drugs for bacterial pulmonary infections Flashcards
describe the 4 major categories of penicillins
- natural penicillins
- anti-staphylococcal (penicillinase-resistant) penicillins
- Amino penicillins (Extended spectrum)
- Anti-pseudomonal
MOA of penicillins
beta-lactams that bind to and inhibit transpeptidation of the peptidoglycan in bacterial cell walls (bacteriocidal)
what is augmentin?
amoxicillin + clavulanic acid
what does augmentin treat?
beta-lactamase producing staph aureus and other anaerobes producing respiratory tract infections
what is unasyn?
ampicillin + sulbactam
how is unasyn administered
parenteral
what is unasyn used for?
amp-resistant H. influenzae
moraxella catarrhalis
mixed G+ and anaerobic infections (CAP)
how do Clavulanic acid, Sulbactam and Tazobactam work?
they are suicide inhibitors that irreversibly acetylate the beta-lactamase enzyme
when should Penicillin V be given?
1 hour before or 2 hours after meal
how does food affect the absorption of penicillins?
generally decreases absorption (except amoxicillin)
gastric juices and decreased pH destroys PCN
how are penicillins metabolized?
hepatic enzymes (increased in pts w/ renal impairment)
how are the penicillins excreted?
renal tubular secretion (90%)
what 2 important things can affect the half life of penicillin?
- physiological state of the kidneys
2. concomitant therapy w/ drugs that are organic acids (drugs compete w/ penicillin for excretion by the kidneys)
if you have a pt w/ renal dysfunction how might you change the way you prescribe penicillins?
increase the dosing interval
what are 5 important adverse effects of penicillins?
- N/V (frequent w/ children)
- diarrhea after oral dose (killed gut flora)
- abnormal plasma electrolytes (in hypokalemic pt)
- renal impairment-dose related (Penicillin G)
- neurotoxicity w/ large doses (likely in pts w/ reduced renal function)
How long do delayed allergic rxns to penicillins take?
2 days (rashes)
how long do accelerated pencillin allergic reactions take?
30 mins to 48 hrs (hives, wheezing ,mild laryngeal edema, local inflamm. rxns)
what are the symptoms associated with penicillin acute allergic reaction?
anaphylaxis
bronchospasm
How do cephalosporins work?
bind to PBPs on bacterial cell membranes and inhibit bacterial cell wall synthesis similar to penicillins
Modifications at position 7(R1) of the beta-lactam ring are associated with_________________
alteration in antibacterial activity
Substitutions at position 3(R2) of the dihydrothiazine ring are associated with changes in ______________________
the metabolism and pharmacokinetic profile of the drug
what were the 3 reasons that cephalosporins were developed?
- be effective in pt allergic to penicillins
- to be effective against bacteria that are resistant to penicillins
- to have a broader spectrum
progression from 1st to 3rd generation cephalosporins are marked by what 4 things?
- broadening in gram negative susceptibility
- diminished activity against G+ bacteria
- increased resistance to beta-lactamase inactivation
- increased capability to enter the CSF
what are the 3rd generation cephalosporins used for?
enteric gram-negative organisms
reserved for very serious infections (crosses the BBB)
-H. influenza, Serratia, Pseudomonas (ceftazadime only)
whats unique about the 3rd generation cephalosporins?
penetrate the CSF enough to treat meningitis
how are the cephalosporins excreted?
renal tubular mechanims
what happens to the serum levels of cephalosporins when taken with probenecid?
increased
what are the adverse reactions to cephalosporins?
hypersensitivity diarrhea & GI distrubance severe pain w/ IM injections Phlebitis from intravenous administration nephrotoxicity at high dosage
which cephalosporin most commonly causes diarrhea and GI disturbance?
ceftriaxone
how do carbapenems work
chemically different than penicillins but still have beta-lactam ring structure (binds to transpeptidase and blocks the cross linking of the cell wall peptidoglycan strands)
what is one big advantage of the carbapenems over the penicillins?
carbapenems have high resistance to bacterial beta-lactamase (potent suicide inactivators)
which drug has the broadest spectrum of any beta-lactam antibiotic?
imipenem
imipenem is administered with what drug?
cilastatin
how does cilastatin work?
inhibitor of dehydropeptidase (in brush border of proximal renal tubule)
prevents breakdown of imipenem and renal toxicity
fixed combination–>primaxin
how is imipenem administered?
IV w/ good distribution to body tissues, but not CSF
how is imipenem excreted?
both glomerular filtration and active secretion
how does probenecid affect the half life of imipenem?
