliin G

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Probenicid (a weak acid) - decreases it's excretion. Procaine - decreases it's absorption

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solution to Pen G acid instability

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Phenoxyacetic acid --> Converts to Pen V (Oral form)

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Penicillin resistant staph is treated with what penicillin derivative(s)?

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methicillin, oxacillin, cloxacillin, nafcillin, dicloxacillin. (Resistance has since developed)

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Pen G has narrow spectrum - what drugs developed to overcome this?

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Ampicillin, carbenicillin

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Degradation products of penicillin? Can treat what genetic disorder/disease?

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β β dimethyl cysteine --> Wilson's (Keyser-fleischer rings)

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Penicilloic acid causes formation of? Resultant side effect?

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Hapten formation (reacts with lysine of protein) --> Hypersensitivity reaction to penicillin

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Rare but serious side effect of Pen G?

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Hemolytic anemia

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1) Skin testing for Penicillin allergy? 2)Treating severe Hypersensitivity reaction? 3) Hidden exposures to penicillin?

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1) PENICILLOYL – POLYLYSINE (WHEAL, ERYTHEMA RESPONSE) 2) Epinephrine. (diphenhydramine-less useful, prophylactic) 3) Treated previously without knowledge, second time it's taken causes a stronger reaction

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1) Narrow spectrum penicillins? 2) useful on what bacteria (generally)

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1) Pen G & V 2) gram positive. (Exception: neiserria gonorrehae & meningitidis)

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Ampicillin 1) Spectrum? 2) Not active against?

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1) Broad: Gram-positive (like old gen), and increasingly gram-negative 2) Ineffective against: Pseudomonas & Klebsiella

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Ampicillin Derivative advantages? 1) Amoxicillin 2) Bacampicillin

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1) Better absorbed from gut than ampicillin 2) Liberates ampicillin after ingestion

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Ticarcillin & Piperacillin - useful against?

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Pseudomonas & Klebsiella! (Broad spectrum derivatives)

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Treating P. Aeruginosa

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(Ticarcillin or Piperacillin) + (Aminoglycoside or Fluoroquinolone)

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MOA of penicillins

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Inhibit last enzyme in bacterial cell wall synthesis (PBPs) -> prevents peptidoglycan cross linking. (Resultant bacterial protoplasts) Also activates autolytic enzymes.

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Bacterial cell wall synthesis: 4 stages

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"Stage 1 + 2 - Cytoplasm - *THESE STEPS REQUIRE ENERGY* (MUREIN SYNTHESIS, Convert Amino Acids to D-Isoforms --> PENTAPEPTIDE) Stage 3: transverse the PM Forming peptide-polysaccharide and crossing membrane Stage 4: In cell wall Cross linking through: **Transpeptidation Reaction** (<-- site of action of penicillins)

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D-Cycloserine MOA

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Inhibits a racemase & ligase that converts L to D alanine in bacterial cell wall synthesis. (Used as Anti-TB)

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How exactly does Penicillin block transpeptidase

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Has a similar structure to D-alanyl-D-alanine, ties up enzyme forming "Penicilloyl-Enz" through covalent bond.

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Mechanism of penicillin resistance in GRAM +

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1) Penicillin may contact beta lactamase on the cell surface --> destroyed
2) If it diffuses into bacteria, binds bacterial ""binding proteins""--> causes cell death"

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Mechanism of penicillin resistance in GRAM -

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1) Penicillin slow entry --> INTERNAL beta-lactamase --> destroys penicillin, bacterial cell survives 2) Penicillin migrates through porins into periplasmic space --> meets Binding Proteins --> Bacterial cell dies.

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Cephalosporins 1) Advantage(s) over penicillin? 2) Major difference(s) with increasing generations?

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1) Less susceptible to beta-lactamase, and has broad spectrum including: PROTEUS, E. COLI, & KLEBSIELLA 2) gain more ability against gram negatives (but lose a FEW gram +) & more likely to be able to cross BBB

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1st generation cephalosporins (Cefazolin, cephalexin), useful for what infections?

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Skin & soft tissue infections. Rarely drug of choice

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2nd generation cephalosporins (Cefamandole, cefoxitin, cefaclor, cefuroxime) 1) Useful for what infections? 2) Major side effects

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1) Sinusitis, otitis, lower RTI 2) Bleeding problems (have to add vitamine K), Disulfram (Antabuse)-like reactions

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3rd generation cephalosporins (cefotaxime, ceftizoxime, ceftriaxone, cefixime, cefpodoxime proxetil) 1) Uses

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1) More potent against gram -Meningitis (+ vancomycin) Sepsis (+ aminoglycosides)

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4th gen& 5th gen cephalosporins (cefepime & ceftobiprole) - Uses?

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4th: Pseudomonas, enterobacteriaceae, staph, haemophilus, neisseria. 5th: MULTIDRUG RESISTANT STAPH AUREUS

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Cephalosporins: Adverse reactions

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potentially all nephrotoxic, caution if severe penicillin rx

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Carbepenems (Imipenem, Meropenem) 1) Class 2) Imipenem must be administered with? 3) Both have cross allergy with?

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1) beta lactam antibiotics (more resistant) 2) imipenem requires CILASTATIN in order to get around renal tubular dipeptidase that breaks down the imipenem 3) Penicillin

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Monobactam (Aztreonam) 1) Class 2) Used against? 3) Cross allergy with penicillin?

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1) beta lactam antibiotics (more resistant) 2) GRAM NEGATIVE RODS 3) No cross reactivity

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3 beta-lacamase inhibitors? MOA?

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Clavulanate, sulbactam, tazobactam ( Have a beta lactam but ring with oxygen replacing sulfur )

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Vancomycin 1) MOA 2) Main use 3) Toxicities

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1) Disrupts cell wall synthesis (inhibits transglycosylase) 2) sepsis endocarditis from MRSA. Clostridium difficile. 3) Ototoxic, nephrotoxic (both rare) "RED MAN SYNDROME" (Due to histamine release)

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Resistance to vancomycin develops how?

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Bacteria substitutes lactate in its transpeptidase

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Teicoplanin - class/family?

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Vancomycin. Less resistance.

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Bacitracin 1) MOA 2) Indications 3) Toxicities

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1) Cell wall inhibitor 2) Staph infections that don't respond to anything else 3) highly nephrotoxic, mainly used topically

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Polymixin B 1) MOA 2) Uses 3) Toxicity

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1) disrupts cell membrane (Detergent) 2) topical. GRAM NEGATIVE INFECTIONS - topical only 3) Nephrotoxicity ***

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Colistin Sulfate (Polymixin E) 1) MOA2) Uses 3) toxicities

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1) Disrupts cell membrane (detergent) 2) GRAM NEGATIVE BACTERIA - topical only 3) basically none unless parenterally

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Daptomycin - similar to?

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vancomycin

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Carbenicillin indanyl + gentamicin

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Chemical interaction, forms precipitate

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ampicillin + oral contraceptives

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Broad spec --> kills gut bacteria. Steroid stays in its water soluble form instead of being cleaved by bacteria, and is excreted -> lose contraceptive effect

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Vancomycin- how to prevent red man syndrome side effect?

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slow infusion rate + simultaneous antihistamine