D1 Pharmaceutical products and drug action

Question 1

Pulmonary administration of drugs.

Answer 1

• Given to the lungs in the form of gases or volatile liquids (general anesthetics) or aerosol/dry powdered inhalers (asthma)
• The lungs have a very large surface area therefore the absorption og the drugs into the blood is very rapid (fast onset of action)
• Useful to treatment of lung disease

Question 2

Rectal administration of drugs.

Answer 2

• Incorporated into suppositories that are useful if the patient is not able to take oral medication (unconscious or vomiting)
• Can have a local effect (hemorroids) or can enter the bloodstream and have an effect on other parts of the body

Question 3

Oral administration of drugs.

Answer 3

• Given by mouth in form of tablets, capsules, syrups and suspensions
• Passed into the stomach and intestines and are then absorbed into the bloodstream through which they can access their site of action
• Convinient and easy to self-administer
• Drug action is relatively slow

Question 4

Explain the administration of drugs by injection.

Answer 4

There are three types.

Intravenous injections
* most common
* used when a rapid, therapeutic response is needed because the drug is directly injected into the bloodstream
* MORPHINE

Intramuscular injections
* directed into the skeletal tissue (usually ark, tight or buttocks)
* Aqueous solutions are easily absorbed by the blood.
* If the drug is dissolved and suspended in oil, it will be slowly releaed from the muscle into the blood to give a sustained release of the drug over a long period.
* VACCINES

Subcutaneous injections
* administered directly under the skin
* Absorption of the drug by the blood is slow, giving a sustained effect
* INSULIN

Question 5

What does the way of administrating a drug depend on?

Answer 5

• Chemical and physical properties of the drug
• Speed at which the drug needs to act
• The condition of the patient (unconscious or conscious))

Question 6

Name the diferent ways of administating a drug.

Answer 6

• Oral
• Rectal
• Pulmonary
• Topical
• By injection (Intravenous, intramuscular and subcutaneous)

Question 7

Why are there two different values for the Therapeutic Index (TI)?

Answer 7

In animal studies, lethal doses are determined. However, in human trials, the upper limit is the toxic dose. This means that the therapeutic index is defined differently in the two groups.

Question 8

What’s the therapeutic Index (TI) and how does it work?

Answer 8

The therapeutic window can be classified as the therapeutic index (TI) which is the ratio of the dose of a drug that produces toxicity or lethality to the dose that produces a clinically effective response in a population.Therefore, TI is a measure of a drug’s safety.
* High (or wide) TI: there is a large difference between the dose that causes therapeutic and toxic effect so there is a big margin. This is desirable.
* Low TI: low margin of safety. A small dosage change can have adverse side effect.

TI= TDv50/ EDv50 or TI= LDv50/ EDv50
* Effective dose (EDv50) = dose producing therapeutic effects in 50% of the population
* Toxic dose (TDv50) = dose that is toxic for 50% of the population
* Lethal dose (LDv50) = dose that is lethal for 50% of the population

TI= TD/ED = 100/1 = 100. It would require a 100-fold increase in the therapeutic dose to cause a toxic effect in 50% of the population.

Question 9

What is the dosage regime?

Answer 9

The specific quantity that can be taken of a drug and the frequency of administration.

Question 10

What does the dosage regime depend on?

Answer 10

Dosages can vary due to age, gender and weight.

Question 11

Explain the therapeutic window.

Answer 11

The therapeutic window is the area/range in which the concentration of a drug must stay in the bloodstream. If the concentration is above this range then there is a risk of facing undesirable side effects. If the concentration is below this range, then there may be no therapeutic effects.

Question 12

What two types of dependance can a patient develop because of drugs?

Answer 12

• Psychological dependace. Need/carving to have the drug to feel good.
• Physical dependance. The body cannot function without the drug.

Question 13

When can we say that a tolerance has developed and what are the risks of it?

Answer 13

Tolerance occurs when the body becomes less responsive to the effects of the drug so larger doses are needed. This can lead to the patient being at a higher risk of toxic side effect.

Question 14

What happens when a drug is given repeatedly to a patient?

Answer 14

They build a tolerance, meaning that the intensity of the therapeutic response to a given dose may change over time

Question 15

What are the two effects that a drug can have?

Answer 15

1. Therapeutic effect. Desirable and beneficial. Alleviates symptoms and treats a particular disease.
2. Side effect. Unintended secondary effect which are usually undesirable.

Morphine is a strong analgesic used to treat pain but in some cases it can cause constipation, nausea and vomit.

Question 16

What defines a good drug synthesis?

Answer 16

A good synthesis will:
* have as few steps as possible
* produce a very good yield (the ratio of the number of good products produced to the total number of units started in any manufacturing operation) at each stage.
* have cheap and easily available starting materials

Question 17

What is drug synthesis?

