Route of drug administration and bioavailability, oral iv nasal

1. ROUTES OF DRUG
ADMINISTRATION
AND
BIOAVAILABILITY
Dr Kalpana Tiwari

2. SYSTEMIC LOCAL
1. Topical
2. Intra arterial
3. Tissue deposits
1. Oral
2. Sublingual
3. Rectal
4. Transdermal
5. Inhalation
6. Nasal
7 Sub cutaneous
8. Intra dermal
10. Intra venous
11. Intra muscular
Routes of drug

3. Factors affecting choice of route
 Physical & chemical properties of drug-
solid/liquid/gas; solubility, stability, pH, irritancy
 Desired Site of action
 Rate & extent of absorption
 First-pass effect
 Rapidity of the desired response-
emergency/routine
 Condition of the patient- unconscious, vomiting

4. First-pass effect
.
 Metabolism of drug in gut wall or portal circulation
before reaching systemic circulation so amount reaching
system circulation is less than amount absorbed
 Results to Low bioavailability

5. Oralroute
 most common route of drug administration.
Advantages
 Safe
 Convenient- self- administered,
 pain free, non-invasive and easy to take
 Economical - compared to other routes
 Absorption takes place along length of GI tract

6. Oral route of drug absorption
Ingestion of tablet
Ionic /non
ionic

7. Site of absorption of drug

8. Disadvantages
 Slow absorption, slow action
 can not used in emergency
 Irritable - nausea and vomiting
 Cannot be used Uncooperative patient
 Variable drug absorption
 First-pass metabolism - Due to Biotransformation
 Food–Drug interactions and Drug-Drug interactions

9. Dosage forms
Of Oral route

10. Sublingual/buccal route
ADVANTAGES
 Drug absorption is quick
 Quick termination
 By pass First-pass
metabolism
 Safe
 Excess dose remove
after effect
 Economical
DISADVANTAGES
 Irritation of oral mucosa
 Large quantities
not given
 Only lipid soluble drug
given
Tab containing drug is placed under tongueor crushed in
mouth and spread over buccal mucosa. Ex- GTN,

12.  ADVANTAGES
 Used in children
 No first pass effect/By pass liver
 (ext haemorrhoidal vein)
 Used in vomiting or
unconscious
 Higher concentrations rapidly
achieved
 DISADVANTAGES
 Inconvenient
 Absorption is slow
 Irritation or inflammation of
rectal mucosa can occur
Rectalroute
 Administered as suppository.
 Drug is mixed with a waxy substance that dissolves or liquefies after it is
inserted into rectum (lipophilic) ex- Diazepam, indomethacin,
paraldehyde, ergotamine

14.  Achieves systemic effects by application of drugs to skin, by
transdermal medicated adhesive patch.
 Rate of absorption vary depending on physical
characteristics of drug (lipid soluble) and skin at site of
application.
 Slow effect (prolonged drug action)
 used for sustained delivery of drugs, such antianginal drug
nitroglycerin, antiemetic scopolamine. nicotine patches
 Site – Upper arm, chest,
abdomen, mastoid region
 By pass first pass metabolism
Transdermal

16. Nasal
 Administration of drugs directly into the nose.
 Agents include nasal decongestants such as anti-
inflammatory corticosteroid.
 Desmopressin is administered intranasally in the
treatment of diabetes insipidus
 Preferred for peptides
 . ex Desmopressin calcitonin, fentanyl

18. Atomizer
Nasal route

19.  Rapid delivery of drug across large surface area of mucous
membranes of respiratory tract and pulmonary epithelium
effect almost as rapidly as with IV injection.
 Used for drugs are gases (for example, anesthetics) or
those can be dispersed in an aerosol.
 Route is effective and convenient for patients with
respiratory complaints
 Drug is delivered directly to site of action and systemic side
effects are minimized.
 Examples albuterol,and corticosteroids, such as
fluticasone.
Inhalation

21. Par-enteralroutes All routes other than oral
can be considered par-enteral (outside GIT)
Direct delivery of drug in to systemic circulation without
GI tract
 Intradermal (I.D.) (into skin)
 Subcutaneous (S.C.) (into subcutaneous tissue)
 Intramuscular (I.M.) (into skeletal muscle)
Intravenous (I.V.) (into veins)

