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Med Pharm > Antibiotics 2 > Flashcards

Antibiotics 2 Flashcards

1
Q

CARBAPENEMS classification and indication

A
  • Broadest spectrum of β-lactams. G+/G-, anaerobes. Reserved for resistant infections.
  • Urinary tract infectionss
  • Lower respiratory tract infections
  • Bone, joint & skin infections
  • Intra-abdominal & gynecological infections, bacterial septicemia
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2
Q

Carbapenems

A
  • Impenem- with cilastatin- inhibits dehydroxypeptidase. resistant to most B-lactams. nausea, vomiting and increased risk of seizures
  • meropenem- fewer seizures
  • Ertapenem
  • Doripenem- intra abdominal and UTI’s. Not pneumonia
  • Side effect- decrease valproic acid–> increase risk of seizures
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3
Q

Aztreonam

A
  • a monobactam w/ a stand-alone β-lactam ring. Active only vs G- aerobes. Resists most β-lactamases of G- organisms
  • MECHANISM: Binds penicillin-binding protein-3 (PBP-3) of G- bacteria creating long unstable filamentous bacteria that lyse.
  • Excreted unchanged in urine - adjust dose for renal failure. Crosses inflamed meninges.
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4
Q

Vancomycin

A
  • IV for MRSA or nonresistant Staph if allergic to β-lactams. Not absorbed orally but has been used for local action for pseudomembranous colitis.
  • MECHANISM: binds to D-ala-D-ala terminus and prevents removal of terminal D-ala of pentapeptide chain attached to N-acetylmuramic acid residues of peptidoglycan.
  • SIDE EFFECTS:- Ototoxicity- Nephrotoxicity- Red man syndrome after rapid IV -> flushing of upper body & face, hypotension, tachycardia & shock. MECHANISM: histamine release (a vasodilator)
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5
Q

TELAVANCIN

A
  • a synthetic lipoglycopeptide derived from vancomycin given IV as a one time dose for hospital-acquired & ventilator-associated bacterial pneumonia from S. aureus only & for G+ complicated skin & skin structure infections
  • CAUTION: Potentially teratogenic. Avoid in pregnant women.
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6
Q

ORITAVANCIN

A
  • a lipoglycopeptide - single IV dose over 3 hrs for adults w/ acute bacterial skin & skin structure infections (ABSSSI) from susceptible G+ organisms including MRSA.
  • SIDE EFFECTS: headache, nausea, vomiting, diarrhea, limb and SQ abscesses. Watch for C. diff – induced colitis
  • CONTRAINDICATED w/ IV unfractionated heparin for 48 hours after administration b/c activated partial thromboplastin time (aPTT) test results remain falsely elevated
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7
Q

DALBAVANCIN

A
  • Vancomycin like antibiotic

- SIDE EFFECTS: nausea, diarrhea, headache

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8
Q

BACITRACIN drug type and mechanism

A
  • Cidal vs various G+ cocci & bacilli
  • MECHANISM: A lipid carrier (bactoprenol) transports the NAG/NAM complex to the outside of the cell where it is attached to the growing end of the peptidoglycan chain. Bactoprenol must be dephosphorylated before it can combine with NAM. BACITRACIN complexes with the pyrophosphate
    preventing dephosphorylation of bactoprenol thus This inhibiting cell wall synthesis.
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9
Q

BACITRACIN indications and side effects

A
  • Topical for minor cuts & scrapes
  • Ophthalmic ointment for ulcerative blepharitis & bacterial conjunctivitis due to various G+/G- organisms
  • Side effets- nephrotoxic
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10
Q

FOSFOMYCIN

A
  • For short course Tx of uncomplicated UTIs in women (Men don’t get uncomplicated UTIs.).

