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ACEM Part 1 > Pharmacology - Antimicrobials > Flashcards

Pharmacology - Antimicrobials Flashcards

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1
Q

How does Chloramphenicol work and what are some adverse effects

A

Mechanism:
Potent inhibitor of protein synthesis by binding to ribosome RNA 50s

Spectrum:
aerobic and anaerobic gram positive and negative, not active against chlamydia

Side effects:
gray baby syndrome
bone marrow suppression
nausea, vomiting, diarrhoea

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2
Q

Name some macrolides and describe their mechanism of action and spectrum

A

erythromycin, clarithromycin, azithromycin

Mechanism:
inhibit bacterial protein synthesis by binding to ribosomal RNA 50s

Spectrum:
Gram positive: strep, staphy, corynebacteria
Gram negative: neisseria, bordatella pertussis, treponema, campylobacter, chlamydia, legionella
other: mycoplasma (no cell wall)

Adverse effects:
anorexia, nausea, vomiting, diarrhoea
inhibit P450 enzymes
liver toxicity

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3
Q

What is the mechanism of action, indications and side effects of Azithromycin

A

Mechanism of action:
macrolide antibiotic acting by inhibiting protein synthesis by inhibiting RNA (50s)

Spectrum: haemophilus influenzae, chlamydia, mycobacteria, staph, strep, legionella

Side effect:
prolong QT interval

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4
Q

How does azithromycin differ from other macrolides

A

high tissue penetration
long elimination t1/2 (2-4 days)
single daily dosing
highly active against chlamydia

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5
Q

What is the mechanism, drug interactions and use of Erythromycin

A

Mechanism:
macrolide antibiotic that inhibits RNA protein synthesis by binding to 50s subunit
bacteriostatic but may be bacteriocidal at high concentrations

Hepatic inhibitor of CYP3A4
increases concentrations of: benzodiazepines, carbemazepine, digoxin, warfarin

Use:
corynebacteria infection, respiratory infection, ocular infection, chlamydia

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6
Q

What is the mechanism of action, spectrum and side effects of Flucloxacillin

A

Mechanism:
Beta lactam antibiotic
inhibits growth by binding to active site of penicillin binding protein
interferes with transpeptidation of bacterial cell wall synthesis, bactericidal

Spectrum:
staphylococci
streptococci
not MRSA, not anaerobes, not gram negatives

Side effects:
allergy/anaphylaxis
GI upset
nephritis
cholestatic jaundice
urticaria

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7
Q

What is the mechanism of action of Penicillin

A

beta lactam antibiotic
inhibits growth by binding to active site of penicillin binding protein
interferes with transpeptidation of bacterial cell wall synthesis
bactericidal

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8
Q

What are the pharmacokinetics of Penicillin

A

oral absorption impaired by food
wide distribution
poor CSF penetration (unless inflammation)
excreted into sputum and breast milk
rapidly excreted by kidney, need renal dose adjustment

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9
Q

What is the mechanism of resistance of Penicillin

A

inactivation by beta lactamase
modification of target PBP
impaired penetration of drug
antibiotics efflux pump

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10
Q

What are the clinical manifestations of a Penicillin allergy

A

anaphylaxis
fever
rash
serum sickness
steven johnson syndrome

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11
Q

What is the antimicrobial spectrum of Penicillin G

A

streptococci
meningococci
enterococci
some pneumococci
treponema pallidum

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12
Q

What antibiotics are used in staphylococcal infections

A

antistaphylococcal penicillins:
flucloxacillin, dicloxacillin, nafcillin

cephalosporins:
cephazolin, cephalexin

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13
Q

What is the mechanism of resistance in methicillin resistant staph aureus

A
  • beta lactam agents normally bind to penicillin binding proteins
  • MRSA produce penicillin binding proteins that have a low affinity for binding beta lactam agents
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14
Q

What is the mechanism of action of Cephalosporins?

