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Pharmacotherapeutics I > Antibacterial Antibiotics Continued > Flashcards

Antibacterial Antibiotics Continued Flashcards

1
Q

Antibacterial Agents

A 
Interfere with protein synthesis by:
Interaction with bacterial ribosomes
Block initiation
Inhibition of tRNA synthesis
Multiple mechanisms leading to disruption of RNA processing
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2
Q

Direct binding to 50S substrate

A

Drug blocks binding of aminoacyl moeity of charged tRNA molecule to acceptor site of complex.
Drug prevents translocation of peptidyl tRNA from acceptor site to donor site on the 50S ribosomal subunit

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3
Q

Direct binding to 30S subunit

A

Drug blocks binding of amino acid charged tRNA to acceptor site of ribosomes mRNA complex
Drugs can block formation of initiation complex b/w ribosomes and mRNA, misread mRNA, block translocation of mRNA.

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4
Q

Protein synthesis inhibitor class may be “-static” or “-cidal” depending on?

A

Drug concentration
Site of infection
Infecting organism
ie. linezolid is -static for enterococi and staph but -cidal for strept

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5
Q

Aminoglycosides

A

Basic structure= aminocyclitol ring

Different side groups; different glycosidic linkages.

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6
Q

Aminoglycosides- 2 effects on bacterial cell resulting in death

A

Bind (-) charges in outer phospholipid membrane displacing cations that link phospholipids together resulting in disruption of wall and leakage of contents
Irreversibly disrupt protein synthesis by blocking initiation, misreading mRNA, blocking translocation.

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7
Q

Aminoglycosides gain access to the cell membrane how?

A

Via porin channels
Inhibited by acidic pH and anaerobic conditions
Enhanced by cell wall active ABX (synergism)

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8
Q

3 known mechanisms of resistance

A

Modification of aminoglycoside molecule by enzyme
Binding of aminoglycosides on rRNA altered
Reduced uptake of aminoglycosides.
To combat resistance use agents that target cell wall in conjunction w/ aminoglycosides.

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9
Q

Aminoglycosides- spectrum of activity

A

Active against aerobic gram-negative bacilli (klebsiella species, enterobacter, psudeomonas aeruginosa)
Little activity against anaerobes due to lack of stability
Tx- UTI, respiratory tract, skin and soft-tissue infections

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10
Q

Aminoglycosides- combination w/ other agents

A

To broaden coverage in serious illness (bacteremia or sepsis and psuedomonal infections)
For synergism w/ vancomycin or penicillins in the tx of endocarditis

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11
Q

Aminoglycosides- spectrum of activity

A

Exhibit concentration-dependent killing and have a pronounced post-antibiotic effect

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12
Q

Aminoglycosides- streptomycin

A

Useful in treating enterococcal infections

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13
Q

Aminoglycosides- gentamicin, tobramycin, amikacin

A

Most widely used Aminoglycosides.

Cross-resistance b/w these drugs

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14
Q

Aminoglycosides- Neomycin, kanamycin

A

Limited to oral or topical due to neprhotoxicity

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15
Q

Aminoglycosides-Spectinomycin

A

Structurally related to Aminoglycosides but lack amino sugars and glycosidic bonds. Used to tx for gonorrhea in PCN allergy patients.

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16
Q

Aminoglycosides- Adverse Effects

A

otoxicity- may be irreversible (sterptomycin is the most ototocix; not reported w/ genatamicin)
Nephrotoxicity- usually reversible

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17
Q

Aminoglycosides- Adverse Effects Neuromuscular blockage

A

Aggravate muscle weakness; respiratory paralysis in myasthenia gravis or Parkinson’s disease due to curare-like effect

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18
Q

Aminoglycosides- hypersensitivity

A

Hypersensitivity rxn not common (rash, fever, urticaria, angioneurotic, edema, eosinophilia)

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19
Q

Aminoglycosides- Rare reactions

A

Optic nerve dysfunction, peripheral neuritis, encephalopathy, pancytopeniam exfoliative, dermatitis, amblyopia

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20
Q

Aminoglycosides- Adverse Effects tobramycin

A

Bronchospam and hoarseness with inhalation solution

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21
Q

Aminoglycosides- streptomycin

A

Contains metabisulfits avoid in sulfite allergies.

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22
Q

Aminoglycosides Phamacokinetics

A

No oral absportion (parenteral administration)
Widley distributed in ECF
Insoluble in lipid
Poor distribution in bile, aqueous humor, bronchial secretions, sputum, CSF
Clearance is proportional to creatinine clearance.

