Antibiotic Classes Flashcards by josh Taverner

Mechanism of antibiotic resistance?

– Prevent access to bug (Pseudomonas sp)

– Bug produces destructive enzyme (penicillins, cephalosporins)

– Bug changes drug binding site (penicillins)

– Drug pumped out of bug (tetracyclines)

– Bug creates bypass pathways to overcome loss of function (sulphonamides)

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Mechanisms of beta lactam resistance

beta- lacatamase

modification of penicillin binding protein

no access to PBP

Efflux pump

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safety issues with penecillins

allergy

hepatotoxicity

renal clearance ↓ by probenecid

oral contraceptive failure

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half life of penicillins?

30-75 mins (with normal kidney clearance)

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What are the classifications of penicillins?

Narrow spectrum

Narrow spectrum with anti-staph action

moderate spectrum

broad spectrum

broad spectrum with anti pseduomonas

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Narrow spectrum penicillins

penicillin G/ Benzyle penicillin

Penicillin V/ phenoxymethyl penicillin

benzathine penicillin

procaine penicillin

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What are narrow spectrum penicillins used for?

pneumococcus

meningococcus

streptococcus

syphilis

actinomycosis

listeria

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What route can narrow spectrum penicillins be given?

IM or IV generally
(not acid stable, degraded in stomach)

Penicillin V can be given orally, except with food

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Narrow spectrum anti-staph penicillin?

flucloxacillin (cloxacillin, dicloxacillin, methicillin)

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What route can narrow spectrum with anti-staph property penicillins be given?

oral or IV

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safety issues with narrow spectrum with anti-staph property penicillins

specific risk of cholestatic jaundice

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moderate spectrum penicillins?

amoxycillin (ampicillin)

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routes of moderate spectrum penicillins?

oral or IV

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Common uses of moderate spectrum penicillins?

bacterial URTIs
bacterial bronchitis
UTIs (not best choice given patchy coverage)

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How does spectrum of moderate spectrum penicillins differ compared to narrow spectrum?

less gram +ve coverage, but more gram -ve

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safety issues with moderate spectrum penicillins

high risk or rash when given during some viral infections such as glandular fever
(does not contraindicate all future penicillin)

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Broad spectrum antibiotics

β-lactam plus β-lactamase inhibitor
- amoxycillin + clavulanate
- tazocin

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What are the broad spectrum with anti Pseudomonas activity penicillins?

carbenicillin, piperacillin, ticercillin (+/- clavulanate)

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How does spectrum of cephalosporins compare to penicillins?

broader spectrum than penicillins but probably less
effective than penicillin for sensitive organisms

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Safety issues with cephalosporins?

risk of allergy in severe penicillin-allergic patients

causes OCP failure

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1st gen cephalosporins?

cefazolin

cephalexin

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3rd gen cephalosporins

cefotaxamine, ceftriaxone, ceftazidime

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which cephalosporins can be given PO?

cephalexin

some 2nd gens (cefaclor, cefuroxime)

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Side effects of cephalosporins?

diarrhoea, rash, electrolytedisturbance, fever, neutropaenia, hepatic toxicity

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Common uses of cephalosporins?

• skin and soft tissue including staph - 1st gen • gonorrhoea (due to penicillin resistance) - 3rd gen • empirical meningitis - 3rd gen • serious enteric infections - 3rd gen • 4th gen – empirical treatment of nosocomial infections

Aminoglycasides

gentamycin, streptomycin, Tobramycin

route of aminoglycasides

IM/ IV – not bioavailable orally but well absorbed from wounds / irrigation

elimination of aminoglycasides

100% renally eliminated – need to adjust dose in renal impairment

safety issues with amino glycasides

nephrotoxicity (reversible) ototoxicity - deafness or balance (usually irreversible)

use of aminoglycasides

Serious Gm-ve infections – Pyelonephritis – Sepsis – Synergistic with penicillin for bacterial endocarditis

route for metronidazole?

IV or PO

metronidazole drug interactions?

alcohol (decreased acetaldehyde function) warfarin

side effects of metronidazole

many • nausea, vomiting, constipation, diarrhoea • dizziness, headache • bitter metallic taste

macrolides

erythromycin, clarithromycin, azithromycin, roxithromycin

Adverse effects of macrolides?

• motilin agonist → high rate of GI upset; dose dependent • cholestatichepatitis • drug metabolising enzyme inhibitor

quinolones

ciprofloxacin, moxifloxacin, norfloxacin, ofloxacin (eye drops only)

spectrum of quinolones

broad Gm-ve coverage including Pseudomonas, variable Gm+ve coverage

use for quinolones

• urinary tract infection • enteric infections including typhoid, shigella, travellers’s diarrhoea • bronchitis, pneumonia, cystic fibrosis • osteomyelitis

AE of quinolones

– GI, – hallucination, delirium, seizures – photosensitive rash – tendon rupture – long QT (moxifloxacin)

lincosamides

clindamycin lincomycin

elimination of lincosamides

mostly through the liver

adverse effects lincosamides And example of lincosamide

very severe diarrhoea (can be c diff) allergy/ rash Clindamycin

elimination of vancomycin

renally

adverse effects of vancomycin

nephrotoxic ototoxic anaphylaxis red man syndrome

tetracyclines

tetracycline, minocycline, doxycycline

uses of tetracyclines

limited due to wide spread resistance • rickettsia, mycoplasma, trachoma, Lyme disease • community acquired pneumonia, • pelvic inflammatory disease • acne

adverse effects of tetracyclines

teeth discolouration (don't give to kids) OCP failure GIT Skin Fungal overgrowth

empiric treatment for mild HAP (ETG)

augmentin duo

empiric treatment for moderate HAP (ETG)

3rd gen cephalosporin (ceftriaxone or cefotaxamine)

empiric treatment for severe HAP (ETG)

tazocin

empiric treatment for mild CAP (ETG)

amoxycillin or doxycyline PO

empiric treatment for moderate CAP (ETG)

Benzylpenicillin IV + doxycycline PO

empirical treatment for severe CAP (ETG)

3rd gen cephalosporin (ceftriaxone or cefotaxamine) + azithromycin

empiric treatment for meningitis?

benzylpenicillin or ceftriaxone

empirical treatment for COPD exacerbation?

amoxycillin or doxycycline

empirical treatment for acute gastroenteritis?

ciprofloxacin or norfloxacin

empirical treatment for mild acute pyelonephritis?

augmentin duo or copra of Ax Then target

empirical treatment for severe acute pyelonephritis?

gentamycin + amoxy/ampicillin

empirical treatment for acute cystitis?

1st line - trimetheprim (unless preggers) 2nd line - cephalexin

empirical treatment for cellulitis (with systemic symptoms)

flucloxacillin (If SA suspected - purulence, skin wound) if SA not suspected - benzylpenicillin