This document discusses various routes of drug administration including local and systemic routes. Local routes deliver drugs directly to the site of action and include topical application to the skin, eyes, ears etc. Deeper local routes use injections into joints, the spine or arteries. Systemic routes administer drugs through the entire body and include oral, sublingual, rectal, transdermal, inhalation, nasal and parenteral routes like subcutaneous, intramuscular, intravenous and intradermal injections. Each route has advantages and disadvantages related to onset of action, side effects, patient convenience and drug properties.

1. Routes of drug administration
Dr. M. Ahsan (MBBS, MD)

2. Types
Routes of administration
Local Systemic

3. Local route
• Site of action is same as site of
administration
• Absorption of drug from this site into
systemic circulation is minimal or absent
• Side effects are minimal

4. Local routes
• Topical
• Deeper tissues
• Arterial supply

5. Topical
External application of the drug to surfaces for
localized action
 On skin
 Nasal mucosa
 Oralmucosa
 Eyes
 Ear canal
 Anal canal
 Vagina
 Non-absorbable drugs given orally
 Inhalation of drugs for local action on bronchi

7. Deeper tissues
• Deep areas can be reached with the help of a
needle…..
• But absorption of drug from this site is
minimal
• Drug acts only locally at the site of
administration

8. Deeper tissues
Intra-articular injection
Intra-thecal injection
Inra-lesional injection
Intra-cardiac
Retrobulbar injection
Infiltration around a nerve

10. Arterial supply
• Contrast media in angiography
• Chemotherapy of limbs

11. Systemic routes
• Oral
• Sublingual
• Rectal
• Transdermal
• Inhalation
• Nasal
• Parenteral

12. Oral route
• Most commonly employed
• Advantages :
 Most convenient, safe & economical
 Non-invasive
 Painless
 Self administration is possible
 Drugs need not be highly purified
 Adverse effect if any, appears slowly

13. Oral route
• Disadvantages:
 Slowly absorbed; so slow onset of action
 Not useful in unconscious, uncooperative patients & in
patients with vomiting
 Unpalatable drugs are difficult to administer
 May cause nausea and vomiting
 Drugs which are either inactivated in gastic juice or not
absorbed or metabolised extensively in the gut & liver
(first-pass metabolism) cannot be given
 pH of the gut, presence of food or other drugs and
motility of gut interferes with absorption

14. Sublingual route
• Drug is placed under the tongue
• It can be crushed and spread over the buccal
mucosa
• Only lipid soluble and non-irritant drugs can
be administered
 The drug is rapidly absorbed through highly vascular
buccal mucosa directly into systemic circulation

16. Sublingual route
• Advantages:
 Rapid onset of action; so can be used in emergency
 Self-administration possible
 Degradation in the gut and liver, ie first-pass
metabolism is bypassed
 After the desired effect is reached, remaining drug
can be discarded

17. Sublingual route
• Disadvantages:
Irritant and distatesful drugs cannot be
administered
Glyceryl trinitrate
Nifedipine
Buprenorphine

18. Rectal route
• Enemas, suppositories and ointments can be
administered by the rectal route
Advantages:
50% of the absorbed drug bypasses first-pass
metabolism
Useful in case of vomiting or unconscious
patients

19. Rectal route
Disadvantages:
 Rectal absorption is often erratic and
incomplete
 Drugs may irritate the rectal mucosa
 It is embarassing
Diazepam – in case of convulsions
Paracetamol suppository

21. Transdermal patch

22. Transdermal route
• Mostly used for sustained delivery of the drug
• Highly lipid-soluble drugs can be absorbed through the
skin to achieve systemic effects
• Absorption can be increased by applying drugs as
ointments, rubbing and occlusive dressing
• Transdermal therapeutic systems (TTS) deliver the drug
at a constant rate

23. Transdermal patch

24. Transdermal patch
• These are medicated adhesive patches that deliver the
drug into blood stream at a controlled rate
• Come in various shapes and sizes (5-20 sq.cm)
• The patch is applied over the chest, abdomen, upper
arm, lower back, buttock, mastoid region
• Lasts for 1-3 days

