Pharmacokinetics - Absorption and Distribution

What are the four steps of pharmacokinetics?

Absorption, distribution, metabolism, excretion

Which type of transport requires a carrier but no energy is used?

Facilitated diffusion

Most of the drugs we use are absorbed by ___

passive diffusion

To be absorbed passively a drug must be ___

lipophilic

Which of the following does not affect absorption?

speed of absorption

3 multiple choice options

What are the factors that affect absorption?

particle size of drug

lipid solubility

ionization

pH

surface area of membrane

The more ___ a drug is, the better it is absorbed

lipophilic

The more hydrophilic a drug is, the more likely it will be ___

excreted

A weak acid will be ___ in a basic medium

ionized

A weak base will be ___ in a basic medium

unionized

Hydrophilic form = ____

ionized

Hydrophobic form = ___

unionized

Almost all drugs are filtered at the ___

glomerulus

If a drug is ___ during its passage down the renal tubule, a significant portion will be reabsorbed

unionized

A drug will be 'trapped' in the urine if most of the drug is in the ___ state

ionized

Weak acids are excreted faster in ___ urine

alkaline

Which substances can be given to acidify urine?

NH4Cl, vitamin C, cranberry juice

Which substances can be given to alkalinize urine?

Sodium bicarbonate and acetazolamide

Phenobarbitone is a ___ drug

weakly acidic

Atropine is a ___ drug

Weakly basic

Chloroquine is a ___ drug

weakly basic

Total body water in a 70kg man?

42 liters

Extracellular fluid volume?

14 liters

Intracellular fluid volume?

28 liters

Plasma volume?

4 liters

Interstitial fluid volume?

10 liters

Drugs distributed to the intracellular compartment must be ___ soluble

lipid

Drugs distributed to the interstitial department must be ___

small enough to cross slit junctions

Drugs that stay in plasma are ___ to cross the slit and tight junctions

too big

Drugs that remain in the plasma may be ___

ionized - cannot cross cell membrane

Some drugs remain in the plasma because they are bound to ___

plasma proteins

___ represents the fluid volume required to contain the total amount of absorbed drug in the body at a uniform concentration

Volume of distribution

Why is Vd called apparent?

Vd calculated can exceed volume in any person

Drugs with HIGH Vd values have higher concentrations in ___

extravascular tissue

Drugs with LOW Vd have higher concentration in the ___

vascular compartment

Which factors affect distribution?

Molecule size, lipid/water solubility, protein binding

Warfarin has a ___ Vd because it is strongly bound to albumin

small

Acidic drugs tend to bind to ___ and basic drugs bind to ___

albumin, alpha acid glycoproteins

Chloroquine is strongly bound to ___ and therefore has a high Vd

tissue proteins

___ bound drugs cannot cross the cell membrane and are restricted to the vascular compartment

protein

___ displaces warfarin leading to excessive bleeding

Sulfonamide