Routes of drug administration: local and systemic

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