HD13 Antibiotics Use and Abuse Flashcards
Can antibiotics be prescribed to manadge pain?
NO- they kill bacteria!
2 ways antibiotics can be directly dangerous?
1, fatal anaphylaxis - with penicillin 1:100,000 (babies/ young children)
2.Unwanted drug side effects
How can the abuse of antibiotics i.e. poor prescribing or pt complaince be indirectly dangerous?
- • Deadly rise in opportunistic infections
- Clostridium difficile = gram positive spore-forming bacteria that cause diarrhoea. Can cause pseudomembranous colitis can cause nasty morbities. - deadly rise in resistant organisms e.g. MRSA, Vantomycin-resistant Enterococcus (VRE), Multi-drug resistant Mycobacterium tuberculosis (MDR-TB)
Who are C.diff spores a concern for?
2) What do they cause?
1) it doesn’t infect healthy people as good/comensal bacteria stops the spores so those taking antiobiotics are 3 times more likely to be infected 2 and 3 months after taking antibiotics, and when taking and before a month after you are 7-10 fold more likely
What is an absolute contraindication to taking antibiotics?
If someone has a known hypersensitivity (however a lot of pencillin allergies are often not actually to penicillin)
What a relative contraindications to the use of antibiotics?
- liver disease: detoxification function of the liver is compromised - substances would normally be metabolized can accumulate in the liver or in the bloodstream – can become toxic to the body
- Kidney disease: kidneys are involved in elimination of drugs,
- HIV- avoid if possible to due interactions
- chronic lymphatic leukaemia
- glandular fever
- pre-exhisting diarrhoea : antibiotics could compound issue make pre-existing gut issues worse
- Preganancy
How does liver disease affect the prescribing of tetracyclines?
preferably avoided (high risk of them increasing to toxis levels) Dose related toxicity. In larger doses = jaundice, fever, and fatty liver. Hepatitis patients = require substitutes
How does liver disease affect the prescribing of Erythromycin?
preferably avoided (high risk of them increasing to toxis levels) damage to liver via bile retention and jaundice. Harmful effects – 10-14 days, incident rate 5-10%
How does liver disease affect the prescribing of metronidazole?
- Reduce metronidazole dose
o Extensively metabolised in the liver by the cytochrome P-450 family of enzymes.
o Hepatic dysfunction = half-life and clearance is prolonged, increased incidence of adverse reactions
How does liver disease affect the prescribing of clindamycin?
- Tetracycline’s, erythromycin and clindamycin preferably avoided (high risk of them increasing to toxis levels)
How does liver disease affect the prescirbing of penicillins?
the most “liver friendly”
o Least liver damage and only patients who are allergic may experience some side effects
o Safe for chronic hepatitis patients
Which antibiotic requires checks before prescirbing?
2) WHat is checked?
3. WHy?
- metronidazole
- dose adjustment is required if renal dysfunction means creatinine clearance is less that 10 mL/min
- Metro –major route of elimination of metro metabolites after liver breakdown is via the urine
What 2 antibiotics are relevant if a pt has chronic lymphatic leukaemia?
ampicillin and amoxicillin
In tonsillitis what antibiotic is not prescribed?
2) What is prescribed?
3) why?
1) - Ampicillin and Amoxicillin
2) Penicillin B
3) For tonisilliti give pencillin B rather than amoxicillin which causes rash associated with glandular fever. Ampicillin and Amoxicillin = irritating rashes unrelated to penicillin allergy in patients with chronic lymphatic leukaemia and glandular fever.
- Widespread maculopapular rash affecting the extensor surfaces of the limbs.
If you prescribe antibiotics, in pregancy what must you do:
Only prescribe if absolutely necessary: avoid first trimester (first day of missed period until 12th week) and monitor breastfed newborn for GI symptoms
Give 5 potential concerns of prescribing antibiotics to pregnant/ breastfeeding:
• Teratogenic (causing malformations/ birth defects) and toxic effects on developing foetus/newborn
• Pharmacokinetics and pharmocodynamic effects
• Blood vol doubles/ mechanism of metabolism is different
• Breastfed infants are exposed to maternal drugs
• Lactation – need to know antibiotic isn’t lost through breast milk
- can alter drug effectiveness
What is the safest antibiotic to prescribe to pregnant?
amoxicillin
What are the guidelines when prescribing metronidazole to woman in or after pregnancy?
- High doses contraindicated in pregnancy and breast feeding
- Avoid in women at risk from preterm delivery
What are the guidelines when prescribing clindamycin to woman in or after pregnancy?
- caution if breastfeeding - strips gut bacteria entirely/ lost to breastmilk
- avoid if possible pregnant, risk of necrotising enterocolitis in newbron
What are the guidelines when prescribing Co-amoxiclav to woman in or after pregnancy?
- Avoid in women at risk from preterm delivery
What are the guidelines when prescribing tetracycline to woman in or after pregnancy?
avoid in preganancy and breastfeeding, due to developmental effects on dentition of baby, can also cause spinobifida
What are the 2 types of hypersensitivity and allergy to antibiotics?
