Routes of Drug AdministrationRoutes of Drug Administration

DR.RAHUL

PHARMACOLOGY

Routes of Drug Administration

The route of administration (ROA) that is chosen may have a profound effect upon the speed and efficiency with which the drug acts

ImportantInfo

Routes Of Administration

SystemicLocal

Deeper Tissues• Intraarticular• Intrathecal• Retrobulbar

Topical • Skin • Mucous

membrane

Arterial• Anticancerous• Angiography

EntralParentral

Routes Of Administration

Systemic routes Of Drug

Administration

Enteral

Parenteral

Oral

Injection

Rectal

Respiratory

Cutaneous

Enteral Routes

• Enteral - Drug placed directly in the GI tract:

• Sublingual - Placed under the tongue

• Oral - Swallowing (p.O., Per os)

• Rectum - Absorption through the rectum

Sublingual/Buccal

Some drugs are taken as smaller tablets which are held in the mouth or under the tongue.

• Examples1. Nitroglycerine

2. Isoprenaline

3. Clonidine

• Disadvantages• Inconvenient

• Small doses

• Unpleasant taste of some drug

• Advantages • Rapid

absorption

• Drug stability

• Avoid first-pass effect

Sublingual/Buccal

Oral route : Advantages

• Convenient • Self-administered

• Pain free

• Easy to take

• Absorption - Takes place along the whole length of the GI tract

• Cheap - Compared to most other parenteral routes

Oral route : Disadvantages

• Sometimes inefficient - only part of the drug may be absorbed

• First-pass effect - drugs absorbed orally are initially transported to the liver via the portal vein

• Irritation to gastric mucosa - nausea and vomiting

Oral route : Disadvantages

• Destruction of drugs by gastric acid and digestive juices

• Effect too slow for emergencies

• Unpleasant taste of some drugs

• Unable to use in unconscious patient

First-pass Effect

• The hepatic metabolism of 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

• Unconscious patients and children

• If patient is nauseous or vomiting

• Easy to terminate exposure • Absorption may be variable • Good for drugs affecting the

bowel such as laxatives• Irritating drugs

contraindicated

Rectal

Parenteral Routes

• Intravascular (IV, IA)- placing a drug directly into the blood stream

• Intramuscular (IM) - drug injected into skeletal muscle

• Subcutaneous - Absorption of drugs from the subcutaneous tissues

• Inhalation - Absorption through the lungs

Routes of Drug Administration

common abbreviations…• PO = per os = oral

• IV = Intravenous = into the vein

• IM = Intramuscular = into the muscle

• SC = Subcutaneous = between the skin and muscle

• IP = Intraperitoneal = within the peritoneal cavity

Oral Administration

Intestines

Liver

IntravenousAdministration

Metabolism

Intravascular

• Absorption phase is bypassed (100% bioavailability)

• Precise, accurate, almost immediate onset of action

• Large quantities can be given, fairly pain free

• Titration of dose possible.• Response is accurately measurable• Greater risk of adverse effects• High concentration attained rapidly • Risk of embolism• OOPS factor or !@#$%

Intramuscular

• Very rapid absorption of drugs in aqueous solution

• Slow release preparations • Pain at injection sites for certain

drugs• Most common sites :• Gluteus• Deltoid

Subcutaneous• Slow and constant absorption • Absorption is limited by blood

flow affected if circulatory problems exist

• Concurrent administration of vasoconstrictor will slow absorption

• Only small volumes can be injected.

• Self inj. Possible

Peridural Anesthesia• This is

accomplished by injecting a local anesthetic into the peridural space, a covering of the spinal cord

Spinal anesthesia• Here, the local

anesthetic is injected into the subarachnoid space of the spinal cord

1.Gaseous and volatile agents and aerosols 2.Rapid onset of action due to rapid access to circulation A.Large surface area b.Thin membranes separates alveoli from circulation c.High blood flowParticles larger than 20 micron and the particles impact in the mouth and throat. Smaller than 0.5 micron and they aren't retained.

Inhalation

Topical•Skin a. Dermal-rubbing in of oil or ointment (local action), paste, powder, cream, dressing, spray, etc b. Transdermal - absorption of drug through skin (systemic action) i. stable blood levels ii. no first pass metabolism iii. drug must be potent or patch becomes to large

• Mouth And Pharynx- Paints, Lozynges, Mouthwash, Gargles.

• Eyes, Ear, Nose- Drops, Ointments, Irrigation, Spray.

• Git- Nonabsorable Drugs Given Orally.

• Bronchi And Lungs- Inhalations, Aerosols.

• Urethra- Jellys

• Vagina- Peseries, Vaginal Tablets, Cream.

• Anal Canal- Ointments.

Mucosal membranes

Factors affecting choice of route

• Physical and chemical properties of drugs.

• Site of desired action

• Rate and extent of absorption of drug from different routes.

• Effect of digestive juices and first pass metabolism.

• Rapidity with which response is desired.

• Condition of patient.

• Accuracy of dosage required.

• Intravenous 30-60 seconds• Intraosseous 30-60 seconds• Inhalation 2-3 minutes• Sublingual 3-5 minutes• Intramuscular 10-20 minutes• Subcutaneous 15-30 minutes• Rectal 5-30 minutes• Ingestion 30-90 minutes• Transdermal (topical) variable (minutes to

hours)

Route for administration -Time until effect-

The ROA is determined by the physical characteristics of the drug, the speed which the drug is absorbed and/ or released, as well as the need to bypass hepatic metabolism and achieve high conc. at particular sites

ImportantInfo

No single method of drug administration is ideal for all drugs in all circumstances

Very Important

Info!