deck_3522262 Flashcards
Penicillin G, V
Prototype β-lactam antibiotics (penicillinase-sensitive)
- Penicilling G → Iv and IM form
- Penicillin V → oral
Penicillin G, V mechanism
Bind penicillin-binding proteins (transpeptidases). Block transpeptidase cross-linking of peptidoglycan in cell wall. Activate autolytic enzymes.
Penicillin G,V clinical use
Mostly used for gram-positive organisms
- S. pneumoniae
- S. pyogenes
- Actinomyces Gram negative cocci
- N. meningitidis Spirochetes
- T. pallidum Bactericidal for gram-positive cocci, gram-positive rods, gram-negative cocci, and spirochetes.Penicillinase sensitive.
Penicilling G, V toxicity
- Hypersensitivity reactions
* Hemolytic anemia
Penicillin G, V resistance
Penicillinase in bacteria (a type of β-lactamase) cleaves β-lactam ring.
Aminopenicillins
- amoxicillin
* ampicllinPenicillinase-sensitive penicillins
Aminopenicillin mechanism
- Same as penicillin → wider spectrum,
- Penicillinase sensitive.
- Also combine with clavulanic acid to protect against destruction by β-lactamase.(amoxicillin and ampicillin)Note that amoxicillin has greater oral bioavailability than ampicllin.
Aminopenicillin clinical use
Exteneded spectrum penicillin
- H. influenzae (gram negative)
- H. pylori (gram negative, oxidase positive, comma shaped)
- E. coli (gram negative rod)
- Listeria monocytogenes (gram positive rod)
- Proteus mirabilis (gram negative rod)
- Salmonella (gram negative rod)
- Shigella (gram negative rod)
- enterococci(gram positive cocci)
Aminopenicillin toxicity
- hypersensitivity reactions
- rash
- pseudomembranous colitis (ie C. dif, a gram positive rod)
Aminopenicillin resistance
Penicillinase in bacteria (a type of β-lactamase) cleaves β-lactam ring.
Penicillinase-resistant penicillins
- Dicloxacillin
- Nafcillin
- Oxacillin
Penicillinase resistant penicillins mechanism
(dicloxacillin, nafcillin, oxacillin)Same as penicillin → narrow spectrum.Penicillinase resistant because bulky R group blocks access of β-lactamase to β-lactam ring.
Penicillinase resistant penicillins clinical use
(dicloxacillin, nafcillin, oxacillin)S. aureus (except MRSA; resistant because of altered penicillin-binding protein target site).
Penicillinase resistant penicillins toxicity
- Hypersensitivity reactions
* interstitial nephritis
Antipseudomonals
- Piperacillin
* Ticarcillin
Antipseudomonal mechanism
(piperacillin, ticarcillin)Same as penicillin. Extended spectrum.
Antipseudomonal clinical use
(piperacillin, ticarcillin)Pseudomonas spp. and other gram-negative rods.Susceptible to penicillinase; use with β-lactamase inhibitors.
Antipseudomonal toxicity
(piperacillin, ticarcillin) Hypersensitivity reactions.
Beta lactamase inhibitors
- Clavulanic Acid
- Sulbactam
- TazobactamOften added to penicillin antibiotics to protect the antibiotic from destruction by β-lactamase (penicillinase).
Cephalosporins (generations 1-4) mechanism
β-lactam drugs that inhibit cell wall synthesis but are less susceptible to penicillinases. Bactericidal.Organisms typically not covered by cephalosporins are LAME:
- Listeria
- Atypicals (Chlamydia, Mycoplasma)
- MRSA
- EnterococciException: ceftaroline covers MRSA.
First generation cephalosporins
- Cefazolin (IV)
* cephalexin (oral)
First generation cephalosporin clinical use
1st generation (cefazolin, cephalexin)—
- gram-positive cocci gram-negative rods
- Proteus mirabilis
- E. coli
- Klebsiella pneumoniae Cefazolin used prior to surgery to prevent S. aureus wound infections.