A

beta lactam class
act by inhibiting cell wall synthesis
bactericidal

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15
Q

How are Cephalosporins classified

A

1st - very active against gram positive cocci (staph and strep), ex. cephazolin, cephalexin
2nd - active against same as 1st with extended gram negative cover, ex. cefaclor, cefuroxime
3rd - expanded gram negative, some active against pseudomonas, some cross BBB, ex, cefotaxime, ceftriaxone
4th - good activity against pseudomonas, cross BBB, ex. cefepime

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16
Q

Side effects of cephalosporins

A

Anaphylaxis
cross allergy with penicillin
rash
nephritis
haemolytic anaemia
thrombophlebitis

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17
Q

What type of antibiotic is cephazolin, how does it work and what is its spectrum

A

first generation cephalosporin
beta lactam agent, act by inhibiting cell wall synthesis

Spectrum:
very active against gram positive cocci (staph and strep)

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18
Q

Why are third generation cephalosporins used in CNS infections

A

expanded gram negative
some cross BBB
good toxicity profile

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19
Q

What pathogens responsible for CNS infection are not covered by Cephalosporins

A

HSV
listeria
resistant e coli

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20
Q

What is the relationship between Penicillin allergy and Cephalosporin allergy

A

5-10% cross allergenicity

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21
Q

What is the mechanism of action of ceftriaxone

A

Third generation cephalosporin
beta lactam
bacteriocidal
inhibits transpeptidation reaction of cell wall synthesis

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22
Q

What are the pharmacokinetics of ceftriaxone

A

t1/2 7-8 hours (given 1x/day)
excretion through biliary tract
no renal adjustment required
crosses the blood brain barrier

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23
Q

What are the indications for ceftriaxone

A

gram positive and extended gram negative over second generation
not active against pseudomonas
effective against haemophilus and neisseria
not degraded by beta lactamase

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24
Q

What is the mechanism of action and target organisms of Vancomycin

A

Mechanism:
inhibit cell wall synthesis by inhibiting transglycosylase enzyme
bactericidal

Spectrum:
gram positive aerobes (beta lactamase producing organisms, MRSA)
gram positive anaerobes (c difficile)

