Lecture 6: solutions 1

Question 1

What is the advantage of solutions?

Answer 1

1. They are easily swallowed
2. They are readily absorbed as its already dissolved in the molecular form
3. Promotes rapid drug action so its useful in emergencies
4. Solutions provide dose uniformity where the liquid solution can be measured accurately
5. Easier to manufature compared to tablets

Question 1

What are the disadvantages of solutions?

Answer 1

1. Inherently unstable and the drug is prone to hydrolysis
2. Many drugs are poorly soluble in water
3. More prominent taste compared to a tablet
4. Bulky for the patient to carry and more expensive to transport compared to solid dosage forms
5. More prone to spillage or leakage

Question 2

What is the minimum quality of water used for the preparation of official substances and other bulk pharmaceutical ingredients?

Answer 2

Drinking water

and that is only used in the early stages for cleaning pharmaceutical manufacturing equipment and product contact components

Question 3

What are the two types of water used in preparation?

Answer 3

Bulk water and packaged water

Question 4

When are non aqueous solvents used?

Answer 4

1. When the drug is insufficiently soluble or stable in aqueous systems
2. When the product is intended for specific properties such as sustained drug absorption.

Question 5

Why are non aqueous solutions limited to intramuscular and topical routes?

Answer 5

Due to their unpalatability, toxicity, irritancy or immiscibility with physiological fluids.

Question 6

How do you choose the appropriate pharmaceutical buffer?

Answer 6

1. Ensure the pH range of the buffer is close to the required pH
2. Ensure the buffer is stable in storage (its pH doesn’t change)
3. Formulation compatibility because some ions are not suitable for biological pH control.

Question 7

Why might pH of buffers change during storage?

Answer 7

1. Glass containers (soda lime glass) are alkaline and can cause the pH to increase
2. Acidity from CO2 from dissolved air

Question 8

Which buffers are unsuitable for biological pH control and why?

Answer 8

1. Phosphate and carbonate buffers
2. They precipitate calcium ions by forming insoluble calcium phosphate or calcium carbonate

Question 9

What is specific acid catalysis?

Answer 9

When an acid accelerates the hydrolysis of drugs in solution.

Question 10

What is specific base catalysis?

Answer 10

When a base accelerates the hydrolysis of drugs in solution.

Question 11

How do you obtain the pH-rate profile of a drug?

Answer 11

1. Subject the drug in solution to various pH and obtain the rate constant (k obs) at each pH
2. Construct the pH-rate profile by plotting log k obs against pH

Question 12

What is the purpose of the pH rate profile?

Answer 12

To study the hydrolysis kinetics of a drug at various pH

Question 13

How do you determine the pH of maximum stability from a pH-rate profile?

Answer 13

The pH of maximum stability is the lowest point(s) on the graph

Question 14

Can there be a range of pH of maximum stability from a pH-rate profile?

Answer 14

Yes
either one point or multiple

Question 15

What is rheology?

Answer 15

A term to describe the flow of liquids and the deformation of solids.

Question 16

What is viscosity?

Answer 16

The expression of the resistance of a fluid to flow

Question 17

What happens to the viscosity of a liquid when temperature is increased?

Answer 17

It decreases

Question 18

In which cases is parenteral administration beneficial over oral?

Answer 18

1. Unconscious patient
2. Get around drug degradation in the GI tract
3. Emergency use for life threatening conditions
4. For drug accumulation at the site of action.

Question 19

What are the key requirements of parenteral formulations?

Answer 19

1. Free of microorganisms, pyrogens and particulate matter
2. Must be aqueous for IV administration
3. pH should be close to physiological pH
4. Isotonic
5. Multi dose products must contain preservatives

Question 20

Which products (aqueous or non aqueous) are sterilized using steam sterilization?

Answer 20

Aqueous

Question 20

What are the ways by which parenteral formulations are sterilized?

Answer 20

1. Steam sterilization: using steam sterilizers or autoclaves to kill microorganisms by causing protein coagulation or degradation
2. Dry heat sterilization: use hot air oven or tunnel to sterilize by causing oxidation of cell components

Question 21

Which products (aqueous or non aqueous) are sterilized using dry heat sterilization?

Answer 21

Non - aqueous

Question 22

What are colligative properties?

Answer 22

They are physical properties that depend primarily on the concentration of solute particles (molecules or ions) in the system

(when the solutions are dilute)

Question 23

What are iso-osmotic fluids?

Answer 23

Solutions which display colligative properties similar to those of biological fluids

Question 24

What are isotonic solutions?

Answer 24

Solutions which have similar colligative properties as biological fluids and have tissue compatibility (non-toxic to tissues)

Question 25

What is Osmole?

Answer 25

The amount of substance that needs to be dissolved to give 1 mole of particles

Question 26

What is the osmolarity of physiological fluids?

Answer 26

270-300 mOsmole/L

Question 27

What is the NaCl equivalent (E) of a solute?

Answer 27

The amount of NaCl that will produce the same osmolarity as 1g of the solute.