D.1 - Pharmaceutical products and drug action

Question 1

What is the therapeutic index for animal studies?

Answer 1

It is the lethal dose of a drug for 50% of the population (LD50) divided by the minimum effective dose for 50% of the population (ED50).

Question 2

What is the therapeutic index for humans?

Answer 2

It is the toxic dose of a drug for 50% of the population of the population (TD50) divided by the minimum effective dose for 50% of the population (ED50).

Question 3

What is the therapeutic window?

Answer 3

It is the range of dosages between minimum amounts of the drug that produce the desired effect and a medically unacceptable adverse effect.

Question 4

What are the considerations of drug administration?

Answer 4

Dosage, tolerance, addiction and side effect.

Question 5

What is bioavailability?

Answer 5

It is the fraction of the administered dosage that reaches the target part of the human body.

Question 6

What are the main steps in the development of synthetic drugs?

Answer 6

Identifying the need and structure, synthesis, yield and extraction.

Question 7

What are drug-receptor interactions?

Answer 7

They are based on the structure of the drug and the site of activity.

Question 8

What are the advantages and disadvantages of pharmaceuticals products?

Answer 8

There have been advances in the development of pharmaceuticals, but there are many limitations to their impact and reach.

Question 9

How are new medicines usually developed?

Answer 9

They are usually developed in collaboration with biologists and physicists.

Question 10

What is the difference between a wide and narrow therapeutic window?

Answer 10

Wide therapeutic window means a greater margin between effective and toxic dose (a safer drug) while narrow therapeutic window means there is a higher risk of an overdose (only a small increase in the effective dose causes toxic or lethal effects).

Question 11

What are the different methods of administrating drugs and how are they administered (chemically)?

Answer 11

Orally - drugs with polar groups and are warmer soluble
Rectally, intramuscular injection, intravenous injection - drugs that are unstable in gastric juices.
Intravenous injection - fast therapeutic effect as drug administered by blood.
Inhalation - volatile (easily evaporated at normal temperatures) drug.
Transdermally (skin) - non-polar compounds.

Question 12

What are the factors that affect bioavailability?

Answer 12

Method of administration, polarity (solubility) of drug, and the type of functional groups present in the drug.

Question 13

What affects the solubility of a drug?

Answer 13

The polarity.

Question 14

What happens in very hydrophilic (polar drugs) in aqueous body fluid?

Answer 14

They are soluble but are poorly absorbed because of their inability to cross cell membranes (which are composed of lipids).

Question 15

What happens in hydrophobic (non-polar) drugs in aqueous body fluid?

Answer 15

They are poorly absorbed because they are insoluble in aqueous body fluids.

Question 16

What must a drug be to be readily absorbed?

Answer 16

It must be largely hydrophobic but also have some solubility in aqueous solutions.

Question 17

What are the two major properties that contribute to the water solubility of a functional group?

Answer 17

It’s ability to ionise and to form hydrogen bonds.
E.g. carbonyl group (acidic functional group (donate a proton to form a negative ion)), hydroxyl group, amine group (basic functional group (can accept a proton to form as positive ion)).

Question 18

What and how do functional groups enhance the lipid solubility of a drug?

Answer 18

It is non-polar meaning that they lack the ability to ionise or to form hydrogen bonds.
E.g. phenyl group, hydrocarbon chain (alkyl group).

Question 19

Is aspirin a polar or non-polar molecule?

Answer 19

Non-polar.

Question 20

How can the solubility of aspirin be increased?

Answer 20

By reacting it with aqueous NaOH forming an ionic salt (and water).

Question 21

What are the main stages of drug development?

Answer 21

Drug is synthesised in the laboratory. The drug is tested on animals to determine the LD50. The drug is tested on humans - half of the group are given the real drug, other half are given a placebo. The risk has to be weighed out with a benefit ratio by balancing between the risks and benefits of the drug. The unwanted side effects must be considered. The drug tolerance where the person need to take larger quantities of a drug to gain the original effect.

Question 22

What should be considered with animal and human tests of drugs?

Answer 22

The ethical and economic reasons. This means that these tests should be kept to a minimum.