ROUTES OF DRUG ADMINISTRATIONDr. Jeevan Jacob

Junior Resident

Dept. Of Pharmacology

Definition:

A route of administration is the path by which a drug, fluid, poison or other substance is brought into contact with the body.

Factors Governing Choice of Route• Physical and chemical properties of the drug• Site of desired action• Rate and extent of drug absorption• Effect of digestion and first pass metabolism• Rapidity of response desired• Accuracy of dosage required• Condition Of patient

Major routes

Enteral Parenteral Topical

Oral

Sublingual, Buccal

Rectal

Injections

Inhalation

Transdermal

Conjunctival,Nasal,Auditory

Vaginal and Urethral

Dermal

ORAL ROUTEADVANTAGES

•Safe•Convenient •Economical•Can be self administered•Painless

DISADVANTAGES

•Slow absorption •Slow action•Irritable and unpalatable drugs•Un co-operative and unconscious patients•Some drugs destroyed•First-pass effect

First-pass Effect

The first-pass effect is the term used for the hepatic metabolism of a pharmacological agent when it is absorbed from the gut and delivered to the liver via the portal circulation. The greater the first-pass effect, the less the agent will reach the systemic circulation when the agent is administered orally

First pass effect:

Examples - Oral

•Solid-Tablet,Capsule,Powder

•Liquid-Syrup,Elixir,Mixture

Sublingual and Buccal

Sublingual: Beneath the tongue

Buccal: Crushed and spread over buccal mucosa

SUBLINGUAL ROUTE

ADVANTAGES

•Economical•Drug absorption is quick•First-pass avoided•Quick termination-Spit off•Can be self administered

DISADVANTAGES

•Unpalatable & bitter drugs•Irritation of oral mucosa•Large quantities not given

Example

Systemic use

• Isosorbide dinitrate• Nitroglycerine• Nifedipine

Local• Antispetic lozenge

RECTAL ROUTEADVANTAGES

Used in childrenLittle first pass effectUsed in vomiting/unconsciousHigher concentrations rapidly achievedCan use gastric irritants

DISADVANTAGES

EmbarrassingInconvenientAbsorption is slow and erraticIrritation or inflammation of rectal mucosa can occur

ExampleLocal Effects• Dulcolax, Glycerine suppository ,enema, ointment

Systemic Effects• Aminophylline, Indomethacin suppositories

Gastric Tube Administration

•Gastric tubes provide access directly to the GI system.

Parenteral RoutesRoutes other than enteral are called parenteral

Administration of drugs by the parenteral route

Intradermal

• Amount of drug small, slow absorption• Example: BCG vaccine, diagnostic tests, allergic sensation testing

Subcutaneous administrationSite: Injection under skin

ADVANTAGES

• Smooth but slow absorption

• depot injections/implants

• Examples• Local effect- Local anaesthetic

• Systemic-Insulin

DISADVANTAGES

• small volume(1 ml)• irritant drugs-sloughing and necrosis

• not suitable in shock

Intramuscular Injections

• Site-Deltoid muscle, Gluteus, Vastus

Intramusular routeADVANTAGES

•Absorption reasonably uniform•Rapid onset of action•Mild irritants can be given•First pass avoided•Gastric factors can be avoided

DISADVANTAGES

•Only upto 10ml drug given•Local pain and abscess•Expensive•Nerve damage

Intravenous Administration

ADVANTAGES• Bypass first pass

metabolism(100%) • Quick onset of action• In uncooperative and

unconscious patients• those with nausea and

vomiting• hypertonic solutions and

irritants• large volumes• amount of drug can be

controlled accurately

DISADVANTAGES

• Antiseptic conditions• Depend on others• Painful and risky• Embolism• Suspensions/oily

drugs/depots cant be given

• Venous thrombosis and phlebitis

• Necrosis due to extravasation

Examples

• IV infusion-Ringer,Dextrose 5%,DNS,Dopamine

• IV bolus-Diazepam,Adenosine,Insulin

Intraarterial • Site: Lumen of artery• ADVANTAGE: Greater concentration of the drug can be delivered

• DISADVANTAGE: Expertise and asepsis

• Examples: Radiopaque contrast for coronary angiography and cerebral angiography

Intraperitoneal• Site-Peritoneal space

• ADVANTAGE -Rapid absorption-large surface area

• DISADVANTAGE -Painful,Risky,Adhesions,Peritonitis

• Example: Dialyzing fluid-poisoning and renal failure

• In lab animals

Intrathecal (Intraspinal)

• Site: Subarachanoid space

• ADVANTAGE: Bypass blood brain barrier and blood CSF barrier-acts directly on meninges and spinal cord

• DISADVANTAGE-Asepsis, Expertise, Painful,Risky

• Example: Radioopaque contrast media, Xylocaine injection

Epidural

•Through vertebral interspace between dura and lining of spinal canal

•Example: Xylocaine injection

Intramedullary

Site:Tibial or Sternal bone marrow

ADVANTAGE: onset of action very fast

DISADVANTAGE: Strict aseptic conditions, expertise and skill required

Painful and risky

Examples: Bone Marrow transplantation

Intraarticular

•Site: Injection directly into the joint space•ADVANTAGE: High concentration in localised area

•DISADVANTAGE: Asepsis, Joint damage, Pain

•Examples: Hydrocortisone, Gold chloride for rheumatoid arthritis

Intracardiac injection

•Left fourth intercostal space into heart muscle

•Eg Adrenaline injection-cardiac arrest

Inhalation

•Site: Inspiration nose/mouth•ADVANTAGE: fast, quick-large surface area, self

•DISADVANTAGE: increased bronchial and salivary secretions

•Examples: Salbutamol ,Na cromoglycate –Metered dose inhalers

Intranasal

•Drugs directly into the nose. •Desmopressin is administered intranasally in the treatment of diabetes insipidus•Salmon calcitonin- osteoporosis•GnRH aanalogues

Topical

• Conjunctival, Nasal ,Auditory Mucosal• drops, sprays

• Vaginal and urethral• Solutions, ointment ,emulsions, suppositories, pessary

• Inunction and dermal• Rubbing into skin• Dust/spray

Transdermal therapeutic system

• Drug in solution or bound to a polymer is held in reservoir between occlusive backing film and rate controlling micro pore membrane under surface of which is smeared with an adhesive impregnated with priming dose of drug.

• Adhesive layer protected with film which is peeled off just before application

• To provide smooth plasma concentration without fluctuations

• More convenient, patient compliance is better

THANK YOU