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SL Chem > Option D: Medicinal Chemistry > Flashcards

Option D: Medicinal Chemistry Flashcards

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1
Q

What do medicines and drugs do?

A

One of the following:
- Alter incoming sensory sensations
- Alter a person’s mood or emotions
- Alter the physiological state of the body including consciousness and coordination

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2
Q

Drug

A

A substance that causes a physiological change in the body

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3
Q

Pharmaceutical drugs

A

Used for the treatment or prevention of disease.

Medicines contain beneficial drugs.

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4
Q

Recreational drugs

A

Chemical substances taken for enjoyment or leisure purposes rather than for medical reasons

Example include alcohol, nicotine, cannabis and ecstasy

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5
Q

Therapeutic effect

A

The beneficial effect of a medicine

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6
Q

Methods of drug administration: Oral

A

Taken by mouth

e.g tables, capsules, pills

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7
Q

Methods of drug administration: Inhalation

A

Vapour breathed in or smoking

e.g asthma medication or drugs such as nicotine

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8
Q

Methods of drug administration: Skin patches

A

Absorbed through the skin into the blood

e.g hormone patches

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9
Q

Methods of drug administration: Suppositories

A

Inserted into the rectum

e.g laxatives for constipation

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10
Q

Methods of drug administration: Eye or ear drops

A

Liquids administered into eyes or ears

e.g treatment of eye or ear infections

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11
Q

Methods of drug administration: Injection (parenteral)

A

Injected into the muscle, blood, or under the skin

e.g vaccines and local anaesthetics

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12
Q

Parenteral methods of drug administration: intramuscular

A

Drug is injected directly into the muscle

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13
Q

Parenteral methods of drug administration: subcutaneous

A

Drug is injected directly under the skin into the subcutaneous tissue

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14
Q

Parenteral methods of drug administration: intravenous

A

Drug is injected directly into the blood stream.

This method has the most rapid effect as the drug is injected directly into the blood

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15
Q

Bioavailability

A

The fraction of the administered dosage of a drug that enters the bloodstream thereby accessing the site of action

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16
Q

Factors that effect the bioavailability

A
  • The method of drug administration
  • The polarity (solubility) of the drug
  • The type of functional groups present in the drug
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17
Q

Bioavailability of drugs that are administered intravenously

A

Drugs that are administered intravenously have a bioavailability of 100% as they are delivered directly into the bloodstream

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18
Q

Bioavailability of drugs that are administered orally

A

Drugs that are administered orally are often broken down during digestion before reaching the bloodstream.

In general, an oral dose of a drug needs to be about four times higher than the dosage of the same drug that is administered intravenously.

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19
Q

How does the polarity of a drug affect its solubility

A

Very hydrophilic (polar_ drugs are soluble in aqueous body fluid but are poorly absorbed because of their inability to cross cell membranes (composed of lipids)

Very hydrophobic (non polar) drugs are also poorly absorbed because they are insoluble in aqueous fluids

For a drug to be readily absorbed it must be largely hydrophobic (non-polar) but also have some solubility in aqueous solutions.

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20
Q

How do functional groups affect solubility of a drug

A

A functional group’s ability to ionise and a functional group’s ability to form hydrogen bonds contribute to the water solubility of a functional group.

Carboxyl groups, hydroxyl groups and amine groups all have the ability to form hydrogen bonds with water molecules.

In addition, carboxyl groups are acid and amine groups are basic. Both of these groups can form ions therefore increasing the solubility of a drug.

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21
Q

Functional groups that enhance the lipid solubility of a drug

A

These functional groups are non-polar. They lack the ability to ionise or to form hydrogen bonds.

examples are phenyl groups and alkyl groups.

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22
Q

Bioavailability of aspirin

A

Aspirin is a largely non-polar molecule and therefore has low solubility in water

It has a carboxyl group, a phenyl group, and an ester group.

The solubility of aspirin can be increased by reacting it with aqueous NaOH to form an ionic salt (increasing bioavailability)

Bioavailability can be increased by administering aspirin intravenously.

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23
Q

Therapeutic window

A

The therapeutic window is a measure of the safety of a drug

The wider the therapeutic window, the safer the drug.

A wide therapeutic window means that there is a wide margin between doses that are effective and doses that are toxic.

