Anti- microbials Flashcards by fintan mccollum

What is the main target of anti-microbials

The bacterial cell wall

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Two groups of cell wall active agents

Beta lactams

Glycopeptides

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Examples of Beta lactams

Penicillins
Cephalosporins
Monobactams
Carbapenems

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Examples of Glycopeptides

Vancomycin

Teicoplanin

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Anti-microbials that act on nucleoside precursors

Trimethorpim

Sulphonamides

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Anti-microbials that act on nucleic acid synthesis

Metronidoazole
Quinolones
Rifampicin
Nitrofurans

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Anti microbials that are protein synthesis inhibitors

Aminoglycosides
Tetracyclines 
Macrolides 
Oxazolidinones 
Fusidic acid

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Mode of action of penicillin

Interfere with bacterial cell wall peptidoglycan
Attach to penicillin binding proteins
Inhibit transpeptidase enzyme activity
Inactivate inhibitor of autolytic enzyme in the cell wall - causing lysis

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Treatement for bacterial meningitis

Benzyl penicillin

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Penicillin used for resp infections UTI and ottis media

Broader spectrum - amoxicillin

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what type of penicillin is fluoxacillin and what does it treat

Beta-lactamase

cellulitis

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Penicillin used to treat severe infections/pseudonomas

Piperacillin

Extended spectrum

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The pharmokinetics of penicillin’s

Oral absorption variable
Widely distributed in body fluids
Mainly renal excretion
short plasma half-life

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Adverse affects of penicillin

hypersensitivity
anaphylaxis
oral antibiotic associated diarrhoea

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Structure of cephalosporins

Chemically structurally similar to penicillin

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Mode of action of cephlopsorins

Similar to penicillins

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Why is there a greater resistance to cephalosporins

due to them being gram -ve

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What excretes cephalosporins

Kidney

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what cephalosporin should be used for meningitis

ceftotaxime

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What cephalosporin should be used for bronchiectasis infections

ceftazidime

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Examples of macrolides

Erythromycin
Clarithromycin
Azithromycin

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Mode of action of macrolides

Inihibit bacterial protein synthesis

Bind to 50S subunit of bacterial ribosome and prevent transolocation of growing peptide chain

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How are macrolides administered

Usually PO

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What are the benefits of macrolides

benefits against atypical pneumonia /COPD benefits

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Adverse effects of macrolides

GI upset Hypersensitivity QT prolongation - arrhythmic

Why do macrolides interact with other drugs?

Due to their effects on cytochrome P450

Examples of quinolones

Ciprofloxacin Levofloxacin Moxifloxacin

Mode of action of quinolones

Inhibits bacterial DNA gyrase | Prevents DNA double helix being supercoiled - no transcription and replication

Features of quinolones

Well absorbed | Good active against Gm -ve coliforms awell as H. influenza and pseudomonas

What do quinolones act poor against

strep pneumonia and staph

What are quinolones usually used for

UTI and pneumonia and levofloxacin

What are adverse affects of quinolones

``` GI Hypersensitivity Caution of QT prolongation Inhibits CYP 450 - increase theophylline toxicity Rare convulsions ```

Examples of aminoglycosides

Gentamycin | Tobramycin

Features of aminoglycosides

INihibit bacterial protein synthesis Require o2 dependent transport to enter bacteria work synergistically with cell-wall-active antibiotics

Mode of action of aminoglycosides

Bind to 30s subunits - interfere with initiation complex of peptide formation - induce misreading's of RNA - cluster for efficiency

Uses of aminoglycosides

Effective against aerobic Gm -ve and some gm +ve Gm -ve sepsis in combination with penicillin

How to treat pseudamonas infections with aminoglycosides

Use tobi plus another anti-pseudomonal antibiotic

What are the pharmacokinetics of aminoglycosides

Highly polar molecules - IV admin Kidney elimination reduce dose and frequency

Adverse effects of aminoglycosides

irreversible ototoxicity CNXIII affected shouldnt be longer than 2 weeks on genti reversible nehprotoxicity

Examples of tetracyclines

Tetracycline | Doxycycline

Features of tetracyclines

inhibits protein synthesis | Broad spectrum

Why not to administer tetracycline in pregnancy

Chelate calcium -never when pregnant | - weakens the bones and teeth of the child

Examples of carbapenems

meropenem | Imipenem

How do carbapenems act

they act the same as other beta lactams | severe resistant infection under infectious disease guidance

adverse affects of carbapenems

GI upset

Example of a monobactam

Monobactams

How are monobactams administered

What are monobactams resistant to?

Only given IV

Adverse effects of monobactams

GI upset

What are monobacams only effective against?

gm -ve aerobic rods ( pseudomonas)

What type of antibiotic is vancomycin

Glycopeptide bacterial antibiotic

How does vancomycin work

Inihibits cell wall synthesis

Administration for vancomycin

C difficile - PO | IV - MRSA

Adverse effects of vancomycin

rash ototoxicity nephrotoxicity

What type of antibiotic is metronidazole and what is it good for?

Anti-protozoal agent | goof anaerobic cover

Adverse effects of metronidazole

``` reaction with alocohol Minor GI disturbance Headache Dizzy Metallic taste ```

What is metronidazole used for as first line

C difficile colitis

Other use for metronidazole

Anaerobic cover in intra-abdominal sepsis

What is trimehtroprim and how does it work

A bacterial dihydrofolate reducatase inihibitor | efectively stops bacteria making DNA

What is trimethroprim used to treat

Simple UTI

Mode of action of nitrofurantoin

Inhibit a no. of different bacterial enzymes for protein synthesis

Use of nitrofurantoin

UTI

When do you not use nitrofurantoin

Septicaemia | Renal impairment - less effective and potential -theres a risk of neuropathy

Adverse effects of Nitrofurantoin

``` GI common Peripheral neuropathy Pulmonary fibrosis Hypersensitivity ( skin and bone marrow) haemolytic anaemia ```

what should be looked out for when prescribing with nitrofurantoin

``` Anaemia DM hepatic/renal impairment Vit B12 + folate deficiency pulmonary disease ```

What is aciclovir

nucleoside analogue

What does aciclovir do?

Inhibits vira DNA synthesis

What enzymes are needed to be active for aciclovir to work?

Viral thymidine kinase | Viral DNA polymerase

Treatment for varicella zoster/ shingles

Higher dose of acicilovir

Adverse effects of aciclovir

GI headache Nephro/neurotoxicity reduce doses in renal impairment

What is famciclovir

Guanosine analogue pro-drug of penciclovir similar action to anciclovir higher cell conc. and more prolonged effect

What is remdesivir

inihbitor of viral RNA polymerase nucleoside analogue remdesivir triphosphate taken up by viral RNA polymerase and stalls RNA production

Why are antifungal agents not given systemically

Toxic

When do you give anti fungal agents topically

When the patient is immunocompromised

when is amphotericin given

when life threatening

MoA of amphotericin

Binds to ergosterol in fungal cell wall FOrms pre of fungal cells walll Leakage of ions leads to cell death

AE of amphotericin

Immediate IV reactions Gradual toxicity Hypokalaemic Abnormal LFT Anaemia/ thrombocytopenia

how is nystatin used

Topically for candida infections

How do triazoles work

Inhibit fungal cytochrome P450 3A enzyme - key enzyme in the synthesis of ergosterol

how is Fluconazole admin

IV caution with other drugs

AE of fluconazole

GI | headache