-dose adjust in renal impairment and obesity

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25
Adverse effects of Vancomycin
local phlebitis chills, fever flushing due to histamine release (red man syndrome) ototoxicity (rare) renal issues
26
What is the mechanism, pharmacokinetics, resistance and adverse effects of tetracyclines
-mechanism: inhibit protein synthesis by binding to RNA 30s, bacteriostatic -pharmacokinetics: variable, depending on which drug generally greater than 60% absorbed, impaired by food, calcium, dairy products, alkaline pH 40-80% protein bound widely distributed in tissues except CSF undergo hepatic metabolism, excreted in bile and urine -resistance: impaired influx, interference with binding to ribosomes, enzymatic inactivation -contraindication for use: pregnancy, children \< 8 years, breast feeding
27
What is the mechanism, pharmacokinetics and use of Doxycyline
Mechanism: inhibit protein synthesis by binding to RNA 30s, bacteriostatic Pharmacokinetics: 95-100% oral absorption not impaired by food 40-80% protein bound no CSF penetration t1/2 shortened by hepatic induction excreted in bile and urine Spectrum: rickettsiae mycoplasma chlamydia, pirochetes vibrio h pylori active in malaria Side effects: photosensitivity discoloration of teeth nausea and vomiting
28
What is the mechanism of action of Gentamicin
aminoglycoside irreversible inhibition of protein synthesis by binding to RNA 30s initial event is passive diffusion via porin channels across outer membrane, then O2-dependant transport
29
What are the pharmocokinetics of Gentamicin
poor oral absorption small volume of distribution low protein binding t1/2 2-3 hours highly polar so does not enter cells readily concentration dependent killing CSF 20% of plasma levels cleared by kidney excreted unchanged renal adjustment dose required
30
Uses and side effects of gentamicin
Spectrum: gram negative (e coli, pseudomonas, proteus, klebsiella, serratia) gram positive no anaerobic activity Resistance: production of enzyme that inactivates drug impaired cell entry deletion of receptor on 30s Side effects: reversible nephrotoxicity irreversible ototoxicity (vestibular dysfunction) prolongs NM blockade
31
What are the benefits of once daily dosing of Gentamicin (how does it improve clinical effectiveness)
- concentration dependant killing: at increased concentration, increased number of bacteria killed as faster rate - reduced toxicity: less time above critical concentration level - post antibiotic effect: activity lasts longer than detectable serum levels
32
How do Penicillins enhance efficacy of Gentamicin
penetration of cell enhanced by inhibition of cell wall synthesis by penicillins
33
What is the mechanism of action of Fluroquinolones (Ciprofloxacin, Norfloxacin)
Blocks DNA synthesis by inhibiting bacterial topoisomerase II (DNA gyrase) and IV
34
What are the pharmacokinetics of Fluroquinolones
Well absorbed, IV or PO High bioavailability renal excretion - need to adjust dose in renal failure
35
Uses of fluroquinolones + side effects
Spectrum: excellent gram negative good gram positive Uses: UTI sometimes TB campylobacter typhoid fever anthrax eradication of meningococcal carrier state side effects: may damage growing cartilage in children less than 18 years old, prolongs QTC, tendon rupture
36
Compare Norfloxacin to Ciprofloxacin:
Ciprofloxacin has greater activity against gram negatives and positives
37
What is the mechanism of action of sulfonamides
reversibly block folic acid synthesis by blocking dihydropteroate synthase
38
Why is Trimethoprim co-administered with sulfonamides
antibacterial synergism: block sequential steps in folic acid synthesis by blocking dihydrofolate reductase
39
What is the mechanism of action of Trimethoprim and how does resistance occur
inhibits bacterial dihydrofolate reductase, which inhibits folic acid synthesis and thus purine synthesis Resistance: reduced cell permeability increased production of enzyme DHF reductase alteration of binding site
40
Which drugs can be used against Pseudomonas?
- Aminoglycosides e.g. Gentamicin - Quinolones e.g. Ciprofloxacin - Cephalosporins e.g. Ceftazadime, Cefepime - Carbapenems e.g. Meropenem - Monobactams e.g. Aztreonam
41
What are the four drugs used for treatment of TB?
Rifampicin Isoniazid Pyrazinamide Ethambutol
42
What are the important principles of treatment of TB?
- Multiple drugs (usually all 4) are used initially - Prolonged course of ~ 6 months - Isoniazid and rifampicin are the most active agents
43
How does Rifampicin work and why is it used?
- Rifampicin works to inhibit RNA synthesis - Clinical indications include TB, meningococcal carriage and prophylactic agent for Haemophilus influenzae and Staphylococcal carriage, in combination therapy for osteomyelitis and prosthetic valve endocarditis
