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65 Cards in this Set
- Front
- Back
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What are the five typical mechanisms of action for anitmicrobials
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1. inhibition of cell wall synthesis
2. inhibition of protein synthesis 3. destruction of cell membrane function 4.altered nucleic acid synthesis 5. miscellaneous |
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What is the definition of Minimum Inhibitory Concentration
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lowest conc. of an antimicrobial that inhibits the visible growth of a microorganism after overnight incubation
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What is the treatment goal for antimicrobials?
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maintain circulating conc. of the drug above the MIC
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What are some of the effects to toxicity of antibiotics
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1. misc. GI effects most common adverse effect
2. by disturbing the normal flora, antibiotics can cause overgrowth of non-susceptible organisms. |
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What is pharmacokinetics?
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time course of antimicrobial conc. in the body
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What is pharmacodynamics?
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relationship between drug conc. and antimicrobial effects.
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What is time-dependent killing?
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the amt. of time that serum conc. is above the MIC.
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What is conc.-dependent killing?
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killing increases as conc. increases above the MIC
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What are the five types of antibiotics?
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1. cell wall synth. inhibitors
2. protein synth. inhibitors 3. nucleic acid synth. inhibitors. 4. disruption of cell membrane function 5. inhibitors of folic acid biosynthesis. |
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What are the broad names for the inhibitors of cell wall synthesis
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1. beta-lactams
2. vancomycin 3. bacitracin 4.fosfomycin 5.cycloserine 6. novobiocin |
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What are the different classes of beta-lactams
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1. penicillin
2. cephalosporin 3. carbapenems 4. monobactams |
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What is the major toxicity of beta-lactams?
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allergic reactions to the drug.
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What is the mechanism of action of beta-lactams?
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covalently bind to enzymes (PBP) in the bacterial cell membrane that function in the building and remodeling of the bacterial cell wall, and especially important process during cell division.
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What is the primary method of resistance to beta-lactams?
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production of beta-lactamase.
b-Lactamases --> microbial enzymes that hydrolyze the b-Lactam ring |
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how is penicillin excreted?
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through urine as an unchanged drug
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What are the four groups of penicillins?
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1. Pen G and its congeners
2. lactamase-resistant penicillins 3. Extended spectrum penicillins 4. Extended spectrum penicillins with -lactamase inhibitors |
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What are the extended spectrum penicillins?
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Activity against Gram pos and Gram neg
Ampicillin Parenteral & oral (poor absorption) Amoxicillin Oral only (absorbed well even w/food) |
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What are the clinical uses for amoxicillin?
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Acute otitis media/sinusitis
Lower respiratory infections |
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What are some of the characteristics of beta-lactamase inhibitors?
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1.Poor antimicrobial effects
2. Irreversibly inhibit bacterial lactamases 3. Used only in combination with penicillins |
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What is a notable use for beta-lactamase inhibitors?
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Mixed aerobic and anaerobic infections such as intra-abdominal infections
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What are some important Cephalosporins?
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Cefazolin - first gen.
Cefoxitin - second gen. Ceftriaxone - third gen. |
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What are the different Carbapenems
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Imipenem
Meropenem Ertapenem |
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What are carbapenems the drug of choice for?
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enterobacter infections (nosocomial pathogens responsible for range of infections: lower resp tract, skin, soft tissue, UTI, ophthalmic, etc)
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What is the only monobactam drug?
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Aztreonam
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Give an overall summary of beta-lactams.
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1. High degree of selective toxicity
2. Most bacteria will respond to b-lactams 3. Resistance most commonly due to inactivation by b -lactamases 4. High incidence of allergic reactions 5. Cross-allergic reactions can occur (~5%) 6. Primarily renal excretion 7. CNS symptoms occur at high levels 8. Carbapenems most problematic |
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Why are other inhibitors of cell wall synthesis beneficial?
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Do not contain beta-lactam rings and therefore are useful against beta-lactamase-producing microbes
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what are the adverse effects of Vancomycin?
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ADVERSE EFFECTS
1. Causes tissue necrosis if given IM 2. Must be given by slow IV infusion 3. Commonly causes thrombophlebitis If infused too quickly --> “red man syndrome”, tachycardia, hypotension due to histamine release 4. Nephrotoxic and is excreted from the kidney (need to monitor kidney function of pts) |
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What is Bacitracin used for?
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Used topically for surface lesions of skin, in wounds, and on mucous membranes
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What is Fosfomycin used for?
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Urinary tract infections; single dose; safe for pregnant women
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What is the site of action for the inhibitors of protein synthesis?
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The bacterial ribosome
Binding the the 50S or the 30S |
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What are the classes of antimicrobials that work on the 50S binding site of a bacterial ribosome?
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Macrolides, lincosamides, streptogramins, chloramphenicol,
Pleuromutilins, streptogramins, and Oxazolidinones (linezolids). |
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What are the classes of antimicrobials that work on the 30S binding site of a bacterial ribosome?
