routes of drug administration.pptशहहहहहहहहह

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1. Routes of Drug
Administration

2. Drug Absorption
Absorptionistheprocessby
whichadrugentersthe
bloodstream withoutbeing
chemicallyalteredor
Themovement ofadrug
fromitssiteofapplication
intothebloodorlymphatic
system

3. Drug Absorption
Factors which influence the rate of
absorption
types of transport
the physicochemical properties of the
drug
protein binding
routes of administration
dosage forms
circulation at the site of absorption
concentration of the drug

4. Drug Absorption
The rate at which a drug
reaches it site of action depends
on:
Absorption-involves the
passage of the drug from its
site of administration into the
blood
Distribution-involves the
delivery of the drug to the
tissues

5. Routes of Drug
Administration
Therouteofadministration
(ROA)thatischosenmayhave
aprofoundeffectuponthe
speedandefficiencywith
whichthedrugacts
Important
Info

6. The possible routes of drug
entry into the body may be
divided into two classes:
Enteral
Parenteral

7. Enteral Routes
Enteral-drug placed directly in the GI
tract:
sublingual -placed under the
tongue
oral -swallowing (p.o., per os)
rectum -Absorption through the
rectum

8. Sublingual/Buccal
Some drugsaretakenassmaller
tabletswhichareheldinthemouth
orunderthetongue.
Advantages
rapid absorption
drug stability
avoid first-pass effect

9. Sublingual/Buccal
Disadvantages
inconvenient
small doses
unpleasant taste of some drugs

10. Oral
Advantages
Convenient-can be self-administered,
pain free, easy to take
Absorption-takes place along the whole
length of the GI tract
Cheap-compared to most other
parenteral routes

11. Oral
Disadvantages
Sometimes inefficient -only part
of the drug may be absorbed
First-pass effect -drugs
absorbed orally are initially
transported to the liver via the
portal vein
irritation to gastric mucosa -
nausea and vomiting

12. Oral
Disadvantages cont.
destruction of drugs by gastric
acid and digestive juices
effect too slow for emergencies
unpleasant taste of some drugs
unable to use in unconscious
patient

13. First-pass Effect
Thefirst-passeffectistheterm
usedforthehepaticmetabolism
ofapharmacological agentwhen
itisabsorbedfromthegutand
deliveredtotheliverviathe
portalcirculation.Thegreater
thefirst-passeffect,thelessthe
agentwillreachthesystemic
circulationwhen theagentis
administeredorally

14. First-pass Effect cont.
Magnitude of first pass hepatic effect:
Extraction ratio (ER)
ER = CL liver / Q ; where Q is hepatic
blood flow (usually about 90 L per hour.
Systemic drug bioavailability (F) may be
determined from the extent of absorption
(f) and the extraction ratio (ER):
F = f x (1 -ER)

15. First-pass Effect

16. 1. unconscious patients and children
2. if patient is nauseous or vomiting
3. easy to terminate exposure
4. absorption may be variable
5. good for drugs affecting the bowel such
as laxatives
6. irritating drugs contraindicated
Rectal

17. Parenteral Routes
Intravascular(IV, IA)-placing a drug
directly into the blood stream
Intramuscular(IM) -drug injected into
skeletal muscle
Subcutaneous -Absorption of drugs
from the subcutaneous tissues
Inhalation-Absorption through the
lungs

20. Intravascular
Absorption phase is bypassed
(100% bioavailability)
1.precise, accurate and almost immediate onset of
action,
2. large quantities can be given, fairly pain free
3. greater risk of adverse effects
a. high concentration attained rapidly
b. risk of embolism
c. OOPS factor or !@#$%

21. Intramuscular
1. very rapid absorption of drugs in aqueous
solution
2.repository and slow release preparations
3.pain at injection sites for certain drugs

22. Subcutaneous
1. slow and constant absorption
2. absorption is limited by blood flow,
affected if circulatory problems exist
3. concurrent administration of
vasoconstrictor will slow absorption

23. 1.gaseous and volatile agents and aerosols
2.rapid onset of action due to rapid access to
circulation
a.large surface area
b.thin membranes separates alveoli from
circulation
c.high blood flow
Particles larger than 20 micron and the particles impact
in the mouth and throat. Smaller than 0.5 micron and
they aren't retained.
Inhalation

24. Inhalation cont.
Respiratory system. Except for IN, risk hypoxia.
Intranasal (snorting) Snuff, cocaine may be partly oral via post-
nasal dripping. Fairly fast to brain, local damage to septum.
Some of the volatile gases also appear to cross nasal membranes.
Smoke (Solids in air suspension, vapors) absorbed across lung
alveoli: Nicotine, opium, THC, freebase and crack cocaine,
crystal meth.Particles or vapors dissolve in lung fluids, then
diffuse. Longer action than volatile gases. Tissue damage from
particles, tars, CO.
Volatile gases: Some anaesthetics (nitrous oxide, ether) [precise
control], petroleum distillates. Diffusion and exhalation
(alcohol).
Lung-based transfer may get drug to brain in as little as five
seconds.

25. Topical
•Mucosal membranes(eye drops, antiseptic,
sunscreen, callous removal, nasal, etc.)
•Skin
a. Dermal -rubbing in of oil or ointment
(local action)
b. Transdermal -absorption of drug through
skin (systemic action)
i. stable blood levels
ii. no first pass metabolism
iii. drug must be potent or patch
becomes to large

26. intravenous 30-60 seconds
intraosseous 30-60 seconds
endotracheal 2-3 minutes
inhalation 2-3 minutes
sublingual 3-5 minutes
intramuscular 10-20 minutes
subcutaneous 15-30 minutes
rectal 5-30 minutes
ingestion 30-90 minutes
transdermal (topical) variable (minutes to
hours)
Route for administration
-Time until effect-

27. Time-release preparations
Oral-controlled-release, timed-
release, sustained-release
designed to produce slow,uniform
absorption for 8 hours or longer
better compliance, maintain effect
over night, eliminate extreme peaks
and troughs

28. Time-release preparations
Depot or reservoir preparations
-parental administration (except
IV), may be prolonged by using
insoluble salts or suspensions in
non-aqueous vehicles.

29. TheROAisdeterminedbythe
physicalcharacteristicsofthe
drug,thespeedwhichthedrugis
absorbedand/orreleased,aswell
astheneedtobypasshepatic
metabolismandachievehigh
conc.atparticularsites
Important
Info

30. No singlemethod of drug
administration is ideal for all
drugs in all circumstances