Medicines and Pharmaceuticals

Pharmaceuticals are substances used to prevent, diagnose, treat, or manage disease and other health conditions. Many pharmaceuticals are organic compounds, meaning their molecular structures are based largely on carbon.

Organic chemistry is especially important in medicine because carbon can form an enormous variety of molecular structures. By changing a molecule's:

• functional groups
• size
• shape
• polarity
• charge
• arrangement of atoms

chemists can change how that molecule interacts with the human body.

Common medicines containing organic compounds include:

• paracetamol (acetaminophen)
• aspirin
• ibuprofen
• penicillin and related antibiotics
• antihistamines
• local anaesthetics
• many antiviral medicines

The central idea is:

molecular structure → molecular interactions → biological effect

What Is a Pharmaceutical?

A pharmaceutical is a substance developed or used for a medical purpose.

A pharmaceutical product may be designed to:

• relieve pain
• reduce inflammation
• lower fever
• fight infection
• reduce allergy symptoms
• alter blood pressure
• control blood glucose
• prevent blood clots
• affect the nervous system
• replace substances the body cannot produce adequately

The molecule responsible for the intended biological effect is called the:

active pharmaceutical ingredient (API)

A tablet or capsule usually contains other substances in addition to the API.

These additional substances are called:

excipients

They may help give the medicine its shape, stability, taste, release properties, or ease of manufacture.

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Medicines Are Chemicals

The word chemical does not mean harmful or artificial.

Everything around us is made from chemicals, including:

• water
• oxygen
• glucose
• DNA
• proteins
• vitamins
• medicines

Some medicines are obtained from natural sources.

Others are manufactured synthetically.

Some begin with molecules discovered in nature and are then chemically modified.

What matters medically is not whether something is "natural" or "synthetic," but properties such as:

• effectiveness
• dose
• purity
• safety
• interactions
• biological activity

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Why Organic Chemistry Is Important

Most drugs must interact with biological molecules.

These biological molecules include:

• proteins
• enzymes
• receptors
• ion channels
• DNA
• RNA
• cell membranes

Many of these targets are themselves organic molecules.

Organic chemistry allows scientists to understand how a drug's structure influences these interactions.

Molecular Shape Matters

Drug molecules have specific three-dimensional shapes.

Biological molecules also have specific shapes.

For a drug to work, it often needs to interact with a particular biological target.

Imagine a receptor containing a binding site.

A drug molecule may fit into this site because its:

• shape
• charge
• functional groups
• polarity

complement the chemical environment of the binding site.

This is sometimes compared to a:

lock and key

However, real molecular interactions are more complicated because molecules can change shape slightly and interact through several different forces.

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Drug–Target Interactions

A drug molecule may interact with its target through:

• hydrogen bonding
• ionic attractions
• dipole interactions
• dispersion forces
• hydrophobic interactions
• sometimes covalent bonding

The positions of functional groups on the drug molecule determine which interactions are possible.

Therefore, moving or replacing even one functional group can significantly change how well a drug works.

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Functional Groups in Medicines

Many functional groups studied in organic chemistry occur in pharmaceuticals.

Examples include:

hydroxyl groups: –OH

carboxyl groups: –COOH

amino groups

esters: –COO–

amides: –CONH–

aromatic rings

halogen-containing groups

These groups can influence:

• water solubility
• acidity
• basicity
• binding to proteins
• membrane crossing
• stability
• metabolism

This is why learning functional groups is directly relevant to pharmaceutical chemistry.

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Paracetamol

Paracetamol, also called acetaminophen, is widely used to relieve pain and reduce fever.

Its molecular formula is:

C₈H₉NO₂

Its structure contains several important features, including:

• an aromatic ring
• a hydroxyl group
• an amide group

These groups affect its:

• polarity
• intermolecular interactions
• metabolism
• biological activity

Paracetamol provides a good example of how several functional groups can occur within a single pharmaceutical molecule.

Benefits and Risks of Paracetamol

When used appropriately, paracetamol can be useful for:

• relieving mild to moderate pain
• reducing fever

However, excessive doses can cause severe poisoning, particularly damage to the liver.

This illustrates a fundamental principle of pharmacology:

A useful medicine can become harmful when used incorrectly.

Safety depends on factors such as:

• dose
• frequency
• duration
• interactions
• individual health circumstances

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Aspirin

Aspirin, chemically known as acetylsalicylic acid, is another important organic pharmaceutical.

Its molecular formula is:

C₉H₈O₄

Its structure contains:

• an aromatic ring
• a carboxyl group
• an ester group

Aspirin can be used for purposes including pain relief and reduction of inflammation. In specific medical contexts and doses, it is also used for its effects on platelet function.

