Drug administration

Routes of Drug Administration

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

Drug Absorption

Absorption is the process by which a drug enters the bloodstream without being chemically altered or The movement of a drug from its site of application into the blood or lymphatic system

Drug Absorption

The rate at which a drug reaches it site of action depends on: Absorption - involves the passage of the drug from its site of administration into the blood Distribution - involves the delivery of the drug to the tissues

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
Important Info



The possible routes of drug entry into the body may be divided into two classes: Enteral Parenteral

Enteral Routes

Enteral - drug placed directly in the GI tract: sublingual - placed under the tongue oral - swallowing rectum - Absorption through the rectum

Sublingual/Buccal

Some drugs are taken as smaller tablets which are held in the mouth or under the tongue. Advantages rapid absorption drug stability avoid first-pass effect

Sublingual/Buccal

Disadvantages inconvenient small doses unpleasant taste of some drugs

Oral

Advantages Convenient - can be 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

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

Disadvantages cont. 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 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

Advantages: 1. unconscious patients and children 2. if patient is nauseous or vomiting 3. easy to terminate exposure 4. absorption may be variable 5. good for drugs affecting the bowel such as laxatives
Rectal

Disadvantages irritating drugs contraindicated

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

Intravascular

Advantages: Absorption phase is bypassed (100% bioavailability) 1.precise, accurate and almost immediate onset of action, 2. large quantities can be given, fairly pain free

Disadvantages: . greater risk of adverse effects a. high concentration attained rapidly b. risk of embolism

Intramuscular

Advantages: 1. very rapid absorption of drugs in aqueous solution 2.repository and slow release preparations Disadvantages: .pain at injection sites for certain drugs

Subcutaneous

1. slow and constant absorption 2. absorption is limited by blood flow, affected if circulatory problems exist 3. concurrent administration of vasoconstrictor will slow absorption


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 flow .
Inhalation

Topical

Mucosal membranes (eye drops, antiseptic, nasal, etc.) Skin a. Dermal - rubbing in of oil or ointment (local action) b. Transdermal - absorption of drug through skin (systemic action)


intravenous 30-60 seconds intraosseous 30-60 seconds endotracheal 2-3 minutes 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-

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

Very Important Info!

THAT’S IT!!