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PHAR 152 Extra* > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What are the major antibiotic catagories?

A

Beta-lactams (penicillins, cephalosporins, carbapenens)

Macrolides and clindamycin

Tetracyclines/glycylcyclines

Glycopeptides

Aminoglycosides

Quinolones

Sulfonamides and trimethoprim

Metronidazole

Linezolid

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2
Q

How is the mechanism of action of penicillins?

A

Penicillins bind to peniciilin-binding protein (PBP), resulting in inhibition of peptidoglycon synthesis and activation of autolytic enzymes in cell wall

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3
Q

How does resistance to penicillins develop?

A

Production of beta-lactamase (increased drug break down)

Lack of penicillin binding proteins

Efflux of drug out of the cell

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4
Q

What is the basic component of all penicillins?

A

The all share the same basic structure, 6-aminopeniciilanic acid (thiozolidine ring attached to a beta-lactam ring)

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5
Q

What are some natural penicillins?

A

Penicillin G:
Destroyed by stomach acid, so it is only given IV or IM

Destroyed by beta-lactamases

Procaine and benzathine can prolong the effect of penicillin

Penicillin V:
More acid stable, but still needs to be taken on an empty stomach

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6
Q

What infections are treated with penicillin as the drug of choice?

A

Streptococci, pneumonococci, meningococci, spirochetes, clostridia, anaerobic gram+ rods and actinomyces

enterococci (hard to treat, but penicillin id best agent)

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7
Q

What are isoxazolyl penicillins (“anti-staphylococcus penicillins”)?

A

These penicillins have relative resistance to beta-lactamases and are designed to treat Staph aureus.

Not intended to be used for other gram + microorganisms like strep or pneumo. Ineffective against MRSA

ex. Methicillin, Cloxicillin, (Flucloxicillin, Dicloxicillin: not covered in sask)

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8
Q

What are aminopenicillins?

A

They are active against both gram + and - organism

Ampicillin: used IV, more acid stabile than natural penicillins, but cannot be used orally due to low bioavailability

Amoxicillin: used orally (better absorption vs. ampicillin). Often combined with clavulanic acid (b-lactamase inhibitor)

Use (gram positive): Strep, enterococci, Neisseria sp.

Use (gram negative):
non-b-lactamase producing H. influenzae, E. coli, P. mirabilis, Salmonella, etc

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9
Q

What are b-lactamases?

A

Beta-lactamases open the beta-lactam ring found in penicillins and cephalosporins and become inactive

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10
Q

What are some b-lactamases that are of particular interest?

A

b-lactamases of interest:

ESBLs (extended-spectrum b-lactamases): They are found in E. coli and K. pneumonia infections of the urinary tract. ESBLs show resistance against b-lactamase inhibitors

NDM-like (New Delhi metallo-beta-lactamase)
ex. acinetobacter baumannii. NDM-like b-lactamases have a grearer ability to destroy b-lactamase inhibitors vs. ESBLs

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11
Q

What are ureidopenicillins?

A

They are broad spectrum, but have increased activity against gram - rods

Piperacillin is used parenterally against P. aeruginosa

Sometimes combined with b-lactamase inhibitor (tazobactam)

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12
Q

What are some general pharmacokinetics among penicillins?

A

Oral bioavailability varies between different types of penicillins (some penicillins are IV only like Pen G)

Wide distribution of drugs across body including CNS

Most are excreted by the kidney (need multiple doses/day)

Most oral penicillins should be taken on empty stomach (except amoxicillin)

Safe for pregnant and lactating women

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13
Q

What is a drug interaction with penicillins?

A

Penicillins can reduce the efficacy of oral contraception. Unplanned pregnancies are rare, but possible

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14
Q

What administration route for penicillins is the most effective?

A

If disregarding patient comfort and convienence, we can give penicillins via IV for best pharmacodynamic effect. The IV is supplying drug continuously (used in severe conditions)

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15
Q

What are some adverse effects following the use of penicillins?