MECHANISM: Inhibits enolpyruvate transferase
blocking the addition of phosphoenolpyruvate to UDP-N-acetylglucosamine, the 2nd step in the synthesis of the Park Nucleotide (UDP-N-acetylmuramyl pentapeptide). NET RESULT: inhibition of cell wall synthesis

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11
Q

Aminoglycosides structure and use

A
  • Amino sugars attached in glycosidic links to an aminocyclitol ring. They are polycations - very polar. Usually given IV. Some given orally to clean out bowel.
  • Cidal G-
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12
Q

Aminoglycosides mechanism of action

A
  • MECHANISM: Enter periplasmic space of G- bacteria through porin channels. Pass through inner membrane by flowing down their electrochemical gradient. In the cell, they:
    a) inhibit initiation of protein synthesis.
    b) cause misreading of mRNA creating faulty proteins that insert into the membrane causing leakage & creating pores that facilitate Rx uptake.
    c) cause premature termination of protein synthesis and breaking up of polysomes into non-functional monosomes that are thought to contribute to their -> POST-ANTIBIOTIC EFFECT in G- rods.
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13
Q

Why are Aminoglycosides not effective against anaerobes?

A
  • AG’s penetrate the cell by traveling down electrochemical gradient created by the electron transport chain. anaerobes do not utilize oxygen therefore do not have electron transport chain
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14
Q

Why are Aminoglycosides often combined with B-lactams?

A
  • Used w/ β-lactams for synergism & G+ coverage.

- MECHANISM OF SYNERGISM: By inhibiting cell wall synthesis, β-lactams facilitate penetration of aminoglycosides.

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15
Q

What two areas do Aminoglycosides accumulate and why is this a concern?

A
  • renal cortex -> nephrotoxicity
  • endolymph of inner ear-> ototoxicity
    Degeneration of the auditory nerve can lead to permanent hearing loss.
    Auditory Sx: tinnitus, high-frequency hearing loss
    Vestibular Sx: vertigo, ataxia, loss of balance
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16
Q

Name the aminoglycosides

A

IV:
- Gentemicin- topical for wounds, catheter, and opthalmic
- Tobramycin
- Amikacin- Enzyme resistant for nosocomial
- Streptomycin
- Kanamycin
IV generally given 1x/day b/c of significant POST-ANTIBIOTIC EFFECT even after Rx levels are below the MIC. Must still adjust dose for renal function
Oral:
- Neomycin
- Paromomycin- to kill cysts of Entamoeba histolytica which cause amebic dysentery

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17
Q

What medical conditions should aminoglycoside use be avoided and why?

A
  • CAUTION IF PREGNANT! These Rxs accumulate in fetal plasma -> neonatal ototoxicity!
  • Myasthenia gravis is an autoimmune disease where there is an antibody against the nicotinic receptor at the neuromuscular junction creating extreme muscle weakness. Since aminoglycosides can also block this receptor, they can exacerbate the condition.
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18
Q

TETRACYCLINES class and mechanism

A
  • Broad spectrum STATIC vs G+/G- & some intracellular organisms. Lipid soluble – penetrate many tissues. Undergo enterohepatic recycling - levels can persist.
    MECHANISM: inhibit binding of aminoacyl tRNA to acceptor site of ribosome
19
Q

Short acting TETRACYCLINES

A
  • 6-8hrs
  • Tetracycline- for acne
  • Oxytetracycline- Opthalmic w/ polymyxin B
20
Q

Intermediate acting TETRACYCLINES

A
  • 12hrs
  • DEMECLOCYCLINE (generic) - For chonic dilutional hyponatremia in the syndrome of inappropriate ADH (SIADH).
    MECHANISM IN SIADH: inhibits a protein kinase in the kidney’s collecting ducts on which ADH depends
21
Q

Long acting tetracyclines

A
  • 16-18hrs- highly lipophilic
  • Doxycycline
  • Minocycline- – used for acne but associated w/ pulmonary complications e.g. polmonary lupus, hypersensitivity pneumonitis, pleural effusions.

Has immunomodulatory & anti-inflammatory activity: blocks synthesis of nitric oxide, activation of microglia, et al. -> ↓ neuronal damage. Thought responsible for improved stroke outcome if given within 6-24 hrs of stroke.

“Might” be neuroprotective in neurodegerative diseases e.g. Parkinson, Huntington’s, ALS, MS and moderately effective in rheumatoid arthritis.

