10. Factors affecting choice of route
Physical and chemical properties of drugs.
Site of desired action
Rate and extent of absorption of drug
from different routes.
Effect of digestive juices and first pass
metabolism.
Rapidity with which response is desired.
Condition of patient.
Accuracy of dosage required.
13. The
possible routes of drug
entry into the body may be
divided into two classes:
Enteral
Parenteral
14. 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
15. Sublingual/Buccal
Some drugs are taken as smaller
tablets which are held in the mouth
or under the tongue.
Advantages
rapid
absorption
drug stability
avoid first-pass effect
17. 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
18. 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
19. 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
20. First-pass Effect
The first-pass effect is the term
used for the hepatic metabolism
of a pharmacological agent when
it is absorbed from the gut and
delivered to the liver via the
portal circulation.
The greater
the first-pass effect, the less the
agent will reach the systemic
circulation when the agent is
administered orally
22. Rectal
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
23. 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
24. Routes of Drug Administration
common abbreviations…
PO = per os = oral
IV = intravenous = into the vein
IM = intramuscular = into the muscle
SC = subcutaneous = between the skin and muscle
IP = intraperitoneal = within the peritoneal cavity
icv = intracerebroventricular =
directly into the ventricle of the brain
29. 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 !@#$%
30. Intramuscular
1. very rapid absorption of drugs in
aqueous
solution
2.repository and slow release preparations
3.pain at injection sites for certain drugs
31. 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
34. Inhalation
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.
35. Inhalation cont.
Respiratory system. Except for IN, risk hypoxia.
Intranasal (snorting) Snuff, cocaine may be partly oral via postnasal dripping.
Smoke (Solids in air suspension, vapors) absorbed across lung
alveoli: Nicotine, opium
Volatile gases: Some anaesthetics (nitrous oxide, ether)
petroleum distillates. Diffusion and exhalation (alcohol).
Lung-based transfer may get drug to brain in as little as five
seconds.
36. Topical
Skin
a. Dermal-rubbing in of oil or ointment
(local action), paste, powder, cream,
dressing, spray, etc
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
39. Time-release preparations
Oral - controlled-release, timedrelease, sustained-release
designed to produce slow,uniform
absorption for 8 hours or longer
better compliance, maintain effect
over night, eliminate extreme peaks
and troughs
40. Time-release preparations
Depot or reservoir preparations
- parental administration (except
IV), may be prolonged by using
insoluble salts or suspensions in
non-aqueous vehicles.
41. Important
Info
The ROA is determined by the
physical characteristics of the
drug, the speed which the drug is
absorbed and/ or released, as well
as the need to bypass hepatic
metabolism and achieve high
conc. at particular sites
42. r t an t
Impo
V e r y fo !
In
No single method of drug
administration is ideal for all
drugs in all circumstances
Editor's Notes
ADVANTAGES-
Routes Of Drug Administration - דרך מתן התרופה
Enteral - דרך מערכת העיכול
Parenteral - שלא דרך מערכת העיכול
Rectal - דרך פי הטבעת (ה-rectum) למשל ע”י נרות
Respiratory - של מערכת הנשימה למשל אינלציה
Topical -מקומי (דרך העור או הרירית) למשל משחת עור או טיפות עיניים
oral - הצורה הכי נפוצה