A

Allergic reactions (most reported are not real allergies)
Anaphylactic shock, serum sickness, and fever should be taken seriously and get MD to take a look

Seizurem encephalopathy delirium

Neutropenia, thrombocytopenia )seen in longer duration use of penicillins)

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16
Q

What are cephalosporins?

A

They are a class of drugs that are structurally characterized by the core molecule (7-aminocephalosporanic acid)

They have similar mechanism of action compared to penicillins

Resistance:
Organisms that lack penicillin binding protein (PBP)
b-lactamases produced by Staph aureus and gram negative bacilli
Drug Efflux
Inability of drug to penetrate

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17
Q

What are first-generation cephalosporins?

A

Oral: cephalexin, cefadroxil

IV/IM: cefazolin

Active against gram positive cocci and some gram negative bacilli (E.coli, Proteus, and Klebisella)

These drugs do not penetrate CNS, therefore do not use in meningitis

They are not the DOC for any condition except for cefazolin for surgical prophylaxis

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18
Q

What are second-generation cephalosporins?

A

Oral: Cefuroxime axetil, cefprozil

IV/IM: cefuroxime

Active against organisms covered by first generation cephalosporins + greater coverage of gnb (H. influenzae), but not P. aeruginosa

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19
Q

What are cephamycins?

A

Cefoxitin is a cephamycin and it is associated with second generation cephalosporins.

Cephamycins are used in mixed aerobic/anaerobic infections (found in diabetic foot infections or punctured pancreas)

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20
Q

What are third generation cephalosporins?

A

These drugs are the most commonly used cephalosporins. Most are IV drugs except cefixime
ex. Cefotaxime, cefttriaxone

Ceftazidime (reserved for P. aeruginosa)

Decreased activity activity against gram positive cocci except Strep pneumoniae

Enhanced activity against hram negative bacilli

Ability to penetrate the CNS (unlike first and second generation cephalosporins)

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21
Q

What are fourth generation cephalosporins?

A

Cefapime (enhanced activity against Enterobacter and Citrobacter); active against P. aeruginosa (Cefapime is almost reserved for P. aeruginosa)

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22
Q

What are fifth generation cephalosporins?

A

Ceftaroline and ceftobiprole have actvity against MRSA, ampicillin sensitive E. faecalis and penicillin resistance S. pneumonia

Due to their usefullness and broad-spectrum, they are rarely prescribed

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23
Q

What are some adverse effects associated with cephalosporins?

A

Cephalosporins in general are considered to be safe

Hypersensitivity
Diarrhea
Skin rash
Fever, granulocytopenia, hemolytic anemia
Gallstones after ceftriazone use

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24
Q

What are carbapenems?

A

These drusg are very broad spectrum, useful but are extremely susceptioble to resistance

Structurally related to beta-lactams

Imipenem-cilastatin and meropenem:
Activity against gram positive and gram negtive, including Pseudomonas and anaerobic organisms

Ertapenem (long half-life):
Poor activity against Enterococcus sp. and P. aeruginosa

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25
Q

What are monobactams?

A

They are characterized by monocyclic beta-lactam ring

Resistant to most beta-lactamases (Not active against ESBLs or AmpC b-lactamases)

Need Special Drug Acess to recieve Azteonam, but it is active against gram negative bacilli including P. aeruginosa

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26
Q

What are macrolides?

A

They are generally bacteriostatic and work by attaching to bacterial ribosomes and inhibiting protein synthesis.

ex. Erythromycin, clarithromycin, and azithromycin

These drugs are reserved for penicillin allergic patients die to side effect profile

Resistance:
Methylated rRNA receptor
Inactivating enzymes
Active Efflux

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27
Q

What is the spectrum of activity for macrolides?

A

Gram positive:
pneumococci, streptococci, and corynebacteria

ex. M. pneumoniae, Chlamydia trachomatis, C. pneumonophillia
Bordatella pertussis, Campylobacter jejuni, and Helicobacter pylori

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28
Q

What is erythromycin?

A

It is a macrolide and it is available as an IV or oral drug. IV formulations can cause phlebitis (burned veins)

Adverse effects:
GI (patients vomit out doses)
Cholestatic hepatitis (especially increased with estolate formulation of erthryomycin)

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29
Q

What is a drug interaction with erythromycin?