A narrow therapeutic window means that only a small increase in the effective dose may produce toxic effects.

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24
Q

Therapeutic index

A

The ratio between the dosage of a drug that causes a toxic effect and the dosage that causes a therapeutic effect

Therapeutic index in humans is calculated by dividing the median toxic dose by the median effective dose

Therapeutic index in animals is calculated by dividing the median lethal dose by the median effective dose

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25
Q

Drug development

A

Main stages of drug development:
- Drug is synthesised in lab
- The drug is tested on animals to determine the LD 50
- The drug is tested on humans - half of the group are given the real drug, the other half are given a placebo. This placebo contains none of the drug being tested.
- This is done double-blind

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26
Q

Placebo effect

A

When the body is fooled into healing itself naturally

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27
Q

Factors that must be determined during clinical drug trials

A
  • Risk : benefit ratio - balance between the risks and benefits of the drug
  • Unwanted side effects
  • Drug tolerance - person needs to take ever larger qu’altistes of a drug to gain the original effect
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28
Q

Synthesis of aspirin

A

Aspirin is produced by reacting salicylic acid with ethanoic anhydride

Salicylic acid is converted to aspirin through esterification, which is a condensation reaction.

The catalyst in the reaction can be either concentrated sulphuric acid or phosphoric acid

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29
Q

Uses of aspirin

A

Aspirin is a mild analgesic.

Mild analgesics block the sensation of pain at the source. Aspirin works by blocking the action of the enzymes that produce prostaglandins.

Prostaglandins are involved in the transmission of pain impulses to the brain, as well of causing fever and swelling.

Aspirin prevents the prostaglandins from being synthesised, thereby reducing or eliminating the pain.

Aspirin is also used as an anticoagulant.

Anticoagulants are a class of drugs that work to prevent the blood from clotting.

They are effective in the prevention of the recurrence of heart attacks and strokes.

Due to its anti-inflammatory properties, aspirin is also taken for arthritis and rheumatism.

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30
Q

Side effects of aspirin

A

The most common side effect of aspirin is that it can cause bleeding of the lining of the stomach.

This effect is increased by drinking alcohol as the same time as taking aspirin, which is known as a synergistic effect.

Two drugs can have a synergistic effect if they increase each other’s effectiveness when taken together.

The synergistic effects of alcohol and aspirin can cause increased bleeding of the stomach lining.

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31
Q

Discover of penicillin

A

Penicillins are a group of antibiotics used to treat a range of bacterial infections.

They are derived from Penicillium fungi and can be taken orally or via injection.

Penicillin was discovered in 1928 by Sir Alexander Fleming, a Scottish microbiologist, whilst working with bacteria cultures.

He noticed that a fungus had contaminated some of his cultures and left a clear region where no bacteria colonies were growing.

Fleming came to the conclusion that something in the fungus was inhibiting the growth of the bacteria.

Despite Flemings’ discovery, it wasn’t until the 1940s that the true potential of penicillin was realised when it was used to save thousands of lives in WW2.

32
Q

Penicillin mode of action.

A

Penicillins (beta-lactam antibiotics) are characterised by the presence of a beta-lactam ring.

The beta-lactam ring is the part of the molecule responsible for penicillin’s anti-bacterial properties.

Beta-lactam antibiotics interfere with cell wall formation in bacteria by inhibiting the enzymes responsible for creating cross-links in the cell wall.

When the beta-lactam ring comes into contact with the bacteria, the ring opens and binds irreversibly to the enzyme responsible for catalysing cross-linking in the cell wall of the bacteria.

Water enters the cell, increasing the osmotic pressure inside the cell, causing it to burst

33
Q

Why are beta-lactam rings fragile?

A

In a beta-lactam ring:
- Two C atoms and the N atom are sp3 hybridised (bond angle of 109.5)
- One C atom in the ring is sp2 hybridised (bond angle of 120)

Then one angles in the ring are reduced to about 90 degrees, which puts a strain on the bonds. Due to the strain, it breaks relatively easily

34
Q

Antibiotic resistance

A

The ability of bacteria to resist the effects of an antibiotic

Bacterial resistance is caused by the misuse or overuse of antibiotics

Examples of misuse include the over-prescription of penicillin for minor illnesses and the failure of patients to complete the course of antibiotics as prescribed by the doctor

35
Q

How are side-chains used to reduce anti-bacterial resistance

A

Modified penicillins are able to withstand the action of the penicillinase enzyme.

