Routes of administration Flashcards
Why is the route of administration important?
Because the route helps with getting the right drug, at the right rate, at the right time and at the right place
What is the drug mixed with to make the medicine?
Drug is mixed with excipients to make the medicine
It is rare to get just the drug
What are excipients responsible for?
Excipients are responsible for getting the drug to the right place at the right time and at the right rate
The route of administration means to (or aims to) get the drug to its site of action in the body
What is the body designed to do ?
Because of this, what do we try to trick the body into thinking?
the body is designed to:
* take in nutrition
* stop bacterial infection
* stop the entry of foreign material
Because of this, we try to trick the body into thinking the drug is a nutrient
2 Categories of Routes of Administration:
- Local (Topical)
- Systemic (There are two subsections of this which are Enteral and Parenteral)
Local (Topical) administration
In local administration, where is medicine applied to?
Where are most topical formulations applied to? Where else?
Is the drug intended for absorption into the body?
In local administration, medicine is applied externally to a mucous membrane or skin
most topical formulations are intended for application to the skin, although topical includes application to the eye, ear or nose (or vagina)
drug not intended for absorption into the body
Name 4 types of topical administration and state what each is mostly used for/mostly used to treat.
Nasal administration
mainly used to treat rhinitis (hay fever
and cold)
Aural administration (ear)
generally used for young children with
otitis media
Ocular administration
most frequently used for infections of the
eye
Skin administration
Treat infection or skin irritation/inflammation
What types of formulations can nasal, aural and ocular medicines come as?
Can be liquid (drops or sprays)
Or semi solid (creams, ointments)
Ocular formulations can also be a solid-dosage form (tablets)
(You can get tiny tablets that go in the eye)
What is the most demanding or difficult type of medicine to make?
making a product for ocular delivery is the most demanding of all medicines,
as it has to be sterile and isotonic (certain ion concentration)
What are the different types of skin formulations?
They are semi-solid formulations:
- Creams- aqueous colloidal preparation
- Ointments- oily in nature
- Gels- colloidal multi-component preparation that can aqueous or oil in nature
Advantages of Topical Delivery
non-invasive
local treatment of ailments without systemic effect
Disadvantages of Topical Delivery
inaccurate dosing (hard to get accurate dosage of gels and creams etc.)
ointments can leave an oily feeling on the skin
possible systemic absorption (even though local effect is targeted)
Could be absorbed into the blood (if cream is not formulated properly)
absorption depends on the site of application (soft skin vs. callused skin such as soles of the feet)
Systemic administration
What are the two types of systemic administration? (give examples of the types of administration)
What is the difference between the two?
Enteral (oral, buccal, sublingual, rectal)
Parenteral (injection, inhalation, transdermal- across the skin)
Enteral- Taken from the alimentary tract (from the mouth to the anus)
Parenteral- anything else other than enteral
In systemic administration, the drug directly enters the bloodstream to reach and affect cells in all areas of the body
Enteral - Oral Administration
What percentage of all medicines are administered orally?
Approximately 60% of all medicines are administered orally
Advantages of oral administration
Convenient and safe
○ Patient can self-administer any time
○ No infection risk- microorganisms don’t grow in tablets (long shelf life)
○ The body is designed to absorb material from the gut
High surface area and therefore excellent absorptive capacity
○ Good blood supply (well vascularised)
○ Blood flows in counter current flow against substance flow in the alimentary tract (good absorption)
Modified release forms have the potential to tailor delivery
Downsides of oral administration
Lag time to effective concentration at the site of action (delay between the time tablet is taken and time of effect)
○ Dissolution (dissolving) is often the rate limiting step
○ Dissolution and adsorption depends on the contents of stomach and small intestine (pH and food?)
Hostile environment (pH, enzymes)
○ not possible to deliver proteins (e.g. insulin)- hydrolysed by enzymes
○ pH of gut can have a significant effect on the solubility of the drug contained in the medicine
Variability
○ GI tract’s capacity for absorption changes with age, gender, ethnicity, etc.
○ disease state can have significant implications on the GI tract
Other problems with the oral route
First pass metabolism
○ hepatic portal vein drains the gut and delivers absorbed drug to the liver where it can be metabolised (chemically altered)
○ can be a problem with drugs that undergo extensive metabolism (not much of the drug will go into the systemic circulation)
Difficult to reverse therapy
○ once you have swallowed a medicine, it’s difficult to get it back
Irritation to gastro-intestinal system
○ some drugs can irritate the mucosa and cause problems such as gastric ulcer
Types of Oral formulations (in order of increasing rate of absorption)
- Tablets (slow at releasing drug)
- Capsules
- Hard gelatin
- Soft gel
- Suspensions
- Emulsions
- Solutions
Should tell patient to take water with medicine (as much as a can of coke) as this helps with absorption.
Enteral - Buccal and Sublingual Administration
What is this often use to treat?
How is a medicine taken by buccal administration and sublingual administration?
They are often used for the treatment of pain
Buccal- medicine placed between gums and cheek
Sublingual- medicine placed under the tongue
What is the benefit of Buccal and Sublingual administration?
Avoids the first pass metabolism
What type of formulation do buccal and sublingual medicines generally come as?
They are generally tablets with strong adhesion characteristics to be retained in the mouth
Enteral- Rectal administration
5 aspects of rectal administration
(3 Benefits, types of formulations, used to treat what?)
Well vascularised region
- erratic absorption
- Rectum is very well perfused with blood (can be absorbed quickly)
Good alternative to the oral route
- used for drugs inactivated in GIT
Local use and systemic delivery
- constipation/inflammation
- epilepsy
Rectal suppository/foams/enemas
(Not often used as such in the UK)
(Mainly) avoid first pass metabolism
