Routes of Medication Administration

A route of administration in pharmacology and toxicology is the path by which a drug, fluid, poison, or other substance is taken into the body. Routes of administration are generally classified by the location at which the substance is applied. Common examples include oral and intravenous administration. Routes can also be classified based on where the target of action is. Action may be topical (local), enteral (system-wide effect, but delivered through the gastrointestinal tract), or parenteral (systemic action, but delivered by routes other than the GI tract).

Route	Methods	Description	Advantages	Disadvantages
Oral	Oral	Through the mouth	It is convenient. It is the cheapest available route. It is easy to use. It is safe and acceptable.	Less amount of drug reaches the target tissue. Some of the drug is destroyed by gastric juices. Absorption has to take place which is slow, so is not preferred during emergencies. It might cause gastric irritation. It might be objectionable in taste. It might cause discoloration of teeth.
	Buccal	Inside the cheek
	Lingual	On the tongue
	Sublingual	Under gums	Rapid absorption takes place. Drug is dissolved easily. Drug enters the blood directly. Less first pass effect. Spitting out of the drug removes its effect.	This method is inconvenient. Irritation of the mucous membrane might occur. Person may swallow the drug. Might be unpleasant in taste.
	Transmucosal	Across mucous membrane
Enteral	Enteral	By way of the intestine
	Nasogastric (Tube)	A feeding tube inserted through the nose into the stomach (NG or NGT)
	Gastrostomy (tube), percutaneous endoscopic gastrostomy (tube)	A feeding tube inserted through the abdominal wall into the stomach (GT or PEG)
	Jejunostomy (tube)	A feeding tube inserted through the jejunum (small intestine) (JT)
Inhalation	Inhalation	Drawn through the mouth into the lungs	Rapid absorption takes place. Rapid onset of action takes place. This route has minimum side effects. No first pass effect takes place. This method is easy. Fewer doses is required.	Special apparatus is required. Irritation of the respiratory tract may take place. Cooperation of the patient is required. Airway must be patent.
Parenteral	Parenteral	By passing the gastrointestinal tract. Not delivered via the intestinal tract.	Parenteral route is rapid. It is useful for uncooperative patients. It is useful for unconscious patients. Inactivation by GIT enzymes is avoided. First pass effect is avoided*. Bioavailability is 100%.	Skill is required. It is painful. This method is expensive. It is less safe.
	Implant	A device inserted into or under the skin
	Intra-arterial	Into an artery (AI)
	Intra-articular	Into a joint (AI)
	Intracardiac	Into the heart muscle (IC)
	Intradermal	Into the top lay of the skin (ID)
	Intratracheal, endotrcheal	Into the trachea (IT)
	intramuscular	Into a muscle (IM)	Absorption is rapid than subcutaneous route. Oily preparations can be used. Irritative substances might be given Slow releasing drugs can be given by this route.	Using this route might cause nerve or vein damage.
	Intraosseous	Into the marrow of a bone
	intraperitoneal	Into the peritoneal (abdominal) cavity
	Intrapleural	Into the pleura (sac that surround the lungs)
	intrathecal	Into space around the spinal cord
	intrauterine	Into the uterus
	intravenous	Into a vein (IV)	Immediate action takes place. This route is preferred in emergency situations. This route is preferred for unconscious patients. Titration of dose is possible. Large volume of fluids might be injected by this route. Diluted irritant might be injected. Absorption is not required. No first pass effect takes place.* Blood plasma or fluids might be injected.	There is no retreat. This method is more risky. Sepsis-Infection might occur. Phlebitis(Inflammation of the blood vessel) might occur. Infiltration of surrounding tissues might result. This method is not suitable for oily preparations. This method is not suitable for insoluble preparations.
	intraventricular	Into the ventricles, or cavities, of the brain
	intravesicular	Into the urinary bladder
	intravitreal or intravitreous	Into the eye
	Subcutaneous	Immediately under the skin (SubQ, SC, SQ)	Absorption is slow and constant. It is hygienic.	It might lead to abscess formation. Absorption is limited by blood flow.
Nasal		Into the nose
Ophthalmic		Into the eye
Otic, aural		Into the ear
Percutaneous		Through the skin
Rectal		Through the anus into the retum	This route is preferred in unconscious or uncooperative patients. This route avoids nausea or vomiting. Drug cannot be destroyed by enzymes. This route is preferred if drug is irritant.	This route is generally not acceptable by the patients. Locally acting drugs include glycerin and Bisacodyl suppository. Systemic acting drugs include Indomethacin (anti inflammatory) and aminophyllin (bronchodilator). Retention enema is diagnostic and is used for finding the pathology of lower intestines. Drugs given by rectal route have 50% first pass metabolism.*
Topical		Applied to the skin or mucous membranes
Transdermal		Through the skin
Vaginal		Into the vagina

*First Pass Effect: First pass effect is the term used for hepatic metabolism of drug when absorbed and delivered through portal blood. Greater the first pass effect, less amounts of the drug reach the systemic circulation.

Time of Action using Different Routes of Administration

Route of Administration	Delay time for Action
Intravenous route	30-60 seconds
Intraosseous route	30-60 seconds
Endotracheal inhalation	2-3 minutes
Sublingual route	3-5 minutes
Intramuscular route	10-20 minutes
Rectal route	5-30 minutes
Ingestion	30-90 minutes