5. Factors determining Route of Administration
• 1) Drug Factors
• Physical Properties-
• Nature of Drug- certain drugs are destroyed by
gastric acid or proteolytic enzymes eg. Insulin,
oxytocin, vasopressin are peptides so
degraded by proteolytic enzyme in gut.
• Absorption- certain drugs do not absorbed
orally eg. Streptomycin is highly ionized at gut
pH so not absorbed orally & given by parental
route.
• Toxicity- admn topically eg. Neomycin.
6. • Bioavailability- poor bioavailability on oral admn
of some drugs eg. Nitroglycerine, morphine
have only 20% bioavailability, so ntg is admn
sublingually while morphine by parenteraly
(SC/IM/IV).
• Plasma t1/2- very short half life drugs are admn by
parenteral route eg. Sod. Nitroprusside
(vasodilator) half life 2-5 mts.
• Distribution- if a drug does not reach at site of
action or does not cross BBB then it has to be given
by such a route that reaches to the site of action.
7. • Metabolism- if drug undergoes extensive first
paas metabolism it is avoided by oral route &
preferably used by
parenteral route eg. Morphine
or Sublingual route eg. Nitroglycerine.
8. - 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 lower the
bioavailability of the drug(the rate and extent of
the drug reaching systemic circulation).
First pass effect :
9. • 2) Patient Factors
• Condition of patient
• Associated disease
• Convenience of patient
• Personality/ psychotic
• 3) Disease Factors
• Emergency situation
• Drug poisoning
• Local action
10. • A drug may produce different effects when
given by different route eg. Magnisium
sulphate
• Orally - Laxative
• Topically - Boil, abscess
• Parenterally - Eclampsia
13. • Intramuscular- in large muscles of arm
(deltoid) or leg (thigh, glutial muscle).
Advantages
1- suitable for injection of drug in aqueous
solution (rapid action) and drug in
Suspension or emulsion.
Disadvantages
1- Pain at injection sites for certain
drugs.
Injections cont…
14. Subcutaneous – in subcutaneous tissue under
the skin. e.g. INSULIN
No more then 1.5 ml should be injected into the
site
• Suspension, oily & colloids
Injections cont…
15. • Intradermal/intracutaneous (ID/IC)- drug
is injected b/w the two layers of skin ie b/w
epidermis & dermis with some times formation
of bleb.
eg. Vaccines BCG, measles.
Injections cont…
16. • Intrathecal- drug is admn in subarrachnoid
space bypassing BBB & CSF.
in spinal anaesthesia.
• Epidural(extradural)- drug is injected b/w
lining of spinal canal & duramater (extradural
space) for purpose of anaesthesia & analgesia in
different regions, used mainly in obstetrics.
Injections cont…
17. • Intramedullary- drug is injected in to bone
marrow such as sternum or tibia. Mainly used
for bone marrow transplantation & for blood
transfusion in children where it is difficult to
find a vein.
• Intraarterial- in this route inj is directly made
in to artery, used in angiography.
Injections cont…
18. • Intra articular admn- drug is admn in the
joint space in synovial fluid providing local effect
& used for certain kinds of arrthritis. Eg steroids
• Intra cardiac- drug is injected directly into
myocardium. Usually adrenaline is admn locally
in case of cardiac arrest.
Injections cont…
19. • Intra ventricular- this route is useful for
admn of drug in brain tumours in which drug is
admn directly in to cerebral ventricles.
• Subconjectival- drug is injected just below
conjunctiva eg. Amphotericin & miconazole that
provides high & effective local c/n with less
systemic toxicity.
Injections cont…
20. • Intra peritoneal (IP)- drug is injected b/w
two layers of peritoneum.
• Used for peritoneal dialysis in case of renal
failure & certain cases of poisoning.
Injections cont…