Allergy is mediated by antibodies (Type I-III hypersensitivity) or T-Cells (Type IV)
Why are anaphylatic reactions life theatening
o due to swelling of airway may block and movement of fluid out of circulation into tissues, can cause circulatory collapse. = Shock (inability to perfuse tissus)
If patients are allergic to penicillin what may you also not prescribe?
2) Why?
1) cephalosporins
2) cross reactivity
What are the minor side effects of antibiotics?
5
- GIT issues
- Candida
- Tongue discolouration
- Diarrhoea
- Stomach pain/cramps
What are the major side effects of antibiotics?
1) - Psuedomembranous colitis (antibiotic associated colitis)
2) liver injury/damadge
3) Hypokalaemia (low potassium) (pencillin)
4) Developmental e..g tetracycline stains teeth, neural tube defects
5) Drug interactions
What neural tube defects can be caused by antibiotics?
anencephaly and spina bifida
What antibiotics can cause liver damage?
o Amoxicillin = Rare instances of idiosyncratic liver injury. can occur after the antibiotic is stopped. Symptoms of hypersensitivity.
o Co-Amoxiclav = most common cause of idiosyncratic acute liver injury. Hypersensitivity or allergy. Recurrence is highly likely.
What is - Psuedomembranous colitis (antibiotic associated colitis)?
o Inflammation of the colon that occurs in some people who have taken antibiotics – almost always associated with C. diff
o Severe, uncontrollable diarrhoea which may be life-threatening
o Clindamycin
What is the symptoms of hypokalaemia? (penicillin can cause this)
o Mild to moderate hypokalaemia may be asymptomatic, weakness, constipation, leg cramps, respiratory difficulties, ECG changes (U waves, T wave flattening, ST segment changes), cardiac arrhythmias, (especially in patients who are ischaemic, on digoxin or in heart failure, ascending paralysis (severe hypokalaemia)
What is the treatment of hypokalaemia?
Remove causes
Gradual replacement of potassium (via oral route) is preferred, if clinically appropriate
An ECG is strongly recommended in patients with severe/symptomatic hypokalaemia, cardiac
Disease or renal impairment
Potassium must be replaced cautiously in patients with renal impairment or Oral potassium should be taken with plenty of fluid, with or after meals
Check magnesium levels - repletion of magnesium stores will facilitate more rapid correction of low potassium
What antibiotic interacts with alcohol?
2) WHat can occur?
1) Metronidazole
2) Disulfiram reaction, build up of aldehyde,
What are the symtoms of a disulfiram reaction that can occur if people drink alcohol while taking metronidazole?
2) How long after completetion of systemic metronidazole therapy should you wait before taking alcohol?
nausea, vomiting, flushing of the skin, tachycardia, and shortness of breath)
2) 48 hours
Which antibiotic interacts with warfarin and why?
- Metronidazole/Warfarin
o Metronidazole limits breakdown of warfarin
o Warfarin effect increased as a result of enzyme inhibition
Which and how do antibiotics increase methotrexate toxicity?
o Penicillins and tetracyclines by reducing excretion as are antimetabolites
Which antibiotic causes a rash if taking allopurinol for gout?
amoxicillin
Which oral contraceptives are not effective when taking antibiotics?
2) Why?
3) What is the solution?d
1) rifampicin or rifabutin
2) - Oral pill is broken down by gut bacteria then absorbed into blood stream
- Reduction in number of gut bacteria results in less contraceptive pill being absorbed into bloodstream
3) Use alternative birth control for dose length + 7 days
How can antibiotics be used as an adjuvant therapy?
- Acute odontogenic infections in addition to operative treatment
- Periodontal conditions in addition to operative treatment (aggressive periodontitis – low dose doxycycline)
What 3 thing sin dentistry are antibiotics not appropriate for?
• Inflammatory Conditions - early pericoronitis/ post-operative oedema
- Swelling increases volume of swelling to decrease [toxins]
• Fibrinolytic conditions - dry socket
• Non bacterial infections – fungal/ viral (no difference)
How can prophylatic antibiotics be used?
- Prevention of wound infection
* Prevention of distant infection
Factors which predispose to wound infection:
- Inherent predisposition due to site
- Procedures lasting longer than 2 hours
- Decreased patient resistance
Prophylatic antibiotics are used in tooth transplantation, why?
2) In advanced implantology what is prescribed?
1) Prevention of radiation induced osteonecrosis
2) 3g amox prescribed 1 hr pre-op reduces failure rate
Principles of the use of antibiotics to prevent wound infection
- Probability of wound infection must be high
- Select the appropriate antibiotic
- Initiate therapy at correct time
- Use for the appropriate length of time
What is usually the appropriate antibiotic?
amoxicillin
In surgery when is the correct time to initiate therapy ? why?
clot is impenetrable to antibiotics 3 hours after formation
