Antibacterial Drugs Flashcards
Mechanism: Aminoglycosides
Gentamicin
Neomycin
Amikacin
Tobramycin
Streptomycin
Bactericidal (unlike other protein synthesis inhibitors)
Irreversible inhibition of initiation complex through binding of 30S ribosomal subunit
Also blocks translocation
Can cause misreading of mRNA
Requires O2 for uptake; ineffective against anaerobes
Resistance: Cephalosporins
Structural change in penicillin-binding proteins (transpeptidases)
Name the monobactam(s)
Aztreonam
Adverse effects: Cephalosporins
- Hypersensitivity reactions
- Autoimmune hemolytic anemia
- Disulfiram-like reaction
- Vitamin K deficiency
- Increased nephrotoxicity of aminoglycosides
- Low rate of cross-reactivity even in penicillin-allergic patients
Class: Streptomycin
Aminoglycoside
Do not take tetracyclines with ___, ___, or ___ because divalent cations inhibit the drugs absorption in the gut
Milk (calcium)
Antacids (calcium or magnesium)
Iron-containing preparations
Imipenem is a board-spectrum beta-lactamase resistant carbapenem that is always administered with ___ (inhibitor of renal dehydropeptidase I) to decrease inactivate of drug in renal tubules.
Cilastatin
Resistance: Macrolides
Azithromycin
Clarithromycin
Erythromycin
Methylation of 23S rRNA-binding site prevent binding of the drug
Clinical use: 3rd generation cephalosporins
Ceftriaxone
Cefotaxime
Cefpodoxime
Ceftazidime
Serious gram (-) infections resistant to other beta-lactams
Organisms typically not covered by 1st - 4th generation cephalosporins
Listeria
Atypicals (Chlamydia, Mycoplasma)
MRSA
Enterococci
Mechanism: Antipseudomonal penicillins
Piperacillin
Ticarcillin
Same as penicillin
Extended spectrum
Susceptible to penicillinase
Use with beta-lactamase inhibitors
Adverse effects: Aminoglycosides
Gentamicin
Neomycin
Amikacin
Tobramycin
Streptomycin
- Nephrotoxicity (especially with cephalosporins)
- Ototoxicity (especially with loop diuretics)
- Teratogen (cause ototoxocity)
- Neuromuscular blockade
Name the antipseudomonal penicillins
- Piperacillin
- Ticarcillin
Resistance: Aminoglycosides
Gentamicin
Neomycin
Amikacin
Tobramycin
Streptomycin
Bacterial transferase enzymes inactivate the drug by:
- Acetylation
- Phosphorylation
- Adenylation
Class: Gentamicin
Aminoglycoside
Adverse effects: Penicillin G, V
- Hypersentivity reactions
- Direct Coombs + hemolytic anemia
Mechanism: Sulfonamides
Sulfamethoxazole (SMX)
Sulfisoxazole
Sulfadiazine
Inhibit dihydropteroate synthase → inhibiting folate synthesis
Bacteriostatic (cidal when combined with trimethoprim)
Name the carbapendems
Older:
- Imipenem
- Meropenem
Newer:
- Ertapenem (limited Pseudomonas coverage)
- Doripenem
Mechanism: Fluoroquinolones
Enoxacin
Ciprofloxacin
Norfloxacin
Levofloxacin
Ofloxacin
Moxifloxacin
Gemifloaxacin
Inhibits prokaryotic topoisomerase II (DNA gyrase) and topoisomerase IV
Bactericidal
Class: Amikacin
Aminoglycoside
Adverse effects: Penicillinase-sensitive penicillins (aminopenicillins)
Amoxicillin
Ampicillin
- Hypersensitivity reactions
- Rash
- Pseudomembranous colitis
Mechanism: Chloramphenicol
Blocks peptidyltransferase at 50S subunit
Bacteriostatic
Mechanism: Tetracyclines
Tetracycline
Doxycycline
Minocycline
Bacteriostatic
Bind 30S and prevent attachment of aminoacyl-tRNA
Limited CNS penetration
Mechanism: Cephalosporins
Beta-lactam antibiotics that inhibit cell wall synthesis but are less susceptible to penicillinases
Bactericidal
Adverse effects: Monobactam
Aztreonam
Usually non-toxic
- Occasional GI upset
Adverse effects: Macrolides
Azithromycin
Clarithromycin
Erythromycin
- GI motility issues
- Arrhythmia (prolonged QT interval)
- Acute cholestatic hepatitis
- Rash
- Eosinophilia
- P-450 inhibitor (except azithromycin)
Adverse effects: Linezolid
- Bone marrow suppression
- Especially thrombocytopenia
- Peripheral neuropathy
