Instrumental Analysis

1
Bioavailability Distribution Absorption and
Transport
2

Volume of Distribution
The volume of distribution is given by the
following equation Therefore the dose
required to give a certain plasma concentration
can be determined if the VD for that drug is
known. The VD is not a physiologic value it is
more a reflection of how a drug will distribute
throughout the body depending on several
physicochemical properties, e.g. solubility,
charge, size, etc.
VD is often calculated per weight of body it is
not volume any more!
3
Medication Vd / kg body weight
heparin 0.05-0.1
insulin 0.05-0.1
warfarin 0.1-0.2
sulfamethoxazole 0.1-0.2
glibenclamide 0.1-0.2
atenolol 0.1-0.2
NXY-059 0.1-0.2
tubocurarine 0.2-0.4
theophylline 0.4-0.7
ethanol 0.7-0.9
neostigmine 0.7-0.9
phenytoin 0.7-0.9
methotrexate 1-2
indometacin 1-2
paracetamol 1-2
diazepam 1-2
lidocaine 1-2
glyceryl nitrate 2-5
morphine 2-5
propranolol 2-5
digoxin 2-5
chlorpromazine 2-5
nortriptyline 2-5
chloroquine 200
4
VD Proportion of Drug in body water 0.1 40 0.1
5 27 1 4 10
0.4
5
Two compartment model
Blood
Tissue
6
Mode of entry of drugs/toxins
Skin transport Respiratory route Oral route
7
Organ pH Surface Area
Time Stomach 1-3 up to 5 m2 0.5-20 h Small
Intestine 5-7 200 m2 2 h Colon 7-8 up to 5 2
h 1 week
logC
Time
8
Drug Bioavailability VD (L/kg
weight) Diazepam 100 0.5-2 Morphine 15-60 3-
5 Pentobarbital 95 0.7-10 Tetrahydrocannabinol
6 9-11
VD Proportion of Drug in body water 0.1 40 0.15
27 1 4 10
0.4
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Surface Area
Solubility
Concentration in bulk
Diffusion Coefficient
Diffusion Layer thickness
Solid
10
Aqeous area
BiLayer Membrane
Hydrophobic area
Aqeous area
Passive Transport
pH1
pH2