Its biological effects are related to interactions with enzymes involved in producing signalling molecules called prostaglandins and related compounds.

Ibuprofen

Ibuprofen is another organic medicine used to reduce:

• pain
• inflammation
• fever

Its molecular formula is:

C₁₃H₁₈O₂

Ibuprofen contains:

• a carboxyl group
• an aromatic ring
• a hydrocarbon-rich region

Different parts of the molecule contribute to different interactions with biological molecules.

Ibuprofen belongs to a group of medicines known as:

non-steroidal anti-inflammatory drugs (NSAIDs)

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Comparing Three Familiar Medicines

These molecules have different structures.

Their different structures lead to different:

• properties
• biological targets
• metabolism
• effects
• risks

Antibiotics

Antibiotics are medicines used to treat bacterial infections.

Many antibiotics are organic molecules with complex structures.

One historically important example is:

penicillin

Penicillin and related antibiotics interfere with bacterial cell-wall formation.

This can prevent susceptible bacteria from successfully growing and dividing.

Antibiotics do not treat viral infections such as the common cold or influenza.

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Penicillin and Organic Chemistry

Penicillin molecules contain several functional groups and ring structures.

One particularly important feature is the:

β-lactam ring

This structure is crucial to the antibacterial activity of penicillins.

Small structural changes can produce different members of the penicillin family with different pharmaceutical properties.

This provides another example of:

structure → function

Antibiotic Resistance

Bacterial populations can evolve resistance to antibiotics.

If an antibiotic kills susceptible bacteria while resistant bacteria survive, those resistant bacteria can reproduce.

Over time, resistant forms can become more common.

Antibiotic resistance can be encouraged by inappropriate or unnecessary antibiotic use.

This creates an important connection between:

• chemistry
• biology
• evolution
• medicine
• public health

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Antihistamines

An antihistamine is a medicine that reduces certain effects of histamine.

Histamine contributes to symptoms associated with allergic responses, such as:

• itching
• sneezing
• runny nose
• watery eyes

Antihistamine molecules can interact with histamine receptors and reduce histamine's ability to produce these effects.

Again, their molecular structure determines how effectively they interact with the receptor.

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Receptors

A receptor is usually a protein that can respond to particular molecules.

A drug may:

activate a receptor

or:

block a receptor

A molecule that activates a receptor is often called an:

agonist

A molecule that blocks or reduces receptor activation is often called an:

antagonist

Many pharmaceuticals work through one of these mechanisms.

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Enzyme Inhibitors

Some medicines work by reducing the activity of enzymes.

These are called:

enzyme inhibitors

An inhibitor may bind:

• directly to an enzyme's active site
• elsewhere on the enzyme

This can change the enzyme's activity.

Because enzymes have specific three-dimensional structures, the structure of the inhibitor is extremely important.

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Drug Structure and Solubility

A medicine cannot work simply because it can bind to a target.

It must also be able to reach that target.

One important property is:

solubility

Functional groups influence whether a drug interacts well with water.

Polar or charged groups can often increase interaction with aqueous environments.

Non-polar regions may help molecules interact with lipid membranes.

Drug designers often need to balance these properties.

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Crossing Cell Membranes

Cell membranes contain a phospholipid bilayer.

The interior of this membrane is largely hydrophobic.

A highly polar molecule may have difficulty crossing the membrane directly.

A more lipid-soluble molecule may cross more easily.

However, many biological transport systems also help molecules cross membranes.

Therefore, drug absorption depends on several factors, including:

• molecular size
• charge
• polarity
• lipid solubility
• transport proteins
• route of administration

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Acids, Bases, and Medicines

Many drug molecules contain acidic or basic functional groups.

For example:

–COOH

can contribute acidic behaviour.

Amines can contribute:

basic behaviour

Whether these groups are charged can depend on the surrounding pH.

This matters because charge can influence:

• water solubility
• membrane crossing
• protein binding
• absorption

Acid-base chemistry is therefore extremely important in pharmaceutical science.

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Chirality

Some organic molecules can exist in forms that are mirror images of one another.

These are called:

enantiomers

This property is related to:

chirality

Two enantiomers contain the same types of atoms and bonds but differ in their three-dimensional arrangement.

Why Chirality Matters in Medicines

Biological molecules are three-dimensional.

Therefore, two mirror-image forms of a drug can interact differently with:

• enzymes
• receptors
• transport proteins

One enantiomer may interact more strongly with a particular target than another.

