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Derm ex1
pharm B-lactams
53
Medical
Professional
11/18/2011

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Term
Antibiotic pharmacodynamics:
Emax?
EC(IC) 50?
bacteriostatic?
bacteriocidal?
Definition
Emax= conc at which the maximum inhibition of bacterial growth is observed
EC 50= conc where half of Emax is reached
bacteriostatic= inhibition of bacterial growth, but no killing (left up to immune system)
bacteriocidal= kills 99.9% of bacteria
Term
reasons for a musculocutaneos AB injection?
Definition
length of action needs to be long, poor venous access
Term
what drives AB dosing?
Definition
the minimum inhibitory conc (min conc of drug needed to inhibits visible growth)

the minimum bactericidal conc (the lowest conc needed to achieve total of 99.9% reduction of bacteria)
Term
difference between time-dependent (conc-independent) and conc.-dependent drugs?
Definition
time dependent drugs exert effects steady at a fixed killing rate once a threshold conc is reached. increasing the conc beyond this point does not have any added benefit.

for conc-dependent agents, extent and rate of killing is increased progressively with higher antibacterial concentrations
Term
when can resistance be seen?
Definition
when Cmax:MIC (maximum inhibitory conc) falls below 3:1
Term
times to considered prophylactic AB therapy
Definition
surgical procedures (given 60 mins prior and not more than 24 hours post), immunosupressed patients, high risk for endocarditis (a dental procedure concern)
Term
what is empiric dosing?
Definition
wide spectrum dosing before the pathogen is identified because delaying could be dangerous
Term
types of resistance
Definition
intermediate resistance= shifting of the IC50 to the right

true resistance= a decrease of the Emax
Term
ways efficacy of drugs is decreased?
Definition
reduced entry- loss of alterations of porin channels (as in gram neg bacteria)

enhanced export- efflux pumps pump drug out of cell

modifying enzymes- produced by bacteria and inactivate drug

modification of activating enzymes- prodrug is unable to become active form
Term
B-lactams MOA
Definition
MOA: B-lactam ring blocks enzyme that inhibits bacs from performing cell wall synthesis (inhibited by LACATAMASE which some bacs produce)
Term
penicillin-binding proteins
Definition
enzymes on the surface of some bacteria which have different affinity for different B-lactams. transpeptidases are also in this family and transpeptidases are essential to PDG linkage in the bacterial cell wall

B-lactam which interrupt this synthesis will activate a cell autolysis
Term
bacteria which are resistant to B-lactams
Definition
legionella pneumophila, clamydia (because they are intracellular bacteria and B-lactam can't penetrate host cell)

mycoplasma (doesn't have PDG)

those with exceptionally small or selective porins
Term
B-lactamase locations
Definition
G pos. bacs produce a lot of it extracellulary

G neg. bacs have some located in their periplasmic space
Term
B-lactamase classes
Definition
Class A:
TEM-1, ESBL, KPC carbapenease, SHV-1
a SERINE protease

Class B:
a Zinc dependent metalloproteinase
broad spectrum against many B-lactams

Class C:
a SERINE protease
AmpC, inducible (often coded on chromosome)

Class D:
a SERINE protease
OXA B-lactamases which confer ampicillin resistance and is highly hydrolytic to oxacillin and cloxacillin
Term
basic Penicillin facts
Definition
-highly effective with low toxicity
-primarily renally excreted
-maybe one of the most common drugs to have hypersensitivity to
-a hapten meaning it is small and cannot elicit an immune response unless it complexes with something bigger
-should not be given inrathecally due to encephalitic risk
-compete at OATP transporters
-may disrupt the effectiveness of oral contraceptive
-may disrupt proton pump which effects stomach acidity, lowering it, causing migration of native flora
-poor prostate, eye, and CSF penetration because they have thighs junctions
Term
C. diff infections
Definition
often nosocomial

usually caused by elimination of a C diff competitor by an AB
Term
Penicillin G
Definition
-aqueous and delivered intramuscularly or intravenously
-long acting (2-4 weeks), good for syphilis when BENZATHINE is added
-largely effective against many G pos. aerobes and anaerobes, some neisseria and haemophilis strains (G neg.)
Term
bacterial resistance to Penicillin G
Definition
-many G neg., intrinsic
-staph aureus, produces penicillinases that inactivate penicillin G
-strep pneumo
Term
cautions of natural penicillins
Definition
hypersensitivity, seizures, electrolyte disturbances, jarisch-herxheimer rxn (complication of syphilis treatment)
Term
what are NAFCILIN, oxacillin, dicloxacillin, and cloxacillin
Definition
penicillinase-resistant penicillins

bulky resides on R-side groups and therefore prevent staphylococcal B-lactamases

best used for methicillin-SENSITIVE staph aureus and staph epidermidis, toxic shock syndrome, septic arthritis (not as active as penicillin G against other microbes)