A

When used concurrently with CYP 3A inhibitors, patients may experience QT prolongation/cardiac arrrhythmias

30
Q

What are clarithromycin and azithromycin used against?

A

Active against staphylococcus and streptococcus, with enhanced activity against a variety of organisms like L. pneumophilia, C. trachomatis, C. pneumoniae, M. catarrhalis, H. influenzae(azithro), M. avium, and other mycobacteria

31
Q

Can clarithromycin and azithromycin be used against MRSA?

A

Yes, some MRSAs are susceptible to these drugs

32
Q

If a microorganism is resistant to erythromycin, are all macrolides also ineffective?

A

Yes

33
Q

What are some unique qualities of azithromycin?

A

It has a long half-life which leads to high intracellular concentrations

5 days of azithro=10 days of claithro/erthyro

Longer ramp up and down of dose leads to more resistance

34
Q

What conditions are macrolides used to treat?

A

Upper respiratory tract infections

STIs

acne

35
Q

What are some drug interactions with macrolides?

A

Significant drug interactions especially with erythromycin and clarithromycin (inhibitors of CYP 3A4)

Many drugs are metabolised by this enzyme, so the use of clarithromycin and erthyromycin greatly affects their clearance
ex. antiarrythmics, antidepressants, benzodiazepines, anticonlvusants, statins

36
Q

What is clindamycin?

A

It has a similar mechanism to macrolides (distinct though). They can be delivered orally or parenterally (used to treat major and minor infections)

Active against anaerobes, S. aureus including some MRSA and streptococci

It is used in patients with penicillin allergies

It is not DOC for any condition

37
Q

What are some side effects associated with clindamycin?

A

Nausea, vomiting, diarrhea
Rash
Elevated LFTs (reduced liver function, but not as bad as macrolides)
Esophageal irritation

38
Q

Can clindamycin use cause diarrhea?

A

Clindamycin is a common cause of antibiotic-induced diarrhea (many patients avoid clindamycin for this reason)

39
Q

What are tetracyclines?

A

Tetracylines are bacteriostastic. Tetracylines work by binding to bacterial ribosomes and inhibiting protein synthesis
ex. Tetracyline, minocyline, doxycycline

Although tetracyclines are active against gram positive and negative organisms, they have high levels of resistance

DOC:
rickettsiae, Bartonella, chlamydiae, M. pneumoniae

Nocardia

P. acnes

40
Q

What are some common side effects associated with tetracyclines?

A

GI upset (nausea, vomitting, and diarrhea)

Skin rashes

Photosenstivity

Yeast overgrowth

Deposited in bones and teeth (do not use in kids under 8)

Hepatitis

Vestibular toxicity (dizziness, vertigo, ataxia) especially with minocycline

41
Q

What are some drug interaction with tetracyclines?

A

Some anticonvulsants may reduce tetracycline levels (phenobarbital, phenytoin, carbamazipine)

Multivalent cations (Fe and Ca) reduce absorption of tetracyclines

Increased INR and bleeding with warfarin

42
Q

What are glycylclines?

A

They are synthetic analogues of tetracyline-tigecycline complex. Can be administered IV or IM

Very broad spectrum:
It is active against many gram positive and negative organisms (MRSA, S. pneumoniae, enterococci, Salmonella, Shigella, Acinetobacter, and anaerobes

Eliminates through billary tract and feces

Due to its broad spectrum, it is reserved for resistant organisms

43
Q

What is vancomycin?

A

Vancomycin is a significant antibiotic, but no activity against gram negative organisms. Used oraaly for C. difficile alone, IV for everything else

Vancomycin works by inhibiting cell wall peptidoglycan (bacteriocidal)

Active against gram positive in some entericocci, penicillin resistant streptococcus pneumonia (PRSP), MRSA, clostridia, and some bacilli

DOC for MRSA infections and clostridioides

Resistance:
Vancomycin-resistant organisms (VRE), S. aureus, VISA

44
Q

What are the adverse effects of vancomycin?

