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Antibiotics Flashcards

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1
Q

Whats mechanism of action of tetracyclines?

A

bacteriostatic that reversibly bind to 30S blocking amino acyl tRNA

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2
Q

How do bugs resist tetracycline?

A

Mg dependent efflux pumps, also changes in ribosomal binding

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3
Q

What are some pharmokinetic factors of tetracyclines?

A

incomplete by P.O. because they chetalate with anatacids and dairy. They can also distribute across fetus, CNS and excreted in urine via GF

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4
Q

What are pharmokinetics of Doxycycline?

A

PO bioavailability almost complete, food/dairy does not significantly dec bioavailability. Has long t1/2 (i.e, 16-18 hrs.), usually once/day or BID administration
Excreted via bile > feces as inactive conjugate or chelate, the only tetracycline that does not accumulate in renal insufficiency

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5
Q

What are clinical indications of doxycycline?

A

Activity against Chlamydia trachomatis, anthrax, cholera, Lyme disease, Rocky Mountain Spotted fever (Rickettisiae)
Doxycycline+Cephalosporin against anaerobic bacteria

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6
Q

What are pharmokinetics of minocycline?

A

Most lipid soluble tetracycline, 100% PO bioavailability, wider distribution, esp. to CNS, longest t1/2 (i.e., 16-18 hrs.)
Undergoes significant metabolism, mostly excretion of metabolites in urine and feces

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7
Q

What is minocycline used to treat?

A

Especially effective in treatment of acne (Propionibacterium acnes)
Used to eradicate meningococcal carrier state

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8
Q

What is anitbacterial spectrum of tetracyclines?

A

Gram (+): susceptible species of staph\ strep, however other drugs preferred due to bacteriostatic action / increased resistance,
Propionibacterium acnes (anaerobe)
Gram (-): H. influenzae, K. pneumonia, helicobacter pylori
*B. burgdorferi (Lyme disease)
*Main indications: Rickettsiae, Mycoplasma pneumonia, Chlamydia trachomatis, V. cholera

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9
Q

What two things are tetracyclines not effective against?

A

pseudamonas and resistant gonococci

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10
Q

What are some ADRs of tetracyclines?

A

GI distress, Phototoxicity, Skeletal effects - chelates teeth and bones during calcification. Contraindications: not use in children (<8 yrs) or during pregnancy, Neurotoxicity, Hepatotoxicity - esp. in pregnancy

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11
Q

What is mechanism of action of aminoglycosides?

A

Bacteriocidal because irreversible binding to 30S, also actively pumped through membrane actively

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12
Q

What are aminoglycosides not active against?

A

anaerobes

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13
Q

What causes resistance of bacteria to aminoglycosides?

A

Most common resistance due to production of microbial enzymes, acetylases, phosphorylases, adenylases; also impaired entry into bacterial cell and altered binding receptor protein on ribosomal unit

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14
Q

What are pharmokinetics of aminoglycosides?

A

Water soluble, poor PO, significant dosage because remains in GI/excretion. Low plasma protein binding, however residual cidal effect that last longer than needed, allows for large once/day dosing.
Exc ≅ GFR; must adjust dosage in renal dysfunction proportional to creatinine clearance

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15
Q

What’s antibacterial spectrum of aminoglycosides?

A

GM (+): Staph > Strep; increased resistance, but used in combination with pens/cephs for serious staph, strep, enterococcal infections

Affects almost all Gm (-) organisms. Adm with 3rd/4th gen. pens for Pseudomonas, and with cephs for Klebsiella and also with other drugs for serious Gm (-) infections

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16
Q

When would you use streptomycin?

A

deep IM injections
With a penicillin for enterococcal endocarditis
Tuberculosis, Tularemia, plague (Y. pestis) usually with P.O tetracyclines
Has less activity against gram (-) rods than other aminoglycosides

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17
Q

When would you use gentamycin?

A

active against Serratia species and better than tobramycin when used in combination with a penicillin against enterococci; however, preferred with Pen

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18
Q

WHen would you use tobramycin?

