Routes of Drug Administration

1. Routes of drug administration
Dr. Nabanit Kumar Jha,PhD
Email: njha@tmsu.edu.vc
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Pharmacology

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•Different Routes of Administration
•Advantages and disadvantages of different routes
Routes of Drug Administration
Drug Delivery System ( Brief Information)
Dosage Form ( Brief Information)
Pharm01-02

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4. Routes of administration
 Taken by mouth (orally)
 Given by injection into a vein (intravenously),
 into a muscle (intramuscularly),
 into the space around the spinal cord (intrathecally),
or
 beneath the skin (subcutaneously)
 Placed under tongue (sublingually) or between gums
& cheek (buccally)
 Inserted in the rectum (rectally) or vagina (vaginally)
 Placed in the eye (by the ocular route) or the ear (by
the otic route)
 Sprayed into the nose and absorbed through the nasal
membranes (nasally)
 Breathed into lungs, usually through mouth (by
inhalation) or mouth and nose (by nebulization)
 Applied to skin (cutaneously) for a local (topical) or
body wide (systemic) effect
 Delivered through skin by a patch (transdermally) for
a systemic effect
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5. Introduction
Drugs can be administered by numerous routes.
The choice of appropriate route in a given situation
depends both on
 Drug
 Patient related factors.
Looking into the several reasons for different routes
of administration used in clinical medicine-
 Convenience (e.g., oral),
 To maximize concentration at the site of action (e.g.
topical),
 To prolong the duration of drug absorption (e.g.
transdermal),
 To avoid the first-pass effect (e.g. parenteral)
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6. Classification
I. Local action
• 1. Topical
• 2. Deeper tissues
• 3. Arterial supply
II. Systemic action
•1. Oral
• 2. Sublingual or buccal
• 3. Rectal
• 4. Cutaneous
• 5. Inhalation
• 6. Nasal
• 7. Parenteral
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Routes can be broadly divided into those for
Fig: Routes of drug Administration

7. Local Routes
1. Topical:
External application of the drug to the surface for localized
action.
Absorption is too erratic for systemic absorption.
A. Skin:
Drug is applied as ointment, cream, lotion, paste, powder,
dressing, spray, etc.
Advantages
-High local concentration cab be achieved without systemic
effects.
Disadvantages
-Absorption can occur especially when there is tissue abrasion or
burn (pediatric pts.) thus resulting in systemic effects.
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8. Local Routes
B. Mucous membranes
The dosage form depends on the site applied
Mouth and pharynx: As paints, lozenges, mouth washes, gargles
(Povidone Iodine Paint, strepsils-lozenges)
Eyes, ear and nose: As drops, ointments, irrigation fluids, nasal
spray
Gastrointestinal tract: As non-absorbable drugs given orally
(Magnesium hydroxide, sucralfate, neomycin)
Bronchi and lungs: As inhalations, aerosols (Salbutamol)
Urethra: As jelly (Lidocaine)
Vagina: As vaginal tablets, creams, powders, Pessary
Anal canal: As ointment, suppositories
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9. Local Routes
2. Deeper tissues:
Certain deep areas can be approached by using a syringe and
needle but the drug should be such that systemic absorption
is slow, e.g., intra- articular injection (hydrocortisone
acetate).
3. Arterial supply:
 Anticancer drugs can be infused in femoral or brachial artery
to localize the effect for limb malignancies.
 Close intra-arterial injection is used for contrast media in
angiography.
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10. Systemic routes
Systemic action
The drug administered through systemic routes is
intended to be absorbed into blood and distributed all
over the body, including the site of action, through
circulation.
Routes are:
1. Oral
2. Sublingual or buccal
3. Rectal
4. Cutaneous
5. Inhalation
6. Nasal
7. Parenteral
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11. Oral Route
Oldest and most widely used mode
Safer, more convenient, does not need assistance, often painless
Both the solid dosage forms (powders, tablets, and capsules) and
liquid dosage forms (elixirs, syrups, emulsions, mixture) can be given
orally.
It is avoided in case of GI intolerance, patients in preparation for
anesthesia, GI surgery.
Advantages
A convenient mode of administration of drug that normally does not
need any assistance
Self administration is possible
The medicine does not need to be sterilized and hence is cheaper
Provides largest area for drug absorption
Drugs can be given in large amounts
Suitable for providing local action in GIT
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12. Oral Route
Disadvantages (Oral Route)
-Action is slower and thus not suitable for emergencies
-Cannot be used in unconscious or vomiting patient
-Unpalatable drugs are difficult to administer
-May cause nausea and vomiting
Absorption may not be proper
First pass effect cannot be avoided
Drugs which are poorly lipid soluble are not absorbed (Neostigmine)
Some drugs are not absorbed at all (Neomycin and streptomycin)
Drugs get destroyed by enterohepatic circulation (Adrenaline)
Others are destroyed by digestive juices (Pen. G) or in the liver (Lidocaine,
Testosterone)
Pathological condition of the GIT can interfere with absorption (E.g.. Peptic
ulcer)
Some drugs may be irritant to gastric mucosa (NSAIDs)
Drugs with objectionable taste and odor are difficult to administer (Quinine)
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10/4/2022