Second generation cephalosporin clinical use
2nd generation (cefoxitin, cefaclor, cefuroxime)—
- gram-positive cocci
- Haemophilus influenzae
- Enterobacter aerogenes
- Neisseria spp.
- Proteus mirabilis
- E. coli
- Klebsiella pneumoniae
- Serratia marcescens
Second generation cephalosporins
- cefoxitin (IV)
- cefaclor
- cefuroxime
Third generation cephalosporins
- ceftriaxone
- cefoxatime
- ceftazidime
Third generation cephalosporin clinical use
3rd generation (ceftriaxone, cefotaxime,ceftazidime)—serious gram-negative infectionsresistant to other β-lactams.Ceftriaxone—meningitis, gonorrhea, disseminated Lyme disease (borrelia).Ceftazidime—Pseudomonas
Fourth generation cephalosporins
cefepime
Fourth generation cephalosporin clinical use
4th generation (cefepime)—gram-negativeorganismswith ↑activity against Pseudomonasand gram-positive organisms.
Fifth generation cephalosporins
Ceftaroline
Fifth generation cephalosporin clinical use
5th generation (ceftaroline)— broadgram-positive and gram-negative organism coverage, including MRSA.Does not cover Pseudomonas.
Cephalosporin toxicity
- hypersensitivity reactions
- autoimmune hemolytic anemia
- disulfiram-like reaction
- vitamin K deficiency
- Exhibit cross-reactivity with penicillins, ↑nephrotoxicity of aminoglycosides.
Cephalosporin resistance
Structural change in penicillin-binding proteins (transpeptidases).
Carbapenems
- imipenem
- meropenem
- ertapenem (limited Pseudomonas coverage)
- doripenem
Carbapenem mechanism
Imipenem is a broad-spectrum, β-lactamase– resistant carbapenem. Always administered with cilastatin (inhibitor of renal dehydropeptidase I) to ↑inactivation of drug in renal tubules.
Carbapenem clnical use
(imipenem, meropenem, ertapenem, doripenem)
- Gram-positive cocci
- Gram-negative rods
- AnaerobesWide spectrum, but significant side effects limit use to life-threatening infections or after other drugs have failed.Meropenem has a ↓risk of seizures and is stable to dehydropeptidase I.
Carbapenem toxicity
- GI distress
- skin rash,
- CNS toxicity (seizures) at high plasma levels
Monobactams
Aztreonam
Monobactam mechanism
Prevents peptidoglycan cross-linking by binding to penicillin- binding protein 3.
- Less susceptible to β-lactamases.
- Synergistic with aminoglycosides.
- No cross-allergenicity with penicillins.
Monobactam clinical use
Gram-negative rods only—no activity against gram-positives or anaerobes.For penicillin-allergic patients and those with renal insufficiency who cannot tolerate aminoglycosides.
Monobactam toxicity
Usually nontoxic; occasional GI upset.
Glycopeptides
- Bacitracin
* Vancomycin
Vancomycin mechanism
Inhibits cell wall peptidoglycan formation by binding D-ala D-ala portion of cell wall precursors.Bactericidal. Not susceptible to β-lactamases.
Vancomycin clinical use
Gram-positive bugs only—serious, multidrug-resistant organisms, including
- MRSA
- S. epidermidis
- sensitive Enteroccocus species
- Clostridium difficile (oral dose for pseudomembranous colitis)
Vancomycin toxicity
Well tolerated in general—but NOT trouble free.
- Nephrotoxicity
- Ototoxicity
- Thrombophlebitis
- diffuse flushing—red man syndrome (can largely prevent by pretreatment with antihistamines and slow infusion rate)
Vancomycin resistance
Occurs in bacteria via amino acid modification of D-ala D-ala to D-ala D-lac.
Aminoglycosides
- Gentamicin
- Neomycin
- Amikaein
- Tobramycin
- Streptomycin
Aminoglycoside mechanism
Bactericidal.Irreversible inhibition of initiation complex through binding of the 30S subunit. Can cause misreading of mRNA. Also block translocation.Require O2 for uptake; therefore ineffective against anaerobes.
