antibiotics Flashcards
How do penicillin antibiotics work
name examples of penicillin antibiotics
penicillins work by inhibiting cell wall synthesis
phenoxymethylpenicillin, flucloxacillin, amoxicillin, co-amoxiclav (contains penicillin)
How do cephalosporins work
name examples of Cephalosporin antibiotics
Cephalosporins attach to penicillin binding proteins to interrupt cell wall synthesis, leading to bacterial cell lysis and death.
cefaclor, cefadroxil and cefalexin
how do tetracyclines work
name examples of tetracycline antibiotics - end in “cycline”
tetracyclines inhibit protein synthesis in bacteria
tetracycline, doxycycline, lymecycline
How do macrolides work
name examples of macrolides antibiotics - end in “thromycin”
Macrolide antibiotics inhibit protein synthesis by targeting the bacterial ribosome
erythromycin, azithromycin and clarithromycin
how do quinolone antibiotics work
name examples of quinolone antibiotics -end in “floxacin”
quinolone work by inhibiting dna replication in bacteria
ciprofloxacin, levofloxacin , Ofloxacin
name some antibiotics that do not fit into a class
metronidazole, nitrofurantoin, chloramphenicol, trimethoprim
how do rifamycin antibiotics work
name examples of rifamycin antibiotics
they interrupt RNA synthesis in bacteria
Rifampin, rifabutin, and rifapentine
how do aminoglycosides work
name examples of Aminoglycosides antibiotics- end in “cin”
aminoglycosides work by inhibiting protein synthesis
gentamicin, amikacin, neomycin sulfate, streptomycin, and tobramycin
which antibiotics should you avoid in patients with a penicillin allergy
phenoxymethylpenicillin, flucloxacillin, amoxicillin, co-amoxiclav (contains penicillin), Tazocin ( Piperacillin and Tazobactam)
which biomarkers indicate infection
- high white blood cells and neutrophils
- increased CRP (c reactive protein)
- platelet count can increase or decrease
- increased cytokine levels (e.g. interleukin-6, tumor necrosis factor, interleukin-8)
- increased erythrocyte sedimentation rate (ESR)
- increased neutrophils
- increase or decrease in white blood cells
- increase in Procalcitonin levels
what are the common side effects of all penicillins
Diarrhoea (which can cause bacterial colitis), hypersensitivity, nausea + vomiting, skin reactions, thrombocytopenia (low platelet count)
risk of encephalopathy - (the risk is increased with very high doses or in severe renal failure)
how do you differentiate between if a person with rash after taking penicillin as an allergy or intolerance
allergy: rash immediately, other signs of anaphylaxis such as swelling, difficulty breathing, dizziness/fainting
not allergic but intolerant: minor, non-itchy rash restricted to a small area of the body or a rash that appears more than 72 hours after penicillin administration. could still give penicillin but try to give alternative instead
note a rash appearing more than 72 hours after administration may also indicate a delayed allergic reaction
why is it that if a patient is allergic to one penicillin, they are allergic to all penicillins
- because the hypersensitivity is related to the basic penicillin structure (which all penicillins have). This is known as cross-sensitivity
can a patient who has had an immediate hypersensitivity reaction to penicillins take cephalosporins and other beta-lactam antibiotics
no
what factors do you need to consider when selecting an antibiotic for a patient
the causative agent and other actors such as:
allergy, renal/hepatic impairment, immune function, availability of oral route, severity, age, taking contraceptive pills, pregnancy or breastfeeding, gender
which penicillin antibiotic is only given by Injection since it is inactivated by gastric acid
what is the alternative that can be given orally
Benzylpenicillin sodium (Penicillin G) inactivated by gastric acid
can use Phenoxymethylpenicillin (Penicillin V) instead. it is less active but it is stable in gastric acid so can be given orally
why should Phenoxymethylpenicillin (Penicillin V) not be given in the treatment of serious infection
because absorption can be unpredictable and plasma concentrations variable
which penicillin is used in infections caused by penicillin-resistant staphylococci
flucloxacillin - it is indicated for penicillin-resistant Staph infections
this is because it is not inactivated by penicillinases (enzymes produced by bacteria to break down penicillin)
what may occur if you use flucloxacillin for more than 2 weeks (rare)
hepatic disorders: Cholestatic jaundice and hepatitis may occur up to 2 months after treatment with flucloxacillin has stopped
note: manufacturer advises to use with caution in patients with hepatic impairment and not to use in patients with history of hepatic dysfunction associated with flucloxacillin
which organisms is Ampicin active against
certain Gram-positive and Gram-negative organisms
why should ampicin be taken on an empty stomach
because it already has poor absorption- can be given by mouth but less than half the dose is absorbed, and absorption is further decreased by the presence of food in the gut.
which rash commonly occurs when patients take Ampicin and Amoxicillin but is not related to a penicillin allergy
Maculopapular rashes ( a flat, red area on the skin that is covered with small bumps)
- rash not usually related to true penicillin allergy. They almost always occur in patients with glandular fever
does the presence of food affect amoxicillin absorption
No. Amoxicillin absorption is not affected by the presence of food so you can either take it with food or without (doesn’t matter)
what does co-amoxiclav contain
amoxicillin with the beta-lactamase inhibitor clavulanic acid
note: clavulanic acid (the beta-lactamase inhibitor) means co-amoxiclav can be used against beta-lactamase-producing bacteria that are resistant to amoxicillin
which infections should the use of co-amoxiclav be reserved for
reserved for infections likely, or known, to be caused by amoxicillin-resistant beta-lactamase-producing strains
note: clavulanic acid (the beta-lactamase inhibitor) means co-amoxiclav can be used against beta-lactamase-producing bacteria that are resistant to amoxicillin
why is co-amoxiclav contraindicated in patients with History of co-amoxiclav/ penicillin-associated jaundice or hepatic dysfunction
because hepatic events have been reported as a side effect mostly in males and elderly patients
- it is associated with prolonged treatment
which drugs interact with penicillin antibiotics
- vitamin k antagonists: Warfarin, Acenocoumarol, Phenindione. severe interaction (increased risk of bleeding)
- Methotrexate. severe interaction (increased risk of toxicity)
- allopurinol (increases risk of rash with amoxicillin.) moderate interaction- consider alternatives
what are in the indications for cephalosporin antibiotics
used for: septicaemia, pneumonia, meningitis, biliary-tract infections, peritonitis, and urinary-tract infections
*cephalosporins= cefalexin, cefadroxil, cefaclor *
what are the common side effects of all cephalosporins
(same ones as penicillin): diarrhoea, nausea + vomiting, skin reactions, thrombocytopenia
plus
vaginal thrush, pseudomembranous enterocolitis (inflammation + swelling of large intestines due to overgrowth of c.difficile)
*cephalosporins= cefalexin, cefadroxil, cefaclor *
give examples of first generation + second generation cephalosporins
- ‘first generation’ cephalosporins: cefalexin, cefradine, and cefadroxil
- ‘second generation’ cephalosporin: cefaclor,
which cephalosporin can be given in pregnancy and breastfeeding
cefalexin
why must aminoglycosides be given by injection for systemic infections
because they are not absorbed from the gut
aminoglycosides = gentamicin, amikacin, neomycin
what is the first choice aminoglycoside in the UK
gentamicin
- note: gentamicin has a broad spectrum but is inactive against anaerobes and has poor activity against haemolytic streptococci and pneumococci*
how do you calculate the loading and maintenance doses of gentamicin
calculated on the basis of the patient’s weight and renal function (e.g. using a nomogram); adjustments are then made according to serum-gentamicin concentrations