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Routes of drug administration:
A route of administration in pharmacology and toxicology is the path by which a drug, fluid, poison, or other substance is taken into the body.[1] Routes of administration are generally classified by the location at which the substance is applied. Common examples include oral and intravenous administration. Routes can also be classified based on where the target of action is. Action may be topical (local), enteral (system-wide effect, but delivered through the gastrointestinal tract), or parenteral (systemic action, but delivered by routes other than the GI tract)
2. Three easy steps for
understanding
pharmacology !
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3. Pharmaceutical process
Drug reaches the patient
Pharmacokinetic process
What body does to the drug
Pharmacodynamic process
What drug does to the body
Pharmacotherapeutic process
Therapeutic effect on the patient
4. Routes of Drug Administration
Route of administration
is the path by which a
drug, is brought into
contact with the body
5. Factors deciding the choice of route
Physical & chemical properties-
Solid/Liquid/Gas, Irritancy, p H
Site of desired action- Local or systemic
Rate of absorption from a route
Effect digestive juice and first pass
metabolism
Routine or emergency
Accuracy of dosage
Condition of Pt.-Unconscious, vomiting
6. Routes of drug administration
Parentral
Enteral
--Oral
--Rectal
Sublingual
Injection -
i.m, i.v, s.c
etc
Topical
inhalational
7.
8. Oral or Enteral route
Advantages:
Safer
More convenient
Economical
Painless
Self administration
possible
Complications of
parenteral therapy
avoided
Disadvantages:
Slow onset
Irritant & unpalatable
drugs can not be given
Vomiting, unconscious
pts.- not useful
Drugs which are
destroyed by digestive
juices -- not
useful
Tab, Cap, Syp, Enteric coated pills / tablets,
Controlled release
10. Enteric coated tablets
Coated with cellulose-acetate, phthalate,
gluten etc
Not digested by gastric juice; get
disintegrated in alkaline juices of intestine
Prevents gastric irritation
Avoids destruction of drug by the stomach
Provide higher conc in small intestine
Slows absorption; prolongs duration of
11. Enteric coated tablets
Advantages Disadvantages
Reduced frequency
of administration
Therapeutic conc is
maintained
specially when
nocturnal
symptoms are to be
treated
Release of entire
amount of drug in a
short time →
toxicity
More expensive
12. Controlled release or time
release preparations
Release the active drug over an
extended period of time
Drug coatings which dissolve at different
time intervals
Coating which dissolves early releases
an amount which establishes its action
quickly
Coating which dissolves more slowly
ensures slow release of remainder drug
13. Hydrophilic polymers, forms a viscous gelling
layers which retard water penetration & act as a
barrier to drug release..drug release is
accomplished by diffusion through and erosion of
this barrier
14. Rectal
Rich blood supply; easily absorbed for
systemic action
Drugs absorbed from upper part → superior
haemorrhoidal vein → portal circulation (can
undergo first pass metabolism)
Absorbed from lower part→ middle &
inferior haemorrhoidal veins → systemic
circulation
E.g. Indomethacin, chlorpromazine,
15. Rectal route
Advantages:
Disadvantages:
Gastric irritation is
avoided
Can be administered
by unskilled persons
Useful in geriatric
patients; others with
vomiting & those
unable to swallow
Rectal irritation
Irregular &
unpredictable
absorption
16. Rectal enemas
Administration of a drug in liquid form into rectum
Evacuant enema: soap water enema
(600ml)
For evacuation of bowel before surgeries,
obstetric procedures & radiological
examinations
In selected cases of constipation
Aim is to remove faecal matter & flatus
Water: stimulates rectum; soap water:
lubricates
Retention enema: drug is administered
17. PARENTERAL ROUTE (s.c, i.m, i.v.,
intradermal)
ADVANTAGES DISADVANTAGES
Unconscious & un-
cooperative pt.
Vomiting & diarrhoea
Emergencies.
Irritant drugs
(I.V.route)
Drugs which are
destroyed by G.I.
enzymes - given safely.