Aminoglycoside clinical use
Severe gram-negative rod infections. Synergistic with β-lactam antibiotics.Neomycin for bowel surgery.
Aminoglycoside toxicity
- Nephrotoxicity
- Neuromuscular blockade
- Ototoxicity (especially when used with loop diuretics)
- Teratogen.
Aminoglycoside resistance
Bacterial transferase enzymes inactivate the drug by
- acetylation
- phosphorylation
- or adenylation
Tetracyclines
- Tetracycline
- Doxycycline
- Minocycline
Tetracycline mechanism
Bacteriostatic.Bind to 30S and prevent attachment of aminoacyl-tRNA.Limited CNS penetration. Doxycycline is fecally eliminated and can be used in patients with renal failure.Do not take tetracyclines with
- milk (Ca2+),
- antacids (Ca2+ or Mg2+),
- or iron-containing preparationsbecause divalent cations inhibit drugs’ absorption in the gut.
Tetracycline clinical use
- Borrelia burgdorferi
- M. pneumoniaeDrugs’ ability to accumulate intracellularly makes them very effective against Rickettsia and Chlamydia. Also used to treat acne.
Tetracycline toxicity
- GI distress
- discoloration of teeth
- inhibition of bone growth in children
- photosensitivity
- Contraindicated in pregnancy.
Tetracycline resistance
↓ uptake or ↑efflux out of bacterial cells by plasmid-encoded transport pumps.
Chloramphenicol mechanism
Blocks peptidyltransferase at 50S ribosomal subunit. Bacteriostatic.
Chloramphenicol clinical use
Meningitis
- Haemophilus influenzae
- Neisseria meningitidis
- Streptococcus pneumoniaeRocky Mountain spotted fever
- Rickettsia rickettsiiLimited use owing to toxicities but often still used in developing countries because of low cost.
Chloramphenicol toxicity
- Anemia (dose dependent)
- aplastic anemia (dose independent)
- gray baby syndrome (in premature infants because they lack liver UDP-glucuronyl transferase).
Chloramphenicol mechanism of resistance
Plasmid-encoded acetyltransferase inactivates the drug.
Lincosamide
Clindamycin
Clindamycin mechanism
Blocks peptide transfer (translocation) at 50S ribosomal subunit. Bacteriostatic.
Clindamycin clinical use
Anaerobic infections (e.g.,
- Bacteroides spp.
- Clostridium perfringensin
- aspiration pneumonia
- lung abscesses
- oral infections.Also effective against invasive group A streptococcal infection (strep pyogenes).[Treats anaerobic infections above the diaphragm vs. metronidazole (anaerobic infections below diaphragm)]
Clindamycin Toxicity
- Pseudomembranous colitis (C. difficile overgrowth)
- fever
- diarrhea
Oxazolidinones
Linezolid
Oxazolidinones mechanism
Inhibit protein synthesis by binding to 50S subunit and preventing formation of the initiation complex.
Oxazolidinones clinical use
Gram-positive species including MRSA and VRE
Oxazolidinones toxicity
- Bone marrow suppression (especially thrombocytopenia)
- peripheral neuropathy
- serotonin syndrome
Oxazolidinones resistance
Point mutation of ribsomal RNA.
Macrolides
- Azithromycine
- Clarithomycin
- Erythromycin
Macrolide mechanism
(Azithromycin, clarithromycin, erythromycin)Inhibit protein synthesis by blocking translocation; bind to the 23S rRNA of the 50S ribosomal subunit. Bacteriostatic.
Macrolide clinical use
Atypical pneumonias
- Mycoplasma
- Chlamydia
- Legionella STIs
- Chlamydia gram-positive cocci
- streptococcal infections in patients allergic to penicillin
- B. pertussis
Macrolide toxicity
- Gastrointestinal motility issues
- Arrhythmia caused by prolonged QT interval
- acute cholestatic hepatitis
- rash
- eosinophilia.
