This document discusses various routes of drug administration including sublingual/buccal, rectal, parenteral (intravenous, intraarterial, intramuscular, subcutaneous), topical, ocular, inhalational, intranasal, and vaginal. For each route, it describes the absorption mechanism, onset of action, examples of drugs used, advantages, and factors influencing drug delivery and absorption. The document provides detailed information on considerations for different administration routes and factors affecting drug absorption through various tissues like skin, nasal mucosa, lungs etc.

1. ABSORPTION OF DRUGS
(Route of Administration)
IV
1
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2. 2
Route of Administration
1. Sublingual / Buccal Administration
2 .Rectal Route of Administration
3. Parenteral Route of Administration
- Intravenous
- Intraarterial
- Intramuscular
- Subcutaneous
4. Topical Route of Administration
5. Ocular Route of Administration
6. Inhalational Route of Administration
- Intranasal
- Pulmonary
7. Vaginal Administration

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SUBLINGUAL / BUCCAL ROUTE

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5. • SUBLINGUAL ROUTE: the dosage form is placed
beneath the tongue.
• BUCCAL ROUTE: Dosage form is placed between the
cheek and teeth or In the cheek pouch.
• Drugs administered by this route are supposed to
produce systemic drug effects, and consequently,
they must have good absorption from oral mucosa.
• Oral mucosal regions are highly vascularized
therefore rapid onset of action is observed.
• For Eg, anti-anginal drug Nitroglycerin.
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SUBLINGUAL / BUCCAL ROUTE

6. • Blood perfuses oral regions drains directly into the general
circulation.
• Barrier to drug absorption from these routes is epithelium
of oral mucosa.
• Passive diffusion is the major mechanism of absorption of
most drugs.
• In general, sublingual tablets are designed to dissolve
slowly to minimize possibility of swallowing the dose.
Exception include: Nitroglycerin, Isosorbide dinitrate tablets
which dissolves within minutes in buccal cavity to provide
prompt treatment of acute anginal episodes.
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SUBLINGUAL / BUCCAL ROUTE

7. Factors to be considered:
Lipophilicity of drug: The lipid solubility should be high
for absorption.
1. Salivary secretion: drug should be soluble in buccal
fluid.
2. pH of saliva: pH of saliva is usually 6.
3. Storage compartment: some drugs have storage
compartment in buccal mucosa. Eg, Buprenorphine
4. Thickness of oral epithelium: Sublingual
absorption is faster than buccal, because former
region is thinner than that of buccal mucosa.
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8. FACTORS LIMITTING DRUG ADMINISTRATION:
1. Limited mucosal surface area.
2. Taste of medicament and discomfort.
EXAMPLES: Nitroglycerin, Isosorbide dinitrate,
Progesterone, Oxytocin, Fenosterol, Morphine.
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SUBLINGUAL / BUCCAL ROUTE

9. RECTAL ADMINISTRATION:
• Absorption across the rectal mucosa occurs by
passive diffusion.
• This route of administration is useful in children, old
people and unconscious patients.
• Eg., drugs that administered are: aspirin,
acetaminophen, theophylline, indomethacin,
promethazine & certain barbiturates.
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10. PARENTERAL ROUTES:
.
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11. INTRAVENOUS ROUTE:
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
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12. INTRAVENOUS ROUTE:
• This route is used when a rapid clinical response is
required like treatment of epileptic seizures, acute
asthmatic and cardiac arrhythmias.
• There may also be a danger of precipitation of drug in
the vein if the inj. is too rapidly. This could result in
thrombophlebitis.
• This mode of administration is required with drugs
having short half lives and narrow therapeutic index.
• Bioavailability is not considered by this route.
• Mainly antibiotics are administered by this route.
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13. Intra arterial injection
• In this route the drugs are injected directly into the
artery.
• It is mainly used for cancer chemotherapy.
• It increased drug delivery to the area supplied by the
infused artery and decreased drug delivery to
systemic circulation.
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14. INTRA MUSCULAR INJECTION
• Absorption of drug from muscles is rapid and
absorption rate is perfusion rate limited.
• Polypeptides of less than approx 5000 gram per mole
primarily pass through capillary pathway
• Greater than about 20000 g/mol are less able to
traverse capillary wall, they primarily enter blood via
lymphatic pathway.
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15. Factors determining rate of drug absorption via IM
route:
1. Vascularity to the inj. Site:
Blood flow rates to intramuscular tissues are:
Arm (deltoid) > thigh (vastus lateralis) > buttocks
(gluteus maximus).
2. Lipid solubility and ionization of drug.
3. Molecular size of drug.
4. Volume of inj. And drug concentration.
5. pH & viscosity of inj. vehicle.
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16. SUBCUTANOUS ROUTE:
1. Slow and constant absorption
2. Absorption is limited by blood flow, affected if
circulatory problems exist.
3. The blood supply to this is poorer than that of
muscular tissue.
4. Concurrent administration of vasoconstrictor will slow
absorption, e.g. Epinephrine.
5. The absorption is hastened by massage, application of
heat to increase blood flow and inclusion of enzyme
Hyaluronidase in drug solution.
By catalyzing the hydrolysis of hyaluronan, a constituent of the extracellular matrix (ECM),
hyaluronidase lowers the viscosity of hyaluronan, thereby increasing tissue permeability. It is,
therefore, used in medicine in conjunction with other drugs to speed their dispersion and
delivery.
eg. Insulin. 16

