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
describe how gentamicin can be used for “blind” therapy
When used for the ‘blind’ therapy of undiagnosed serious infections , gentamicin is usually given in conjunction with a penicillin or metronidazole (or both).
ideally, how long should treatment with gentamicin be for
ideally, do not use gentamicin for more than 7 days
which is preferred: a once daily administration of aminoglycosides or multiple-daily dose regimens
once daily administration is preferred because it is more convenient + provides adequate serum concentrations,.
- need to consult local guidelines on dosage and serum concentrations
- aminoglycosides = gentamicin, amikacin, neomycin*
what are the important side effects caused by all aminoglycosides (particularly gentamicin)
- Ototoxicity (hearing impairment, tinnitus (buzzing in ear) + balance impairment)
- nephrotoxicity (occurs most commonly in patients with renal impairment, who may require reduced doses; monitoring is particularly important in the elderly.)
- aminoglycosides = gentamicin, amikacin, neomycin*
what are the risks associated with using aminoglycosides in pregnancy
There is a risk of auditory or vestibular nerve damage in the infant when used in the second + third trimesters of pregnancy
- avoid use of them unless essential.
- aminoglycosides = gentamicin, amikacin, neomycin*
why do patients with renal impairment have an increased risk of ototoxicity and nephrotoxicity when taking aminoglycosides
Aminoglycosides are primarily renally excreted and accumulation can occur in renal impairment (causing increased risk of ototoxicity and nephrotoxicity)
aminoglycosides = gentamicin, amikacin, neomycin
what monitoring should occur when taking aminoglycosides
- serum-aminoglycoside concentration (parenteral administration)
- Renal function should be assessed before + during treatment
- Auditory and vestibular (inner ear responsible for balance) function should also be monitored during treatment
- aminoglycosides = gentamicin, amikacin, neomycin*
why is gentamicin a high risk drug
because it has a narrow therapeutic index
why should you avoid giving gentamicin + furosemide (a loop diuretic) at the same time
because there is an increased risk of both nephrotoxicity + ototoxicity
name the infections tetracyclines are used to treat
chlamydia, acne, exacerbations of chronic bronchitis, rickettsia , brucella, Lyme disease
note: tetracyclines are broad spectrum antibiotics. tetracycline = tetracycline, doxycycline, lymecycline
why should you be cautious when using tetracyclines in patients with Myasthenia gravis or systemic lupus erythematosus
because tetracyclines may worsen muscle weakness in Myasthenia gravis and exacerbate systemic lupus erythematosus
tetracycline = tetracycline, doxycycline, lymecycline
why can’t you give tetracyclines to children under 12 or women pregnant/breastfeeding
because the tetracyclines deposit in growing bones and teeth which causes discolouration of child teeth (grey-yellow colour)
- also affects skeletal development in 1st trimester
- tetracycline = tetracycline, doxycycline, lymecycline*
what should be avoided at least 2 hours before or after administering tetracyclines
Avoid: Antacids (indigestion remedies), iron, or zinc salts
- this is because they decrease intestinal absorption of tetracyclines
- tetracycline = tetracycline, doxycycline, lymecycline*
what must patients do (counselling point) when taking tetracyclines because they can cause photosensitivity reactions
Protect their skin from sunlight—even on a bright but cloudy day. Do not use sunbeds
tetracycline = tetracycline, doxycycline, lymecycline
what are the common side effects of tetracyclines
Angioedema, diarrhoea, photosensitivity reaction, skin reactions, systemic lupus erythematosus exacerbated, Henoch-Schönlein purpura (inflamed blood vessels which shows as a reddish-purple rash)
tetracycline = tetracycline, doxycycline, lymecycline
which class of antibiotics is normally used as an alternative in penicillin-allergic patients
macrolides =erythromycin, azithromycin and clarithromycin
which infections are macrolides used for
respiratory infections, skin infections, chlamydia + lyme disease
macrolides =erythromycin, azithromycin and clarithromycin
why should we not give erythromycin to patients with:
- a history of QT interval prolongation or
- ventricular arrhythmia (including torsade de pointes), or
- those with electrolyte disturbances
because erythromycin causes QT-interval prolongation so has an increased risk of cardiotoxicity
what are the common side effects for macrolides
diarrhoea, nausea + vomiting, skin reactions , hearing impairment, vision disorders
macrolides =erythromycin, azithromycin and clarithromycin
which class of medicines interacts with macrolides and increases the risk of myopathy
statins
macrolides =erythromycin, azithromycin and clarithromycin
which medication interacts with macrolides and causes increased risk of bleeding
macrolide + warfarin = increased anticoagulant effect of warfarin
macrolides =erythromycin, azithromycin and clarithromycin
why should patients not take NSAIDs whilst taking quinolone antibiotics
because quinolones can induce convulsions in patients with or without a history of convulsions. Taking NSAIDs at the same time further increases risk of this
quinolone antibiotics= ciprofloxacin, levofloxacin, ofloxacin
*note this is with intravenous use or oral use or when used by inhalation (everything except eye drops)
what increases the risk of tendon damage as a side effect of taking quinolones
Tendon damage (including rupture) can occur within 48 hours of taking quinolones. risk increased if:
- patients has a history of tendon disorders related to quinolone use (contra-indicated in these patients)
- patients over 60 years of age
- concomitant use of corticosteroids
quinolone antibiotics= ciprofloxacin, levofloxacin, ofloxacin