ADVERSE SE: hepatitis and interstitial nephritis
Term
aminopenicillin facts
Definition
ampi and amox (amino group adds hydrophilicity thereby increasing their infiltration of enterobacteriacae)

ampicillin has been shown to positively effect meningitis by entering CSF, may lead to C diff superinfection, and is useful for UTI

amos and amp have a similar equivalent spectrum to penicilin G with pneumococi added

Highly susceptible to Class A B-lactamases, usually needs to be administered with an class A inhibitor

pseudomonas aeruginosa in inherently highly resistant
Term
therapeutic uses of Aminopencilins
Definition
amox and amp are best for pen-sensitive and pen-resistent s. pneumoniae, UTIs, meningisitis, upper and lower respiratory tract infections

ADVERSE SE:
non-allergic rash (especially when allopurinol has also been used); need to be sure its non-allergic though, not a hypersensitivity rxn
Term
ampicilin/sulbactam
Definition
good for G pos. cocci including B-lactamas-producing S. aureus (NOT MRSA), and G neg. anaerobes

good for mixed intrabdominal and pelvic infections
Term
amoxicilin/clavulanate
Definition
good for treatment of acute otitis in children, sinusitis, animal bite wounds, cellulitis
Term
piperacillin, ticaracillin pharmacokinetics and other facts
Definition
piperacillin (a uridopenicillin), ticaracillin (a carboxypenicillin) are both are given parentally because they are unstable in gastric acid

ideal for patients suffering from severe infections by gram negative bacteria

both are antipseudomonal penicillins, piperacillin being the superior of the two with added effectiveness against klebsiella and some enterbacteracae
Term
piperacillin-tazobactam
Definition
widest spectrum of all penicillins
Term
clavuanate, sulbactam, tazobactam
Definition
B-lactamase inhibitors frequently partnered with antipseudomonal penicillins

they are suicide inhibitors meaning they irreversibly bind to many B-lactamases

effective against many class As, and plasmic encoded B lactamase produced by staph

they are INEFFECTIVE against class C
Term
some cephalosporin facts
Definition
-structurally and functionally closely related to penicillins
-widely distributed
-acid stable so can be IV, IM, or oral
-CSF penetration increases through generations
-mainly renally excreted (except for ceftriaxone, which is through bile and fecal and cefotaxime which undergoes partial hepatic)
Term
added features of cephalosporins through generations
Definition
1st - good for G pos. and some aerobes G. neg.
2nd - some added G neg. microbes
3rd - good for G pos. and aerobic G. neg. and enterobacteriacae. some are able to cross CSF
4th - some added resistance to hydrolysis from many plasmid and chromosome based B-lactamases except for KPC in Class A
5th - added strep, staph, and MRSA. no activity against extended-spectrum B-lactamases in Class A
Term
cephalosporin is Ineffective against:
Definition
G. pos: pen-resist. S. pneumo, meth-resist. S. epiderm., C. diff, enterococcus

G. neg: KPC producing enterobacteraceae, campylobacter jejuni

mycoplasma, L. pneumo, chlamydia

ESBLs, class C
Term
First Gen Cephalosporins of importance
Definition
CEFAZOLINE - 60 mins prior to surgery CEPHALEXIN - oral, every 6 hours
Term
Second Gen Cephalosporins of importance
Definition
CEFOXITIN and CEFOTETAN - cephomycins with activity against B. fragilis which is needed around surgery CEFOTETAN- activity against B. fragilis
Term
severe potential side effect of antipseudomonal ABs
Definition
they are formulated with Na+ salts, therefore, any person at risk for cardiac failure should be careful due to the likely increase in BP
Term
how are almost all B-lactams eliminated?
Definition
through OATPs
Term
define biofilm
Definition
an accumulation of like organisms in a tissue or organ region.  the population is very increased, growth slows, and there is a lot of sharing of resistance genes
Term
requirement for the efficacy of B-lactams
Definition
the bacteria need to be proliferating meaning their cell walls need to be remodeling
Term

add benefits of gen. 3 cephalosporins

 

name four

Definition

increased ability to pass BBB (for meningitis), broad spectrum for G pos and G neg

