Sunday 12 June 2011

Routes of Drug Administration

Routes of Drug Administration (Enteral, Parenteral, Topical)

                    I.                        Enteral Routes: Placement of drug directly into any part of the GIT is called an 'enteral' mode of administration

a)                  Oral: Swallowing a drug through mouth

  
 

        Advantages:

  •   Most commonly used method as it is safe, convenient & painless procedure
  •  Economical as sterilization of drug products is not essential
  •  No need of any assistant

      Disadvantages:

  •   Onset of action is slower 
  •   Polar drugs can't be given as they are not absorbed (eg: Streptomycin) 
  •   Drugs are destroyed by the digestive juices (Eg: Penicillin-G, Insulin, Oxytocin)
  •  1st pass effect (those destroyed in liver before reaching systemic circulation) (eg: Morphine, Isoprenaline) 
  •     Bad test & Bad smell & irritant drugs can't be given 
  •   Drugs can't be given to unconscious & uncooperative patients
  • Drugs can't be given during emesis

b)                Sublingual / Buccal


The drug is place beneath the tongue (sublingual) or crushed in mouth and spread over the buccal mucosa (Buccal).

Advantages:

  • Quick onset of action because of rapid absorption due to more blood supply in that region

  • Bypasses the portal circulation
  • no 1st pass metabolism

  • Drug action can be terminated at any time when side effects are observed

    Disadvantages:

  • Distasteful, irritant drugs can't be given
  • Higher molecular weight drugs can't be absorbed (eg; insulin)

    Examples

    Isosorbide dinitrate tablets & Nitroglycerin tablets (for Angina), Isopranline  sulfate tablets (for Bronchial Asthma), Nifedipine in powder form (in Hypertension)


     

c)                  Rectal: Through Rectum  (Suppositories, Enema)

Advantages:


    Useful in patients with nausea and vomiting

    1st pass metabolism is greatly bypassed as a major portion of the drg is absorbed from external haemorrhoidal veins

    Useful for gastric irritant drugs

Disadvantages:

    Chances of rectal inflammation

    Absorption is irregular

    Inconvenient and embarrassing to the patient

Examples

    Dulcolax & Glycerine suppositories, enemas, ointments for Local action

    Aminophylline (Bronchodillator) & Indomethacin (Anti-inflammatory agent) Suppositories for Systemic action


 

                  II.   Parenteral Routes:
Routes other than "Enteral" are called 'Parenteral' routes of administration. Administration of drugs by injection, by topical application to skin or by inhalation through the lungs are all parenteral.

a)                  Intravenous:Through lumen of the veins


 

Advantages:

    Directly enters into the systemic circulation & no 1st pass effect & quicker onset of action

    Less dose is needed to achieve greater therapeutic effects

    Valuable in emergency

    Can be given evening unconscious, uncooperative patients those are having nausea, vomiting & diarrhea

    Hypertonic solutions & GIT irritant drugs can be infused

    Large volume of fluids can be infused at a uniform rate

    Amount of the drug can be controlled with an accuracy

Disadvantages:

    Strict aseptic conditions are needed

    Patient has to depend upon other person for administration of drug

    Painful

    Risky because once the is injected it can't be recalled

    Introduction of any air or particulate matter produce embolism which is fatal

    Drugs in suspensions & Oily drugs can't be given

    Depot injections can's be given

    Venous thrombosis & Thrombophlebitis of the vein injected

    Necrosis around the site of action

Examples: Glucose, Glucose normal saline, Dopamine & Norepinephrine drips


 

b)                 Intramuscular

    Deltoid muscle or gluteal mass of left or right buttock

    Vastus muscle underlying the lateral surface of the thigh

Advantages:

    Absorption is more predictable, less variable & rapid compared to Oral route

    Depot injections can be given

Disadvantages:

    Perfect aseptic conditions are needed

    Chances of abscess at the site of injection

    Chances of nerve damage leading to paresis of muscle supplied by it

    Large volumes can't be given (maximum 5 – 10 ml)


 

Examples: Depot injection of Testosterone, Antibiotics, Antiemetics


 

c)                 Intraperitoneal


 

    Into the peritoneal space

    Rapid absorption due to large surface area

    Painful, risky

    Antirabies injection can be given

d)                Intrathecal (Intraspinal)


 

    Into the subarachnoid space

    They crosses BBB & Blood CSF barrier

    Strict aseptic conditions & grater expertise is needed

    Its painful & risky procedure

    Many radiopaque contrast media for myelography (to visualize spinal cord) are given through this route

    Xylocaine injection for providing Spinal Anesthesia


 

e)                  Intramedullary:
Injection into the tibial or sternal bone marrow

f)                   Intra-arterial:
into the lumen of the desired artery

g)                  Intra-articular: injection directly into the joint space

h)                 Subcutaneous: Injection into the subcutaneous tissue under the skin

Inhalation: Inspiration through nose or mouth


 

III.                        Topical Routes

a)                 Transdermal

    Transdermal Patches

    In these adhesive patches, the drug is incorporated into a polymer (usually Polyisobutylene) which in turn is bonded to an adhesive plaster

    The drug is delivered at the skin surface by diffusion, for percutaneous absorption into circulation

    These preparations are designed to provide steady & smooth plasma concentration of the drug for a period ranging from 1-3 days from the site of their application

    Site of application: Chest, Abdomen, Upper arm or Mastoid region

    Examples: Transdermal Patches of Nitroglycerine, Scopalamine, Clonidine, Estradiol

    For diagram refer KD Tripathi Text book

b)                 Conjuctival: into the conjuctiva for local effects eg: Sulfacetamide

c)                  Vaginal and Urethral: Pessaries are used for local actions

d)                 Inunction (Rubbing): rubbing onto the skin


 

Newer Drug Delivery Systems: To improve drug delivery and to prolong its duration of action, special drug delivery systems have recently been developed.

    These include: Ocuserts, Progestaserts, Transdermal Adhesive Patches, Prodrugs, Computerised Miniature Pumps, Use of Monoclonal Antibodies and Liposomes as drug carriers.


 


 


 


 

9 comments:

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Unknown said...

Its bad . I want more information

Unknown said...

Vaginal,topical and inhalation route are not broadly explained..

Unknown said...

Please give detailed information with images

bachu said...

the information concerning the intra articular is not more convinient as there are no advantages and disadvantages of using the route

Shanelavi said...

Thank A Lot Really Helpful 🙂

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