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Tetracyclines, Aminoglycosides, and Spectinomycins
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What are the four important Macrolides?
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Erythromycin, Clarithromycin, Azithromycin, and Telithromycin (this one is not as important).
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What are the pharmacokinetics of erythromycin?
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Eryth base is very acid labile --> enteric coating and salt forms created to increase stability (stearate, ethyl succinate, estolate)
Estolate salt is the best absorbed oral form |
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What are the adverse effects of erythromycin?
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Acute cholestatic hepatitis (standing still of the bile. Obstruction of the intrahepatic bile ducts -- fever, jaundice, impaired liver function) -- believed to be an allergic rxn
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What are the advantages of clarithromycin over erythromycin?
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Advantages over erythromycin
1. Relatively more potent 2. Acid stable 3. Better absorbed, less GI upset 4. Longer half-life --> BID dosing versus QID for erythromycin |
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What is the only drug under the lincosamides class?
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Clindamycin
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What is an important use for Clindamycin?
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it is highly effective against anaerobic pathogens.
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What are some important things are Chloramphenicol
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1. One of few antibiotics for Salmonella--treat Typhoid fever
2. Effective against anaerobes 3. Excellent penetration into CSF, ocular and joint fluids |
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What are the four drugs under the class of aminoglycosides
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Amikacin,
Tobramycin, Streptomycin, Gentamicin. |
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What is the mechanism of action for aminoglycosides?
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They are bacteriocidal
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What are the classes of nucleic acid inhibitors?
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These Specifically interfere with microbial DNA replication, transcription, or structure
Fluoroquinolones, Rifamycins, Metronidazole, Sulfonamides and trimethoprim |
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What is important about Quinolones?
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Inhibit DNA gyrase
Highly active against Gram (-) bacteria |
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What are some adverse effects of fluoroquinolone
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1. Effects on cartilage development (permanent in animals, not known in humans)
2. Contraindicated for pregnancy 3. Not recommended for children < 18 yrs old |
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What are the four drugs under the Rifamycin class?
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Rifampin
Rifabutin Rifapentin Rifaxamin |
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When are Rifamycins most commonly used?
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in treatment of mycobacterial diseases
PRIMARILY USED IN TREATING TB |
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Why are inhibitors of cell membrane function not commonly used?
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these drugs are too toxic for routine use. They are last-resort drugs.
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What are the classes of drugs that are inhibitors of intermediary metabolism
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Sulfonamides and Trimethoprim
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What is the mechanism for "Sulfa" drugs?
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“Sulfa” drugs compete with para-aminobenzoic acid (PABA) for the enzyme Dihydropteroate synthase
Most are highly protein bound in serum (i.e., not active when protein bound) --> can displace other protein-bound drugs and proteins and limits renal elimination of sulfonamides |
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What is the most serious complication of "Sulfa" drugs and toxicity
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crystalluria
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What are some results of toxicity in "Sulfa" drugs.
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1. Crystalluria
2. Kernicterus possible in neonates (displacement of bilirubin from albumin) 3. Fever, skin rash, photosensitivity Stevens-Johnson syndrome (rare, skin and mucous memberane eruptions --> detachment of epidermis --> potentially fatal) |
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What does Trimethoprim do?
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Inhibits dihydrofolate reductase
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What is the most common bacterial cause of UTIs?
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E. Coli. 80% of the time.
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What is important about Fosfomycin?
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1. Inhibits pyruvyl transferase (cell wall synthesis enzyme)
2. Bacteriocidal for UTI pathogens 3. Single dose (3 g for adults) cure for uncomplicated UTIs 4. Safe to use in pregnant patients |
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What is the best route of action in treating TB?
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Long-term treatment with combinations of drugs
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What two primary drugs are used in combination to treat TB?
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Isoniazid (INH)
Rifampin |
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What is important about Isoniazid
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1. Drug of choice for prophylaxis and therapy
2. Inhibits mycolic acid biosynthesis (cell wall) |
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What does Ethambutol do?
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Inhibits mycobacterial cell wall synthesis by blocking arabinosyl transferase
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What are some adverse effects of Ethambutol?
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Retrobulbar neuritis --> loss of visual acuity; red-green color blindness --> Vision checks recommended periodically
Contraindicated in children too young to permit assessment of red-green color blindness |
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What is important about pyrazinamide?
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it is highly effective as combo therapy with INH and rifampin for short term (6 month) regimens
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What are some adverse effects of pyrazinamide?
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Liver toxicity (1-5% of pts) - must monitor pt liver function
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What are the four drugs in the initial "four drug standard" for treating TB?
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Isoniazid, rifampin, pyrazinamide, ethambutol
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When is streptomycin sulfate used in treating TB?
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Used when an injectable drug needed
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What are some treatment options for Leprosy?
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Dapsone - drug of choice
Similar to sulfonamides Once a week dosing Adverse effects: RBC hemolysis, anemia (take Fe2+) Rifampin |
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What is the most prominent and important use of prophylaxis?
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prevent bacterial endocarditis.
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