22. A) Intradermal –inj into skin
B)Subcutaneous - Absorption of drugs from subcutaneous
tissues
C)Intramuscular (IM) drug injected into skeletal muscle
D)Intravascular (IV)- placing a drug directly into the blood
stream

23. Subcutaneous route
 Drug is deposited in loose subcutaneous
tissue – rich nerve supply
 Irritant drugs cannot be injected
 Slow absorption than im route ---Leads
prolonged duration of action
 Only Small volume can be injected
 Minimizes risks associated with
intravascular injection
 Biodegradable implants, insulin,
contraceptive
Intradermal Route
Inj into skin raising bleb – BCG Vaccine,
Sensitivity test

25. ADVANTAGES
 Absorption reasonably uniform
 Rapid onset of action
 Mild irritants can be given
 By pass first metabolism
DISADVANTAGES
 Only upto 10ml drug given
 Local pain and abcess
 Infection Nerve damage
 Local hematoma can
occur in anticoagulant treated pt.
Intramuscular route
Large skeletal muscle- Deltoid, triceps, gluteus maximus, rectus femoris

27. Intravenous route
 Most common parenteral route for drugs are not
absorbed orally.
 Avoids first-pass metabolism by liver.
 Peptides with high molecular weight are given
 Titration of dose with response
 large quantities can be given
 (100% bioavailability)
Disadvantages
 Acute toxicity occur
 Thrombophlebitis of vein
 Embolism of foreign particles or air
 Once injected, drugs cannot be recalled.

28. Steps of intravenous route

29.  Produce local effect to Skin (percutaneous) e.g.
allergy testing, topical local anesthesia
 Eye drops e.g. conjunctivitis
 Ear drops e.g. otitis externa
 Intranasal, e.g. decongestant nasal spray
Topical Route

30. Skin topical
 Dermal - Oil or ointment for localaction
Antiseptic cream and lotion
 Sunscreen lotion and powders

31. Arterial supply
Used for anticancer drugs (femoral or brachial artery )
Intra arterial injection is used for angiography

32. Deeper tissues
 Drug with systemic absorption is slow eg.intra articular inj
for knee joint
 Hydro cortisol in retrobulbar injection

33. Intrathecal/intraventricular
It is sometimes necessary to introduce drugs directly into
the cerebrospinal fluid.
For example, amphotericin B is used in treating Cryptococcal
meningitis

35. Bioavailability
Bioavailability describes the fractional extent to which an
administered dose of drug reaches its site of action or a
biological fluid (usually the systemic circulation) from
which the drug has access to its site of action.
F = Quantity of drug reaching systemic circulation
Quantity of drug administered

36. BIOAVAILABILITY
Dose
Metabolised
in gut
Not
absorbed
Metabolised
by gut wall
Metabolised
by liver
to
systemic
circulation

39. Factors affecting bioavailability
 Molecular weight of drug.
 Drug Formulation (ease of dissolution).
(solution > suspension > capsule > tablet)
 Drug solubility of the drug
 pH of gut
 Weakly acidic drugs: Aspirin, Barbiturates→
Stomach, duodenum
 Weakly basic drugs: Pethidine, Ephedrine→ Small
intestine
 Strongly acidic / basic drugs: highly ionized &
poorly absorbed

40.  Chemical instability in gastric pH
 (Penicillin & insulin )
 Blood flow to absorptive site
Greater blood flow increases bioavailability
 Intestine has greater blood flow than stomach
 Surface area available for absorption.
Intestinal microvilli increases it
 Rate of gastric emptying
rapid gastric emptying fast transit to intestine
 Drug drug interactions and with Food
Factors affecting bioavailability

41.  Presence of other agents:
Vitamin C ↑ Iron absorption,
Calcium ↓ absorption of Tetracyclines
 Disease states:
Malabsorption, Cirrhosis, Biliary obstruction
Factors affecting bioavailability

43. References
RANG AND DALE’S pharmacology
Basic & clinical Pharmacology
The pharmacological basis of Therapeutics13 th
edition

44. Thankyou