17. TOPICAL ADMINISTRATION:
• MUCOSAL MEMBRANES
(eye drops, antiseptic, sunscreen, nasal, etc.)
•SKIN
a. Dermal - rubbing in of oil or ointment
(local action)
b. Transdermal - absorption of drug through
skin (systemic action)
i. stable blood levels
ii. no first pass metabolism
iii. drug must be potent.
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18. Skin consist of three layers :
• Epidermis
• Dermis
• Subcutaneous fat tissue
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19. • The stratum corneum is the outermost layer of the
epidermis and is composed mainly of dead keratinized
cells (from lack of oxygen and nutrients). It has a
thickness between 10 - 40 μm.
• The dermis is the layer of skin beneath the
epidermis. It contains the hair follicles, sweat glands,
sebaceous glands, apocrine glands, lymphatic vessels
and blood vessels.
• Hypodermis - Its purpose is to attach the skin to
underlying bone and muscle as well as supplying it
with blood vessels and nerves. The main cell types are
fibroblasts, macrophages and adiposities (the
hypodermis contains 50% of body fat).
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20. SKIN
• The main route for the penetration of the
drugs is generally through epidermal layer
• Stratum corneum is the rate limiting barrier
in passive percutaneous absorption of drug.
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21. OCULAR ADMINISTRATION
• Eye is the most easily accessible site for topical
administration of a medication.
• Topical application of drug to eyes meant for :
Mydriasis, miosis, anaesthesia, treatment of
infection, glaucoma etc.
• Opthalmic solution are administered into cul-de-sac.
• Barrier to intra occular penetration is cornea. It
possess both hydrophilic and lipophilic characterstics.
• pH of lacrimal fluid is 7.4.
• pH of lacrimal fluid influences absorption of weak
electrolyte like Pilocarpine.
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22. OCULAR ADMINISTRATION
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23. Composition of eye
• Water - 98%
• Solid -1.8%
• Organic element –
Protein - 0.67%, sugar - 0.65%, Nacl - 0.66%
• Other mineral element sodium, potassium and
ammonia - 0.79%
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• High pH of formulation: decrease tear flow and
• Low pH of formulation: increases tear flow.
• Human eye can hold around 10 microlitre of fluid.
So small volume in concentrated form increases
effectiveness.
• Viscosity empartners increases bioavailability eg,
oily solutions, ointment etc.
• Systemic entry of drug occur by lacrimal duct which
drains lacrimal fluid into nasal cavity.
OCULAR ADMINISTRATION

25. Characteristics required to
optimize ocular drug delivery system
• Good corneal penetration.
• Prolong contact time with corneal tissue.
• Simplicity of instillation for the patient.
• Non irritative and comfortable form (viscous solution
should not provoke lachrymal secretion and reflex
blinking)
• Appropriate rheological properties concentrations of
the viscous system.
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26. Advantages
• Increase ocular residence….. Improving bioavailability
• Prolonged drug release….. better efficacy
• Less visual & systemic side effects
• Increased shelf life
• Exclusion of preservatives
• Reduction of systemic side effects
• Reduction of the number of administration
• Better patient compliance
• Accurate dose in the eye…. a better therapy
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27. FACTOR INFLUENCING PERCUTANEOUS
ABSORPTION
1. Drug release from dosage form
2. Drug concentration in the formulation
3. Drug oil water partition coefficient.
4. Drug affinity to the skin tissue
5. Surface area
6. Site of application
7. Hydration of skin
8. Nature of vehicle used
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9. Rubbing
10. Contact period
11. Permeation enhancers