A

2-4X more potent against Pseudomonas than gentamicin; however, it is less effective against enterococci and ineffective against mycobacteria

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19
Q

more resistant to microbial enzymes, used in gentamicin resistance, otherwise it is comparable to these drugs

A

Netilmicin

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20
Q

exhibits the greatest resistance; used in gentamicin & tobramycin resistance; less vulnerable to microbial enzymes because of protective side chain substitutions, more $$$

A

amikamicin

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21
Q

What are toxicities of aminoglycosides?

A

Ototoxicity - cochlear (esp. amikacin) and vestibular (esp. strepto and gentam), hair cell damage, esp. in combo with loop diuretics
contraindicated in pregnancy
Nephrotoxicity - induced renal failure
Neuromuscular blockade - respiratory difficulties

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22
Q

When would you use spectinomycin?

A

Only used as alternative to treat gonorrhea in patients allergic to pens/cephs or where gonococci are resistant to other drugs (i.e., fluroquinolones)
May also be used during pregnancy
Single IM injection

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23
Q

What’s mechanism of action of macrolides?

A

block 50S ribosome via lactone ring

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24
Q

How do bacteria become resistant to macrolides?

A

alteration of binding site, methylation in gram + bacteria 50S ribosome site)

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25
What's mechanism of action of erythromycin?
Primarily bacteriostatic, binds 50 S of bacterial ribosomes, inhibits protein synthesis. Bacteria resist via chaning binding site by methylation
26
What is pharmokinetics of erythromycin?
Decomposed by gastric HCL to irritant, adm PO as enteric-coated or esterified preps to reduce this decomposition Primarily biliary\GI exc; urinary minor
27
What are ADRs of erythromycin?
GI disturbances, rash, allergy, cholestatic hepatitis, ototoxicity / tinnitus/ hearing loss
28
What is antibacterial spectrum of erythromycin?
Gm (+): alternative to pens/cephs for streptococcal and pneumococcal minor throat/ear infections, e.g. in pen/ceph allergy; resistant to penicillinases Gm (-): Legionella pneumophila, Mycoplasma pneumonia, Genital infections: Chlamydia, syphilis, gonorrhea, C. diphtheriae
29
What is erythromycin not valid against?
Gm - enteric organisms
30
What are indications to use clarithromycin?
Gm (+) spectrum ≅ ERY, but greater potency, t ½ Increased Gm (-) activity over others for Leg. pneumophila, C. trachomatis, Mycobacterium avium complex (AIDS); Helicobacter pylori, Borrelia burgdorferi
31
Whats pharmokinetics of clarithromycin?
Forms active metabolite in first pass Inhibits hepatic drug metabolizing enzymes Excretion primarily by urinary tract
32
What is the clinical use for Azithromycin?
Gm (+) strept activity ≅ ERY; alternates to B-lactams for pharyngitis, sinusitis, community-acquired pneumonia Increased Gm (-) H. influenzae, N. gonorrhoeae, Mycoplasma pneumoniae, Legionella pneumophila, B. burgdorferi, Chlamydia trachomatis
33
What's pharmokinetics of azithromycin?
Long t1\2 (2-3 days), initial loading doses may be indicated, adm once/day Primarily biliary/GI excretion unchanged; urinary minor, similar to erythromycin
34
What are drug interactions of erythromycin and clarithromycin?
inhibit cytochrome P-450s > to increase adverse effects Cardiac arrhythmias (increase QT interval) leading to possible sudden death. Drugs that inhibit the metabolism of & increase blood levels of ERY may cause ERY-induced arrhythmias
35
What is mechanism, indication, and ADRs of Clindamycin
Bacteriostatic, binds 50S Spectrum: most gm (+) & anaerobes, Bacteroides/Clostridium Main clinical use: Gm (+) strepto- and staphylococcal infections, anaerobic infections Gm (-) usu. resistant ADRs: GI / diarrhea, superinfections, esp. pseudomembranous colitis due to overgrowth of Clostridium difficile within GI tract
