The Common Antibiotics Flashcards
(29 cards)
Carbapenems
Beta lactam antibiotics that are structurally similar to penicillins and cephalosporins
Broad spectrum
Imipenem and meropenem are used for severe hospital acquired infections eg. Septicaemia, complicated uti,skin and soft tissue and hospital acquired pneumonia
Imipenem partially inactivated by kidney enzymes 0 give cilastatin
Meropenem, dorpenem and ertapenem are stable to renal enzyme, don’t need to be given with cilastatin
Carbapenems side effects
Diarrhoea
Headaches
Nausea
Vomitting - Allergy and cross sensitivity
- Avoid if history of immediate hypersensitivity reaction to beta lactam anti bacterials(eg. Pens, cephlosporins)
- use with caution in patients with sensitivity to beta lactam antibacterials
Cephalosporins
- broad spectrum antibiotics
- attach to penicillins, binding to proteins to intercept cell wall biosynthesis, leading to bacterial cell lysis or death
Cephlosporins indications
Septicaemia, pneumonia, meningitis, biliary tract infection, peritonitis and urinary tract infections
Structurally similar to penicillins
Excreted renally
Cefotaxime and ceftriaxone are suitable for infections of the CNS - eg. Meningitis
Cephalosporins Side effects
Main side effect is hypersensitivity( allergy and anaphylaxis)
- About 0.5-6.5% of penicillin sensitive patients are allergic to cephlosporins
- 1st and 2nd generation cephalosporins have similar antimicrobial spectrum
1st gens = Cefalexin,cefradine and cefadroxil
2nd gens = cefuroxime, cefactor
3rd gens =cefotaxime,cefixime,ceftazimide,Ceftriaxone = T is third
Antibiotic associated colitis with 2nd gens and 3rd gen
Vancomycin - TDM
Glycopeptide antibiotic
- Bactericidal activity against aerobic and anaerobic gram positive bacteria
Indication and use - C- difficile
Treatment of antibiotic associated colitis caused by clostridium difficile infections
- Not absorbed effectively by mouth so should not be given orally, IV route preferred
- Side effects - agranulocytosis, dizziness, drug fever, hypersensitivity, neutropenia, skin reactions, red man syndrome ( infusion related reaction)
- discontinue if tinnitus occurs
Vancomycin monitoring
Higher risk of Nephrotoxicity than telcoplanin
What to monitor?
- initial doses based on body weight
- Subsequent doses based on serum vancomycin concentration
- Trough concentration range 10-20 mg.L
- Monitor full blood count, renal and hepatic function
- Monitor vestibular and auditory function (avoid recurrent use of Ototoxic drugs. Eg. Furosemide)
Clindamycin
- active against gram positive bacteria
Indication
- Bone and joint infections (eg. Osteomyelitis, peritonitis bone and joint infection)
- alternative to macrolides, especially in penicillin sensitive patients
Contraindications diarrhoeal states
Side effects of Clindamycin
- antibiotic associated colitis (fatal) occurs most frequently with Clindamycin than other antibiotics
- discontinue if c.difficle infections Structurally similar is suspected or confirmed (diarrhoea, watery stool)
- discontinue if diarrhoea occurs and contact doctor
- monitor liver and renal function if treatment exceeds 10 days
Macrolides
Erythromycin, azithromycin and clarithromycin
Bacteriostatic - stops bacterial growth
- Antibiotic is broad spectrum and similar but not identical to penicillins
- Active against many penicillin resistant staphylococci( but some now also resistant to macrolides)
- Alternative for penicillin allergic patients
Common macrolides indications
1) Respiratory and skin/soft tissue infections
2) severe pneumonia
3)eradication of H. Pylori (with PPI + amoxicillin/metronidazole)
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Macrolides interactions
- Clarithromycin and erythromycin are both inhibitors
- Increase plasma concentration of warfarin and statins as they are substrates
Erythromycin
