Methods of administration

Chapter 15 Methods of administration



Chapter contents


Enteral administration 115

Different types of oral delivery system 117

General gastrointestinal tract health 119

Parenteral administration 120

A drug can be administered in different ways. Supplements and herbs are generally administered orally, although other forms of delivery are possible:


• Enteral: administered through the gastrointestinal tract, including the mucosa of the mouth, stomach, small intestine, colon and rectum.

• Parenteral: not administered via the gastrointestinal tract but one of the following:
• respiratory tract: including nasal cavity and lungs

• vagina

• topically/transdermally: absorption through skin

• subcutaneous injection

• intravenous injection

• intramuscular injection

• spinal injection.


Enteral Administration


Oral administration is the most common way to get drugs or remedies into the body. The gastrointestinal tract is essentially a long tube with a varied and complex ecosystem.




• Advantages



• Ease of administration: patients are used to ingesting food, so this form of administration is generally acceptable.

• Ease of absorption: in many places, the lining of the digestive tract is only one cell thick and moist, which is ideal for absorption.

• Large surface area for absorption: the gastrointestinal tract is very long, which allows substances to be absorbed over a long period of time.

• Each area of the digestive tract has different qualities: this allows a wide range of remedies to be absorbed.


• Disadvantages



• Some patients find administration difficult due to taste, texture, etc.

• The variety of environments encountered by the substance in the passage down the gut can prevent proper delivery, for example, insulin cannot be ingested as its structural integrity is destroyed in the stomach.


Sublingual Administration



• Advantages



• Rapid access to the bloodstream.

• Easy to use.

• Initially bypasses liver: nitroglycerine (for angina) has a very short half-life and is rapidly metabolized by the liver. For this reason, it is given under the tongue to get to the heart quickly and at a high enough dosage.


• Disadvantages



• Short action: the drug might be almost entirely removed in the liver.


Administration via the Stomach



• Advantages



• Large surface area for absorption.


• Disadvantages



• Thick mucous layer slows absorption time.

• Drug only in place for a short period of time.


Administration via the Small Intestine



• Advantages



• Large surface area for absorption.


• Disadvantages



• Blood from small intestine passes directly to the liver.

• Intestinal microflora might inactivate drug.


Administration via the Colon



• Advantages



• Direct access to the treatment site.

• Less hostile environment with less diversity and intensity of activity than the stomach and small intestine


• Disadvantages



• Requires complex delivery system to enable the drug to be released at this stage in the gut.



Administration via the Rectum


This is a possible method of delivering herbal remedies.



• Advantages



• Bypasses liver.

• Common way to getting anti-inflammatories into the body as it bypasses the gut and therefore any irritation of the gut lining. It can also be used for drugs that can produce nausea if taken orally.

• Also used in treatment of haemorrhoids.


• Disadvantages



• Possible adverse reaction as dosage not tempered by liver metabolism.

• There might be problems with patient compliance.


Factors Affecting Absorption Through the Gastrointestinal Tract



• Surface Area


Absorption of a drug or remedy is greatest in the small intestine due to the large surface area created by the villi.



• Gut Motility


The more active the stomach movement, the shorter the transit time. This decreases the amount of drug or remedy that can be absorbed in the stomach.



• Gastric Emptying


The faster this occurs, the faster the drug or remedy can reach the small intestine and start to be absorbed.



Factors Increasing Gastric Emptying



• Fasting.

• Anxiety.

• Antacids.

• Hyperthyroidisms increase gastric emptying.

• Fluids: giving herbs with plenty of fluid will speed up the time it takes to reach the main area of absorption, the small intestine.


Factors Decreasing Gastric Emptying



• Fatty foods.

• Large, bulky foods: get in the way of the drugs and the gut wall.

• Hyperacidity.

• Peptic ulcers.

• Hypothyroidism.

• Clinical depression.
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Jul 22, 2016 | Posted by in PHARMACY | Comments Off on Methods of administration

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