13. Sublingual or buccal Route
The tablets or pellets containing the drug is placed under the
tongue or crushed in mouth and spread over the buccal
mucosa. When only small amount of drug is required for
therapeutic effect this route can be used. Only a few drugs
are given sublingually –nitroglycerine, isoprenaline.
Advantages
 Rapid absorption and effect (e.g., glyceryl trinitrate in
angina)
 Effect can be terminated by spitting out tablets.
 Drugs do not undergo first pass metabolism.
Disadvantages
 Inconvenient for frequent use
 Large dose cannot be given
 Irritation of oral mucosa and excessive salivation
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14. Rectal Route
 Certain irritant and unpleasant drugs can be inserted into rectum as
suppositories or given as retention enema for systemic effect. Drugs may have
local or systemic action following absorption.
 Drugs are given rectally when patient is either unconscious or cannot
retain anything when administered orally (vomiting).
 Drugs are absorbed more slowly from the rectum than from small
intestine. But the effect of digestive enzymes on the drug is avoided in this
route.
 However, owing to the improvements of other dosage forms, this
route of administration is in decline.
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Fig: Suppository

15. Rectal Route
Advantages
Drug irritant to stomach can be given as suppository (Indomethacin)
Suitable in vomiting, motion sickness, migraine or when a patient cannot
swallow.
Particularly important for children and elderly patients who cannot swallow
or do not prefer sublingual route.
Drugs do not undergo first pass metabolism
Retention enema may be a useful substitute for oral route.
Disadvantages
Absorption is irregular and improper
Self-medication is difficult
First pass effect is not fully avoided
Psychological discomfort in that the patient may be embarrassed
Rectal inflammation may occur with repeated use
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16. Cutaneous route
 Highly lipid soluble drugs can be applied over the
skin for slow and prolonged absorption .
 The liver is also bypassed.
 The drug can be incorporated in an ointment and
applied over specified area of the skin.
Diclofenac Gel
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17. Inhalation Route
Volatile liquids and gases are given by inhalation for systemic
action, e.g., general anesthetics. Absorption takes place through
the pulmonary epithelium. Oxygen is given to prevent or relieve
hypoxemia.
Particle size should be greatly controlled while preparing this
type of formulation, since the
particles >1micron settles in the bronchioles and
those <0.5 micron get exhaled.
It is preferred when the site of action is the respiratory tract.
(Isoproterenol-Asthma)
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18. InhalationRoute
Advantages
Drugs as gases or aerosols can be rapidly taken up or
eliminated.
Disadvantages
Special apparatus is needed
Drugs must be non-irritant for conscious patient.
Irritant vapors can cause inflammation of respiratory tract
and increase secretion.
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19. Nasal Route
The mucous membrane of the nose can readily absorb many
drugs; digestive juices and liver are bypassed.
However, only certain drugs can be applied as a spray or
nebulized solution have been used by this route.
This route is being tried for some other drugs like insulin.
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Inhaled Insulin Today
In June 2014, the FDA approved
Afrezza. It's an inhaler with pre-
measured, rapid-acting insulin you use
before meals.

21. Intramuscular (I.M)
 The drug is injected in one of the large
muscles deltoid, triceps, rectus femoris, etc.
 Muscle is less richly supplied with sensory
nerves (absorption is faster). It is less painful but self
injection is often impracticable -- deep penetration is
needed.
 Depot preparations can be injected by this
route.
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22. Intramuscular (I.M)
Advantages
It is easier to administer as compared to IV
route.
Absorption is predictable, uniform and quicker
than in SC route.
Disadvantages
Highly irritant drugs cannot be given
Insoluble drugs cannot be given because they
do not get absorbed
Defective technique can result in damage to
nerve and blood vessels
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23. Intravenous (I.V)
 The drug is injected directly into the blood
stream , so it gets diluted in the venous blood
instantaneously and immediate effects are
produced ( great value in emergency).
 The drug is injected as a bolus (in large
volume) or infused slowly over hours in one of
the superficial veins .
 The intima of veins is insensitive and drug
gets diluted with blood, therefore even highly
irritant drugs can be injected i.v , but hazards are –
thrombophlebitis of the injected vein and necrosis
of adjoining tissues if extravasation occurs.
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24. Intravenous (I.V)
Advantages
Maximal therapeutic effect can be achieved rapidly
Greater predictability of maximal concentration and easier
dose calculation precision based on response of the patient
(anesthesia)
Route of choice in emergency
Can be given to unconscious or vomiting patients
Large doses of drugs can be given
Highly irritant drugs can be given owing to instantaneous
dilution in large volume of blood, also intima layer of vein is
relatively insensitive to drugs.
The dose of the drug required is smallest (bioavailability is
100%).
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25. Intravenous (I.V)
Disadvantages
Only aqueous solutions (not suspensions) can be injected
IV and there are no depot preparations for this route.
 This is the most risky route - vital organs like heart brain
etc. get exposed to high concentrations of the drug, since
withdrawal of drug is not possible.
Defective technique can lead to pain and inflammation
Acute, serious, allergic reactions are more likely to occur by IV
route.
Drug shock can occur since there is a rapid rise in the
concentration of drugs
Sometimes IV route fails to provide
adequate drug levels at the site of action. Therefore,
intrathecal and intraventricular injection are also used for the
purpose.
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26. Intradermal
 The drug is injected into the skin raising a
bleb (e.g., BCG vaccine, sensitivity testing )
multiple puncture of the epidermis through a
drop of the drug (small pox vaccine) is done.
 This route is employed mainly for diagnostic
purpose only (Penicillin allergic response).
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Routes for test dose is Intradermal

