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Ph

armacokinetics

Lecture#

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Pharmacologic Principles

Quantitative Analysis and Data ProcessingIn Nuclear Medicine

Pharmacologic Principles

Chemical

name

●

‐^2

‐(p

‐isobutylphenyl

)^

propionic

acid

●

(p

isobutylphenyl

)^

propionic

acid

Generic

name

●

ibuprofen

Trade

name

●

Motrin

Pharmacologic Principles

●

Pharmaceutics

●

Pharmacokinetics

●

Pharmacodynamics

●

Pharmacotherapeutics

●

Pharmacognosy

Pharmacologic Principles

Pharmaceutics

Pharmacologic Principles

Pharmacokinetics

●

The

study

of

what

the

body

does

to

the

drug:

y^

y^

g

Absorption Distribution Metabolism Excretion

Pharmacologic Principles

Pharmacokinetics

●

Absorption

●

Absorption

Enteral Route

Drug

is

absorbed

into

the

systemic

circulation

through

the

oral

or

gastric

mucosa,

the

small

intestine,

or

rectum.

Oral SublingualSublingual Buccal Rectal

Pharmacologic Principles

Pharmacokinetics

●

Distribution

●

Distribution

The

transport

of

a

drug

in

the

body

by

the

bloodstream

to

its

site

of

action.

Protein

‐binding,

water

soluble

vs.

fat

soluble,

blood

‐brain

barrier

Areas

of

rapid

distribution:

heart,

liver,

kidneys,

brain

Areas

of

slow

distribution:

muscle,

skin,

fat

Pharmacologic Principles

Pharmacokinetics

●

Metabolism

The

biologic

transformation

of

a

drug

into

an

inactive

metabolite,

a

more

soluble

compound,

or

a

more

potent

metabolite.

Liver (main organ), kidneys, lungs, plasma, intestinal mucosaLiver

(main

organ),

kidneys,

lungs,

plasma,

intestinal

mucosa

Factors

that

decrease

metabolism

Cardiovascular

dysfunction,

renal

insufficiency,

starvation,

obstructive jaundice slow

acetylator

Erythromycin or

obstructive

jaundice

,^

slow

acetylator

,^

Erythromycin

or

ketoconazole drug

therapy.

Factors

that

increase

metabolism

Fast acet lator Barbit rates Rifampin therapFast

acet

ylator,

Barbit

urates,

Rifampin

therap

y

Delayed

drug

metabolism

results

in

Accumulation

of

drugs,

prolonged

action

of

the

effects

of

the

dd

rugs

Pharmacologic Principles

Pharmacokinetics

●

Excretion

●

Excretion

The

elimination

of

drugs

from

the

body

Kidneys

(filtration

secretion)

Liver

(metabolism

secretion)

Lungs

(exhalation)

Oth

(b

t^

ilk

t^

li

t )

Others

(b

reast

milk,

sweat,

saliva,

etc)

Pharmacologic Principles

Pharmacokinetics

●

Half

‐Life (Biological)

●

Half

Life

(Biological)

The

time

it

takes

for

one

half

of

the

original

amount

of

a

drug

in

the

body

to

be

removed.

A

measure

of

the

rate

at

which

drugs

are

removed

from

the

body.

Most

drugs

are

considered

to

be

effectively

removed

after

about

five

half

‐lives

Pharmacologic Principles

Pharmacokinetics

●

A drug has a half life of 10 seconds You give a patient a

●

A

drug

has

a

half

life

of

seconds

.^

You

give

a

patient

a

dose

of

6mg.

After

seconds

how

much

of

the

drug

remains?

Time

Amount

0 sec

6 mg

10 sec

3 mg

20 sec

1.5 mg

30 sec

0 75 mg

30 sec

0.75 mg

Pharmacologic Principles

PK

in

Drug

Development

●

In the preclinical testing we administer different doses of

●

In

the

preclinical

testing

,^

we

administer

different

doses

of

the

drug

and

the

responses

(the

safety).

●

The

best

‐select

from

the

preclinical

studies

are

scaled

up

for

patients

in

three

phases.

Pharmacologic Principles

PK

in

Drug

Development

●

Phase I

●

Phase

I

It

is

usually

a

small

study

with

small

groups.

The

dose

is

escalated

keeping

in

mind

the

concern

for

safety,

not

efficacy.

The

escalation

continues

till

toxicity

appears.

However,

in

oncology

we

can

go

pretty

far

because

it’s

a

life/death

situation.

If

you

are

only

studying

a

small

number

of

patients,

then

you

can

get

a

lot

of

measurements

and

hence

a

lot

of

levels.

So

if

you

get

a

lot

of

drug

levels,

y

ou

can

characterize

the

numbers

well

in

the

g^

, y

small

number

of

individuals.