36
What does clindamycin not do?
C. dificile
37
What is mechanism, and indication for linezolid (oxazolidinones)?
blocks 50S. Indicated for MRSA, Vancomycin resistant Enterococcus faecium / E. faecalis Bacteriocidal for streptococci, including those resistant to penicillins/cephalosporins
38
What are ADRs of linezolid?
Adverse: diarrhea, headache, rash, dec platelets/anemia with prolonged treatment MOA inhibitor, caution with sympathomimetics
39
What is spectrum of cloramphenicol (inhibit 50S)?
Broad spectrum: gm (+), gm (-), anaerobes, esp. H. inf. meningitis, Salmonella typhi, Rickettsia; not effective for Pseud. aeruginosa or Chlamydia
40
What are ADRs of chloramphenicol?
gray baby syndrome, inhibits CYP450 enzymes, anemia
41
What are indications for metronidazole?
Effective against protozoa & anaerobic bacteria, DOC Clostridium difficile Forms reactive intermediate (radical) > damages DNA
42
Contrindications of metronidazole
GI disturbs/metallic taste, headache \ paresthesias, ataxia, liver dysfunction Disulfiram rx (alcohol) Contraindicated in pregnancy, mutagenic
43
What is mechanism of quinupristine-Dalfopristine
Classified as a streptogramin, two drug synergistic combination inhibiting protein synthesis, binds 2 sites on 50S ribosomal subunit; IV adm
44
What are indications and ADRs of quinupristine-dalfopristine?
Main indication resistant gram (+) infections; MRSA, drug resistant Strep. pneumoniae, vancomycin-resistant Enterococcus faecium (VREF), but not VRE faecalis ADRs: GI/N-D, pain/phlebitis @ inj site, arthralgia, myalgia,inhibitor (CYP3A4)
45
What is mechanism of Fosomycin?
Blocks cell wall synthesis by inhibiting enolypruvate transferase
46
What are indications and ADRs of fosfomycin?
New cidal drug approved for UTIs due to common Gm (+) / Gm (-) urinary pathogens Excreted unchanged in urine ADRs GI-diarrhea, headache, vaginitis
47
broad spectrum
chloramphenicol, tetracyclines, aminoglycosides
48
moderate spectrum
macrolides and ketolide
49
narrow spectrum
streptogrammins, lincosamides, and linezolid
50
What is mechanism of action of penicillins/cephalosporins?
Drugs bind / inhibit PBPs (penicillin-binding-proteins), the bacterial transpeptidase enzymes required for new bacterial cell wall synthesis (i.e., peptioglycan cross-linking)
51
Which strain of staph is able to modify PBPs to reduce binding
MRSA
52
What's pharmokinetics of 1st gen Penicillin G?
low oral bioavailability, acid-labil, H2O soluble drugs, low penetration CNS very little, t 1/2 Excretion – unchanged in urine via tubular secretion so Probenecid given to slow tubular secretion antibiotics
53
Which first generation penicillin is reliably absorbed orally?
penicillin V
54
What is spectrum of penicillin G does it cross rxn?
Staph (non-R); Strep species (pneumonia), Spirochetes ,Borrelia burgdoferi (Lyme disease) Serious enterococcal (gram +) infections with aminoglycosides Pen G not resistant to B-lactamases Cross-reactivity to other pens regarding the allergic reactions
55
What is spectrum of penicillin R?
Indicated only for resistant staphylococcal infections, if serious add an aminoglycoside; i.e. B-lactamase-producers nafcillin (not effective against MRSA) Used in initial therapy when resistance with these organisms is suspected. If cultures are negative for B-lactamase, switch to regular penicillin if practical
56
What is spectrum of 2nd generation penicillins?
reliable oral bioavailability vs pen G Gm (+) spectrum same as Pen G and some Common gram (-) rods: E. coli, P. mirabilis, H. influenzae, Salmonella / Shigella, anaerobes
57
Whta do 2nd generation penicillins not work against?
Not effective against gram (-) Proteus vulgaris, Pseudomonas aeruginosa, Serratia, Gonococci Not resistant to B-lactamases
58
What are indications and and faults of 3rd generation penicillins?