Answer 17

Drug synthesis is the creation of a compound/drug at a molecular level. When you synthesise something, you are making something from combining different things.

Question 18

Explain the process of clinical trials in humans.

Answer 18

1. Small number of healthy volunteers. Used to find the dose range of the drug that gives a therapeutical effect and also to identify side effects.
2. Small number of patients who have the disease or contraction on which the drug acts on. Establishes whether the drug is effective in these patients and also identifies any side effects.
3. Asseses if the drug is truly effective or whether any beneficial effects are due to placebo effect. The drug is tested on a larger group of volunteering patients. Some of them are given a fake drug and the rest the real one.

Question 19

How do animal testings work?

Answer 19

Drugs are tested inhealthy andinfectedanimals. The effectiveness can be determined by looking for specific responses in animals like lowering of blood pressure or the suppression of the production of a particular enzyme.

Question 20

Explain the drug development process

Answer 20

1. Identification oflead compounds that have a desirablr biological activity which is therapeutically relevant
2. Chemically modify these compounds to get rid of the undesirable side effects.Lead optimisation.
3. Test for toxicity inanimals.
4. Find out the effectiveness of the drug in humans and see if it is safe to ue. For this stage there are three phases of clinical trials
5. If the drug passes the clinical trials, it getsmarketing authorisation by a pharmaceutical company and can enter the market.

Question 21

What are drugs?

Answer 21

Drugs are chemical substances that alter incoming sensory sensations, a pearson’s mood and emotions and the physiological state of the body.

Question 22

Name and explain the different types of drugs

Answer 22

• Pharmaceutical drugs: used for treatment or prevention of diseases
• Recreational drugs: chemical substances taken for enjoyment or leisure purposes

Question 23

Topical administration of drugs.

Answer 23

• Applying a drug to the skin in the form of creams, oinments or lotions
• Used primarly for local effects (acne, dermatitis, skin infections)
• Transdermal patches (containing nicotine) allows penetration of the drug through the skin for access to the blood circulation

Question 24

What’s the bioavailability of a drug?

Answer 24

Bioavailability is the fraction of the administered dose that reaches the bloodstream thereby accessing the site of action.

Question 25

What are the factors that affect the bioavailability of a drug?

Answer 25

Administration
* Drugs that are administered orally are often broken down during digestion before reaching the bloodstream
* Intravenous administration places the drug directly into the bloodstream (100% bioavailability)

Polarity (which affects it’s solubility)
* Very hydrophilic (polar) drugs are soluble in aqueous body fluid but are poorly absorbed because of their inability to cross cell membranes (which are composed of lipids)
* Very hydrophobic (non-polar) drugs are also poorly absorbed because they are insoluble in aqueous body fluids
* For a drug to be readily absorbes, it must be largely hydrophobic, but also have some solubility in aqueous solutions

Functional groups
* The two major properties that contrbute to the water solubility of a functional group are its ability to ionize and to form hydrogen bonds
* Functional groups that enhance the lipid solubility og a drug are non-polar.They lack the ability to ionize or to form hydrogen bonds

Question 26

What are drug receptors and in what ways do they act?

Answer 26

Drug action depends on their interaction with special receptors in the body. Receptors are often proteins
* Receptor agonist: drug binfs to a cell-membrane protein receptos and it mimicks the effect of the normal molecule
* Receptor antagonist: drug binds to a cell-membrane receotir si that the normal messenfer olecule can’t. It prevents a particular responde from the cell

Question 27

What must be taken into consideration before administering a drug?

Answer 27

• Dosage
• Tolerance
• Addiction
• Side effects

Question 28

What are the drug-receptor interactions based on?

Revisar

Answer 28

The structure of the drug and the site of activity

Question 29

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

Answer 29

1. identifying the need and structure
2. synthesis
3. yield
4. extraction

YIELD: the ratio of the number of good products produced to the total number of units started in any manufacturing operation

EXTRACTION: once the drug has been synthesised, it must be extracted from the reaction mixture and purified by recrystallisation or solvent extraction

Question 30

Why should animal and human tests of drugs should be kept to a minimum?

Answer 30

For ethical and economic reasons, animal and human tests of drugs should be kept to a minimum.

Question 31

Discuss the term therapeutic window.

Your answer should include its meaning, a quantitative description and an explanation of wide and narrow therapeutic windows.

Answer 31

• measure of the relative margin of safety of a drug (for a particular treatment for a typical population
• ratio of the lethal dose to the therapeutic or effective dose
• narrow: no much difference between effective dose and lethal/toxic dose
• wide: big margin between effective and lethal/toxic dose