IT DOESNT
Which carbapenem is contraindicated in pts w/ CNS seizures?
imipenem
what is the typical indication for imipenem-cilastatin combo?
serious infections of aerobic gram-negative bacilli, anaerobes, and staph aureus
how do aminoglycosides work?
protein synthesis inhibitor by binding to 30S subunit:
- block formation of initiation complex
- cause misreading of the code on mRNA template
- inhibit translocation
what’s so great about the aminoglycosides?
broad spectrum of activity
valuable in treating nosocomial infections
how do the macrolides work?
binds reversibly to 50s ribosomal subunit and inhibits protein synthesis (bacteriostatic)
Name the 3 macrolides?
erythromycin
azithromycin
clarithromycin
which macrolide do you have to make sure that you are reaching the minimal inhibitory concentration?
erythromycin
which macrolide diffuses into prostatic fluid and macrophages and is primarily excreted in bile and feces?
erythromycin
What are the drugs of choice in legionnaire’s disease?
erythromycin, azithromycin
what is the most frequent side effect of erythromycin?
GI upset
what is an important drug interaction involved with erythromycin?
inhibits cytochrome P450 3A (possible QT elongation in combo w/ other CYP3A inhibitors)
which drug causes cholestatic hepatitis and transient deafness?
erythromycin hypersensitivity reaction to estolate form (also contraindicated in pts with liver dysfunction b/c it accumulates in liver)
Name this drug: more acid stable than erythromycin, absorption increases w/ food, undergoes rapid first pass metabolism with active primary metabolite, eliminated by kidney and liver.
clarithromycin
Name this macrolide: t 1/2 40-68 hours
azithromycin
how is the majority of azithromycin excreted?
in bile
which macrolide has a major advantage over the others in that it doesn’t inhibit any CYP enzymes?
azithromycin
how do the quinolones work?
inhibits DNA replication via binding to DNA gyrase and topoisomerase IV (bactericidal)
What are 2 ways that resistance is developing to fluroquinolones by less drug getting to the target enzyme?
- decrease number of porin proteins in the outer membrane (impairing access to intracellular gyrase) 2. decreased intracellular accumulation of drug via efflux pumps
what can bind to and negatively affect the absorption of oral fluoroquinolones?
divalent, trivalent cations (iron, zinc supplements)
what are the important side effects of fluoroquinolones?
photosensitivity
prolongation of QT interval (moxifloxacin)
articular cartilage erosion
GI upsets
how do the tetracyclines work?
inhibit protein synthesis by reversible binding to 30S ribosome (bacteriostatic, MIC must be maintained)
how can resistance to tetracyclines develop?
- increased efflux of tetracycline from cell
- decreased transport
(resistance to one tetracycline provides resistance to all )
what are the main indications for tetracyclines?
atypical pneumonias, dental disease
what can inhibit the absorption of tetracyclines?
di, trivalent cations
how are most tetracyclines removed from the blood?
removed by liver, also undergoes enterohepatic cycling
how are tetracyclines distributed?
- wide tissue distribution and cross the placental barrier
- bone and teeth when undergoing calcification (discolors teeth)
what are some adverse effects of tetracyclines?
- GI disturbance (N/V/D, avitaminosis, superinfections)
- chelation of Ca2+ (discoloration of teeth)
- depression of bone growth
- hepatic toxicity
- photosensitivity (doxycycline)
which tetracycline is less likely to cause superinfections?
doxycycline
what are the advantages to using doxycycline over other tetracyclines?
- requires fewer doses (100% bioavailability)
- less GI disturbance
- available oral and parenteral
- no dosage adjustment required for reduced renal function
what are the therapeutic uses of tetracyclines?
atypical pneumonia (doxycycline) Lyme disease Rickettsial infections periodontal disease acne
what is first line therapy for nocardiosis?
TMP/SMX
none of the cephalosporins work against which bug?
enterococcus
what are the adverse effects of imipenem?
SEIZURES (beware w/ renal insufficiency)
CNS toxicity
allergic reactions
expensive!
how can resistance to erythromycin develop?
plasmid mediated processes
- decreased transport
- modification of target by methylases
- hydrolysis of drug from hydrolases
name of the phenotype that has a gene that encodes methylases that modify the macrolide binding to the ribosome and confers resitance to all 3 macrolides?
MLSb from the erm gene via a plasma mediated process
how is erythromycin excreted?
in bile and feces
what are the important drug interactions for clarithromycin?
also CYP3A4 inhibit but not as much as erythromycin
which macrolide has impaired absorption with food?
azithromycin
how is resistance developing against fluorquinolones regarding DNA gyrase binding?
Mutation in QRDR of DNA gyrase enzyme
which tetracycline can be given to pts w/ renal dysfunction without adjustment of dose?
doxycycline
what patients don’t get tetracyclines?
pregnant women and kids under 9 yrs
what do the fluoroquinolones treat?
Pneumococcus (levofloxacin, moxifloxacin)
Staph Aureus
bunch of gram negatives