- Serotonin syndrome (when mixed with other serotonergic agents)
Resistance: Penicillin G, V
Penicillinase in bacteria (a type of beta-lactamase) cleaves beta-lactam ring
Clinical use: 5th generation cephalosporins
Ceftaroline
Broad gram (+) and gram (-) organism coverage
Unlike 1st - 4th generation, covers:
- Listeria
- MRSA
- Enterococcus faecalis
Does NOT cover pseudomonas (vs 4th generation)
Adverse effects: Metronidazole
- Disulfiram-like reaction (severe flushing, tachycardia, hypotension) with alcohol
- Headache
- Metallic taste
Resistance: Sulfonamides
Sulfamethoxazole (SMX)
Sulfisoxazole
Sulfadiazine
Altered enzyme (bacterial dihydropteroate synthase)
Decreased uptake
Increased PABA synthesis
In general:
___ treats anaerobic infections above the diaphragm
___ treats anaerobic infections below the diagphram
Clindamycin (above)
Metronidazole (below)
Adverse effects: Carbapenems
Imipenem
Meropenem
Ertapenem
Doripenem
- GI distress
- Skin rash
- CNS toxicity (seizures)
Mechanism: Tigecycline
Glycylcycline - tetracycline derivative
Binds 30S → inhibiting protein synthesis
Bacteriostatic
Clinical use: 4th generation cephalosporins
Cefepime
Gram (-) organisms
Increased activity against:
- Pseudomonas
- Gram (+) organisms
50S inhibitors
Chloramphenicol (static)
Clindamycin (static)
Macrolides (static)
Linezolid (variable
Adverse effects: Daptomycin
- Myopathy
- Rhabdomyolysis
Adverse effects: Sulfonamides
Sulfamethoxazole (SMX)
Sulfisoxazole
Sulfadiazine
- Hypersensitivity reactions
- Hemolysis if G6PD deficient
- Nephrotoxicity (tubulointerstitial nephritis)
- Photosensitivity
- Stevens-Johnson syndrome
- Kernicterus in infants
- Displace other drugs from albumin (e.g., warfarin)
- P-450 inhibitor
Mechanism: Penicillinase-resistant penicillins
Dicloxacillin
Nafcillin
Oxacillin
Methacillin (D/C)
Same as penicillin
Narrow spectrum
Penicillinase-resistant because bulky R-group blocks access of beta-lactamase to beta-lactam ring
Use of ___ is limited owing to its toxicities, but is still often used in developing countries due to low cost.
Chloramphenicol
Name the penicillinase-resistant penicillins
- Dicloxacillin
- Nafcillin
- Oxacillin
- Methicillin (D/C)
Mechanism: Daptomycin
Lipopeptide that disrupts cell membranes of gram-positive cocci by creating transmembrane channels
Resistance: Penicillinase-sensitive penicillins (aminopenicillins)
Amoxicillin
Ampicillin
Penicillinase in bacteria (a type of beta-lactamase) cleaves beta-lactam ring
Adverse effects: Dapsone
Hemolysis if G6PD deficient
Resistance: Linezolid
Point mutation of ribosomal RNA
Mechanism: Trimethoprim
Inhibits bacterial dihydrofolate reductase
Bacteriostatic
___ is a carbapenem that is stable to renal dehydropeptidase I (no need for cilastatin) and has less risk for seizures
Meropenem
Adverse effects: Chloramphenicol
- Anemia (dose dependent)
- Aplastic anemia (dose independent)
- Gray baby syndrome (premature infants because they lack liver UDP-glycuronyltransferase, which metabolizes the drug)
Adverse effects: Tetracyclines
Tetracycline
Doxycycline
Minocycline
- GI distress
- Discoloration of teeth
- Inhibition of bone growth (children)
- Photosensitivity
- Contraindicated in pregnancy
Clinical use: 1st generation cephalosporins
Cefazolin
Cephalexin
- Gram (+) cocci
- Proteus mirabilis
- E. coli
- Klebsiella pneumoniae
- Cefazolin used prior to surgery to prevent S. aureus wound infections
Name the penicillinase-sensitive penicillins (aminopenicillins)
- Amoxicillin
- Ampicillin
Fluoroquinolones must NOT be taken with ___
Antacids
Mechanism: Carbapenems
Inhibit peptidoglycan (cell wall) synthesis
30S inhibitors
Aminoglycosides (cidal)
Tetracyclines (static)
Tigecycline (tetracycline derivative)
Class: Neomycin
Aminoglycoside
Fluoroquinolones are contraindicated in ___, ___, and ___ due to possible damage to cartilage
