Drug Formulations and Routes of Administration

Question 1

What is formulation?

Answer 1

Also known as “dosage” form, it is the form in which a pharmaceutical product is presented for therapeutic use (eg tablet, cream, aerosol)

Question 2

What is route of administration?

Answer 2

One of many ways by which a drug is delivered to the body

Question 3

What factors determine the most appropriate route of administration?

Answer 3

1. Site of action
2. Symptoms (oral delivery impossible if patient vomits)
3. Technical / formulation capability (tablet cannot be applied in the same kind of way as a syringe, however usually same route of administration can be used for both local and systemic delivery depending on purpose of treatment)

Question 4

What is oral (enteral) administration?

Answer 4

Administration to or by way of the mouth
Most common route, involves swallowing the formulation into GI tract, followed by intestinal absorption of the drug
Usually for systemic drug delivery

Question 5

What are the advantages of oral administration?

Answer 5

Non-invasive
Patient can self-administer
Simple and convenient
Economical formulation production because sterilisation is not needed

Question 6

What are the disadvantages of oral administration?

Answer 6

Slower onset of action
High acidity in stomach and digestive enzymes in the GI tract can destroy the drug eg insulin
First-pass metabolism by the liver
Not suitable for bitter or strong smelling drugs
Not suitable for unconscious or vomiting patients

Question 7

What are types of oral formulations?

Answer 7

Solids = tablets and capsules
Liquids = syrup, elixer, and oral drops

Question 8

What are tablets?

Answer 8

Powder containing the drug and excipients (diluents, binders, lubricants etc) compressed into a hard mass
Can be for immediate or controlled/sustained drug release
Most tablets are swallowed whole but there are also chewable, orally disintergrating or effervescent tablets

Question 9

What are capsules?

Answer 9

Power or liquid contained in a shell made from a polymer, usually gelatin
Available as hard and soft capsules

Question 10

What are the differences between the oral formulations: syrup, elixer, and oral drops?

Answer 10

Syrup = solution containing a high concentration of sucrose or other sugars

Elixir = Flavoured / sweetened hydroalcoholic solution

Oral drops = solution, emulsion, or suspension administered in small volumes by a suitable device (eg dropper)

Question 11

In terms of liquid formulations, what is a solution?

Answer 11

Drugs and excipients dissolved in a solvent (water only) or a mixture of miscible solvents (eg water and ethanol)
One-phase system, homogenous

Question 12

In terms of liquid formulations, what is an emulsion?

Answer 12

One liquid dispersed as small droplets throughout another liquid
Oil-in-water or water-in-oil
Two-phase system

Question 13

In terms of liquid formulations, what is suspension?

Answer 13

Solid particles dispersed throughout another liquid
Solid-in-liquid
Two-phase system

Question 14

What is sublingual administration?

Answer 14

Administration beneath the tongue

Available as sublingual tablets or sublingual sprays

Question 15

What is buccal administration?

Answer 15

Administration directed toward the cheek, generally from within the mouth
Buccal tablet placed on the inside of the cheek between the gum and lip

Question 16

What are the advantages of sublingual and buccal administration?

Answer 16

Good for systemic drug delivery - fast onset of action due to a high blood supply in oral mucosa, leading to rapid drug absorption, no first-pass metabolism

Sublingual / buccal tablets can be removed anytime when adverse effects occur

Question 17

What are the disadvantages of sublingual and buccal administration?

Answer 17

Not suitable for bitter or strong smelling drugs

High molecular weight drugs (eg proteins and peptides) cannot be absorbed

Question 18

What are injections / parenteral administration?

Answer 18

Administrations by needle
Liquid, sterile formulations
Numerous possible sites of injection depending on the treatment of purpose

Question 19

What are the possible sites / depths of injections?

Answer 19

Intravenous - within veins (chemotherapy, antibiotics)

Intramuscular - within muscles (vaccines)

Subcutaneous - beneath the skin (insulin)

Intradermal - within the skin (allergy testing)

Question 20

The angle / depth of the needle determines the route of injection. What are the correlating depths and angles?

Answer 20

Intramuscular = 90 deg, deepest
Subcutaneous = 45 deg
Intravenous = 25 deg
Intradermal = 10 - 15 deg, shallowest

Question 21

What are the advantages of intravenous administration?

Answer 21

Directly delivers the drug into systemic circulation
By definition, 100% bioavailable
Fast onset of action so valuable in an emergency, suitable for unconscious or vomiting patients
Small (several ml eg bolus) and large volumes (up to litres eg infusion) can be injected
Drug does can be controlled accurately

Question 22

What are the disadvantages of intravenous administration?

Answer 22

Invasive, painful
Needs qualified healthcare profession to administer
Needs aseptic technique
Risky because once the drug is injected it cannot be recalled
Introduction of air (bubble) or particulate matter may cause embolism and potentially fatal

Question 23

What are the advantages of intramuscular administration?

Answer 23

Drug absorption is more predictable, less variable, and more rapid compared to oral route due to blood vessels serving the muscles
Sustained release formulations can be injected
No first-pass metabolism

Question 24

What are the disadvantages of intramuscular administration?

Answer 24

Invasive, painful
Needs qualified healthcare professional to administer and needs aseptic technique
Only small volumes (typically 2 - 5ml) can be injected

Question 25

What are the different formulations for nasal administration?

Answer 25

Nasal spray, nasal ointment, or nasal powder

Good for local (eg nasal congestion or infection) or systemic (eg migraine) treatments

Question 26

What are the different formulations for inhalation?

Answer 26

Aerosols produced from various devices

Good for local and systemic treatments

Question 27

What is topical administration?

Answer 27

Medication applied to the skin (external body surface)

Semi-solid formulations usually only for local treatment

Question 28

What are the different formulations for topical administration?

Answer 28

Cream = oil in water emulsion
Lotion = oil in water emulsion, more runny than cream
Ointment = oily, thick semisolid
Gel = suspension of small particles interpenetrated by a liquid, may contain a gelling agent to promote stiffness
Paste = semisolid with a high concentration of solids (20 - 50%) and stiff consistency

Question 29

What is transdermal administration?

Answer 29

Administration through the skin to systemic circulation by diffusion
Available as transdermal patches for systemic drug delivery (eg nicotine replacement therapy)
Applied onto dry, flat skin area

Question 30

What is ophthalmic administration?

Answer 30

Administration to the eye
Usually for local treatments
Available as eye drops or eye ointments
Formulation MUST be produced sterile

Can only use for a 28 day maximum after opening due to potential microbial contamination

Question 31

What is otic / auricular administration?

Answer 31

Administration to the ear

Solutions or suspensions usually for local treatment (ear wax removal, ear infection)

Question 32

What formulations can be administered rectally?

Answer 32

Solid = suppository
Liquid = enema
Semi-solid = cream, ointment, foam enema
Used for local (constipation, haemorrhoids) or systemic (fever, comiting) treatments

Question 33

What are the advantages of rectal administration?

Answer 33

Suitable when oral route cannot be used (Nausea, vomiting, GI problems, post-operative, unconscious)

Suitable for drugs that cannot be orally delivered (Adverse GI effects, unpleasant taste, prone to degradation in GI tract, extensive first-pass metabolism)

Question 34

What are the disadvantages of rectal administration?

Answer 34

Poor compliance, inconvenience
Absorption is slow and prone to high variability (presence of faeces)
Some drugs can cause local irritation of rectal mucosa, causes bowel evacuation

Question 35

What administrations can be administered vaginally?

Answer 35

Vaginal creams and suppositories for local treatment