Antibiotics Flashcards

1
Q

Name anaerobic antibiotics

A

Metronidazole

Orala or IV or Gel

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2
Q

Indications of using metronidazole

A

1) C.Diff (gram +ve) - this is 1st line
2) Oral infections - due to gram -ve in the mouth
3) Aspiration pneumonia
4) Surgical and gynae infections due to gram -ve anaerbobes from the colon
5) Protozoal infections e.g. trichomonal vaginosis, dysentry, giardasis

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3
Q

Mechanisms of metronidazole

A

Passively diffuses into anaerobic bacterial cells
Reduced to generate a nitroso free radical
Binds to DNA
Reduces syntheses causing widespread damage - DNA degradation and cell death

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4
Q

Why doesnt metronidazole work on aerobic bacteria

A

As they dont reduce it to a nitrosos free radical

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5
Q

Is there resistance to metronidazole

A

Generally low resistance

But can be resistanct due to decreased uptake and decreased generation of nitroso free radicals

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6
Q

ADverse effects of metronidazole

A

1) GI Upset
2) Hypersensitivity
3) Neuro effects –> if at high doses or prolonged courses e.g. peripheral and optic neuropathy, seizures and encephalopathy

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7
Q

Warnings of metronidazole

A

Metabolised by hepatic CP450 ensymes –> reduce dose in hepatic impairment

Inhibits acetalderhyde dehydrogenase enzye –> this clears intermediate alcohol metabolite –> hence if you drink a disulfram-like reaction occurs –> flushing, headach, nausea and vomiting

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8
Q

What cant you do whilst taking metronidazole

A

Drink alcohol

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9
Q

Interactions of metronidazole

A

1) inhibitory effect on CP450 en`ymes
2) Excitory effect on CP450 inducers
3) Increased risk of lithium toxicity

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10
Q

What do we measure if we treat longer than 10 days on metronidazole

A

Measure FBC and LFTs

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11
Q

Indications of nitrofurantoin

A

1) Uncomplicated lower UTI - 1st line

Reaches therapeutic concentration in the urine through renal excretion

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12
Q

Action of nitrofurantoin

A

Metabolised in bacterial cells by nitrofuran reuctase

Its active metabolite damages bacterial DNA causing cell death

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13
Q

what organisms is nitrofurantoin active against

A

Gram +ve (staph. saprophyticus) and gram -ve (E. Coli) that cause UTIs commonly

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14
Q

What bacteria are resistant to nitrofurantoin

A

Bacteria with reduced nitrofuran reductase activity

Also less common causes of UTIs e.g. Klebsiella, Proteus have intrinsic resistant

Relatively rare for E. Coli to develop resistance

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15
Q

Adverse effects of nitrofurantoin

A

1) GI upset
2) Hypersensitivity
3) Chronic pulmonary reactions - pneumonitis, fibrosis
4) Hepatitis and peripheral neuropathy
5) haemolytic aneamia in neonates –> as immature RBCs are unable to mop up nitrofurantoin stimulated superoxides which damages RBCs
6) can turn urine dark yellow or brown

Patiet whousl warn if any unexplained symtpoms e.g.breathlessness

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16
Q

Contrainidcatinos of nitrofurantoin

A

1) Pregnancy towards term
2) Under 3 months old
3) Renal impairment - as impaired excretion increases its toxicity and decreases its efficacy

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17
Q

Caution of using nitrofurantoin in who

A

Long term UTI prevention –> high risk of adverse effects

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18
Q

Interactions of nitrofurantoin

A

No significant interactions

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19
Q

How can we minimise GI upset in nitrofurantoin

A

Take with food or mulk

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20
Q

Why shouldn’t we prescribe nitrofurantoin for pyelonephritis

A

As tissue concentrations are low

Use co-amoxiclav or gentamicin instead

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21
Q

What does co-trimoxazole contain

A

Trimethoprim and sulfamethoxazole

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22
Q

Indications of trimethprim

A

1) UTI - 1st line for uncomplicated

2) Pneuocytis Pneumonia - use co-trimoxazole

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23
Q

Action of trimethoprim

A

Inhibits bacterial folate synthesis by inhibiting dihydrofolate reductase

Bacteria are unable to use external folate for DNA synthesis –> therefore inhibiting it is bacteriostatic

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24
Q

What organisms is trimethoprim effective against

A

Broad spectrum against gram -ve and gram +ve - Particularly E. Coli

BUT widespread bacterial resistance

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25
Q

How do sulfonamide antibiotics work

A

Inhibits bacterial folate syntheisis - but inhibits dihydropteroate syhnthetase as structual analoge of PABA

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26
Q

Why do we combine trimethoprim and sulfomethoxazole?

