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Drug
Administration
Lesson 3
Definitions
Pharmacokinetics
 What the body does to the drug.
 Administration, absorption,
distribution, & fate
 Focus of next 2 sections
 Pharmacodynamics
 What the drug does to the body.
 drug effects
 Coming soon ~

How To Get From Here To There?
Drug
Target
Complex Journey ~
Routes of Administration
Critical to efficacy
 Rapidity of onset
 Duration of effects
 Magnitude of effects
 Systemic administration
 Drug into circulatory system via ...
 Enteral routes
 Parenteral routes
 Drug effects throughout body ~

Oral

Per Os (PO)
by
mouth
absorption across
membrane in GI
 most common
 most variable
st pass metabolism
 1
 Cooperation required
 Can recall ~

Oral

Sublingual
 Absorption:
mucous membrane
 salivary glands

e.g., nitroglycerin,
buprenorphine
 Chewing
 absorbed across
lining of mouth ~

Injection

Intravenous (iv)
 directly into vein
 rapid onset of effects
Fastest
~
Injection
Intramuscular (im)
 Location important
 Deltoid - rapid
 Thigh - moderate
 Buttocks - slowest
 Difference in blood
supply & distance ~

Injection
Subcutaneous (sc)
 under skin
 slow, steady absorption
 Disadvantages
 Variable absorption
 limited volume
 skin irritations ~

Injection
Intraperitoneal (ip)
 into peritoneal cavity of abdomen
 Can deliver large amounts
 Not used in humans much
 Danger of infection ~

Injection

Intrathecal (epidural)
 under sheath of nerve fibers,
spinal cord
 Mostly as local anesthesia
 little importance for psychoactive
drugs ~
Injection



Intracranial
 directly into brain
 direct access to cells
intraventricular - into CSF
Peripheral vs. central effects
 e.g. curare
peripheral
---> paralysis
central ---> convulsions ~
Inhalation
Smoking
 Lungs
 gases or vapors
 densely lined with capillaries
 large surface area
 Fast absorption
 Similar to iv ~

Intranasal
Particles of drug
 insufflation = sniffed
 Absorption across
mucous membrane of
nose
 Not in lungs!
 Slower absorption
 effects not as strong as
inhalation ~

Other routes

Transdermal patches
 absorbed by skin
 slow continuous release
also
liposomes: via injection
Suppositories - rectal or vaginal
 absorption incomplete &
unpredictable
 Pellets - Norplant
 Microcatheter & pump ~

The Future: Part 1

Polymer-to-gel
 drug + water + biodegradeable polymer
 45 C: liquid & injectable
 37 C: solidified gel capsule
 70% of drug released over 12 days ~
The Future: Part 2

Injections without NEEDLES!?
 only some drugs enter via patch


e.g. nicotine, scopolamine
VLF - very low frequency sound
 disrupts lipid layer of skin
 more room for molecules to enter
 insulin, interferon gamma, etc

works in rats & cadavers ~
Choice of route

Consider factors
 Patient characteristics
 Concentration in blood
 Amount delivered
 Rapidity of onset
 Duration of effects
 Magnitude of effects ~
related
In general...
Rapid onset of effects
 higher magnitude
 shorter duration
 Slow onset of effects
 lower magnitude
 longer duration ~

i.v. & inhalation
Blood
Level
im, sc, ip
p.o.
sec min
hr
Time
hrs