Reports of an SLE-like syndrome (systemic lupus erythematosus). Reversible.

Rarely, chronic use -> nail, skin & sclera pigmentation but generally reversible. Black pigmentation of thyroid is asymptomatic. Blue-black pigmentation of gums from bone pigmentation is permanent.

22
Q

Tetracycline side effects

A
  • GI upset – Take with food
  • Brown discoloration of teeth – permanent!
  • Slowed growth -
    Photosensitivity, particularly with demeclocycline (1-2% of pts)
  • Expired Rx -> FANCONI-LIKE SYNDROME from nephrotoxic metabolite epianhydrotetracycline -> nausea, vomiting, polyuria, polydipsia, glucosuria, aminoaciduria, hyperchloremic metabolic acidosis.
    Rx INTERACTION: Absorption of all tetracyclines is ↓ by dairy products & antacids.
    MECHANISM: chelation with calcium phosphate
23
Q

Tigecycline

A

– A parenteral, long acting derivative of minocycline w/ similar side effects.

MECHANISM:  Same as tetracyclines but cidal in some species.  Greater activity vs tetracycline-sensitive G+/G- and MRSA from greater steric hindrance.

USES: complicated skin & intraabdominal infections; community acquired bacterial pneumonia

FDA: ↑ Risk mortality if hospital-acquired pneumonia, particularly if ventilator-associated pneumonia, complicated intra-abdominal infections or complicated skin and skin- structure infections.

↓ Dose in patients w/ severe hepatic impairment or ↓ clearance will ↑↑ t ½ & risk of toxicity
24
Q

Macrolides structure, class info and mechanism

A
  • Lactone ring + 1 or more deoxy-sugars. All are effective vs methicillin sensitive Staph aureus (MSSA), Moraxella catarrhalis, H. influenza

MECHANISMS:

    a) inhibit translocation from A to P site on ribosome
b) release peptidyl tRNA from ribosomes
c) block formation of initiation complex
25
Q

Name the macrolides

A
  • Erythromycin
  • Azithromycin
  • Clarithromycin
26
Q

Erythromycin

A
  • Macrolide
  • 1st Rx effective vs LEGIONNAIRES’ DISEASE ( intracellular pathogen Legionella pneumophila). It is now an alternate.
      Metabolites complex w/ cytochrome heme Fe2+ & inhibit CYP3A4, the isozyme that also metabolizes erythromycin.
  Can prolong cardiac repolarization -> Torsades de Pointes.  Risk ↑ if used w/ another Rx that inhibits CYP3A4 -> ↑ erythromycin levels.

  Doubles risk of sudden death.  Risk ↑ 5x if used w/ diltiazem or verapamil which are also 						metabolized by CYP3A4.

  PROKINETIC: Stimulates GI motility via motilin receptors.  Used post-op to stimulate peristalsis & speed gastric emptying.  Also causes abdominal cramps, nausea etc
27
Q

Azithromycin

A
  • Macrolide
  • Concentrates intracellularly
    USES: - Community acquired pneumonia
  • Legionnaires disease
  • Mycobacterium avium complex (MAC)
      T ½ 70 hrs.  It does not inhibit P450 and is excreted unchanged in the bile.  Monitor liver.

  FDA: It can cause abnormal changes in the electrical activity of the heart that might lead 				to potentially fatal irregular rhythms.  Risk in greater in patients with known Q-T prolongation or low K+ or Mg2+ levels.
28
Q

Clarithromycin

A
  • Macrolide
  • For community acquired pneumonia & Mycobacterium avium complex (MAC)
      Macrolides as a class appear immumodulatory.  They inhibit transcription of mRNA for proinflammatory cytokines (IL-8, NF-κB, AP-1).  Clarithromycin is particular 								active in this regard.

  CAUTION: Clarithromycin has caused dangerously low blood sugar.