28. INHALATIONAL ROUTE
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 may impact in the mouth
and throat. Smaller than 0.5 micron and they aren't
retained.
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29. INTRA NASAL ADMINISTRATION
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30. INTRA NASAL ADMINISTRATION
• Drugs generally administered by intra nasal route for
treatment of local condition such as perennial
rhinitis, allergic rhinitis and nasal decongestion etc.
• Absorption of lipophilic drugs through nasal mucosa
by passive diffusion and absorption of polar drugs
by pore transport.
• Rate of absorption of lipophilic drugs depend on
their molecular weight.
• Drugs with molecular weight less than 400 daltons
exhibit higher rate of absorption.
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31. cont…
• Drugs with molecular weight 1000 daltons
show moderate rate of absorption.
• Presently nasal route is becoming popular for
systemic delivery of peptide and proteins,
this is because of high permeability of nasal
mucosa.
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32. Advantages
• Rapid drug absorption via highly-vascularized
mucosa
• Rapid onset of action
• Ease of administration, non-invasive
• Avoidance of the gastrointestinal tract and first-pass
metabolism
• Improved bioavailability
• Lower dose/reduced side effects
• Improved convenience and compliance
• Self-administration.
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33. Disadvantages
• Nasal cavity provides smaller absorption surface
area when compared to GIT.
• Relatively inconvenient to patients when compared
to oral delivery since there is possibility of nasal
irritation.
• The histological toxicity of absorption enhancers
used in the nasal drug delivery system is not yet
clearly established.
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34. Enhancement in absorption
• Following approaches used for absorption
enhancement :-
 Use of absorption enhancers
 Increase in residence time.
 Administration of drug in the form of microspheres.
 Use of physiological modifying agents
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35. Enhancement in absorption
 Use of absorption enhancers:-
• Absorption enhancers work by increasing the rate
at which the drug pass through the nasal mucosa.
• Various enhancers used are surfactants, bile salts,
chelaters, fatty acid salts, phospholipids,
cyclodextrins, glycols etc.
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36. Various mechanisms involved in absorption
enhancements are:-
• Increased drug solubility
• Decreased mucosal viscosity
• Decrease enzymatic degradation
• Increased Paracellular transport
• Increased transcellular transport
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37. Various mechanisms involved in
absorption enhancements are:-
 Increase in residence time:-
• By increasing the residence time the increase in
the higher local drug concentration in the mucous
lining of the nasal mucosa is obtained.
• Various mucoadhesive polymers like methylcellulose,
carboxy methyl cellulose or polyarcylic acid are used
for increasing the residence time.
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38. Various mechanisms involved in
absorption enhancements are:-
 Use of physiological modifying agents:-
• These agents are vasoactive agents and exert their
action by increasing the nasal blood flow.
• The example of such agents are histamine,
leukotrienene D4, prostaglandin E1 and β-adrenergic
agents like isoprenaline and terbutaline.
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39. Applications of nasal drug delivery
A. Nasal delivery of organic based pharmaceuticals :-
• Various organic based pharmaceuticals have been
investigated for nasal delivery which includes drug
with extensive presystemic metabolism.
• E.g. Progesterone, Estradiol, Nitroglycerin,
Propranolol, etc.
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40. Applications of nasal drug delivery
B. Nasal delivery of peptide based drugs :-
• Nasal delivery of peptides and proteins is depend
on –
 The structure and size of the molecule.
 Nasal residence time
 Formulation variables (pH, viscosity)
• E.g. calcitonin, secretin, albumins, insulin,
glucagon, etc.
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41. PULMONARY ADMINISTRATION
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42. PULMONARY ADMINISTRATION
• The drugs may be administered for local
action of bronchioles or their systemic effects
through absorption of lungs.
• Inhalation sprays and aerosols are used to
deliver the drugs to the lungs.
• Larger surface area of alveoli, high
permeability of alveolar epithelium for drug
penetration, and a rich vasculature are
responsible for rapid absorption of drugs by
this route
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43. PULMONARY ADMINISTRATION
• In general particles greater than 10mm are
retained in the throat and upper airways
whereas fine particles reach the pulmonary
epithelium
• Drugs generally administered by this route are
bronchodilators (e.g.. Salbutamol, isoproterenol),
antiallergic (e.g.. Cromolym sodium), and
antiinflammatory (e.g.. Betamethasone,
dexamethasone).
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44. Advantages
• Smaller doses can be administered locally.
• Reduce the potential incidence of adverse systemic
effect.
• It used when a drug is poorly absorbed orally, e.g. Na
cromoglicate.
• It is used when drug is rapidly metabolized orally, e.g.
isoprenaline
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45. Vaginal Administration
• Passive diffusion
• Intended to act locally
• Treatment of bacterial or fungal infections or prevent
conception
• Systemic delivery of contraceptives and other
steroidal hormones
• No first-pass effect
• Controlled delivery and termination of drug action
when desired
• Influencing factors: pH (4-5), vaginal secretions, and
microorganisms present in vaginal lumen may
metabolize the drug 45