Drug Formulation and design

Question 1

What is pharmacodynamics?

Answer 1

The study of the actions, effects and interactions of drugs in the body

Question 2

What is pharmaceutics?

Answer 2

The mode of administration of the drug

Question 3

What is pharmacokinetics?

Answer 3

How the drug is absorbed, distributed, metabolised and excreted

Question 4

What is bioavailability?

Answer 4

The rate and extent to which the drug is absorbed

Question 5

What is biotransformation?

Answer 5

The rate and extent to which the drug is metabolised or degraded

Question 6

What are the possible rates of administration?

Answer 6

Topical
Oral
Injection
Eye drops
Eye ointments
Ballistic
Iontophoresis

Question 7

Give some advantages to oral administration

Answer 7

Convenient
Relatively inexpensive and safe

Question 8

Give some disadvantages to oral administration

Answer 8

Absorption rate is variable
Drug may be inactivated by digestive acids and enzymes
Requires px to take when needed

Question 9

Give some advantages to intravenous administration

Answer 9

Rapid onset
No barriers to absorption

Question 10

Give some disadvantages to intravenous administration

Answer 10

Infection risk
Irreversible

Question 11

What should be considered when choosing the method of administration for a drug?

Answer 11

Where the action is needed - is it on the inside or outside of the body?
How long is the action needed for?
Drug stability - what’s its shelf life?

Question 12

What happens immediately after an eye drop is instilled?

Answer 12

Blink causes immediate loss of drug
Concentration goes from 50% 1 minute after to 0.1% after 8 minutes

Question 13

How are eye drops absorbed by the body?

Answer 13

Systemic - drains from the eye via conjunctiva and punctae into the nasolacrimal gland, goes to the stomach and is metabolised.
Ocular - absorbed via the cornea, into the aqueous humour which is drained via the trabecular meshwork

Question 14

What does trans-corneal diffusion require to work?

Answer 14

A concentration gradient

Question 15

Where does the drug need to be lipophilic (uncharged) in trans-corneal diffusion?

Answer 15

At the epithelium and endothelium

Question 16

Where does the drug need to be hydrophilic (charged) in trans-corneal diffusion?

Answer 16

At the stroma

Question 17

Why can’t fluorescein cross/enter the cornea unless it’s damaged?

Answer 17

Charge is too high at pH 7.4 (tear pH)

Question 18

What is pKa?

Answer 18

Dissociation constant
the pH at which a drug is 50% charged (concentrations of charged and uncharged forms equal)

Question 19

Can pKa be changed?

Answer 19

No
pH change can be changed to achieve desired result

Question 20

What factors can affect eyedrop bioavailability?

Answer 20

Drug formulation and design
Corneal integrity - increased absorption if damaged
Topical anaesthetic administration
Iris pigmentation
Px specific factors

Question 21

What can affect the stability, irritation and efficacy of the delivery of a drug?

Answer 21

pH
Tonicity
Oxidation
Sterility

Question 22

Outside what pH range will eyedrops sting?

Answer 22

6.6-7.8

Question 23

Outside what tonicity range will eyedrops sting?

Answer 23

0.5-2% NaCl
150-650 mOsm

Question 24

How can drug delivery to the eye be enhanced?

Answer 24

Ointments
Local anaesthetic
Benzalkonium chloride
Multiple drops
Slow delivery inserts (gels, CLs)

Question 25

What is drug toxicity?

Answer 25

Overdose

Question 26

What is drug hypersensitivity?

Answer 26

An exaggerated normal response to a drug

Question 27

What is drug allergy?

Answer 27

Body reacts to the drug as if it is an allergen
Atopic pxs particularly susceptible

Question 28

Who is more likely to have an adverse drug reaction?

Answer 28

Pregnant and breastfeeding women
Elderly people
Children
Pxs with underlying illness/disease