Medicines formulations

Question 1

What are the different types of enteral route? (10)

Answer 1

Mouth

• directly absorbed by mucosa
• few number of drugs are administered this way

Stomach

• limited absorption drugs
• aspirin, warfarin

Small intestine

• Most drugs
• Passive diffusion and active transport

Nasogastric tube

• liquid preparation, dissolved, crushed
• displacement- aspiration risk
• short term due to comfortability

Percutaneous endoscopic gastromtomy/ jejunotomy

• flexible feeding tube placed through the abdominal wall into the stomach
• longer term- risk of infection

Question 2

What are some considerations for the enteral route? (3)

Answer 2

• Gastrointestinal disturbances due to excipients
• Safe to swallow
• Significant first pass metabolism

Question 3

What are some features of IV administration? ( 5)

Answer 3

100% bioavailability
Always in hospital setting

-Bolus injection
Higher, quick peak concentration, such as in antibiotics
- Infusion
Requires large volume
Requires more constant blood volume to avoid toxic effects and ensure consistent effects

Question 4

What are some features of buccal and sublingual administration? (4)

Answer 4

• Quickly absorbed by the mucosa
• Taste should be tolerable,
• Limited to a few drugs, low molecular weight, high lipid solubility
• Useful when drug is unstable at gastric pH or nauseated

Question 5

What are some features of intranasal administration? (3)

Answer 5

Local effects- anticongestant

Systemic effect- naloxone, desmopressin

Question 6

What are some features between intrathecal and epidural administration and what is the difference between them? (8)

Answer 6

Intrathecal
- Directly to CSF
- Limited drugs
- Single dose analgesia- such as Caesarean section, but has risk of respiratory depression
- Few antibiotics and chemotherapy
Eg: Baclofen

Epidural

• Diffuses through the dura into the CSF
• More common
• Slower onset
• Complications include dural headache, high block, epidural abscess

Question 7

What are some features of subcutaneous administration? (4)

Answer 7

• Bolus/ infusion
• Low volume
• Mainly hospital
• Insulin and oestradiol

Question 8

What are some features of rectal administration? (5

Answer 8

• Local effects such as diarrhea and ulcerative colitis
• Systemic delivery
  Bioavailability hard to determine
  Useful when oral/ IV not possible

Almost never for outpatient use

Question 9

What are some features of inhaled administration? (3)

Answer 9

Local effects, sometimes systemic absorption
Systemic effects- ease of delivery, rapid exchange but bioavailability varies

Different types
Consider: conscious inhalation, inspiratory flow rate and hand breath coordination

Question 10

What are some advantages and disadvantages of the nebulised route? (6)

Answer 10

Advantages

• Effective when someone cannot breathe in
• Emergencies or high dose
• Cognitive or physical disability friendly

Disadvantages

• Bulky and inconvenient
• Requires regular cleaning
• Rarely used as outpatient due to slower drug delivery

Question 11

What are some features of the transdermal route and what are some advantages and disadvantages of this (11)

Answer 11

• Steady rate of delivery - smoother plasma concentration
• Interperson variability,
  Oestrogen, nicotine
• Lipid soluble molecules

Advantages:
Convenient, no pain
Prolonged drug action
Better adherence

Disadvantages
Skin reactions
Requires potent drug 
Slow delivery 
Risk of double dosing

Question 12

What are some features of the intramuscular route? (6)

Answer 12

• Requires small volumes
• Some formulated with hyaluronidase- enhance permeation of injections
  Naloxone- when IV not available
  Depo preparations- slow absorption
  Contraindicated in haemophillia
  Not used in regular outpatient

Question 13

What are some emergency access routes of administration? (2)

Answer 13

Endotracheal

Intraosseous- through bone marrow

Question 14

How may drugs be modified for pharmacokinetic variation? (2)

Answer 14

Modified release- insulin- slow, intermediate, long acting. More expensive
Enteric coating- reduces breakdown in the stomach, reducing gastric irritation

Question 15

When may mediations be unsafe and what are the alternatives (6)

Answer 15

If medications are unsafe, it will be via the oral route due to difficulties in swallowing
This may be due to strokes, brain tumours, throat/ oesophageal cancers, drowsiness

If necessary, you can use:
Parenteral route
Dissolved/ crushed medication
Liquid medications

PEG/ PEJ/ nasogastric may be considered- clinically difficult

Question 16

When may liquid medications be used? (3)

Answer 16

Swallowing difficulties
Intolerances to excipients

However, formulation of liquid medication is expensive