  Inhibits CYP3A.  Caution using w/ colchicine -> ↑ risk fatal colchicine toxicity.  Try azithromycin which doesn’t inhibit P450.
29
Q

Telithromycin

A
  • A ketolide (macrolide derivative) w/ ↑ G+ activity. Same mechanism as macrolides but binds 2 separate domains on ribosome -> ↓ risk of resistance -> broader activity.USE: community acquired respiratory infections. Concentrates in pulmonary tissues & WBCs. Active vs β lactam & macrolide resistant organisms.Inhibits CYP3A4. Prolongs Q-T interval. Rarely, serious hepatotoxicity.BLACK BOX WARNING: contraindicated if myasthenia gravis. Fatal or life-threatening respiratory failure
30
Q

Chloramphenicol

A
  • IV for resistant & serious aerobic/anaerobic G+/G- infections, e.g. meningitis. Associated w/ serious & FATAL BLOOD DYSCRASIAS.MECHANISM: Inhibits binding of aminoacyl-tRNA to acceptor site (same as tetracyclines)PROBLEM: Inhibits mammalian mitochondrial peptidyltransferase. Erythropoietic cells are most sensitive -> leucopenia, thrombocytopenia & fatal aplastic anemia. ↓ G6PD predisposes to hemolytic anemia.
    Also inhibits cytochrome P450.GRAY BABY SYNDROME from CAMP is caused by:a) insufficient glucoronyl transferase by which to conjugate the drug for elimination.
    b) underdeveloped renal function by which to eliminate the drug.↑ Rx levels interfere with mitochondrial ribosomes -> a) depressed respiration

b) cardiovascular collapse
c) cyanosis (gray baby)

31
Q

QUINUPRISTIN/DALFOPRISTIN

A
  • Streptogramins given IV for MRSA & vancomycin- resistant infections. Together, they are synergistic.MECHANISM: Quinupristin releases peptidyl-tRNA from donor site of peptidyltransferase. Dalfopristin inhibits binding of aminoacyl-tRNA to acceptor site & of peptidyl-tRNA to donor site of peptidyltransferase.
    Inhibit CYP3ARARELY USED b/c only available IV & b/c of SIDE EFFECTS:
  • Superinfection -> colitis
  • Arthralgias/myalgias (30-40%)
  • Venous irritation (requiring a central catheter)
  • Hyperbilirubinemia (25%)
  • Vancomycin-resistant strains of Enterococcus faecium
32
Q

LINEZOLID

A
  • An oxazolidinone for Enterococcus faecium, MSSA, MRSA & other vancomycin-resistant infections. Can be STATIC or CIDAL depending on organism.Oral & IV. Risks: myelosuppression -> blood dyscrasias & colitis. Recommend weekly CBC.MECHANISM: Inhibits formation of the initiation complex on the ribosome.Weakly inhibits MAO-A and thus may cause 5-HT syndrome (restlessness, tremor, delirium, rigidity, myoclonus, hyperthermia, hyperreflexia, sweating, shivering, blunted senses, seizures, coma) when used with Rxs that enhance 5-HT activity (certain antidepressants).
	Chronic use can cause:		
a) reversible optic neuropathy
b) irreversible peripheral neuropathy
c) lactic acidosis
Do not use more than 28 days
33
Q

TEDIZOLID

A

– Another oxazolidinone. Pro-Rx given oral or IV for ABSSSI (acute bacterial skin & skin structure infections) from susceptible organisms, including MRSA.

MECH: Binds 50S ribosomal subunit thus inhibs prot synth.	 SIDE EFFECTS: nausea, vomiting, diarrhea, headache
34
Q

CLINDAMYCIN

A
  • risk of pseudomembranous colitis. WHAT CAUSES IT? Killing off other bacteria allow C. difficile to grow w/o competition for nutrients (see earlier discussion).Penetrates most tissues well except CNS, even if meninges inflamed.Many dosage forms. Uses: topical for acne / suppository for bacterial vaginosis / oral / IVMECHANISM: inhibits translocation from the A site to the P site of the ribosome.Has some immunomodulatory activity & has been used w/ high dose PCN for group A strep
35
Q