A

As both are bacteriostatic and in combination they cause more inhibition making it bacteriacidial

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27
Q

Adverse effects of trimethoprim

A

1) GI upset - common
2) Skin rash - 3-7%
3) Severe hypersensitivity reactions
4) Haematological disorders –> as a folate anatgonists can cause megaloblastic aneamia, leucopenia and thrombocytopenia
5) Hyperkaelamia and eleation of plasma creatinine

28
Q

Why can trimethoprim cause megaloblastic anaemia, leucopenia and thromboyctopenia

A

As it is a dihydrofolate reductase inhibitor hence this means that it reduces the amount of folate available

29
Q

Contraindications of using trimethoprim

A

1) 1st trimester –> increased risk of foetal abnormalities

30
Q

Caution in which patients when using trimethoprim

A

1) Folate deficiency - more susceptible to haematological effects
2) Renal impairment —> may need dose reduction as exreted mostly unchanged by the kidneys
3) Neonates, elderly, HIV infection –> more susceptible to adverse effects

31
Q

Interactions of trimethoprim

A

1) Potassium raising drugs –> predisposes to hyperkaleamia
2) Folate antagonists (e.g. methotrexate) and drugs that increase folate metabolism (e.g. phenytoin) –> increase the risk of adverse effects
3) Enhances warfarin –> as it kills the gut flora that synthesise vitamin K

32
Q

What would use as prophylaxis for UTIs

A

Low dose trimethoprim

33
Q

What do we need to monitor if we give long term trimethoprim

A

FBC monitoring

For the early detection of haematological disorders

34
Q

What is the relationship between trimethoprim and creatnine

A

Trimethoprim competitively inhibits creatinine secretion in the renal tubules

This causes a small reversible increase in creatining without reducing GFR

Hence this means trimethoprim is less effective in those with renal impairment as it is outcompeted by creatinine for secretion into the urinary tract

35
Q

Name a glycopeptide

A

Vancomycin

36
Q

Indications for vancomycin

A

1) Gram +ve infections –> if severe infection and penicillines cant be used
2) Antibiotic associated colitis due to C. Diff - 2nd line to metronidazole

37
Q

Action of glycopeptides

A

Inhibit frowth and cross-linking of peptidoglycan chains –> hence inhibiting the synthesis of the cell wall of gram +ve bacteria

38
Q

Why are glycopeptides inactive against gram -ve bacteria

A

Due to a different cell walll structure

39
Q

Adverse effects of glycopeptides

A

1) Thrombophlebitis –> common at infusion site
2) Red Man Syndrome –> general erythema, hypotension and bronchospasm

Anaphylactoid reactions are NOT antigen-mediated hence they are not true allergies They are due to the non-specific degranulation of mast cells

3) Nephrotoxicity –> when IV
4) Ototoxicity –> report any changes in hearing
5) Blood disorders: Neutropenia and thrombocytopenia

40
Q

Warnings of using glycopeptides

A

Caution and dose reduction in elderly and renal impairment

41
Q

Interactions of glycopeptides

A

1) Aminoglycosides, loop diuretics and ciclorpin

Increased risk of ototoxicity/nephrotoxicity if used together!!

42
Q

What is vancomycin good for C. Diff reatment

A

As it is a large hydrophilic molecule so is poorly absorbed across lipid membranes

43
Q

Indications for tetracyclines

A

1) Acne vulgaris
2) LRTI –> including COPD exacerbations and atypical pneumonia
3) Chlamydia
4) Typhoid, anthrax, malaria and Lyme Disease

44
Q

Action of tetracyclines

A

Bind to 30S ribosome –> inhibits bacterial protein synthesis

Relatively broad spectrum but widspread resistance due to a pump that allows bacteria to pump out tetracyclines

45
Q

Adverse effects of tetracylcines

A

1) GI upset - take with food to reduce risk
2) Hypersesntivity
3) Oesophageal irritation, ulceration and dysphagia
4) Photosensitivity
5) Discououration and/or hypoplasia of tooth enamel in chilren
6) Intracreanial hypertesnin –> headaches and visual disturbatnces