44
Pharmacokinetics of Rifampicin?
- Readily absorbed orally and widely distributed - Enters the CSF only when the meninges are inflamed - Excreted through liver and bile
45
Side effects of Rifampicin
orange coloured urine/sweat/tears rashes thrombocytopaenia nephritis hepatitis, cholestatic jaundice Can also cause a flu like illness if administered less than twice weekly, with fever, chills, myalgias, anaemia and thrombocytopaenia CYP-450 inducer - increased elimination of anti-coagulants, methadone, contraceptives and some anticonvulsants
46
What is the main side effect of ethambutol to be aware of?
Optic neuritis
47
How does Isoniazid work?
- Most active drug - Inhibits synthesis of mycolic acids, which are required to build cell walls – inhibits cell wall synthesis - Readily absorbed orally and wide distribution, including into CSF - Metabolised by liver and excreted in urine - Adverse reactions include provocation of vitamin B6 deficiency (therefore recommended to give doses of pyridoxine in patients at high risk for neuropathy), Isoniazid-induced hepatitis, tinnitus, fever and skin rashes
48
What are the different classes of anti-fungal medications for systemic infections?
Azoles (Ketoconazole, Fluconazole) Echinocandins (Caspofungin, Micafungin, Anidulafungin) Polyenes (Amphotericin B, Terbinafine) Mucocutaneous infections (Griseofulvin, Terbinafine) Topical therapy (Nystatin, Topical azoles e.g. Clotrimazole, Topical allylamines e.g. Terbinafine)
49
What agents are used to treated HSV and VZV?
Acyclovir Valacyclovir Famciclovir
50
What are the indications for Acyclovir in the ED?
- Viral encephalitis - Shingles (i.e. VZV) - Patients with HIV - Genital herpes
51
Describe the mechanism of action of Acyclovir
DNA polymerase inhibitor which inhibits DNA synthesis
52
What agents can be used to treat CMV?
* Valganciclovir * Ganciclovir * Foscarnet * Cifofivir
53
What is the mechanism of action, pharmacokinetics and indications for Acyclovir
-mechanism: inhibition of viral DNA synthesis by inhibiting viral DNA polymerase -pharmacokinetics: short half life of 2.5 hours (5 x daily dosing), low oral bioavailability, excreted unchanged wide distribution and CSF levels of 20-50% - indications: HSV encephalitis, VZV, HIV, genital herpes - side effects: nausea, vomiting, diarrhoea, headache, reversible renal toxicity, tremour, delirium, seizures
54
List some anti-influenza agents
oseltamivir amantadine
55
Details about Oseltamivir
-mechanism: neuraminidase inhibitors, disrupt viral replication, active against influenza a and b -indication: uncomplicated influenza, 5 day course if given within 36-48 hours of symptoms onset shortens duration and lessens severity of illness - use in ED: high risk groups, elderly, pregnant women, immunocompromised - prevention with vaccination is preferred
56
What are the mechanisms of action of Metronidazole?
- Anti-protozoal agent with potent anti-anerobic actions e.g. Bacteriodes, Fusobacterium, Clostridium, Trichomoniasis, Giardiasis, Amoebiasis - Disruption of the electron transport chain
57
How does Mupirocin work? What is it used for?
- Mupirocin is active against GP cocci, including MSSA and MRSA - Inhibits Staphylococcal tRNA synthetase - Topical treatment for minor skin infections and ? Staph carriage
58
What are the different chemotherapy options?
Primary chemotherapy refers to chemotherapy administered as the primary treatment in patients who present with advanced disease for which no alternative treatment exists e.g. chemotherapy Neoadjuvant therapy refers to the use of chemotherapy in patients who present with localised cancer e.g. chemotherapy + radiotherapy Adjuvant therapy is where chemotherapy is administered after surgery
59
What are some common anti-helminthic drugs?
- Albendazole - Ivermectin - Praziquantel
60
What are the indications for Pentamidine?
anti-protozoal indications: Pneumocystis jiroveci Trypanosomal infections Interferes with nuclear metabolism
61
What drugs are used for malaria prophylaxis?
- Chloroquine → areas without resistance P. falciparum e.g. Central America, Dominican Republic, Egypt and most areas in the Middle East - Malarone (Atovaquone and proguanil) and Mefloquine → areas with chloroquine-resistance P. falciparum e.g. all other areas except above and below - Doxycycline → areas with multidrug-resistance P. falciparum e.g. Thailand - Primaquine → terminal prophylaxis of P. vivax and P. ovale infections
62
CYP 450 Inducers
63
CYP 450 Inhibitors
64
Ribosome 30s v 50s inhibitors
Buy AT 30 CELL at 50 30: Amioglycasides, Teteracycline 50: Chloramphenicol, Erythromycin, Linezolid, Lincosamides (clindamycin)

ACEM Part 1 (38 decks)

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