PK, PD, PV, PG Flashcards
When a drug has lots of protein binding a low Vd and a narrow theraputic window, what factors will effect the distribution of the drug?
Factors effecting protein binding:
- hypoalbuminuria, pregnancy, renal failure, other drugs
What characteristic of a drug will mean weight needs to be taken into account when calculating dose?
large Vd- as will need much more drug in larger person to get the same plasma concentration
What will be the Vd in a 92kg man with a drug of 18L/kg vs a man of 46Kg taking the same drug?
92x18= 1656 L
46x 18= 828 L
How long dose it take to reach a steady sate of [drug] when repeated administration is given?
It takes 3-5 half lives- so if drug has long half life it will take longer to get to a steady state
How is half life of a drug related to Vd and clearance?
proportional to Vd- distributed well= long half life
Inversely proportional to clearance
When are loading doses given?
For drugs which have a long half life and you need to get up to steady state therapeutic doses quickly
How can a loading dose be calculated?
Vd x desired [drug] at target
If GFR drops by from 120ml/min to 60mil/min, what will happen to the rate of clearance?
It will half
Name 3 CYP inducers
cranberry juice, phenytoin & carbemazepine (antiepileptics), rifampicin, chronic alcohol use, sulphonylureas, st johns wort
Name 3 CYP inhibitors
ompeprazole, disulfiram, erythromycin, valproate (antiepileptic), isoniazid, cimetidine, ciprofloxacin, acute alcohol, sulphonamines
Give 3 factors which will influence an individuals response to a drug
- genetics
- age
- organ function
- drug interactions
- nature of disease
Give 3 reasons why elderly are at greatest risk of polypharmacy
- multiple comorbitities
- worsening comorbities with age
- hospitalisation
- multiple practitioners
- pt and relative expectations
