Distribution Flashcards
Rate and extent of distribution depends on:
- Relative arterial blood perfusion rate of different organs
- Permeability characteristics of barriers
- Binding in blood or tissues
Order of blood flow to different groups of tissue
Highly-perfused lean tissue group
- Blood cells, heart, lung, liver, kidney, glands, brain, uterus & placenta
Poorly-perfused lean tissue group
- Muscle, skin
Fat group
- Adipose tissue, bone marrow
Neglible perfusion
- Teeth, hair, bone, tendon, cartilage
Illustrate alpha and beta phase of anasthesia
Illustrate 2 compartment model
a-phase: DISTRIBUTION + ELIMINATION
b-phase: ELIMINATION
Illustrate 3-compartment model
Characteristics of BBB with regards to transport
- Extreme form of lipid barrier
- Few intercellular pores
- Tight juntions
- Sorrounded by glial cells
- Lipid soluble drugs penetrate
- Water soluble/polar drugs have limited access
- Sedating vs non-sedating antihsistamines
Special features of BBB in meningitis
Less effective, leaky. Can give ABs that don’t normally pass through e.g benzylpenicillin
Domperidone vs Metocloperamide
- Both anti-emetics
- Both dopamine receptors anatognists
- Metocloperamide crosses BBB and causes drug-induced parkinsonism
- Domperidone does not cross BBB
As an exception from the rule, which drug does not cross placenta
Heparin, high MW and polarity
Plasma protein site at which many acidic drugs bind
To a common site on albumin
e.g. warfarin, sulphonamides, salicylic acid
Common plasma protein site where basic drugs bind
Alpha1-acid glycoprotein
e.g. Diazepam, propanolol, lidocaine
Characteristics of a protein bound drug
- NOT transferred across membrane
- NOT pharmacologically active
- NOT excreted or metabolised
Typical distribution if Vd is 3L
Only distribured in plasma
e.g. heparin, plasma expanders, MABs
Typical distribution of a Vd 12L
Drug is distributed in plasma + interstitial fluid
Warfarin/ibuprofen = 7L
Polar, water soluble drugs
Typical distribution if Vd is 40L
Drug is distributed in total body water
