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Year 3 - Drug Profiles > antibiotics > Flashcards

antibiotics Flashcards

1
Q

how do penicillins work?

A

Inhibits enzymes responsible for corss-linking peptidoglycans in bacterial cell walls, weakening the causing cell swelling, lysis and death

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2
Q

for what infections would you use benzylpenicillin or phenoxymethylpenicillin?

A

Streptococcal infection (including tonsillitis, pneumonia, endocarditis and skin and soft tissue infections).
Clostridial infection e.g. tetanus.
Meningococcal infection e.g. meningitis, septicaemia.

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3
Q

what are the side effects of taking penicillins?

A 
penicillin allergy (affects 1 in 10-100)
central nervous system toxicity
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4
Q

what are the contraindications to taking penicillins?

A

renal impairment
allergy
current C. diff. infection

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5
Q

what are the interactions with all penicillins?

A

Methrotrexate (reduce renal excretion, increasing toxicity); warfarin (enhance anticoagulant effect)

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6
Q

what two drugs make up tazocin?

A

piperacillin with tazobactam

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7
Q

what is tazocin used to treat?

A

pseudomonal infections

reserved for severe infections, broad spectrum of potential pathogens

e.g. Lower respiratory tract infection.
Urinary tract infection.
Intra-abdominal sepsis.
Skin and soft tissue infection.

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8
Q

what are the side effects of tazocin?

A

Gastrointestinal upset
antibiotic-associated colitis
hypersensitivity

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9
Q

what are the broad spectrum penicillins?

A

amoxicillin, co-amoxiclav

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10
Q

what are amoxicillin and co-amoxiclav used to treat?

A

Empirical treatment of pneumonia (Gram-positive (e.g. Streptococcus pneumoniae) or Gram-negative
pathogens (e.g. Haemophilus influenzae)

Empirical treatment of urinary tract infection (most commonly caused by Escherichia coli).

hospital acquired infection or intra-abdominal sepsis

combination treatment for H. pylori-associated peptic
ulcers.

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11
Q

what makes up co-amoxiclav and what extra function does this have?

A

β-lactamase inhibitor clavulanic acid increases the spectrum of antimicrobial activity further to include β-lactamase-producing bacteria
(e.g. Staphylococcus aureus, Gram-negative anaerobes).

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12
Q

what extra function does flucloxacillin have?

A

acyl side chain protects the β-lactam ring from

β-lactamases. This makes flucloxacillin effective against β-lactamase producing staphylococci.

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13
Q

what infections is flucloxacillin used to treat?

A

Staphylococcal infection, including:
Skin and soft tissue infections such as cellulitis
Osteomyelitis and septic arthritis.
Other infections, including endocarditis.

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14
Q

name 2 cephalosporins and 2 carbapenems.

A

cefalexin, cefotaxime, meropenem, ertapenem

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15
Q

what are the indications to take cephalosporins or carbapenems?

A

second- and third-line treatment options for
urinary and respiratory tract infections.

reserved for the
treatment of infections that are very severe or complicated, or caused
by antibiotic-resistant organisms. Due to their broad antimicrobial
spectrum they can be used for most indications

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16
Q

how do cephalosporins and carbapenems work?

A

inhibit enzymes responsible for cross-linking peptidoglycans in bacterial cell walls. This weakens cell
walls, preventing them from maintaining an osmotic gradient, resulting in bacterial cell swelling, lysis and death.
Both types of antibiotic have a broad spectrum of action. naturally more resistant to β-lactamases than penicillins

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17
Q

what are the side effects of cephalosporins and carbapenems?

A

GI upset
antibiotic-associated colitis
Hypersensitivity
central nervous system toxicity including seizures (particularly where carbapenems are prescribed in high dose or to patients with renal impairment)

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18
Q

what are the contraindications to taking cephalosporins and carbapenems?

A

risk of C. difficile infection,
allergy
epilepsy
renal impairment

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19
Q

what are the interactions with cephalosporins and carbapenems?

A

enhance the anticoagulant effect of warfarin
Cephalosporins may increase nephrotoxicity of
aminoglycosides.
Carbapenems reduce plasma concentration and efficacy of valproate.

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20
Q

what class of drug is trimethoprim?

A

diaminopyramidine

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21
Q

how does trimethoprim work?

A

inhibits bacterial folate synthesis, slowing bacterial growth

broad spectrum of action against Gram-positive
and Gram-negative bacteria, particularly enterobacteria, e.g. Escherichia
coli.

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22
Q

what infections is trimethoprim used to treat?

A

first choice for uncomplicated urinary tract

infections (UTI).

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23
Q

what are the side effects with trimethoprim?

A

GI upset, skin rash, hypersensitivity

haematological disorders such as megaloblastic anaemia, leucopenia and thrombocytopenia. (folate antagonist)

hyperkalaemia and elevation of plasma creatinine concentrations.

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24
Q

what are the contraindications to taking trimethoprim?