For treating certain diseases like TB, a ‘cocktail’ of different types of antibiotics are required.

The bacteria that cause TB are extremely resistant to penicillin therefore a mixture of different antibiotics must be used.

36
Q

How are side-chains used to reduce the effects of stomach acid

A

The side chan can also be modified to give increased resistance to breakdown by stomach acid, which means that the antibiotic can be taken orally.

Penicillin G had to be injected as it was broken down by stomach acid.

Ampicillin is a modified penicillin and can be taken orally.

37
Q

Strong analgesics

A

Morphine and codeine are example of opiates and are used as strong analgesics.

Opiates are natural analgesics that are derived from opium- found in poppy seeds

Strong analgesics are given to relieve severe pain caused by injury, heart attacks, or diseases such as cancer

38
Q

How do opiate analgesics work?

A

They work by temporarily bonding to receptor sites in the brain, preventing the transmission of pain impulses without depressing the central nervous system.

39
Q

Opiate analgesics and side effects

A

Opiate analgesics can cause side effects and can lead to dependency and addiction.

For these reasons, they are only available on prescription and their usage is monitored through medical supervision.

40
Q

Advantages of strong analgesics

A
  • Strong analgesics provide relief for acute or extreme pain
  • They have a wide therapeutic window
  • They can relieve anxiety, induce relaxation, or improve the quality of life
  • Because they are administered intravenously there is a faster distribution of the drug
41
Q

Disadvantages of strong analgesics

A
  • Users feel euphoria, a lack of self-control, and can indulge in dangerous behaviour
  • Regular usage can lead to addiction, dependence, and withdrawal symptoms
  • Users build up a tolerance to the drug with increased risk of overdose upon prolonged use
  • Increased risks associated with intravenous drug administration
42
Q

Blood-brain barrier

A

A layer of tightly packed cells that protect the brain by restricting the passage of substances from the bloodstream into the brain

It is largely composed of lipids which are non-polar, hydrophobic molecules

The blood-brain barrier is not easily crossed by polar, hydrophilic molecules

For a drug to penetrate the blood-brain barrier and enter the brain, it must be non-polar and lipid soluble

43
Q

What do the analgesic properties of opiates depend on?

A

Their ability to move from the blood, where aqueous solubility is important, to the brain, where lipid solubility is important to cross the blood- brain barrier.

44
Q

Opioid receptors

A

Once in the brain, opiates attach to opioid receptors. When opiates attach to the opioid receptors, they reduce the perception of pain.

45
Q

Differences in structures of codeine, morphine, and diamorphine

A

Codeine has one hydroxyl group and morphine has two hydroxyl groups

Codeine has two ether groups whilst morphine and diamorphine only have one

Diamorphine has two ester groups whilst morphine and codeine have none

46
Q

What are the implications of morphine having two hydroxyl groups

A

The presence of the two hydroxyl groups make it a polar molecule.

Polar molecules are more soluble in water, but less soluble in lipids which limits their ability to cross the blood-brain barrier

47
Q

Synthesis of diamorphine

A

Diamorphine is produced from morphine in an esterification reaction in which both OH groups are converted into ester groups

In the reaction, morphine reacts with ethanoic acid or ethanoic anhydride to produce diamorphine

The two hydroxyl groups are turned into ester groups.

This makes the diamorphine less polar- making it more lipid soluble. This means that it is able to cross the blood-brain barrier more rapidly- as a result it is much more potent than morphine, but its effects do not last as long

48
Q

Synthesis of codeine

A

Codeine is produced from morphine in a methylation reaction.

In the reaction, an OH is converted into a methoxy group.

This reaction makes codeine a less polar molecule than morphine and therefore more able to cross the blood-brain barrier

However this reaction also reduces the ability of codeine to bond at the opioid receptors, which makes codeine a weaker analgesic than morphine

49
Q

Antacids

A

Used to reduce excess stomach acid.

The stomach contains HCl that kills bacteria in food and provides the optimum pH for digestive enzymes.

Excess stomach acid can cause health effects such as acid indigestion, heartburn, and stomach ulcers.

