Routes of administration
Content
General Pharmacology
• Routes
of administration
• Advantages
and disadvantages of various routes of administration
• Differentiate
between oral and parental route
Intended Learning Outcomes
At the
end of this lecture, student will be able to
• Classify
various routes of administration
• Explain
the advantages and disadvantages of various routes of administration
• Differentiate
between oral and parenteral route of administration
Routes of administration
Parenteral
Route
• Advantages
– Unconscious,
unco-operative patient
– Patients
with vomitting and diarrhoea
– Drugs
irritating stomach
– Avoid
FPM, drug modification by GIT juices or liver enzymes
– Rapid
action
– Accuracy
of dose
• Disadvantages
– Inconvenient
– No
self-medication
– Liable
to cause infection
– Injury
to arteries/ nerves
– Expensive
Parenteral Route – Injections
Intradermal
• BCG
vaccine
• Given
to the layers of skin, Painful
• Small
quantity can be administered
• Employed
for testing drug sensitivity
Subcutaneous
• Commonest
– insulin
• s.c.
drug implants depot therapy – Sex hormone implants
• Only
non-irritant substances
• Absorption
slower than i.m.
• Unreliable
in shock
Intramuscular
• Soluble
substances, mild irritants, suspensions, colloids
• Rate
of absorption – Reasonably uniform, rapid onset
• Volume
should not exceed 10 ml
• Diazepam,
hydrocortisone, phenytoin, digoxin
• May
cause local pain or necrosis – Quinine, paraldehyde
• Care
to avoid nerve damage
• Child
– to the lateral thigh
Intravenous
• Directly
into the vein and rapid action
• Desired
blood conc obtained rapidly with well-defined dose
• Precautions:
– Needle
position should be ensured
– Irritating
solutions – Piggybacking into a running i.v. drip
• Disadvantages:
– Local
irritation can lead to phlebitis
– No
Self medication
– Extravasation
– severe irritation, sloughing
• Drug may be injected:
– As
a bolus (Furosemide)
– Over
5-10 min (Aminophylline in 10-20 ml of isotonic glucose/ saline
– In
an infusion 50-100 ml
– Infusion
is employed:
– To
slow the administration of drug to avoid toxicity – Morphine
– To
maintain a constant plasma level – insulin/ dopamine
– To
administer larger volume– Fluid in shock / dehydration
Intra-arterial route
– Into
artery
– Used
in diagnostic studies – Angiogram, embolization therapy
– Antimalignancy
compounds – localised malignancies
Intraperitoneal route
– Large
surface area for absorption
– Infants
– giving fluids
– Peritoneal
dialysis
Intrathecal
– Into
sub-arachnoid spaces
– Drugs
act directly on CNS
– Strict
asceptic precautions
– Antibiotics
– Antimalignancy
compounds
Epidural/ Extradural
– Over
the dura mater
– Lignocaine
Intraosseous
– Into
bone marrow of iliac crest or tibia
– Rapid
absorption
– Adrenaline
in severe shock with sudden cardiac arrest
Intra articular
– Directly
into a joint
– Hydrocortisone
acetate in RA
– High
local conc of drug
II. Transcutaneous
• Iontophoresis
– Galvanic
current allows the penetration of drugs applied into the skin into the deeper
tissues
– Anode
Iontophoresis: for +ve compounds
– Catode
Iontophoresis: for –ve compounds
– Eg.
salicylates
• Inunction
– Rubbed
into the skin
– NG
ointment in Angina Pectoris
• Jet
injection
– High
velocity jet produced through a micro fine orifice
– No
needle
– Insulin
• Adhesive
unit
– Deliver
the drug slowly
– Scopolamine
for motion sickness
III. Transmucosal
• Sublingual
– NG
in angina pectoris
– Buprenorphine
as analgesic
• Transnasal
– GnRH,
calcitonin
• Transrectal
– Indomethacin
in RA
– Diazepam
in SE
• Endotracheal
– Adrenaline,
atropine, diazepam, lignocaine
IV. Inhalation Route
• Produce
rapid effects
• Drugs
directly to the left side of the heart
• May
produce cardiac toxicity
• By
pressurised metered aerosols – Salbutamol, beclomethasone in bronchial asthma
• Dry
powders from inhalers – Salbutamol
• Oxygen
or compressed air driven nebulised solution
• Gases- General anaesthetics
Summary
• Routes
of administration: Oral and Parenteral
• Parenteral
includes intravenous, intramuscular, intrathecal, intradermal, subcutaneous
• Parenteral
routes are useful in unconscious, unco-operative patient, patients with vomitting
and diarrhea, drugs irritating stomach
• Inhalational
routes produce rapid effects, drugs directly enter into left side of the heart and may produce
cardiac toxicity