 

poor against B. fragilis

 

Ceftriaxone and Cefotaxime and Cefdinir (Lacks anaerobic activity) Ceftazidine (for pseudomonas)

Term
when to use a generation 4 cephalosporin
Definition
use CEFEPIME for severe infection, psuedomonas
Term
some side effects of CEFTRIAXONE
Definition
Cholestatic hepatitis/gallbladder disease
Hyperbilirubinemia in neonates (could cause encephalopathy)
Precipitation of Ca2+-containing solutions
Term
some side effects of CEFETAN
Definition
Hypoprothrombinemia by inhibition of Vitamin K activation
Disulfuram-like reaction
Term
what is imipenem-cilastatin used for?
Definition

in the carbapenem family, it penetrates CSF

-has a large spectrum for G pos and neg including pen-resistant s. pneumo and pen-sens enterococcus faecilis

 

*treatment of choice for ESBL-expressing enterobacteriacae

 

primarily renal excretion

 

cilistatin is an inhibitor of the dehydrogenase that inactivates imipenem

Term
some points on ERTAPENEM
Definition

it is for G pos organism, but has inferior activity against pseudomas and acintobacter

 

like all carbapenems, it is inactivated by class A and B

Term
adverse effects of carbapenems
Definition
Seizures: greatest risk with the use of imipenem; patients with renal insufficiency are at increased risk
Hematologic: Bleeding, agranulocytosis, leukopenia have been reported.
GI: Nausea, vomiting, diarrhea are relatively common
C. difficilesuperinfection
Term
aztreonam
Definition

a MONOBACTAM

 

highly effective against G neg aerobic  cocci and bacilli, but is too narrow to be used for empirical dosing

 

used for pseudomonal lung infections in patients with cystic fibrosis

 

has a relatively low immunogenic potential (limited crossing-over with other B-lactams)

 

hydrolyzed by Class C and D

Term
what is vancomycin?
Definition

a glycopeptide that is poorly absorbed, renally eliminated, good penetration to CSF

 

MOA- stops cross linking of sugars by preventing incorperation of NAM and NAG which is the step for transpeptidization; binds to D-Ala-D-Ala 

 

it is only for G pos because cannot penetrate porins, MRSA, MRSE E. faecalis and facieum

 

resistant to enterococci which express a VanA gene and sometimes S. aureus

Term
what to use vancomycin on?
Definition

MRSA

Enterococcal endocarditis

Pneumococcal infections (penicillin res.)

C. diff

pen. res. S. pneumo (bacterial meningitis)

Term
vanomycin side effects
Definition
Hypersensitivity reaction
Red man syndrome
Phlebitis at injection site
Ototoxicity (rare)
Nephrotoxicity (currently uncommon)
Reacts with AMINOGLYCOSIDES
Term
what is daptomycin?
Definition

renally excreted, poor slow distribution

 

conc. dependent

 

innactivated by pulmonary surficants

 

MOA: binds to cell membrane and starts creating a Calcium complex which will form a pore from which intracellular potassium can escape depolarizing bacteria

Term

what daptomycin works on, what it doesn't.

 

 

Definition

works on:

ALL G POS BACTERIA

MRSA, MRSE, VISA, VRSA, VRE

 

resistance:

ALL G neg BACTERIA

any left side endocarditis and pneumonia (due to pulmonary surficant inactivation)

Term
side effects of DAPTOMYCIN
Definition
myopathy; HMG CoA reductase inhibitors have been linked to additive muscle toxicity
Term
What is the antibiotic of choice for surgical prophylaxis (an appendectomy) in this type of procedure (non-allergic patient)? Why?
Definition

Cefoxitin

To reduce the incidence of septic complications
For coverage of anaerobes that populate the distal parts of the intestine, particularly B. fragilis
Term
what are some good beta-hemolyzers
Definition
all Group A and Group B Streptococci, most strains of S. aureus, some strains of Clostridia, and about half of all strains of E. coli
Term
only B-hemolytic staph?
Definition
aureus
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