Antacids work by neutralising the excess acid in the stomach

They are weak bases such as calcium hydroxide, magnesium hydroxide, aluminium hydroxide, sodium carbonate, and sodium bicarbonate

Strong bases should not be used as they are harmful to the body.

50
Q

Alginates

A

A group of medicines called alginates are found in some brands of antacid medication

They produce a neutralising layer which prevents acid in the stomach from rising into the oesophagus.

51
Q

Stomach acid inhibitors

A

Stomach acid inhibitors inhibit the production of stomach acid.

Proton pump inhibitors (PPIs) and H2 receptor antagonists (H2 blockers) are both stomach acid inhibitors.

PPIs inhibit the proton pumps in the stomach.

H2 blockers work by blocking the histamine receptors in acid-producing cells in the stomach.

52
Q

Proton pump

A

The gastric proton pump pumps protons into the stomach.

PPIs inhibit the proton pump which prevents the release of protons into the stomach

PPIs have a longer lasting effect (up to 3 days)

They are used to treat stomach ulcers and also provide relief from the symptoms of acid-reflux

53
Q

H2 blockers

A

Reduce the amount of acid produced by the cells in the lining of the stomach.

Histamine stimulates the secretion of stomach acid by interacting at H2 receptors in the stomach lining.

H2 blockers compete with histamine for binding at the H2 receptors.

They block the interaction between histamine and the H2 receptors, preventing the release of stomach acid.

54
Q

Comparing stomach acid inhibitors

A

Both PPIs and antacids relieve the symptoms of acid reflux, heartburn and indigestion.

PPIs inhibit the production of stomach acid and antacids neutralise the excess acid in stomach

PPIs have longer-lasting effects than antacids

55
Q

Calculating concentration of buffer solution

A

Use the Henderson-Hasselbalch equation (found in section 1 of the data booklet)

56
Q

Viruses

A

Viruses are sub-microscopic organisms that replicate inside the living cells of other organisms.

They have two main components- a protein coat, and nucleic acid (either DNA or RNA).

Viruses do not carry out metabolic processes and are considered to be non-living.

They derive their energy from the host cell.

57
Q

Bacteria

A

Bacteria are single-called microorganisms

Unlike viruses, bacteria are self-reproducing units (they do not require a host to reproduce)

Bacteria contain various cell subunits together with a cell wall

Bacteria carry out metabolic processes and are considered to be living

58
Q

Comparing viruses and bacteria

A

Bacteria are self-reproducing units while viruses need living hosts to multiply.

Bacteria carry out metabolic processes while viruses do not.

Bacteria contain organelles that perform specific functions while viruses consist only of generic material and a protein coat.

Bacteria are many times larger than viruses.

59
Q

Antiviral drugs

A

Viruses lack a cell structure and so are more difficult to target with drugs than bacteria.

Antibiotics are effective against bacteria and work by disrupting the formation of the bacteria cell wall.

They are ineffective against viruses because they lack a cell wall.

Viral infections are treated buy medicines known as antivirals.

60
Q

Reasons that viruses are more difficult to treat than bacteria

A
  • Viruses mutate quickly so adapt to drugs
  • Bacteria are more complex and can be targeted in more ways, whereas viruses lack subunits that can be targeted by antibacterials
  • Bacteria can be killed by simple chemical agents but viruses must be targeted on a genetic level
61
Q

How do antiviral drugs work

A
  • Alter the cells genetic material so that the virus cannot use it to multiple
  • Prevent viruses from multiplying by blocking enzyme activity within the host cell
  • Bind to cellular receptors targeted by viruses
  • Prevent or hinder the release of viruses from the cell
62
Q

Oseltamivir and Zanamivir

A

Oseltamivir and Zanamivir are both used as antivirals to prevent the spread of the flu virus.

Zanamivir is taken by inhalation due to its low bioavailability when taken orally.

Oseltamivir can be taken orally as its bioavailability is not affected by this method of administration.

63
Q

Comparing structures of Oseltamivir and Zanamivir

A

Oseltamivir has an alkenyl group, a carboxamide group, amine group, ester group, and ether group

Zanamivir has an alkenyl group, a carboxamide group, amine group, ether group, carboxyl group, 3 hydroxyl groups

The presence of the hydroxyl groups in Zanamivir makes it more soluble in polar solvents than Oseltamivir.