46
Q

Contraindication of tetracyclines

A

1) Pregnancy
2) Breastfeeding
3) Under 12

As tetracylicnes bind to teeth and bones during development

47
Q

When should we also avoid tetracyclines

A

Renal impairment

Their anti-anabolic effect can raise plasma urea and reduced excretion increase the risk of adverse effects

48
Q

Interactiosn of tetracyclines

A

Bind to divalent cations –> seperate 2 horus from calcium, antacids or Iron

Wargarin –> exacerbates antcoagulant efffects as kills normal gut flora

49
Q

How should you take a tetracycilne tablet

A

Swallow whole with plenty of water to avoid oesophageal irritation

50
Q

Name macrolides

A

Clarithromycin
erythryomycin
Azithromycin

51
Q

Indicatinos of macrolides

A

1) Respiratory and soft tissue infections (penicillin alternative)
2) Severe pneumonia –> add to penicilin to cover atypical
3) H. Pylori eradicated –> incombo with either PPI and amoxicillin or metronidazole

52
Q

Action of macrolides

A

Inhibits bacterial protein synthesis –> binds to the 50S ribsosome and blocks translocation. This prevents elondation of polypeptide

It is bacteriostatic so the immune system can then kill it and remove it from the body

53
Q

What organisms does each type of macrolide have on?

A
Eryhtormucin --> broad spectrum against +ve and -ve
Synthetic molecules (clarithromycin + azithromycin) hace increaesd activity against gram -ve (particularly H. Infunenzae)
54
Q

Adverse efecs of macrolides

A

Most ommon and sever
1) Macrolides are irritant –> nause, ovmitng, thrombophlebiti

20 Antibitoics associated colitis
2) Liver abnormlaities
4) Prolongation of the QT interval
5 Ototoxicity

55
Q

Contrainidication ofsing macrolides

A

1) Macrolide hypersensitivity

56
Q

Caution of using macrolides

A

Severe hepatic and renal impairment

57
Q

Interactino of macrolides

A

1) the drugs are metablised by the P450 enzymes (ecept emma)

2) Drugs that prolong the QT intervatl e.g. amiodarone, antipsychoics and quinin , SSRI

58
Q

Do macrolides cover penicillin resistant organsimis

A

Yes they cover things such as legionella that cause pneumonia but not other organisms that cause LRTI

59
Q

Name quinolones

A

Ciprofloxacin
Moxifloxacin
Levofloxacin

60
Q

Indicitatios for use of quinolones

A

Generally reserved for 2nd or 3rd line treatment due to potential for rapid resistance and C. Diff

1) UTI
2) Severe GI infection e.g. Shigella or campulobacter –> ciprofloxacin
3) LRTI - use moxi or levo
4) Pseudomonas aureginos

61
Q

What antibitoic should we treat pseudomonas with

A

Ciprofloxacin - this is the only oral antibiotic with action against it

62
Q

Action of quinonones

A

Inhibit DNA synthesis - particularly active against anaerbovin gram -ve hence useful in UTI and GI infections

Moxi and levo hace enhaved activity against gram _ve hence can be used to treat LRTIs that are caused by gram_ve and -ve

63
Q

How does rapid resistance arise to quinolones

A

Prevent intracellular accumumlation be reducing permeablility/increasing efflux
Mutations in target enzymes

64
Q

Adverse effects of quinonlones

A

1) GI Upset
2) Hypersesnitivty
3) Neuro adverse effects –> lower the seizure thresholod
4) INflammation and rupture of muscle tendons
5) Prolong the QT interval –> Arrhythmias risk –> particularly moxi
6) Promote C. Diff

65
Q

Warnings of using quinolones

A

At risk of seizures
Growing - increased risk of arthropaty
Risk factosr for QT prolongation e.g. electroloye disturbances or cardiac diseases

66
Q

Interactions of quinolones

A

1) Drugs containing divalent cations –> e.g. calcium and atacids –> these decrease its absorption and efficacy
2) Cipro inhibits certain CP450 enzymes
3) Co-prescription with NSAIDS –> high risk of seizures
4) Co-prescription with prednisolone increaess risk of tendon rupture
5) Caution with other drugs that prolong the QT interval or cause arrhytmias e.g. amiodarone, antipsychotic, SSRIs, macrolides, quinine

67
Q

What happens if co-prescription of quinolones and prednisolone

A

Increased chance of tendon rupture