what should you do if you suspect tendinitis in a patient taking quinolone antibiotics
the quinolone should be discontinued immediately
quinolone antibiotics= ciprofloxacin, levofloxacin, ofloxacin
why are quinolones generally not recommended in children and growing adolescents
cause arthropathy (joint diseases) in the weight-bearing joints of children and growing adolescents
quinolone antibiotics= ciprofloxacin, levofloxacin, ofloxacin
what are the cautions for quinolone antibiotics
- can prolong the QT interval
- conditions that predispose to seizures/ epilepsy
- diabetes (may affect blood glucose)
- exposure to excessive sunlight and UV radiation should be avoided during treatment and for 48 hours after stopping treatment
- G6PD deficiency
what foods/drinks should patients avoid whilst taking ciprofloxacin (a quinolone antibiotic)
dairy products and mineral-fortified drinks with oral ciprofloxacin because it reduces exposure of ciprofloxacin
describe the interaction between ciprofloxacin (a quinolone antibiotic) and theophylline (for asthma/copd)
Ciprofloxacin is predicted to increase the exposure to theophylline. Theophylline has a narrow therapeutic index so need to reduce dose of theophylline whilst on antibiotics
what are the counselling points for ciprofloxacin (a quinolone antibiotic)
- Do not take milk, indigestion remedies, or medicines containing iron or zinc, 2 hours before or after you take this medicine
which antibiotic is most frequently associated with antibiotic-associated colitis
clindamycin ( a lincosamide antibiotic). If C. difficile infection is suspected or confirmed, discontinue the antibiotic if appropriate
what should a patient do if they are taking clindamycin (lincosamide antibiotic) and they experience severe, prolonged or bloody diarrhoea
discontinue and contact a doctor immediately. (clindamycin can cause antibiotic-associated colitis)
what are the common side effects of metronidazole
dry mouth, myalgia, nausea, oral disorders, taste metallic, vomiting, furry tongue
describe the interaction between macrolides and statins
macrolides increase exposure of statins so increase side effects of statins (e.g rambodhymylysis)
advise patient to stop taking statins temporarily whilst taking macrolides antibiotics. patient can restart 48 hours after finishing course
macrolides =erythromycin, azithromycin and clarithromycin
describe the interaction between trimethoprim and methotrexate
Both trimethoprim and methotrexate can increase the risk of nephrotoxicity (can be fatal)
Never prescribe/dispense trimethoprim + methotrexate
describe the interaction between metronidazole and alcohol
causes a disulfiram-like reaction when given with metronidazole.
advise to avoid alcohol during course and for at least 48 hours after stopping treatment
describe the interaction between Tetracyline antibiotics and iron
Oral iron decreases the absorption of oral tetracycline.
Take Tetracycline antibiotics should be taken 2 to 3 hours after iron
Tetracyclines = tetracycline, doxycycline, lymecycline
describe the interaction between Rifampicin ( a rifamycins antibiotic ) and combined hormonal contraceptives
rifampicin (potent enzyme inducer) decreased efficacy of combined hormonal contraceptive
use additional precautions e.g IUD/ condoms
what is systemic chloramphenicol used for
Life threatening infections particularly those caused by Haemophilus influenzae,
Typhoid fever
what is vancomycin used for
- c.diff infection
- pneumonia (community, hospital +ventilator associated
- complicated skin + soft tissue infections
- surgical prophylaxis where there is a high risk of MRSA
why should you not give vancomycin orally for systemic infections
because it is not absorbed significantly orally
what monitoring should happen in all patients taking vancomycin
IV use: auditory function, blood counts, urinalysis, hepatic and renal function tests.
Oral use- serial auditory function tests.
which tetracyclines can be taken with milk
Does Like Milk (DLM) acronym
Doxycycline
Lymecycline
Minocycline
which tetracyclines can’t be taken with milk
DOT acronym
Demeclocycline
Oxytetracycline
Tetracycline
what are the main side effects of vancomycin
- Avoid rapid infusion as there is a risk of an anaphylactic reaction
- High incidence of blood disorders such as neutropenia
- Nephrotoxicity and ototoxicity (discontinue if tinnitus occurs)
why is vancomycin a high risk antibiotic
because it has a narrow therapeutic index
what is “Red man syndrome” that can occur when a patient is given vancomycin
the upper body flushes with a characteristic red, itchy, burning rash on the neck, face and upper torso. if this occurs the infusion must be stopped
how do you prevent “Red man syndrome” from vancomycin
Prevent by having a slow infusion
how do you treat “Red man syndrome” that can occur when a patient is given vancomycin
- first antihistamines and in some cases corticosteroids
- In severe cases adrenaline may need to be given if there are symptoms of anaphylaxis
why should you monitor blood counts before and during treatment with chloramphenicol (systemic treatment)
because when chloramphenicol is given systemically, it is associated with serious haematological side effects
why should you avoid giving chloramphenicol to a pregnant woman in her 3rd trimester
if chloramphenicol is given during 3rd trimester, neonatal ‘grey-baby syndrome’ can occur
- symptoms; grey skin colour, low blood pressure
which antibiotics are usually safe in pregnancy
- penicillins: phenoxymethylpenicillin, flucloxacillin, amoxicillin
- cephalosporins: cefaclor, cefadroxil and cefalexin
- Erythromycin (use only if benefit outweighs risk)
- Clindamycin (with systemic use can use in 2nd + 3rd trimester. caution in 1st trimester)
which antibiotics can be used with caution during pregnancy
- Nitrofurantoin (Safe to take throughout pregnancy but should be avoided at term - risk of neonatal haemolysis)
- Metronidazole (only if benefit outweighs risk. avoid in high dose regimens)