A

pregnancy (1st trimester)
folate deficiency
renal impairment
children, elderly, immunosuppressed (more at risk of side effects)

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25
Q

what are the interactions with trimethoprim?

A

Use with potassium-elevating drugs (e.g. aldosterone antagonists, ACE inhibitors) leads to hyperkalaemia.

Use with folate antagonists (e.g. methotrexate)
and drugs that increase folate metabolism (e.g. phenytoin) increases the risk of adverse haematological effects.

Trimethoprim can enhance the anticoagulant effect of warfarin by killing normal gut flora that synthesise vitamin K.

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26
Q

how does nitrofurantoin work?

A

active metabolite damages bacterial DNA and causes
cell death

active against the Gram-negative (e.g. Escherichia coli) and Gram-positive (Staphylococcus saprophyticus) organisms that commonly cause urinary tract infections.

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27
Q

what infections is nitrofurantoin used to treat?

A

uncomplicated lower urinary tract infection (UTI)

particularly suited to the treatment of UTI as it is effective against the common causative organisms, reaches therapeutic concentrations in urine through renal excretion, and is most bactericidal in acidic
environments such as urine.

28
Q

what are the side effects of nitrofurantoin?

A

GI upset, hypersensitivity, turn urine dark yellow or brown

chronic pulmonary reactions (including
inflammation [pneumonitis] and fibrosis), hepatitis and peripheral neuropathy (more likely with prolonged administration)

In neonates - haemolytic anaemia (immature red
blood cells are unable to mop up nitrofurantoin-stimulated superoxides which damage red blood cells)

29
Q

what are the contraindications to taking nitrofurantoin?

A

pregnant women or babies
renal impairment
long term prophylaxis

30
Q

name 2 tetracyclines.

A

doxycycline, lymecycline

31
Q

how do tetracyclines work?

A

inhibit bacterial protein synthesis
bacteriostatic’ (stops bacterial growth), which assists the immune system in killing and removing bacteria from the body
relatively broad spectrum of antibacterial activity.

32
Q

what infections are tetracyclines used to treat?

A

Acne vulgaris

Lower respiratory tract infections - infective
exacerbations of COPD (e.g. Haemophilus influenzae), pneumonia and atypical pneumonia

Chlamydial infection including pelvic inflammatory disease.

Other infections such as typhoid, anthrax, malaria and Lyme disease

33
Q

what are the side effects of tetracyclines?

A

nausea, vomiting and diarrhoea (lowest
risk antibiotics for C. diff infection)

oesophageal irritation, ulceration
photosensitivity
discolouration and/or hypoplasia of tooth enamel Intracranial hypertension causing headache and visual disturbance.

34
Q

what are the contraindications to taking tetracyclines?

A

pregnancy, breastfeeding, children <12, renal impairment

35
Q

what are the interactions with tetracyclines?

A

bind to divalent cations - not be given within 2 hours of calcium, antacids or iron, which will prevent
antibiotic absorption.

enhance the anticoagulant effect of warfarin by killing normal gut flora that synthesise vitamin K

36
Q

what class of drug is gentamicin?

A

aminoglycoside

37
Q

what infections is gentamicin used to treat?

A

Severe infections, particularly those caused by Gram-negative aerobes

Severe sepsis, including where the source is unidentified.

Pyelonephritis and complicated urinary tract infection.

Biliary and other intra-abdominal sepsis.

Endocarditis.

38
Q

why should aminoglycosides not be give alone unless the bacteria is known?

A

Aminoglycosides lack activity against streptococci and anaerobes so should be combined with penicillin and/or metronidazole when the organism is unknown.

39
Q

how to aminoglycosides work?

A

inhibit protein synthesis
enter bacterial cells via an oxygen-dependent
transport system. Streptococci and anaerobic bacteria do not have this transport system

40
Q

what are the side effects of aminoglycosides?

A

nephrotoxicity and ototoxicity

41
Q

what are the contraindications to taking aminoglycosides?

A

neonates and the elderly
renal impairment.
impair neuromuscular transmission so should not be
given to people with myasthenia gravis

42
Q

what are the interactions with aminoglycosides?

A

Ototoxicity is more likely if aminoglycosides are co-prescribed with loop diuretics (e.g. furosemide) or vancomycin.

Nephrotoxicity is more likely if aminoglycosides are co-prescribed with ciclosporin, platinum
chemotherapy, cephalosporins or vancomycin.

43
Q

give 3 examples of macrolides.

A

clarithromycin, erythromycin, azithromycin

44
Q

how do macrolides work?

A

inhibit bacterial protein synthesis

broad spectrum of activity against Gram-positive and some Gram-negative organisms

resistance is common

45
Q

what infections are macrolides used to treat?

A

Treatment of respiratory and skin and soft tissue infections when penicillin is contraindicated by allergy.

In severe pneumonia added to a penicillin to cover atypical organisms including Legionella pneumophila and Mycoplasma pneumoniae.