- Increases serum concentration of theophyllines, oral anticoagulants.
- Clarithromycin and erythromycin inhibit cytochrome P-450.
Macrolide resistance
Methylation of 23S rRNA-binding site prevents binding of drug
Floroquinolones
- Ciprofloxacin
- norfloxacin
- levofloxacin
- ofloxacin
- moxifloxacin
- gemifloxacin
- enoxacin
Floroquinolone mechanism
Inhibit prokaryotic enzymes topoisomeraseII (DNA gyrase) andtopoisomerase IV.Bactericidal. Must not be taken with antacids.
Floroquinolone clinical use
- Gram-negative rods of urinary and GI tracts (including Pseudomonas)
- Neisseria
- some gram-positive organisms
Floroquinolone toxicity
- GI upset
- superinfections
- skin rashes
- headache
- dizziness
- Less commonly, can cause leg cramps and myalgias.
- Contraindicated in pregnant women, nursing mothers, and children < 18 years old due to possible damage to cartilage.
- Some may prolong QT interval.
- May cause tendonitis or tendon rupture in people > 60 years old and in patients taking prednisone.
Floroquinolone resistance
- Chromosome-encoded mutation in DNA gyrase
- plasmid-mediated resistance
- efflux pumps
Lipopeptide
Daptomycin
Daptomycin mechanism
Lipopeptide that dirsupts cell membcane of gram-positive cocci.
Daptomycin clinical use
S. aureus skin infections (especially MRSA) bacteremia endocarditis VRE(vancomycin resistant eneterococcus)Not used for pneumonia (avidly binds to and is inactivated by surfactant).
Daptomycin toxicity
Myopathy rhabdomyolysis
Nitroimidazole
Metronidazole
Metronidazole mechanism
Forms toxic free radical metabolites in the bacterial cell that damage DNA.Bactericidal, antiprotozoal.
Metronidazole clinical use
Treats
- Giardia
- Entamoeba
- Trichomonas
- Gardnerella vaginalis Anaerobes
- Bacteroides
- C. difficile Used with a proton pump inhibitor and clarithromycin for “triple therapy” against H. Pylori.Treats anaerobic infection below the diaphragmvs. clindamycin (anaerobic infections above diaphragm).
Metronidazole toxicity
Disulfiram-like reaction with alcohol
- severe flushing
- tachycardia
- hypotension
- headache
- metallic taste
Sulfonamides
Sulfamethoxazole (SMX) (short acting) Sulfisoxazole (topical) Sulfadiazine (short acting)
Sulfonamide mechanism
Inhibit folate synthesis. Para-aminobenzoic acid (PABA) antimetabolites inhibit dihydropteroate synthase.Bacteriostatic (bactericidal when combined with trimethoprim).(Dapsone, used to treat lepromatous leprosy, is a closely related drug that also inhibits folate synthesis.)
Sulfonamide clinical use
- Gram-positives
- gram-negatives
- Nocardia
- Chlamydia
- Triple sulfas or SMX for simple UTI
Sulfonamide toxicity
- Hypersensitivity reactions
- hemolysis if G6PD deficient
- nephrotoxicity (tubulointerstitial nephritis)
- photosensitivity
- kernicterus in infants
- displace other drugs from albumin (e.g., warfarin)
Sulfonamide resistance
Altered enzyme (bacterial dihydropteroate synthase), ↓uptake, or ↑PABA synthesis.
Trimethoprim mechanism
Inhibits bacterial dihydrofolate reductase.Bacteriostatic.
Trimethoprim clinical use
Used in combination with sulfonamides (trimethoprim-sulfamethoxazole [TMP- SMX]), causing sequential block of folate synthesis.Combination used for
- UTIs
- Shigella
- Salmonella
- Pneumocystis jirovecii pneumonia treatment and prophylaxis
- toxoplasmosis prophylaxis
Trimethoprim toxicity
- Megaloblastic anemia
- leukopenia
- granulocytopenia(May alleviate with supplemental folinic acid)