A

Nephrotoxicity (especially if used in combo with nephrotoxins)

Ototoxicity (hearing and balance impairment)

Red-man syndrome (flush, nausea, but can be prevented if dosing rump up is more gradual)

Granulocytopenia (seen in prolonged therapy and must be monitored with vancimycin serum concentration tests)

45
Q

What are some drugs similar to Vancomycin?

A

Teicoplanin (structually similar to vancomycin)

Daptomycin (it is a lipopeptide and used once daily parenterally. myopathy is a side effect)

46
Q

What are aminoglycosides?

A

Aminoglycosides inhibit protein synthesis by binding to bacterial ribosomes. Administered via IV or IM. These drugs cannot enter the CNS and have a hard time penetrating other tissues as well.

This drug is eliminated by the kidneys, so it requires dose adjustment (need lab testing)

ex. Streptomycin, gentamycin, tobramycin, and amikacin (gentamycin is used most commonly)

Resistance:
Mutation or methylation of bacterial ribosomes
Enzyme breakdown of drug
Low permeability to drug
Efflux

47
Q

What is streptomycin used for?

A

It is a known TB drug in the aminoglycoside drug class

48
Q

What are some adverse effects follwing aminoglycoside use?

A

Nephrotoxicity
Ototoxicity
Neuromuscular blockade
Allergies are rare

49
Q

What are some drug interactions with aminoglycosides?

A

Other nephrotoxic drugs

Other ototoxic drugs

Neuromuscular blocking agents

50
Q

What are fluoroquinolones?

A

They inhibit DNA gyrase or topoisomerase II & IV (bacteriocidal and have concentration dependent killing). They have excellent oral bioavailability, so they are given orally in most cases
ex. Ciprofloxacin, levofloxacin, moxifloxacin

Activity against gram negative bacillus, Haemophilus sp., neisseriae, chalmydiae, etc. Reserve for resistant organisms and situations
where you cannot use the DOC

Resistance:
Alteration of the A or B subunit of DNA gyrase
Mutation in ParC or ParE of topoisomerase IV
Change in outer membrane permeability
Efflux pumps

51
Q

What is the unique spectrum covered by ciprofloxacin?

A

Ciprofloxacin (most active against P. aeruginosa, it was a breakthrough drug, needed IV drugs before. Do not use in upper respiratory inf. or anerobes)

52
Q

What is the unique spectrum covered by levofloxacin?

A

It has gram + and i activity, but usually used for gram +. It also has actviity against S. pneumoniae (gram-positive cocci)

53
Q

What is the unique spectrum covered by moxifloxacin?

A

It has actvity against anaerobes (unlike other fluroquinolones)

54
Q

What are fluoroquinolones used against?

A

Uses: urinary tract infections, STIs (formerly used against gonnorhea, but too much resistance now), lower
respiratory tract infections, enteritis/travellers
diarrhea, drug resistant mycobacterial
infections

55
Q

What fluoroquinolone is a bad choice for urinary infections?

A

Moxifloxacin is eliminated by the billiary pathway, it does not enter the urine. This means the antibiotic is never able to attack microbes in the urinary tract

56
Q

What side effects are associated with fluroquinolone use?

A

Fluroquinolones are infamous for killing people (many drugs in this class have been made unavailable for sale)

Side effects:
Nausea, vomiting, diarrhea
Insomnia, headache and dizziness
Other CNS effects including seizures
Skin rashes
Impaired liver function
Tendinitis/tendon rupture (reduce quality of life)
Prolongation of QTc interval
Hypo/hyperglycemia (can cause siezures in diabetics)
C.difficile
Peripheral neuropathy (nerve damage in extremities)

57
Q

What are some drug interactions with fluroquinolones?

A

Multivalent cations (Mg, Ca, Fe) can lower absorption of drug
Other drugs that prolong QTc interval
CYP 1A2 inhibition can increase levels of other drugs
Increased INR with warfarin

58
Q

What are some toxicities associated with fluoroquinolones?

