Routes Of Administration Oral (Solutions)

Question 1

What are the advantages of oral solutions?

Answer 1

• Fast onset of action
• Dose uniformity is assured
• Easy to swallow and manufacture

Question 2

What are the disadvantages of oral solutions?

Answer 2

• Unpleasant taste/ odour
• Packaging and transportation costs
• Some drugs are poorly soluble in water
• Less stable than solid dosage forms

Question 3

What are the 3 major signs of instability of oral solutions?

Answer 3

• Precipitation
• Colour change
• Microbial growth

Question 4

What are the main properties of solutions?

Answer 4

• Must be stable/ palatable
• Appropriate viscosity for pourability
• Acceptable to patients
• At physiological pH where possible
• Dose in multiples of 5ml (convenience)

Question 5

What is the main solvent and why does the drug concentration have to be lower?

Answer 5

• Water
• Lower than saturation solubility to avoid drug precipitation

Question 6

What are the main excipients for solutions?

Answer 6

• Preservatives : prevent microbial growth (glycerol)
• Viscosity enhancers : better pour (hydroxyethyl cellulose)
• Flavouring agent : mask unpleasant taste (vanilla)
• Antioxidants : Improve stability minimising oxidation (ascorbic acid)
• Sweeteners and Colouring agents

Question 7

What are the main properties of excipients?

Answer 7

• Stable and reproducible
• No unwished interaction with drug
• Desired functionality
• Cost effective
• Pharmacologically inert

Question 8

What are factors that affect chemical degradation?

Answer 8

• Increase in temperature
• Catalyst
• pH
• O2
• Uv light

Question 9

What are the properties that must remain the same for the entire shelf life of solution?

Answer 9

• Physical colour, odour, taste
• Therapeutic
• Toxicological
• Chemical
• Microbiological

Question 10

What can enhance the drug stability?

Answer 10

• Antioxidants
• Excipients
• Reduce light transmission
• Formulate at suitable pH

Question 11

Why increase drug solubility?

Answer 11

• Avoid drug precipitation
• Achieve desired dose

Question 12

What does drug solubility depend on?

Answer 12

• Molecular/ crystal structure
• pKa
• Solvent
• pH of medium

Question 13

How can solubility be increased?

Answer 13

• Co-solvents
• Complexation (cyclodextrins)
• Surfactants
• pH modification

Question 14

Where does base have high solubility and why?

Answer 14

• High solubility in stomach and low in small intestine
• Due to more protonation. Weak base ionised at low pH (ion attraction to polar water molecules)

Question 15

What are examples of buffers?

Answer 15

• Citrate (3 - 6.2)
• Acetate (3.6 - 5.6)

Question 16

What are co-solvents?

Answer 16

• Enhance drug solubility
• Used for non-ionic drugs where solubility can’t be adjusted by pH
• Add a water miscible liquid with low polarity (ethanol)

Question 17

What are the 3 most important cyclodextrins ?

Answer 17

• 6 membered sugar ring (a-CD)
• 7 membered sugar ring (B-CD
• 8 membered sugar ring (y-CD)

Question 18

What are cyclodextrins and how do they work?

Answer 18

• Made of sugar molecules bound in a ring (glucose based oligosaccharides)
• Have hydrophilic outer wall and hydrophobic inner wall. Can capture hydrophobic drugs via non-covalent bonds. Make combination and released and absorbed. Increasing drug solubility

Question 19

What are surfactants?

Answer 19

• Possess 2 regions : hydrophilic head and hydrophobic tail
• Can form micelles
• Enhances drug solubility

Question 20

How do surfactants work?

Answer 20

• Reduce the surface tension of liquids - allow lipophilic drugs (reduce interfacial energy barrier between drug and medium)
• Form on surface of liquids and assemble to form micelles at the critical micelle concentration (CMC) when the surface is saturated with surfactant