Eradication of Helicobacter pylori in combination with a proton pump inhibitor and either amoxicillin or metronidazole.

46
Q

what are the side effects of macrolides?

A

nausea, vomiting, abdominal pain and diarrhoea when taken orally
thrombophlebitis when given IV.

allergy, antibiotic-associated colitis, cholestatic jaundice, prolongation of the
QT interval (predisposing to arrhythmias) and ototoxicity at high doses.

erythromycin has worst side effects

47
Q

what are the contraindications to taking macrolides?

A

severe hepatic impairment and severe renal impairment.

48
Q

what are the interactions with macrolides?

A

Caution with drugs which prolong QT interval (amiodarone, antipsychotics, quinine, quinolone antibiotics, SSRIs), drugs metaboliseed by P450 enzymes (warfarin, statins etc)

49
Q

give three examples of quinolones.

A

ciprofloxacin, moxifloxacin, levofloxacin

50
Q

what infections are quinolones used to treat?

A

reserved as second or third-line treatment due to
the potential for rapid emergence of resistance

Urinary tract infection (UTI).
Severe gastrointestinal infection, e.g. with Shigella, .
Lower respiratory tract infection (LRTI)
Ciprofloxacin is the only oral antibiotic in common use with activity against Pseudomonas aeruginosa.

51
Q

how do quinolones work?

A

inhibiting DNA synthesis
particularly active against aerobic Gram-negative bacteria
Bacteria rapidly develop resistance to quinolones

52
Q

what are the side effects with quinolones?

A 
neurological effects (lowering of the seizure threshold and hallucinations)
inflammation and rupture of muscle tendons.
prolong the QT interval - increase the risk of arrhythmias.
promote Clostridiumdifficile colitis
53
Q

what are the contraindications with quinolones?

A

risk of seizures
growing (potential risk of arthropathy)
risk factors for QT prolongation

54
Q

what are the interactions with quinolones?

A 
divalent cations (e.g. calcium, antacids) reduce
absorption and efficacy of quinolones

inhibits certain cytochrome P450 enzymes, increasing risk of toxicity with some drugs e.g. theophylline.

NSAIDs increases the risk of seizures, and of prednisolone increases the risk of tendon rupture.

drugs that prolong the QT interval or cause arrhythmias, such as amiodarone, antipsychotics, quinine, macrolide antibiotics and SSRIs.

55
Q

what infections is metronidazole used for?

A

of infections caused by anaerobic bacteria

Clostridium difficile

Oral infections (such as dental abscess) or aspiration pneumonia

Surgical and gynaecological infections

protozoal infections including trichomonal vaginal infection, amoebic dysentery, giardiasis.

56
Q

how does metronidazole work?

A

reduction of metronidazole generates a nitroso free radical.

This binds to DNA, reducing synthesis and causing widespread damage, DNA degradation and cell death.

57
Q

what are the side effects of metronidazole?

A

peripheral and optic neuropathy, seizures and encephalopathy.

gastrointestinal upset (such as nausea and vomiting) and hypersensitivity

58
Q

what are the contraindications to taking metronidazole?

A

metabolised by P450 enzymes, so the dose reduced in severe liver disease.

alcohol - inhibits acetaldehyde dehydrogenase, which
is responsible for clearing the intermediate alcohol metabolite acetaldehyde from the body.
taking metronidazole as the combination can cause a ‘disulfiram-like’ reaction, including flushing, headache, nausea and vomiting.

59
Q

what are the interactions with metronidazole?

A

inhibitory effect on cytochrome P450 - reducing metabolism of warfarin and phenytoin (increasing the risk of toxicity, including impaired cerebellar function)

cytochrome P450 inducers (e.g. phenytoin, rifampicin) reduce efficacy

60
Q

what class of drug is vancomycin?

A

glycopeptide

61
Q

how does vancomycin work?

A

inhibiting synthesis of the cell wall of Gram-positive bacteria

specific activity against Gram-positive aerobic and
anaerobic bacteria and is inactive against most Gram-negative bacteria

62
Q

what infections is vancomycin used for?

A

Treatment of Gram-positive infection, e.g. endocarditis, where infection is severe and/or penicillins cannot be used due to resistance (e.g. MRSA) or allergy.

Treatment of antibiotic-associated colitis caused by Clostridium difficile infection (usually second-line where metronidazole is ineffective or poorly tolerated).

63
Q

what are the side effects of vancomycin?

A

thrombophlebitis

red man syndrome - generalised erythema and may be associated with hypotension and bronchospasm

nephrotoxicity, including renal failure and
interstitial nephritis

ototoxicity, with tinnitus and hearing loss

blood disorders, including neutropenia and thrombocytopenia.

64
Q

what are the contraindications to taking vancomycin?

A

renal impairment and the elderly

65
Q

what are the interactions with vancomycin?

A

increases the risk of ototoxicity and/or nephrotoxicity when prescribed with aminoglycosides, loop diuretics or ciclosporin

Year 3 - Drug Profiles (9 decks)

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