A

Not used in children in fear of issues with bone development, we might have to begrudgingly use fluoroquinolones in kids for gram negative infections in kids with cystic fibrosis

59
Q

What are sulfonamides/trimethoprim?

A

Most common formulation is a combo of sulfamethoxazole and trimethoprim (also known as co-trimoxazole , do not confuse with clotriamazole). They are bacteriostatic on their own, but bacteriocidal together. It is available in oral dosing (single and double dose)

60
Q

What microbes are sulfonamides/trimethoprim active against?

A

Active against gram +, gram -, chlamydiae, nocardiae, and protozoa (no activity against anaeorobes)

Staphylocci (including MRSA)
Step. pneumonia (not Group A Strep)
S. maltophilia
Moraxella
H. influenza
Enterobacteriaciae
Brucella
Pneumocystitis jirovecii (commonlty seen in HIV-infected patients and drufgs from this class are used as prophylaxis)

61
Q

What is the mechanism of action for sulfamethoxazole (SMX)?

A

It is the most commonly used sulfonamide antibiotic. It is a structural analog of PABA and it competivtively inhibits DNA synthesis

62
Q

What is the mechanism of action for trimethoprim?

A

It inhibits enzymes involved in DNA synthesis (halts production of tetrahydrofolic acid)

63
Q

What are the uses of sulfamethoxazole/trimethoprim?

A

Urinary tract infections

Skin and soft tissue infections

MRSA

PJP

Many others

64
Q

What are some side effects associated with sulfamethoxazole/trimethoprim?

A

Most are caused by the sulfa component

Adverse reactions:
Skin rashes (can be lethal)
Hypersensitivity
headache
GI (N,V,D)
Bone marrow supression (reduced blood cell count, WBC and platelets are hit first)
Hyperkalemia & hyponatremia
photosensitivity

65
Q

What are some drug interactions with sulfamthoxazole/trimethoprim?

A

Drug interactions:
2C9 inhibitor; 3A4 substrate
Increased levels of
carvedilol, digoxin, phenytoin
Increased INR and bleeding with warfarin
Hypoglycemic agents
Increased risk of
hypoglycemia
Drugs which increase potassium levels

Contraindications:
First and third trimester of pregnancy (drug can bind to sites usually occupied by billibrubin, this can cause brain damage to fetus)

Caution in renal dysfunction

66
Q

What is metronidazole?

A

It’s mechanism of action is unknown, but maybe due to inhibition of nucleic acid synthesis. Mostly given orally due to excellent oral bioavailability

Active against anaerobes (including C. difficile)
Protozoa (trichomonas, Giardia)

Resistance: (unknown because susceptibility testingin anaerobes is tough)
Proprionibacterium

67
Q

What conditions are treated with metronidazole?

A

In community used for STIs, but used to deal with anaerobes in severe infections in hospitalized patients

68
Q

What are some adverse effects associated with metronidazole?

A

GI
Metallic taste
Headache
Dark urine
Peripheral neuropathy
Disulfiram-like reaction with alcohol (vomit, flush, nauseous)
Insomia
Stomatitis (mouth sores)

69
Q

What are some drug interactions with metronidazole?

A

Alcohol:
Disulfiram reaction

Warfarin:
increased INR and bleeding

70
Q

What is Linezolid?

A

Linezolid inhibit protein synthesis. Linezolids are usually bacteriostatic, but are bacteriocidal against Steptococci. It is available IV and oral.

Active against Streptococci (better agents available), Enterococci (including VREs), Staphylococci (including MRSA)

This drug is reserved for multi-drug resistant organisms and serves as an alternative to vancomycin

71
Q

What are some side effects associated with linezolid?

A

Headache
Nausea, vomiting diarrhea
Rash
Increased LFT’s
Myelosupression (decreased blood cell production)
Optic/peripheral neuropathy
Lactic acidosis
Decreased seizure threshold

72
Q

What are some drug interactions associated with linezolid?

A

Increased serotonin syndrome risk with SSRIs
and MAOIs

Rifampin decreases linezolid levels

PHAR 152 Extra* (4 decks)

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