Less safe
More expensive
Inconvenient
Self medication is difficult
Painful
Chances of local tissue
injury,& injury to nerves
Requires sterilization of
instruments & skill
18. Intravenous route
Drug is injected into a superficial vein→
directly
reaches circulation → immediately available
for action
Drugs can be given IV as
Bolus e.g. heparin
Slowly e.g. aminophylline
Slow infusion e.g. oxytocin, dextrose, saline
Employed
To slow administration to avoid toxicity e.g.
morphine
19. Intravenous route
Advantages:
Most useful during
emergency
Provides
predictable blood
conc with 100%
bioavailability
Larger volumes can
be given
Irritants can be
given
Disadvantages:
Once injected, cannot
be withdrawn
Thrombophlebitis
Extravasation →
severe
irritation/sloughing
Only aqueous
solutions can be
given
Self administration
20. Administration of IV solutions
Maintain strict asepsis
IV line should be flushed with saline
before starting infusion
Watch for
extravasation/thrombophlebitis
No air bubbles
Carry sterile container
21. Intramuscular
route
Aqueous soln is injected into deltoid, triceps,
gluteus or rectus femoris
Absorption into plasma occurs by simple
diffusion
Larger molecules enter through lymphatic
channels
Rapid & uniform absorption
Volume should not exceed 10ml
In infants, rectus femoris is used instead of
gluteus
Soluble solutions, mild irritants, depot
25. Intra cardiac
The procedure is
performed by
inserting a
long spinal
needle into
the ventricular
chamber. The needle
is inserted in the
fourth intercostal
space between the
ribs.
26. Intraperitoneal injection or IP injection
Into the peritoneum (body cavity).
It is more often applied to animals than to humans.
Preferred when large amounts of blood
replacement fluids are needed or when low blood
pressure or other problems prevent the use of a
suitable blood vessel for intravenous injection
In humans, the method is widely used to
administer chemotherapy drugs to
treat ovarian cancer :- Fluids are injected
intraperitoneally in infants, also used for
peritonial dialysis.
27. Intra-arterial(i.a.):
directly into arteries
Requires great care &
experts.
Injections are used to
localise effects of a
drug to a particular
tissue or organ
e.g. in the treatment of
renal tumours or
head/neck cancers,
drugs can be injected
into the renal artery or
carotid artery,
28. Intrathecal: into the cerebral spinal fluid
It is Used with local anaesthetics to give
spinal/regional anaesthesia, often prior to
perform operations on low limbs.
Opioid µ-receptors mediate pain are in the
spinal cord. Drugs that are administered to the
cerebral spinal fluid are being delivered to this
site of pain mediation. Thus, the intrathecal
route of administration can be used with the
opioid agonist morphine to give good pain relief.
29. Epidural route:
An epidural is an injection into the epidural, which is the
area above the dura mater, the layer before the cerebral
spinal fluid.
With local anaesthetics during childbirth prevent the
pain associated with childbirth.
31. Intradermal
Drug is injected into layers of skin
Raising a bleb e.g. BCG vaccine, allergy
tests
By multiple punctures of epidermis e.g.
small pox vaccine
Only small quantities
May be painful
32. Subcutaneous injection
Advantages
Disadvantages Tissue is less vascular;
slow & uniform
absorption; long-acting
Reliable & patients can
be trained for self
administration
Absorption can be
enhanced by addition of
Richly supplied with
nerves; irritant drugs
cannot be given
Not dependable in
shock due to
vasoconstriction
Repeated injections →
Drug is deposited in subcutaneous tissue
e.g. insulin, heparin
34. Subcutaneous injection
Dermojet: High velocity jet of drug solution is
projected from a fine orifice using a gun
Gets deposited in SC tissue →
absorbed
Painless; does not require needles
Suitable for vaccines
Pellet implantation: pellets packed with
drugs implanted SC E.g. testosterone, des-
oxy corticosterone acetate
Slow release to provide constant blood
levels
35. Subcutaneous route
Sialistic implants
Biodegradable & non biodegradable
Crystalline drug is packed in tubes &
implanted under the skin
Slow & uniform leaching → constant
blood levels
E.g. Norplant
36. Sublingual
placed under the tongue e.g. glyceryl
trinitrate (nitroglycerin) – Buprenorphine
Advantages:
Rapid onset of action
First pass metabolism is avoided
Avoids degradation of drug in stomach
Termination of drug action is immediate
Disadvantage: Buccal ulceration can occur
38. Inhalation
Dry powders inhalers (DPIs): require you
to breathe in quickly and deeply e.g.
salbutamol
Hard to use in Asthma attack when you can’t
fully catch a deep breath.