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23
Q

Gentamicin Dosing Strategies

A

Once daily dosing- Recommended for most clinical situations. Exclusion of Gram (+) infections, CrCl<30 ml/min, CF, spinal cord infections and burn patients
Multiple daily dosing- smaller amounts more times a day

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24
Q

Aminoglycoside drug interactions

A

Increased nephrotoxicity w/ loop diuretics
Respiratory depression when given w/ non-depolarizing muscle relaxants
Neomycin effects digoxin levels

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25
Aminoglycosides- special populations-Category D
Amikacin, streptomycin, tobramycin, kanamycin
26
Aminoglycosides- special populations-Category C
Gentamicin, neomycin (minimal absorption of PO dose)
27
Aminoglycosides- special populations Breastfeeding
American academy of pediatrics (AAP) compatible
28
Tetracyclines- Semisynthetic
Tetracycline Doxycycline Minocycline
29
Tetracycline- broad spectrum
Gram (+), gram (-), aerobic and anaerobes. Mycoplasma pneumoniae. chlamydia, rickettsia, borrelia burgdorferi, inflammatory acne, sinusitis, inhalation anthrax, Concern for opportunistic infections
30
Tetracyclines- 3 groups based on PK traits
Short acting- Oxytertracycline, tertracycline (frequent dosing needed) Intermediate acting- demeclocycline (Tx of SIADH) Long acting- doxycycline and minocycline (BID dosing)
31
MOA of tetracycline
Inhibit protein synthesis by reversibly binding to the 30 S subunit of RNA
32
Tetracycline resistance
Bacterial efflux pump is the most important mechanism | Mutations that prevent entrance of TCN into the cell cause resistance.
33
Tetracyclones ROA and ADRs
Oral, parenteral, and ophthalmic GI- N/V/D most common, Modified GI flora can develop candidiasis C diff Bony-structures and teeth- binds to newly formed/forming bones and teeth Photosensitization Vestibular rxns- dizziness, vertigo Pseudotumor cerbri Lupus like rxn
34
Tertracyclines- pharmacokinetics
Absorption- Incomplete absorption from GI, impaired further by concurrent ingestion (Dairy, aluminum, Ca2+, Mg2+, iron, zinc, bimuth subsalicylates) Distribution- throughout the body including meninges, accumulation in the liver, spleen, bone marrow, bone, and enamel of unerupted teeth Elimination- mostly kidneys (except doxycycline through hepatic)
35
3rd Generation TCN- Tigecycline (tygacil)
Broad spectrum antimicrobial activity including MRSA Indicated for tx of complicated intra-abdominal infections and complicated skin and skin structure infections in adults Develped to overcome bacterial resistance mechanisms to TCNs
36
Chloramphenicol
50S inhibitor Broad spectrum- gram (+), gram (-) Due to blood dyscrasias it is reserved for life threatening infections such as typhoid fever, RMSF, and meningitis in pts allergic to PCN
37
Chloramphenicol- MOA
Both bactericidal and bacteriostatic depending on bacterial species Reversibly binds 50S inhibiting formation of peptide bonds Inhibits mitochondrial protein synthesis in mammalian cells Broad tissue distribution, CNS and CSF.
38
Chloramphenicol- contraindications
very limited use- never in neonates or pregnant women
39
Chloramphenicol-ADRs
Myelosuppression Reversible anemia Neutropenia and thrombocytopenia Gray baby syndrome in neonates (pallor, abd distention, vomiting, and collapse)
40
Chloramphenicol resistance
Plasmid born decreased cellular permeability Modification of enzymes- acetyltransferases Mutation leading to ribosomal insensitivity
41
Macrolides
50S inhibitors Erythromycin Semisynthetic derivatives: Clarithromycin and Azithromycin
42
Macrolides- MOA
Inihibit protein synthesis by binding to 50 S ribosomal unit, blocking translocation and preventing peptide elongation Bacteriostatic; at high concentrations or with rapid bacterial growth -> bactericidal
43
Macrolides- spectrum of activity
Erythromycin is effective against most gram (+) bacteria and spirochetes (Legionella pneumophila, N gonorrhoeae, N meningitidis) poor anaerobic coverage Clarithromycin- active against gram (+) and anaerobic bacteria (H. influenzae, H. pylori, mycobacterium avium) Azithromycin- as above with anaerobic coverage.