Gm (+) activity less than 1 or 2-gen Main indication: Gram (-) P. vulgaris, P. aeruginosa (often in combo with an aminoglycoside) Not resistant to B-lactamases (e.g., ticarcillin, poor oral bioavailability)
59
What is spectrum of 4th generation and is it resistant to Beta lactamase?
broad Requires parenteral administration Spectrum similar to 3-gen pens with greater potency/effectiveness against more gm (-) strains/species; Gm (+) similar to ampicillin Often used with an aminoglycoside Not resistant to B-lactamases
60
What are the beta lactamase inhibitor combos
clavulanic acid, sulbactam, tazobactum amoxicillin-clavulanic acid; piperacillin-tazobactam Basic antibacterial spectrum usually the same or slightly increased, hopefully the inhibitor ties up the lactamase so that the antibiotic is not inactivated
61
What are carbapenems and are they cross rxn?
M/A similar to Pens; Adm. I.V.; Broad spectrum: gm (+), gm( -), and anaerobes, doc for Enterobacter infections, not effective for MRSA; cross-reactivity with Pen allergic rxn. Cilastatin-inhibits breakdown of imipenem by inhibiting dipeptidase in renal tubules and reduces nephrotoxicity.
62
What are monobactams and are they crozz rxn?
Monobactams (e.g., Aztreonam) MA similar to pens; Adm. I.V.; high affinity for PBP of gm(-); poor affinity for PBPs of gm (+) or anaerobes; no cross-reactivity with Pen allergic rxn.
63
a glycopeptide that inhibits transglycosylase (cell wall synthesis) bactericidal for gm (+) bacteria (e.g. methicillin resistant S. aureus [MRSA]); Adm. I.V. except colitis; renal elim.(acute nephrotoxicity) ; no cross-reactivity with Pen allergic rxn
Vancomycin
64
cyclic lipopeptide, antibacterial spectrum is similar to vancomycin and also indicated for vancomycin resistant strains. Potential for muscle injury, especially in combination with statins.
daptomycin
65
1st and 2nd gen cephlasporins are more... than 3rd/4th
hydrophilic
66
Which cephs are excreted biliary?
cefoperazone and ceftriaxone
67
What is spectrum for 1st generation cephs?
Gm(+) similar to pen G, but often effective against lactamase + staphylococci Gm (-) similar to 2nd-gen pens – not effective against gm (-) Proteus vulgaris, Pseudomonas aeruginosa, Serratia, Gonococci Preferred use for surgical prophylaxis (cefazolin); has longer t ½ than others
68
What is spectrum of 2nd generation cephs and is it active against pseudamonas?
against beta-lactamase-producing H influenzae or K pneumoniae and penicillin-resistant pneumococci Effective against Bacteroides fragilis & most anaerobes (cefoxitin) Not active against P. aeruginosa
69
What is 3rd generation spectrum?
used in Gm (+) meningitis (e.g. pneumonococci) due to good lipid solubility to penetrate CNS Ceftriaxone doc for resistant gonorrhea (N. gonorrhoeae), and meningitis Cefixime and cefdinir can be used orally in place of ceftriaxone Increased Gm (-) potency, covers most Enterobacteriaceae & anaerobes (Cefotaxime) Some activity against P. aeruginosa, but only ceftazidime and Cefoperazone
70
What is spectrum of 4th gen cephs (ex. cefpime)?
Good activity against Enterobacteriaceae (Enterobacter) that are resistant to 2nd /3rd generation cephalosporins
71
What is limitation of 4th gen cephs?
MRSA
72
What's mechanism of action of quinolones/fluros?
Bactericidal, MA inhibits bacterial DNA gyrase, bacterial enzyme more susceptible than human counterpart Resistance involves decreased binding to gyrase and uptake by bacteria, and increased efflux of drug
73
What's indications and pharmokinetics of 1st gen quinolones (nalidixic acid and cinoxacin)?
Used infrequently for lower Urinary Tract Infections (UTIs) for common Gm negative organisms, e.g. E. coli Rapidly absorbed, rapidly excreted ADRs: rash / GI disturbances
74
What are pharmacokinetics of 2nd gen fluroquinolones (ciprofloxacin, oflofloxacin)?
Good PO, but interference by antacid formulations with Al, Mg, Zn, Fe, Ca may result in 50% decrease. Mixed excretion: urine/GI, and accumulate in renal failure except moxifloxacin (biliary excretion) Ciprofloxacin inhibits CYP-450 drug metabolizing enzymes, may increase t1/2 of other drugs