Nebuliser : through a mouth piece
or mask ,Oxygen or compressed air driven
Easier to use, good for children and
Severe asthma – who may not use DPI,HFA
e.g. salbutamol in bronchial asthma
Gases: e.g. general anesthetics
39. Inhalation route
Advantages:
Disadvantages :
Instant absorption
Local route in
pulmonary
diseases
Avoids first pass
metabolism in liver
Blood levels of
volatile anesthetics
Irritant gases can
increase pulmonary
secretions
Drugs go directly to the
left side of the heart
through pulmonary
veins → cardiac
toxicity
40. •To prevent dry mouth and
hoarseness, rinse mouth after each
use.
•It is important to practice good oral
hygiene to prevent mouth infections
•Tooth decay ?
NebulizerMetered dose inhaler
41. Nasal :
Local and systemic effects
Oxytocin spray for systemic
absorption
Oxymetazoline nasal drops for local
decongestant action
Budesonide nasal spray for allergic
rhinitis
42. Transcutaneous route
Highly lipid soluble drugs applied over skin for
slow & prolonged absorption e.g. nitroglycerine
ointment in angina pectoris
Iontophoresis : ionic medicinal
compounds driven into the body through the skin
by a local electric current.Eg: iontophoresis of
Acetylcholine, pilcocarpine iontophoresis used to
stimulate sweat secreation.
44. Transdermal
therapeutic systems
Drug is delivered at skin surface by
diffusion for percutaneous absorption
Applied on chest, abdomen, upper arm,
lower back, buttock and mastoid region
E.g. Nitroglycerine, fentanyl, nicotine,
estradiol, isosorbide dinitrate, hyoscine,
clonidine
Last for 1-7 days
45. Transdermal therapeutic system
Advantages: Disadvantages:
Smooth plasma
conc without
fluctuations
Minimize inter
individual variations
Less side effects
More convenient;
patient compliance
Local irritation,
erythema
46. Local Route
Topical: Local action
Skin: ointment, cream, lotion, paste,
powder, dressing, spray
Inunction: rubbing on the skin
Mucous membrane: paints, lozenges,
mouth washes, gargles, drops, ointment,
nasal spray, jelly, irrigating solutions
47. Local Route
Vaginal
Suppository-shaped medications are available for
vaginal administration, known as pessaries- are
designed to obtain a local effect.
clotrimazole, an anti-fungal drug for the treatment
of vaginal candidiasis (thrush).
48. Eye
liquid/drop form:
it is placed on the conjunctiva- drug dissolves in the tears,
and following blinking, is distributed to the site of absorption,
the cornea.
Local effects usually require absorption of the drug through
the cornea.
It can lead to systemic effects as the drug is drained from the
eye through the nasolacrimal canal.
Eg: β-blocker timolol -glaucoma
Ointment : A small amount of ointment is put along the
inside of the lower eyelid. Then, blinking will spread the
ointment over the cornea, and the drug will be
absorbed. This provides a more prolonged contact time with
enteral, which means into the gastrointestinal tract,
or parenteral (not into the gastrointestinal tract)
Routes that are enteral (into the gastrointestinal tract) are oral and rectal.
Routes that are parenteral include sublingual (under the tongue) and injection, which can be to a variety of sites
e.g. into the vein (intravenous), into the muscle (intramuscular), under the skin (subcutaneous).
Other parenteral routes include topical, which is to a body surface, such as the skin, nose, eyes etc.
and pulmonary, which is delivery to the lungs.
These routes of drug administration are considered in sequence.
The route of administration used for a drug may also depend on whether a systemic (around the body) effect is required.
Local administration is a way of trying to limit the effects of a drug to a local area.
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