pharmacokinetics

what is pharmacokinetics?

what the body does to the drug

what does pharmacokinetics determine? (3)

- how much drug reaches the target

- how quickly the drug starts to have an effect

- the duration of the effect

what are the different routes of administration? (5)

- oral

- inhalation

- topical (creams)

- injection

- rectal/vaginal

what determines a drugs pharmacokinetics? (4)

Absorption

Distribution

Metabolism

Excretion

what determines the absorption of the drug? (2)

- bioavailability

- gut absorption

what is bioavailability?

the fraction of the administered dose that reaches the systemic circulation unchanged

what is the bioavailability of intravenous administration?

100%

for orally given drugs, what is bioavailability determined by? (3)

- stability in gut contents

- absorption across gut wall

- degree of first pass metabolism

what determines the gut absorption of a drug? (3)

- surface area

- gastric emptying (delayed will increase absorption)

- gut motility (decreased gut motility will increase absorption)

what does distribution mean?

movement and storage around the body

what is the equation for volume of distribution?

Vd = Q/C

C - plasma concentration

Q - dose of drug

Vd - volume of blood

what is the half-life of a drug?

the time taken for the plasma concentration of the drug to fall to half of its original value

what does decreased drug metabolism lead to?

- increased plasma drug conc

- increased biological response

what does increased drug metabolism lead to?

- decreased plasma drug conc

- decreased biological response

decreased renal excretion leads to?

- increased plasma drug conc

- increased biological response

what is drug clearance?

the rate of elimination of the drug from the body in terms of the volume of blood

what is the equation for drug clearance?

clearance = elimination rate/concentration