This means pharmaceutical chemists must consider not only:

which atoms are present

but also:

how those atoms are arranged in three dimensions.

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Dose Matters

A dose is the quantity of medicine administered.

The appropriate dose should produce a useful therapeutic effect while minimizing harmful effects.

Too little medicine may:

fail to produce the desired effect

Too much may:

increase the risk of toxicity

Therefore:

more medicine does not mean better treatment.

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Therapeutic Effects and Side Effects

A drug may produce several biological effects.

The intended beneficial effect is the:

therapeutic effect

An unintended effect is commonly called a:

side effect

Side effects occur because biological systems are complex.

A drug may:

• interact with more than one target
• affect the same target in different tissues
• be converted into other molecules during metabolism

A medicine can therefore provide substantial benefits while also carrying risks.

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Drug Metabolism

The body can chemically modify drug molecules.

This process is called:

drug metabolism

The liver plays a major role in the metabolism of many medicines.

Chemical reactions may make a drug:

• less active
• more active
• easier to eliminate
• occasionally more toxic

Enzymes perform many of these reactions.

Organic chemistry helps scientists understand these molecular transformations.

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Drug Elimination

After a drug has performed its role, it or its metabolites may be removed from the body.

Important organs involved include:

• liver
• kidneys

The kidneys can remove many substances from blood and eliminate them through urine.

The chemical properties of a molecule influence how easily it can be eliminated.

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From Discovery to Medicine

Developing a pharmaceutical is usually a long process.

Scientists may begin by identifying a biological process involved in a disease.

They then identify a:

target

such as:

• enzyme
• receptor
• protein
• ion channel

Researchers search for molecules capable of interacting with that target.

Promising molecules are called:

lead compounds

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Modifying a Lead Compound

Once a promising compound is identified, chemists can modify its molecular structure.

For example, they might:

• add a functional group
• remove a functional group
• replace one group with another
• change a carbon chain
• change a ring structure
• alter stereochemistry

They then investigate whether the new compound has improved properties.

This process is sometimes called:

lead optimization

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What Are Drug Designers Trying to Improve?

A potential drug may need improvements in:

• effectiveness
• selectivity
• solubility
• stability
• absorption
• duration of action
• toxicity
• metabolism

For example, a molecule might bind strongly to its intended target but be poorly absorbed.

Chemists might modify its structure to improve absorption while trying to preserve biological activity.

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Structure–Activity Relationships

Scientists often compare related molecules to determine how structural changes affect biological activity.

This is called studying:

structure–activity relationships (SAR)

Suppose molecule A works well.

Chemists modify one part of its structure to produce molecule B.

If B works better, the change may have improved its interaction with the target.

If B stops working, the changed part may have been essential.

Repeated comparisons help scientists understand which molecular features are important.

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Computer-Aided Drug Design

Modern pharmaceutical research can use computer models to study possible drug molecules.

Computational tools can help scientists:

• visualize molecular structures
• model drug-target interactions
• compare candidate molecules
• predict some molecular properties
• prioritize compounds for laboratory testing

However, computer predictions do not replace experimental evidence.

Promising compounds still require laboratory and clinical testing.

Testing New Medicines

Before a new medicine can be widely used, scientists need evidence about:

effectiveness

and:

safety

Research progresses through stages that can include:

• laboratory studies
• preclinical studies
• clinical trials
• regulatory review
• continued monitoring after approval

Not every candidate drug succeeds.

Many potential medicines are abandoned because they are ineffective, unsafe, or unsuitable for practical use.

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Clinical Trials

Clinical trials study medicines in human participants under controlled research conditions.

Depending on the stage and purpose, researchers may investigate:

• safety
• appropriate dose
• effectiveness
• side effects
• comparison with existing treatments

Well-designed trials attempt to reduce bias and produce reliable evidence.

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Placebos and Controls

Some clinical trials use a:

control group

When scientifically and ethically appropriate, a control may receive a:

placebo

A placebo resembles the treatment but does not contain the tested active ingredient.

Researchers can compare outcomes between groups.

However, placebo use must be ethically appropriate; withholding an effective treatment can sometimes be unacceptable.

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Benefits of Pharmaceuticals

Medicines have transformed human health.

Benefits can include:

• treating infections
• controlling pain
• managing chronic diseases
• reducing inflammation
• preventing complications
• improving quality of life
• extending life expectancy
• preventing some diseases

Modern medicine depends heavily on pharmaceutical chemistry.

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Risks of Pharmaceuticals

Medicines can also involve risks.

Possible risks include:

• side effects
• allergic reactions
• toxicity
• interactions with other medicines
• incorrect dosing
• misuse
• antibiotic resistance
• environmental contamination from pharmaceutical residues

The existence of risk does not automatically mean a medicine should not be used.