POLYMYXIN B

A
  • Effective vs G- organisms. Very nephrotoxic and neurotoxic – has caused neuromuscular block. Generally limited to topical use. IV on rare occasion.
    MECHANISM: cidal cationic detergent. It has a POSTANTIBIOTIC EFFECT.
    USES: Common bacterial infections of the conjunctiva & lids
    POLYMYXIN B is available alone or with other Rxs e.g.:
    - Neosporin ophthalmic solution/drops (polymyxin B + gramicidin + neomycin)
    - Neosporin G.U. irrigant for instillation into bladder (polymyxin B + neomycin)
    - Polymyxin B + bacitracin ophthalmic ointment
36
Q

COLISTIMETHATE

A
  • Colistin = polymyxin E and, like polymyxin B, it is a cidal cationic detergent. Very nephrotoxic and can be neurotoxic. IV/IM for various G- rods
37
Q

RIFAXIMIN

A
  • No significant systemic absorption.
    USES:
  • travelers’ diarrhea from noninvasive strains of E. coli
  • ↓ risk of hepatic encephalopathy in patients with advanced liver disease by ↓ the number of ammonia-producing bacteria.MECHANISM: binds DNA-dependent RNA polymeraseSide effects: flatulence, abdominal pain, urgency to defecateBecause of structural similarity to rifampin, may lead to cross-resistance & emergence of rifampin-resistant Staph
38
Q

MUPIROCIN

A
  • Topical for IMPETIGO from group A Strep, S. aureus or S. pyogenes.

MECHANISM: inhibits bacterial isoleucyl t-RNA synthetase

39
Q

RETAPAMULIN

A
  • A pleuromutilin topical ointment for IMPETIGO

MECHANISM: blocks acceptor & donor sites of peptidyl transferase

40
Q

NITROFURANTOIN

A
  • For prevention & Tx of G+/G- UTIs. Concentrates in renal tubules for a local effect.MECHANISM: Reduced by urinary tract bacteria to reactive intermediates that damage DNA, ribosomes, cell wall, etc.
    CAUTION: Discolors urine brown.Pulmonary reactions have been reported & may have contributed to deaths.
		Acute Sx: fever, chills, cough, pulmonary infiltrates during 1st week of tx.  Reversible
		Chronic Sx (6 months of Tx): malaise, DOE, cough, altered PFTs, pneumonitis, fibrosis.
Do NOT use if Hx of cholestatic jaundice or hepatic dysfunction with prior use.  Rarely, has led 					to hepatitis, jaundice, hepatic necrosis and death
41
Q

DAPTOMYCIN

A
  • Cidal parenteral lipopeptide for G+ & MRSA skin & systemic infections. NOT for pneumonia b/c inactivated by pulmonary surfactant.MECHANISM: forms pores in cytoplasmic membrane -> loss of K+ -> depolarization & inhibition of DNA, RNA & protein synthesisSIDE EFFECT: ↑ creatine kinase (CK) Excreted by kidneys unchanged
42
Q

QUINIDINE

A
  • IV for life-threatening Plasmodium falciparum.

CAUTION: can cause arrhythmias. Monitor ECG continuously

43
Q

RIFAMPIN

A
  • Penetrates tissues & biofilm well. Effective vs most G+ & many G- organisms. Good activity vs staph & MRSA.MECHANISM: Inhibits DNA-dependent RNA polymerase thus inhibiting RNA synthesis.Kills intracellular & extracellular organisms. Penetrates lung cavities & abscesses but use only in combination w/ other Rxs to prevent emergence of resistant organisms.Excreted mostly through bile -> enterohepatic recirculation. Adjust dose for liver function.Do not administer for less than 2 weeks or may cause a flu-like syndrome (fever, chills, myalgia)SIDE EFFECTS: - Red-orange color to urine, feces, saliva, sweat, tears (can stain soft contacts!)
  • Rash, fever, nausea, vomiting
  • Jaundice but fatalities rare
  • Hepatitis rare if normal liver – liver disease, alcohol, ↑ age all ↑ risk.
  • Enzyme inducer

Med Pharm (2 decks)

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