64
Q

How do oseltamivir and zanamivir work?

A

By inhibiting the enzyme neuraminidase by binding to its active site.

Neuraminidase is an enzyme found on the surface of the influence virus that enables the virus to be released from the host cell.

By inhibiting this enzyme, the virus is prevented from leaving the host cell and cannot infect other cells.

65
Q

The difficulties associated with treating HIV

A
  • HIV destroys T-cells (the cells that protect the body from infection)
  • HIV can mutate rapidly
  • HIV uses host cells to replicate
  • Drugs used to treat HIV may also harm the host cell
  • High price of antiretroviral drugs
66
Q

Sociocultural factors related to the AIDS problem

A
  • Condom use (the availability, cost, or cultural resistance)
  • Cultural factors (ignorance, misinformation, social stigma)
  • Illegal activities (drug use, prostitution)
  • Resources / medical factors (availability of medical services, cost of drugs)
67
Q

Radioactive waste

A

Can be classified as low-level, intermediate-level or high-level waste.

High-level waste gives off large amounts of ionising radiation for a long time (long half-life).

Low-level waste gives off small amounts of ionising radiation for a short time (short half-life).

68
Q

Low-level waste: examples and disposal methods

A

Examples:
- Gowns / protective clothing
- Shoe covers
- Tissues / needles
- Mops

Disposal method:
- Stored in shielded containers until the isotopes have decayed and then disposed of as non-radioactive waste

69
Q

Intermediate-level waste: examples and disposal methods

A

Example:
- Radioactive sources (cobalt-60 and caesium-137)

Disposal method:
- Stored in shielded containers in underground repositories

70
Q

Antibiotic waste

A

Antibiotics are released into the environment in three ways:

  • The use of antibiotics in animal feeds (carry antibiotics into the soil and ground water)
  • Improper disposal of antibiotic medicines by hospitals and households
  • Antibiotics excreted in human urine (enter the sewage system at low concentrations. Then they can end up in the drinking water supply)
71
Q

Solvent waste

A

The majority of medicines and drugs are produced by chemical synthesis.

The production of these medicines and drugs requires multiple steps such as reaction, separation, and purification to form the end product.

Solvents are used as reaction media and in product recovery and purification

These solvents must be disposed of carefully to avoid causing harm to the environment

72
Q

Green Chemistry solvent guide:

A

Preferred solvents: (white people eat my eggs)
- Water
- Propan-1-ol
- Ethyl ethanoate
- Methanol
- Ethanol

Useable: (certain objects end every morning)
- Cyclohexane
- Octane
- Ethanenitrile
- Ethanoic acid
- Methyl benzene

Undesirable: (people dont do their chores)
- Pentane
- Dichloromethane
- Dichloroethane
- Trichloromethane
- Carbon tetrachloride

73
Q

VOCs

A

Many undesirable solvents are VOCs

VOCs are used as solvents due to their high volatility (easy to remove by evaporation)

They have the potential to cause nose and throat discomfort, nausea and fatigue.

They can also result in the formation of low level ozone and smug

74
Q

Principles of green chemistry

A
  • Prevent waste
  • Maximise atom economy
  • Design less hazardous chemical syntheses
  • Design safer chemicals and products
  • Use safer solvents and reaction conditions
  • Increase energy efficiency
  • Use renewable feedstocks
  • Avoid chemical derivatives
  • Use catalysts, not stoichiometric reagents
  • Design chemicals and products to degrade after use
  • Analyse in real time to prevent pollution
  • Minimise the potential for accidents
75
Q

Green chemistry: problems associated with the production of oseltamivir

A

Oseltamivir is used as an antiviral to prevent the spread of the flue.

The synthesis requires shikimic acid- extracted from star anise pods

Star anise has a limited worldwide supply- in 2005 a shortage was caused by its use in the productive of the drug.

Another shortage in 2009 caused by the swine-flu outbreak caused the price of star anise to increase dramatically

The synthesis requires a complex ten-step process. The time required for its production is between 6-8 months. 30kg of star anise produces only 1 kg of shikimic acid.

76
Q

Green chemistry: advancements to the production of oseltamivir

A
  • The production of shikimic acid from the fermentation of genetically engineered bacteria
  • The extraction of shikimic acid from pine needles

SL Chem (11 decks)

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