Used to treat - respiratory tract infection, legionella,skin and oral infections, early syphillis, chlamydia and non-gonococcal urtheritis
- has poor activity against H. Influenza (clarithromycin and azithromycin do not)
Side effects:
- Nausea, vomitting and diarrhoea(give lower dose to avoid in mild infections but higher sores are needed in more serious infections
- cautionary labels - 5,9,25
Erythromycin - pregnancy and breastfeeding
Use only if potential out weighs the risk
- may cause hepatoxicity
- renal impairment - can cause Ototoxicity in adults and children at high doses
Azithromycin
- less active than erythromycin over gram positive but enhanced activity over gram negative (eg. H influenza)
- long tissue half life and once daily doses recommended
- pregnancy and breastfeeding - use only if no alternative
- Cautionary labels 5,9,23(for capsule)
Azithromycin OTC- rxxxxx
Chlamydia - asymptomatic (need a private rx)
Mazximum single dose of 1g, maximum daily dose of 1g and a pack size of 1g
16 years +
2nd line - doxycycline
Clarithromycin
- its an erythromycin derivative with greater activity
- most commonly prescribed macrolides, more stable and causes fewer side effects
- Tissue concentrations higher than with erythromycin
- Given twice daily
- Also used in regimens for H.pylori eradication
- erythromycin,azithromycin and Clarithromycin used in the treatment of Lyme disease
Clarithromycin Pregnancy and breastfeeding
- avoid especially in 1st trimester, only use if benefit outweighs risk
- Avoid in hepatic and renal impairment
- Cautionary labels 9,21,25,13
Trimethorpim
Indication - UTI and respiratory tract infections( chronic bronchitis, pneumonia)
Mode of action - bacteriostatic - broad spectrum antibiotics
- folate antagonist - therefore bacteriostatic, all antifolates are tetrogenic and can cause blood disorders
Contraindications - blood disorders
Side effects - diarrhoea, electrolytes imbalance, fungal overgrowth,headaches,nausea, skin reactions and vomitting,blood disorders
- pregnancy - avoid in 1st trimester (teterogenic) and pregnancy in general. Folate antagonist - causes fetal abnormality
Monitor full blood counts on long term therapy
Trimethoprim patient and carer advice
- recognise signs of blood disorders and seek medical advice if symptoms occur
Label 9
Linezolid
MHRA
- severe optic neuropathy - particularly if used longer than 28 days
- warn patients to report symptoms of visual impairment (blurred vision, visual field defect, changes in colour vision and visual activity immediately
2) blood disorders Side effects- monitor blood count including platelet count weekly
Avoid consuming large amounts of tyrannies rich foods eg.bovril - can cause hypertensive crisis, Linezolid is reversible, non selective inhibitor of monamine oxidase - however its dose used as an antibiotic doesn’t have anti depressant effects as a MAOI
Nitrofurantoin
- UTI
- Treatment duration - usually 3 days ( 7 days in males and pregnant women)
- Contraindcation - Acute prophyria, G6PD,infants less than 3 months old
- Caution- anaemia, diabetes, electrolytes imbalance, folate deficiency, pulmonary disease, Vitamin B deficiency
- Pregnancy- avoid at term, may produce neonatal haemolysis
Renal impairment and Nitrofuratoin
Risk of peripheral neuropathy
Avoid if eGFR is less than 45 ml/min , may be used up caution if eGFR is 30-44 as a short course of only 3-7 days to treat uncomplicated lower UTI cause by suspected or proven multidrug resistant bacteria and only if potential benefits out weigh the risk
Monitoring - long term therapy - monitor liver function and monitor pulmonary symptoms, especially in elderly (discontinue if deterioration in lung function)
Adult doses for lower urinary tract infections
Nitro - 50mg QDS (IMMEDIATE) or 100mg (Modified release) - 3 day duration, 7 days in males, 7 days in pregnancy
Trimethoprim - 200mg BD - 3 days - 7 days in males
