Lecture 6 - general principles of treatment

Question 1

Difference between primary and secondary prophylaxis ?

Answer 1

1 - prevent initial infection

2- prevent recurrent episodes

Question 2

Name the five questions asked in accurate diagnosis of an infection

Answer 2

1- infection?
2- source?
3- microorganism?
4- need antibiotics or self limiting?
5- urgent or can diagnosis me made?

Question 3

If a positive culture has been identified, when would you not start antibiotics ?

Answer 3

if culture is from a non sterile sit e.g. wounds

could just be colonisation

Question 4

When would you use a broad spectrum antibiotic (2) what is the risk (1)

Answer 4

when microbiology is uncertain or infection is caused by a mixture of organisms. promotes resistance

Question 5

What 5 things must you consider when evaluating if the drug is safe to give a particular patient

Answer 5

1) does the patient have impaired excretion
2) any drug interactions with preexisting prescriptions
3) is there a high risk of toxic effect e.g. CNS toxicity in epileptic, BM toxicity in transplant patients
4) does the patient have a known hypersensitivity?
5) is there a risk of Abx associated diarrhoea

Question 6

When would a bacteriostatic antibiotic be effective?

Answer 6

if the toxin is the main pathogenic agent, bacertiocidal drugs would cause lysing of cells and therefor release more toxins

Question 7

Name three situations when bacteriocidal drugs are preferred

Answer 7

the immunocompromosed (ill or stedoid therapy)
the immunodeficient (neutropenia or HIV)
difficult sites (meningitis or endocarditis)

Question 8

Name some positives of changing from iv to oral antibiotics

Answer 8

reduces potential of line infection
saves nursing time
reduces patient discomfort
reduces treatment costs 
reduce risk of adverse effects

Question 9

What is the criteria for changing from iv to oral antibiotics

Answer 9

Clinical improvement observes
Oral route is not compromised
Markers showing trend towards normalising
Specific indication/ deep seated infection

Question 10

How long should most infections take to respond to treatment?

Answer 10

5-7 days according to severity of condition

Question 11

What is outpatient parenteral antibicrobial therapy and when is it appropriate?

Answer 11

iv at home - long term semi-permanent line and self administered. used in long term treatment to reduce hospital bed days and less hospital acquired infections

Question 12

Give three reasons why combination therapy would be more effective than monotherapy

Answer 12

broader spectrum cover
prevent resistance e.g. tb
synergistic e.g. penicillin and gentamicin

Question 13

State two negatives to combination therapy

Answer 13

increase costs and increased risks of toxicity

Question 14

When is it appropriate to give oral vancomycin and not systemic

Answer 14

with infections in the gut e.g. cdiff. dont use oral for systemic infections as wont work - use iv

Question 15

Name 4 situations that may need extra considerations when prescribing

Answer 15

pregnancy
lactation
newborn
old age

Question 16

Name some of the pharmacokinetic considerations in newborns

Answer 16

• high ECF volume so lower plasma conc of drug
• immature hepatic enzymes
• lower g6pD concs (risk haemolysis)
• renal immaturity (30-60% of adult GFR)
• prolonged half life and raised cMAX

Question 17

Name some infection risks in pregnant women

Answer 17

URTI
LRTI
UTI
interuterine infection
amnionitis

Question 18

Name 5 antibiotics that are contraindicated in pregnancy (and what they cause)

Answer 18

sulphonamides (kernicterus), streptomycin (ototox), tetracyclines (tooth discolour and bone growth interfere), chloramphenicol (CV collapse), sulfonamides and nitrofurantoin (haemolysis)

Question 19

which antibiotic should you avoid when breast feeding and why

Answer 19

metronidazole as 1:1 serum to breast milk ratio

Question 20

when may Abx treatment in the elderly not be effective?

Answer 20

• organ function in decline
• often affected by multiple diseases/ on multiple long term meds
• compliance may be compromised

Question 21

Name some of the pharmacokinetic considerations of the elderly

Answer 21

• reduction in total bod water + distribution
• GI surgery?
• ph altered by drugs or diseases?
• hepatic involution
• reduced GFR with age
• lower renal blood flow

Question 22

Name 6 life threatening infections that require immediate treatment

Answer 22

Meningitis, meningococcal sepsis, epiglottitis, encephalitis, Necrotising fascilitis, toxic shock syndrome

Question 23

Name some factors involved in the selection of appropriate antibiotic therapy

Answer 23

site of infection, seriousness, likely organism, patient circumstances, cost, toxicity and side effects, local/ national resistance rates, other underlying disease, contraindications

Question 24

What pharmokinetics must be considered when prescribing?

Answer 24

absorption (bioavailability, food, other drugs) distribution (serum tissue concs, protein binding, crossing natural boundaries), metabolism (half life), excretion

Question 25

Name three questions that must be asked when considering HOW much drug to dose a patient with

Answer 25

- do they need a loading dose? - do they have renal failure (some drugs will need reduced dose)? - does dose need to be done by weight?

Question 26

Name three bacteriocidal drugs and there bacteriostatic

Answer 26

``` CIDAL = penicillin, ciprofloaxin and gentamycin STATIC = tetracyclines and sulphonamides ```

Question 27

What kind of infections would need to be treated longer?

Answer 27

deep seated infections e.g. liver abscess, osteomyelitis, empyema, cavitating pneumonia

Question 28

Name four drugs that have reduced elimination in the elderly

Answer 28

penicillins, cephalosporins, vancomycin and aminogycosides