Pharmacodynamics

Question 1

Define receptors

Answer 1

molecules to which a drug binds to bring about a change in function of the biological system

Question 2

Define effectors

Answer 2

molecules that translate the drug-receptor interaction into a change in cellular activity

Question 3

Define efficacy

Answer 3

the minimum amount of the drug to produce maximum effect

Question 4

Define potency

Answer 4

the concentration of a drug to produce 50% of the drugs’ maximal effect

Question 5

Define therapeutic window

Answer 5

the dosage range between minimum effective concentration and minimum toxic concentration

Question 6

What are the two major properties of receptors?

Answer 6

1. Binding
2. Signal transduction (a functional response, can be biological or physiological)

Question 7

What are the different receptor types?

Answer 7

1. Ligand gated ion channels (e.g. Nicotinic receptor)
2. G protein coupled receptors (e.g. muscarinic)
3. Kinase linked receptors (e.g. VEGF)
4. Nuclear receptors (e.g. Steroids/hormones)

Question 8

What are the requirements of ophthalmic preparations for the anterior segment?

Answer 8

1. Stability (chemically, physically and microbiologically stable)
2. pH, buffer ( for Px comfort. 4.5 - 8 )
3. Tonicity (the eye can tolerate 0.6 - 2% NaCl)
4. Sterility (Need to be free from microorganisms)
5. Viscosity enhancers (so longer time with the eye to allow more time for drug absorption, also slows drainage rate)
6. Preservatives (For multi dose - Benzalkonium chloride, antimicrobial)

Question 9

What are the characteristics of Benzalkonium chloride?

Answer 9

Good:
1. highly effective
2. well tolerated
3. stable
4. rapid acting

Side effects:
1. Disrupts the oily layer of tears, so prevents evaporation
2. Binds soft contact lenses, causing corneal irritation

Question 10

Define Ophthalmic solutions

Answer 10

Type of dosage form. Contains active ingredients which are completely soluble so doesn’t cause blurry vision

Question 11

Define Ophthalmic suspensions

Answer 11

Type of dosage form. Contains particles of insoluble drug in an aqueous vehicle

Question 12

How to ensure dose uniformity for Ophthalmic suspensions?

Answer 12

Pxs should be told to shake the formulation each time as settling of the drug particles may occur

Question 13

Define Ophthalmic ointments

Answer 13

Type of dosage form. Drug is incorporated into mineral oil and white petrolatum base. Increases contact time for greater bioavailability. But does cause blurry vision so tell to apply at bedtime.

Question 14

Define Ophthalmic gels

Answer 14

Type of dosage form. Contains polymers like carbomer that form an aqueous semisolid form. Formulated as a solution but turns into a gel upon contact with eye. Increases contact time for greater bioavailability. But does cause blurry vision so tell to apply at bedtime.

Question 15

Define Ophthalmic emulsions

Answer 15

Type of dosage form. Drug dissolved in nonaqueous vehicle which is emulsified using a surfactant.

Question 16

Name all the dosage forms

Answer 16

1. Solutions
2. Suspensions
3. Ointments
4. Gels
5. Emulsions