Pregnancy women
Nursing mothers
Children <18 year old
Adverse effects: Tigecycline
- N/V
Name the tetracyclines
Tetracycline
Doxycycline
Minocycline
Mechanism: Penicillinase-sensitive penicillins (aminopenicillins)
Amoxicillin
Ampicillin
Same as penicillin
Wider spectrum
Penicillinase sensitive
Can combine with clavulanic acid to protect against destruction by beta-lactamase
Mechanism: Macrolides
Azithromycin
Clarithromycin
Erythromycin
Inhibit protein synthesis by blocking translocation
Bind to 23S rRNA of the 50S subunit
Mechanism: Monobactam
Aztreonam
Inhibits cell wall synthesis
Prevent PTG cross-linking by binding to penicillin-binding protein 3
Less susceptible to beta-lactamases
Synergistic with aminoglycosides
No cross-allergenicity with penicillins
___ is used prior to surgery to prevent S. aureus wound infections
Cefazolin (1st gen cephalosporin)
Adverse effects: Fluoroquinolones
Enoxacin
Ciprofloxacin
Norfloxacin
Levofloxacin
Ofloxacin
Moxifloxacin
Gemifloxacin
- GI upset
- Superinfections
- Skin rashes
- Headache
- Dizziness
- Leg cramps, myalgias (less common)
- P-450 inhibitor
- Prolonged QT interval
- Tendonitis or tendon rupture
- In patients >60 years old
- In patients taking prednisone
Mechanism: Penicillin G, V
D-Ala-D-Ala structural analog
Bind penicillin-binding proteins (transpeptidases) → block transpeptidase cross-linking of peptidoglycan in cell wall
Activates autolytic enzymes
Penicillinase sensitive
Adverse effects: Vancomycin
- Nephrotoxicity
- Ototoxicity
- Thrombophlebitis
- Diffuse flushing (red man syndrome)
- Largely preventable by pretreatment with antihistamines and slow infusion rate
Mechanism: Metronidazole
Forms toxic free radical metabolites in the bacterial cell that damage DNA
Bactericidal and antiprotozoal
Resistance: Chloramphenicol
Plasmid-encoded acetyltransferase inactivates the drug
Adverse effects: Penicillinase-resistant penicillins
Dicloxacillin
Nafcillin
Oxacillin
Methicillin (D/C)
- Hypersensitivity reactions
- Interstitial nephritis
Mechanism: Linezolid
Inhibits protein synthesis by binding to 50S subunit and preventing formation of the initiation complex
Mechanism: Vancomycin
Inhibits cell wall PTG formation by binding
D-ala-D-ala portion of cell wall precursors
Bactericidal against most bacteria (bacteriostatic against C. difficile)
Not susceptible for beta-lactamase
Resistance: Vancomycin
Occurs in bacteria (Enterococcus) via amino acid modification of D-ala-D-ala → D-ala-D-lac
Adverse effects: Clindamycin
- Pseudomembranous colitis (C. difficile)
- Fever
- Diarrhea
Adverse effects: Trimethoprim
- Megaloblastic anemia
- Leukopenia
- Granylocytopenia
Adverse effects may be alleviated with supplemental folinic acid
Name the beta-lactamase inhibitors
- Clavulanic acid
- Avibactam
- Sulbactam
- Tazobactam
Adverse effects: Antipseudonomal penicillins
Peperacillin
Ticarcillin
- Hypersensitivity reactions
Most protein synthesis inhibitors are ___ with the exception of ___
Bacteriostatic
Exception: Aminoglycosides
Resistance: Tetracyclines
Tetracycline
Doxycycline
Minocycline
Decrease uptake and increase efflux out of bacterial cells by plasmic-encoded transport pumps
Daptomycin is NOT used for ___
Pneumonia - daptomycin avidly binds to and is inactivated by surfactant
Mechanism: Clindamycin
Blocks peptide transfer (translocation) at 50S subunit
Bacteriostatic
Class: Tobramycin
Aminoglycoside
___ is an aminoglycoside used for bowel surgery
Neomycin
Clinical use: 2nd generation cephalosporins
Cefaclor
Cefoxitin
Cefuroxime
- Gram (+) cocci
- Proteus mirabilis
- E. coli
- Klebsiella pneumoniae
- H. influenzae
- Enterobacter aerogenes
- Neisseria spp.
- Serratia marcescens
Mechanism: Dapsone
Similar to sulfonamides (inhibits dihydropteroate synthase) , but structurally distinct