75
What is spectrum of 2nd gen fluroquinolones?
Broad gram (-): most Klebsiella, Enterobacteriaceae, Pseudomonas (Cipro most active/potent), Hemophilius, Mycobacteria, Legionella Selected gram (+): some Staph. aureus, active against penicillinase producer
76
What is clinical indication for 2nd gen fluroquinolones?
(Travelers diarrhea), respiratory (community-acquired pneumonia), otitis media; advantage of PO in serious gram negative infections, e.g., Pseudomonas; use for prophylaxis in neutropenic patients (e.g. Ofloxacin)
77
Whatare ADRs of fluros?
GI/ CNS probs Skin: rash, allergy, photosensitivity (2 types): photoallergic (uncommon) and phototoxicity, highest incidence with lomefloxacin, crystalluria may occur in alkaline urine, swelling joints. Not used in pregnancy
78
What are pharmokinetics of 3rd gen fluro
increased PO absorption, inc Vd Spectrum: increased Gm +, esp. for streptococci; Gm – similar to Cipro; however Cipro generally considered most active against Gm – bacteria *Levofloxacin, t ½ - 7 hr *Moxifloxacin, t ½ - 10 hr
79
What's mechanism of action for sulfanoamides? and does is cross rxn
Bacteriostatic, synthetic analogs of PABA essential for bacterial synthesis folate Inhibit dihydropteroate synthase, enzyme catalyzing conversion PABA to dihydrofolic acid required for DNA synthesis No cross-reactivity with Pen allergic rxns.
80
What is spectrum of sulfanomides?
Gm (+): strepto-, gono-, meningococci , but generally not used alone due to inc resistance and preference for bactericidal drugs Gm (-): E. coli, P. mirababilis for uncomplicated UTIs; this is main indication for systemic use of sulfonamides and H. influenzae/ H. ducreyi and Chlamydia trachomatis, Nocardia asteroides infections (lung/brain infection/abscess)
81
What are pharmakokinetics of sulfanoamides?
Good PO bioavailability Excretion: mainly urinary, both metabolites and unchanged, alkaline urine favors solubility and excretion
82
What are clinical indications of sulfanomides
Systemic use: sulfisoxazole and sulfamethoxazole, primarily for UTIs Local use: sulfasalazine, bowel lumen (ulcerative colitis) Topical use: sulfacetamide (ophthalmic infections)
83
What are ADRs of sulfanoamides?
Allergy - Hematologic - hemolytic anemia esp. with G-6-PD deficiency, bone marrow suppression CNS- newborn at risk to dev. Kernicterus (yellow pigment in basal ganglia due to Bili “the bully” rubin) Renal – nephrotoxicity / crystalluria in acidic urine (low pH) GI disturbances May decrease absorption / drug levels of oral contraceptives and folic acid
84
What are sulfas and TMPSMX not good for
Not effective for enterococci, Pseudomonas aeruginosa, or anaerobes
85
What is spectrum of TMPSMX?
Gm (+) activity against Staph (MRSA) and strept, but increased resistance and variability Gm (-) activity is main indication and includes most Gm (-) bacteria and Enterobacteriaceae, not Pseudomonas Indications: UTIs, GI, respiratory infections (doc for Pneumocystis jiroveci), prostatitis / vaginitis, otitis media
86
What's ADRs of TMPSMX?
rashes Increase risk life-threatening toxic epidermal necrolysis GI disturbances Less renal effects; usually no urinary crystalluria; weak base Increased incidence of adverse effects in AIDS patients with TMP/SMX : fever, rash, decreased blood cells; folate deficiency may cause macrocytic anemia; supplement w/folinic acid
87
How do you treat UTI?
Caused by Microbiology: E. coli (80%), Staph saprophyticus, Proteus, Enterococci, Klebsiella, Pseudomonas, other Gm negatives Treatment (PO); FQ; TMP/SMX:– 3 days treatment. In pregnancy usually 7 days (no FQ, no sulfonamides near term)
88
How do you treat prostatitis?
Males < 35 with infection often due to C. trachomatis – Ofloxacin Older males infection usually Enterobacteriaceae (E. coli) or Pseudomonas or enterococcus – FQ usually Cipro or ofloxacin or TMP/SMX

Pharm (9 decks)

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