Routes of administration

Question 1

Why is the route of administration important?

Answer 1

Because the route helps with getting the right drug, at the right rate, at the right time and at the right place

Question 2

What is the drug mixed with to make the medicine?

Answer 2

Drug is mixed with excipients to make the medicine
It is rare to get just the drug

Question 3

What are excipients responsible for?

Answer 3

Excipients are responsible for getting the drug to the right place at the right time and at the right rate

Question 4

The route of administration means to (or aims to) get the drug to its site of action in the body

Question 5

What is the body designed to do ?
Because of this, what do we try to trick the body into thinking?

Answer 5

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

Question 6

2 Categories of Routes of Administration:

Answer 6

• Local (Topical)
• Systemic (There are two subsections of this which are Enteral and Parenteral)

Question 7

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?

Answer 7

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

Question 8

Name 4 types of topical administration and state what each is mostly used for/mostly used to treat.

Answer 8

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

Question 9

What types of formulations can nasal, aural and ocular medicines come as?

Answer 9

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)

Question 10

What is the most demanding or difficult type of medicine to make?

Answer 10

making a product for ocular delivery is the most demanding of all medicines,
as it has to be sterile and isotonic (certain ion concentration)

Question 11

What are the different types of skin formulations?

Answer 11

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

Question 12

Advantages of Topical Delivery

Answer 12

non-invasive

local treatment of ailments without systemic effect

Question 13

Disadvantages of Topical Delivery

Answer 13

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)

Question 14

Systemic administration

What are the two types of systemic administration? (give examples of the types of administration)

What is the difference between the two?

Answer 14

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

Question 15

In systemic administration, the drug directly enters the bloodstream to reach and affect cells in all areas of the body

Question 16

Enteral - Oral Administration

What percentage of all medicines are administered orally?

Answer 16

Approximately 60% of all medicines are administered orally

Question 17

Advantages of oral administration

Answer 17

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

Question 18

Downsides of oral administration

Answer 18

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

Question 19

Other problems with the oral route

Answer 19

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

Question 20

Types of Oral formulations (in order of increasing rate of absorption)

Answer 20

• 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.

Question 21

Enteral - Buccal and Sublingual Administration

What is this often use to treat?
How is a medicine taken by buccal administration and sublingual administration?

Answer 21

They are often used for the treatment of pain

Buccal- medicine placed between gums and cheek
Sublingual- medicine placed under the tongue

Question 22

What is the benefit of Buccal and Sublingual administration?

Answer 22

Avoids the first pass metabolism

Question 23

What type of formulation do buccal and sublingual medicines generally come as?

Answer 23

They are generally tablets with strong adhesion characteristics to be retained in the mouth

Question 24

Enteral- Rectal administration

5 aspects of rectal administration
(3 Benefits, types of formulations, used to treat what?)

Answer 24

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

Question 25

Respiratory administration

What is this?

Answer 25

Respiratory administration is delivery to the lungs

Question 26

Local or systemic type of administration and what is possible because of this? Which form is it delivered in and what is the significance of particle size? If used for local effect what is the benefit?

Answer 26

It has a local and systemic effect
- Delivery of proteins is possible

Delivered in gaseous, mist or aerosol form
- drug particle size is critical for good drug deposition
- too large particle size leads to deposition (build up) in the mouth
- too small particle size leads to exhalation of the particles
- The smaller the particle, the deeper in the lungs it can go

Minimal side effects when used for local effect
e.g. asthma

Question 27

Respiratory formulations

What is needed to deliver drugs?

Answer 27

Need to use inhalers (special devices) to deliver drugs
- pressurised metered-dose inhaler (pMDI)
- dry powder inhaler (single & multiple) (DPI)
- nebulizer

Question 28

Advantages of the Respiratory Route of Delivery

Answer 28

Advantages
- many different devices to deliver drug to the required part of the lungs
- lung has very large surface area - good for drug absorption
○ Lungs have the second largest surface area
- possible to use lungs to deliver macromolecules systemically
provides fast relief for asthma

Question 29

Disadvantages of the Respiratory Route of Delivery

Answer 29

patient needs to be trained to use inhalers

dry powder inhalers are not suitable for children or patients with decreased lung capacity

formulation of an inhaler medication is very difficult

unwanted systemic effects are possible due to swallowing of drug

Question 30

Parenteral- Administration by injection

Answer 30

Injected directly into the body either as bolus or infusion

Question 31

Parenteral - Administration by injection

What are 3 main routes?

Answer 31

Subcutaneous (under the skin)
Intramuscular (into muscle)
Intravenous (into a vein)

There’s many other routes but these are the main ones

Question 32

Advantages of Injection for Delivery

Answer 32

rapid onset

drug enters general circulation without hepatic passage

can deliver proteins & macromolecules

can be applied to unconscious patients or patients with swallowing problems

many different injection sites – pharmacokinetics can be controlled by this
○ Can alter rate of administration of a drug

Question 33

Disadvantages of Injection for Delivery

Answer 33

pain

only liquid preparations can be administered

some injections cannot be administered when patient moves

irreversible administration

Question 34

Parenteral- Transdermal Administration

What is this?

Answer 34

When medicine is delivered across the skin

Question 35

What kind of formulation is used for transdermal administration and 2 aspects of it

Answer 35

Formulations include patches

• Controlled release of high potency drugs e.g. fentanyl, nicotine
• Drugs delivered at less than maximal rate so the drug will pass across the skin
  (If drug released slowly, it will pass across the skin quickly)

Question 36

Advantages and Disadvantages of Transdermal Delivery

Answer 36

Advantages
- achieves sustained blood level of drug
- avoids first pass metabolism
- avoids food effects
- compensates for rapid clearance

Disadvantages
- drugs needs to be of low molecular mass, high potency, exhibit a Log of 1-2 infection risk. A low log P
allergic and inflammatory responses may occur

Question 37

Choice of route of administration

What is the route of administration determined by?

Answer 37

The route of administration is determined by:

physical characteristics of the drug
- solubility, permeability, potency etc.

rate at which the drug is released and/or absorbed
- ADME properties

need to bypass hepatic metabolism
- if drug is highly metabolised in the liver (can’t be given orally)

the therapeutic use of the medicine
- in order to achieve the required concentration of drug at a particular site(s)

May depend on the disease of the patient