44
Macrolides-resistance
H. Influenzae resistant to erythromycin alone, susceptible in combo with sulfonamide Resistance is usually plasmid mediated.
45
Erythromycin Pharmacokinetics
Erythromycin base is destroyed by stomach acid and must be administered as enteric coated tablet or capsule. Widely distributed including prostate and macrophages Available PO, IV, and ophthalmic Erythro, azithro excreted unchanged in bile Clarithromycin excreted unchanged in bile and urine
46
Erythromycin Adverse Effects
GI- N/V/D and cramps, binds to motilin reveptor and increased peristalsis Cholestatic jaundice (most common with estolate salt form) CV- concern w/ macrolide ABX IV Ventricular arryhtmias (Erythro), palpitations, CP, Dizziness, HA, IV- QT prolongation
47
Semisynthetic Macrolides- Clarithromycin (Biaxin)
Spectrum of activity = to erythromycin + enhanced coverage of atypical mycobacteria. Less GI upset and BID dosing ADRs- N/D, abnormal taste, dyspepsia, HA, tooth discoloration, transient anxiety and behavioral changes
48
Semisynthetic Macrolides- Azithromycin (Zithromax)
Spectrum of activity- atypical mycobacterial and heamophilus influenza coverage Great tissue penetration and pronlonged intracellular 1/2 life Angioedema
49
Macrolide Drug Interactions
Extensive Erythro and clarithromycin= CYP3A4 substrates and inhibitors (erythro and clarithromycin are contraindicated w/ current use of cisapride. many interactions that increase/decrease effect- statins, ergots, dixogin, cabamezepine, warfarin) Azithromycin NOT metabolized by CYP3A4
50
Ketolides
New gen of macrolide ABX Semi-synthetic derivative of erythromycin Higher binding affinity to 50S subunit DIsplays greater potency against gram (+) organisms Displays activity against macrolide-resistant strains
51
Telithromycin (Ketek)
Tx of respiratory tract infects in 2004 Tx of CAP, sinusitis, bronchitis Feb 2007 dropped chronic bronchitis and sinusitis 2006 black box linked to liver failure and death
52
Telithromycin (Ketek)
Hepatic metabolism w/ elimination in bile and urine ADRs- N/D, HA, Dizziness, V, reversible LFT elevation, hepatitis, reversible blurred vision, diplopia, exacerbation of myasthenia gravis, and QT prolongation
53
Lincosamides: Clindamycin (cleocin)
Inhibits protein synthesis Spectrum of activity- gram (+)- strep, staph, pneumococci, anaerobes = gram (+) and (-) except C diff Available oral, IV, and topical
54
Clindamycin (cleocin)- clinical uses
Tx of anaerobic or mixed (polymicrobial infections) Perforated viscus, infections of the female GU tract, decubitis, venous stasis, or arterial insufficiencyulcers Aspiration pneumonia Mild inflammatory acne- topical
55
Clindamycin (cleocin)- Adverse effects
Gi-N/V/D Hepatotoxicity Neutropenia Most common ABx to cause Clostridium difficile toxin mediated to diarrhea
56
Streptogramins: Quinupristin Dalfopristin (Synercid)
Inhibit protein synthesis Bacteriostatic Indications- life threatening infections associated with VRE bactermia Tx of complicated skin/structure infections by Methicillin-suspeptible S aureus or S. pyrogenes
57
Quinupristin Dalfopristin (Synercid)
P450 3A4 inhibitor (nifedipine, cyclosporin drug interactions) IV only, limited tissue distribution, metabolized in the liver to active metabolites
58
Quinupristin Dalfopristin (Synercid) ADRS
Phelbitis, arthralgias, myalgias, hyperbilirubinemia
59
Ozazolidinones: Linezolid (Zyvox)- indications
Vanco-resistant enterococcus faecium (VRE), nosocomial pneumonia due to S aureus including MRSA or S. pneumoniae; complicated/uncomplicated skin/structure infections; gram (+) CAP
60
Ozazolidinones: Linezolid (Zyvox)- MOA
Prevents function of initiation complex Mechanism distinct from other 50S ribosomal inhibitors -> active bacteria that is resistant to other protein synthesis inhibitors.
61
Linezolid
Bacteriostatic against enterococci and staph; bactericidal against strept Oral and IV preps available Metabolized by non-P450 enzymes, excreted in urine
62
Linezolid- ADRs
GI, HA, thrombocytopenia, linezolid=MAOI-> HTN if used with adrenergic and serotonergic drugs

Pharmacotherapeutics I (23 decks)

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