ADME & pharmacokinetics
ADME, which stands for absorption, distribution, metabolism, and excretion, collectively describes the field of pharmacokinetics, or PK. Pharmacokinetics traces …
Welcome to Chem Help ASAP.
Cp-time curves are great tools for discussing
how a drug flows through the body.
The four key processes for drug flow are absorption,
distribution, metabolism, and excretion – more
commonly known by the acronym ADME. [turn
On the screen, to the left, we find some definitions
to the letters we find in ADME.
On the right is a sample Cp-time curve for
an oral drug.
At time = 0, the patient has no drug in his
or her system, so the plasma concentration
of the drug, Cp, is 0.
Once the patient takes the drug, it passes
into the stomach.
Very soon, the drug pill or capsule will break
down and release the drug into the patient’s
The drug will then be *absorbed* into the
Absorption is the movement of drug from the
site of administration to the plasma.
At this point, the drug will be detectable in the
plasma of the patient, and the Cp value will rise.
As soon as the drug enters the plasma, it
will be transported throughout the bloodstream
and *distribute* into all the tissues of the
Distribution is movement of a drug to or from
the plasma and the tissues in the body.
In a short amount of time, perhaps 2-3 hours
for most oral drugs, the drug will be completely
absorbed from the gastrointestinal tract.
The Cp-time curve will reach its peak and
continue with a downward trend.
There are two processes that cause Cp to decrease.
One is *metabolism*, which is the chemical
destruction of a molecule.
Metabolism mostly occurs in the liver.
The other is *excretion*, which is the removal
of drug from the bloodstream.
Excretion mostly occurs through filtration
by the kidneys.
As the drug is removed from the plasma through
metabolism and excretion, the drug that is
in the different tissues will continue to
distribute back into the blood for eventual
Therefore, absorption tends to dominate the
early part of the Cp-time curve.
Metabolism and excretion dominate the later
Distribution is at work across the entire
curve as the drug moves to and from the plasma
and the tissues.
We’ve now described the main topics of the field
*pharmacokinetics* – often abbreviated PK.
Pharmacokinetics, which studies how a drug
travels to and from its target or site of
action in the body.