25. Transdermal patch
• Advantages:
 Convenient and painless
 Bypasses first pass metabolism
 Ideal for drugs that are lipophillic and
require prolonged administration

26. Transdermal patches
• Disadvantages:
 Some patients are allergic to patches, may cause
irritation – (change the site of application)
 More expensive
 Can be used for only few drugs which are highly lipid-
soluble

27. Transdermal patches
• GTN patches
• Nicotine patches
• Fentanyl patches
• Scopolamine patches

28. Inhalation
• Volatile liquids or gases are given by inhalation for
systemic action – eg. General anesthetics
• Absorption takes place from the surface of alveoli –
action is rapid
• When drug is discontinued, it diffuses back from the
blood into the alveoli and is exhaled out
• Thus, controlled administration is possible
• Irritant vapors can cause inflammation of respiratory
tract

29. Nasal
• Drug is absorbed from the nasal mucosa
• Bypasses gastric juices and first-pass
metabolism
Desmopressin spray – diabetes insipidus
Calcitonin spray - osteoporosis

30. Parenteral route
• Subcutaneous
• Intra-muscular
• Intra-venous
• Intra-dermal

31. Parenteral routes

32. Parenteral routes
• Advantages:
 Drug action is rapid
 Gastric irritation and vomiting is not induced
 Can be used in unconscious, uncooperative and
vomiting patients
 No interference with food or digestive juices
 No first-pass metabolism

33. Parenteral routes
• Disadvantages :
 Preparation has to sterilized- so expensive
 Technique is invasive
 Painful
 Assistance is required
 Chances of local tissue injury
 Adverse effects are more

34. Subcutaneous route
• Drug is deposited in loose connective tissue
• This tissue is richly supplied by nerves
• Subcutaneous tissue is less vascular
Thus,
 Irritant drugs cannot be given
 Absorption is slower
 Only small volumes can be injected s.c
 Self-injection is possible
 Depot preparations can be given

35. Subcutaneous route
Special forms of s.c route:
Dermojet
High velocity jet of drug solution is projected from microfine
orifice using a gun. Solution passes through the superficial
layers and gets deposited in subcutaneous tissue
….painless
...mass innoculations
Pellet implantation
Solid pellet is introduced with trochar and cannula
…sustained release of DOCA, testesterone

36. Subcutaneous route
Sialistic (nonbiodegradable) and
biodegradable implant
Crystalline drug is packed in tubes and
implanted under the skin
…slow and uniform release of drug over months
…non-biodegradable implant has to be removed while
biodegradable implant is left
…hormonal contraceptive eg. NORPLANT

37. Intramuscular route
• Drug is injected in large skeletal muscle
…deltoid, gluteus maximus
• Muscle has rich blood supply
• Less nerve supply
Thus,
 Mildly irritant drugs can be given
 Absorption is faster (for aqueous soln)
 Less painful….but self-administration not possible
because of deep penetration
 Depot preparations (oily soln) can be injected

38. Intramuscular route
• Warning:
Avoided in patients on anticoagulant therapy
….risk of hematoma

39. Intravenous route
• Drug is injected into one of the large veins
….bolus/slow infusion
• Intima is insensitve
• Drug directly reaches into bloodstream
• Only aqueous soln can be givens…..no depot
preparation

40. Intravenous route
• Advantages:
• Highly irritant drugs can be given
• Useful in emergencies
• Dose required is small as bioavailablity is 100%
• Large volumes can be infused
• Response can be measured accurately
• Titration of dose can be done fore short acting drugs

41. Intravenous route
• Disadvantages:
• Risk of thrombophlebitis of the injected vein
• Necrosis of adjoining tissue in case of extravasation
• Most risky route – as vital organs get exposed to high
concentrations of drug

42. Intradermal route
• Drug is injected in the skin to raise a bleb
• Multiple puncture/scarring of the epidermis
• Used for special pusposes:
 BCG vaccination
 Sensitivity testing