Science underpinning CDM Flashcards
What is the difference between simple and complex decisions?
Simple- intuitive
Complex- evidence based, analytical
What is the dual processing theory?
Pattern processor for decision making
System 1- recognised
System 2- not recognised and have to think about it more. With repetition and pattern recognition, it will go into system 1
What are the limitations of EBM and NICE guidelines?
- Many patient have factors that result in non-guideline therapy being optimal e.g. poor renal function and contraindications
- Many trials exclude “real world” patients e.g. pregnant women, elderly patients, comorbidities
Do humans prefer system 1 or 2 and why?
System 1 as it requires less effort
It can be difficult to use system 2 if you believe system 1 is correct
When making a decision about a patient’s treatment, what factors will affect system 2?
Everything to do with the patient and the drug e.g. PD, PK, guidelines
Benefits vs risks
Medication factors
Often medicines are prescribed for an acute time but carrying on for a long time without anyone reviewing the patient. True or false?
True
What are the 3 targets for all treatments?
- Improve QOL
- Decrease mortality
- Decrease morbidity
What are the 5 key questions in CDM for pharmacy?
- What therapy would we expect for this patient and condition?
- Any factors that would alter the clinical pharmacology of these medicines?
- Are these medicines indicated, effective, safe and convenient?
- Identify any problems caused by medicines
- Any potential problems the medicine may cause?
What is a type A ADR?
- Predictable and common
- Usually not serious
What is type B ADR?
- Allergy/idiosyncratic
- Unpredictable
- Rare, usually serious (high mortality)
- Often discovered after marketing
What are the pharmaceutical causes for Type A ADR?
- Formulation/excipients affecting bioavailability or absorption e.g. digoxin
- Delivery systems can cause toxicity e.g. indometacin
What are the pharmacodynamic causes for Type A ADR?
- Altered target organ sensitivity e.g. warfarin doses in the elderly need reducing as liver is more sensitive
- Altered homeostatic mechanisms as a side effect e.g. beta blockers
What are the pharmacokinetic causes for Type A ADR?
- Renal and liver functions
- 1st pass metabolism
- GI absorption
What are the pharmaceutical causes of Type B ADR?
- By products/degradation products causing allergic reaction
- Components e.g. lactose
What are the pharmacodynamic causes of Type B ADR?
- Genetic abnormalities e.g. G6PD deficiency
What are the pharmacokinetic causes of Type B ADR?
- Formation of unusual metabolites
- Immune mediated
Who are more at risk of ADRs?
- Pregnancy
- Children and elderly
- Female
- Poor/rapid metabolisers
- Previous ADRs
- Renal or liver impairment
- HIV patients (immune related problems)
- Polypharmacy
- Ethnicity has an impact too
Drug interactions are responsible for what % of ADRs?
20%
What is phase 1 metabolism?
CYP450
Isoenzymes e.g. CYP1A2
Oxidation, hydrolysis and reduction
What is phase 2 metabolism?
Conjugation of drug with glucuronic or sulphuric acid
How do you calculate Cockcroft and Gault to estimate creatinine clearance?
CrCl (ml/min) =(F x (140-age) x weight)/ S.Cr
F= 1.23 for males and 1.04 for females
How do you calculate loading dose?
(Vd x Cp)/(S x F)
where F= salt factor
Cp= target plasma concentration
What is a salt factor?
Proportion of active drug
How do you calculate volume of distribution?
D/Cp
What are the 5 stages of CKD?
In terms of eGFR (mL/min/1.73m^2)
- > 90
- 60-89
- 30-59
- 15-29
- <15 - kidney failure
How do you calculate maintenance dose?
Drug rate in = drug rate out
(S x F x D)/T = Cp xCl
What is the PK profile of phenytoin?
- Largely insoluble so has added ingredients in formulation- salt
- Narrow therapeutic window
- Zero order kinetics (non-linear, saturation)
- Highly protein bound ~ 90% to albumin
- half life = 12-14 hours
- CYP3A4 and 2C19 inducer
- Small increase in dose, large increase in serum conc, accumulation risk
- vd = 0.65 L/kg
If phenytoin levels are unusual, what test can you do?
Albumin levels in the plasma as it is so highly protein bound
Normal range = 45-55 g/dL
If albumin levels are fine and there is no free phenytoin in the plasma, question adherence
What is the plasma target range for phenytoin?
10-20 mg/L
How can ciprofloxacin interact with epilepsy?
Can lower the seizure threshold
What are the NICE guidelines for an uncomplicated UTI?
- Offer symptomatic relief with paracetamol and a NSAID if needed
- Offer an antibiotic to all women with a suspected urinary tract infection
(UTI) — Prescribe:
• Trimethoprim 200 mg twice daily orally, or
• Nitrofurantoin 50 mg four times daily orally, or 100 mg (modifiedrelease)
twice daily
for 3 days
do not recommend cranberry or urine alkalinising agents