27. The important parenteral routes are:
Subcutaneous (S.C)
Intramuscular (I.M)
Intravenous (I.V)
 Intradermal
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Remember:
Rate of absorption-
Inhalational > IM > SC > Oral

31. Drug Delivery System
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Drug delivery system
Conventional Drug
delivery System
E.G
Oral
Rectal
Intravenous
Subcutaneous
Novel Drug Delivery
system
Modes
Target Drug Delivery system
(TDDS)
Control drug Delivery system
(CDDS)
Modulated Drug Delivery
System

33. Drug delivery system
 Method of administering pharmaceutical compound to
achieve a therapeutic effect in human or animals.
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Advanced
technique
New
dosage
Form
Novel Drug
delivery
system
(NDDS)
Improves drug Potency
Control drug release
Target Oriented
Greater safety
Advantages of NDDS

34. Implants
 These are drug delivery systems implanted under the skin,
from which the steroid is released slowly over a period of 1-
5 years. E.g. NORPLANT, PROGESTASERT (IUD)
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Transdermal drug delivery systems TDDS
Transdermal drug delivery systems
(TDDS) are topically administered
medicaments in the form of patches that
deliver therapeutically effective amount
of drug for systemic effects at a
predetermined and controlled rate across
a patient’s skin.
Control Drug Delivery
system
Ocular drug delivery system

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Modified Drug Delivery system:
Controlled and modulated by device
e.g. MDI (Meter dose inhalers)
Drug
Carrier
in NDDS
Liposomes
Nanosomes
Microsphere
Nanosuspension
Nanoparticles

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Target Drug
Delivery
system
(TDDS)
Localization
Control
Distribution
Reduced
Dose
Reduced
Side effects
Increase
Efficacy
 Targeted drug
delivery system
(TDDS) is applied to
precisely target and
treat the tumors.
 Polymeric
nanoparticles (PNPs)
are used as carrier of
anticancer agents in
TDDS.
 Cancerous tissue-
colon targeted drugs

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Magic Bullet
Concepts
The concept of
targeting of drugs to
their site of action
A century ago, Paul
Ehrlich envisioned the
concept of selectively
targeting a pathogen
without harming the
host organism using
“magic bullets.”
Magic
bullet

38. Dosage Form
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API
(Drug)
Excipients
Dosage
Form
Dosage Form:
 Physical form by which drug is delivered to
site of action within body
API- Active pharmaceutical
ingredients

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Semi Solid
Creams
Paste
Gel
Ointme
nts
Solid
Unit Solid
Tablet
Capsules
Lozenges
Bulk dosage
form
Powder
Granules
Liquid
Mono
Phasic
Elixirs
Syrup
Solution
Bi Phasic
Emulsion
Suspension
Liniments
Gas:
Inhalers
Aerosols

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NG/G- Tube
J-Tube
Z track method IM ??????
Assignment

44. Practice questions
1. Which of the following routes of drug
administration has 100% bioavailability?
A. IM
B. SC
C. IV
D. Intradermal
E. Inhalational

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2. Absorption is fastest in which of the following routes?
A. IM
B. SC
C. IV
D. Intradermal
E. Inhalational
Practice questions
Answer
1.C

46. 3. Lipid solubility is the pre-requisite for the which of
the following routes and or preparations?
A. Transdermal
B. Inhalational
C. Intramuscular
D. Subcutaneous
E. Intravenous
Practice questions
Answer
2.E

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4. Which of the followings is the riskiest route?
A. Transdermal
B. Oral
C. Intramuscular
D. Subcutaneous
E. Intravenous
Practice questions
Answer
3.A

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Answers
4. E

49. Thank you
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