Instead, the important question is:

Do the expected benefits outweigh the risks for the intended use?

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Benefit–Risk Analysis

Imagine a medicine produces a major improvement in a serious disease but causes a mild temporary side effect in some patients.

The benefits may greatly outweigh the risks.

Now imagine another drug provides very little benefit but causes serious harmful effects.

Its benefit-risk balance may be poor.

Therefore, pharmaceutical decisions require evaluation of:

benefit + probability + severity + alternatives + risk

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Medicines and Individual Differences

A medicine may not affect every person identically.

Differences can arise from:

• age
• body size
• genetics
• kidney or liver function
• other medicines
• diet
• other biological factors

This is one reason pharmaceutical treatment and dosing can require careful medical guidance.

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Natural Products and Drug Discovery

Many important medicines or lead compounds have originated from natural organisms.

Scientists have studied chemicals produced by:

• plants
• fungi
• bacteria
• marine organisms

These molecules may provide starting points for pharmaceutical development.

Penicillin, for example, originated from observations involving Penicillium fungi.

Chemists can then study, produce, and modify biologically active compounds.

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Synthetic Medicines

Other pharmaceuticals are produced through chemical synthesis.

Organic chemists may construct complex molecules through sequences of reactions.

Advantages of chemical synthesis can include:

• controlled purity
• large-scale production
• structural modification
• reliable supply
• development of molecules not readily available from nature

Natural-product chemistry and synthetic chemistry therefore both contribute to medicine.

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Organic Chemistry Connects to Biology

Drug development combines many scientific fields.

Organic chemistry explains molecular structure and reactions.

Biochemistry explains interactions with biological molecules.

Cell biology explains effects on cells.

Physiology explains effects on organs and systems.

Pharmacology studies how drugs interact with biological systems.

Toxicology investigates harmful effects.

Together, these sciences help scientists develop useful medicines.

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Worked Example: Functional Groups

A drug molecule contains:

–COOH

What functional group is present?

Carboxyl group

What behaviour might this contribute?

Acidic behaviour

What other property might it influence?

Possible answers include:

• water solubility
• charge
• protein binding
• membrane crossing

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Worked Example: Amines

A pharmaceutical contains an amine group.

What chemical behaviour might you predict?

The nitrogen can often accept H⁺.

Therefore, the molecule may show:

basic behaviour

Its charge may change depending on pH.

This can influence its solubility and movement through biological systems.

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Worked Example: Molecular Shape

Two molecules contain the same atoms but have different three-dimensional arrangements.

Could they behave differently as medicines?

Yes.

Biological targets are three-dimensional.

Different arrangements may interact differently with receptors or enzymes.

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Worked Example: Changing a Functional Group

A drug candidate binds strongly to its target but dissolves poorly in water.

A chemist modifies part of the molecule to increase its polarity.

Why?

Increasing suitable polar interactions may improve:

water solubility

However, the chemist must also determine whether the modification changes:

• target binding
• absorption
• metabolism
• toxicity

Drug design involves balancing several properties simultaneously.

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Worked Example: Benefits and Risks

Suppose Medicine A greatly reduces symptoms but causes mild nausea in some patients.

Medicine B produces little improvement and causes serious liver toxicity.

Which has the more favourable benefit-risk profile?

Based only on the information provided:

Medicine A

because its potential benefit is greater while the described adverse effect is less severe.

Real pharmaceutical decisions require much more evidence, but the same principle applies.

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Common Mistakes

Thinking "Organic" Means Natural

In chemistry, organic refers mainly to carbon-based chemistry.

Synthetic medicines can be organic compounds.

Thinking Natural Means Safe

Natural substances can be:

• beneficial
• harmless
• toxic
• deadly

Origin alone does not determine safety.

Thinking Synthetic Means Dangerous

Synthetic compounds can be safe and useful.

Safety depends on properties, dose, and use.

Thinking All Medicines Work the Same Way

Different medicines act through different molecular mechanisms.

Ignoring Molecular Shape

Three-dimensional structure can be critical to drug function.

Ignoring Functional Groups

Functional groups influence solubility, acidity, basicity, reactivity, and biological interactions.

Thinking More Medicine Works Better

Increasing the dose can increase toxicity rather than benefit.

Confusing Side Effect with No Effect

A side effect is an unintended effect, not the absence of a therapeutic effect.

Thinking Antibiotics Treat Viruses

Antibiotics target bacteria and do not treat ordinary viral infections.

Thinking a Drug Must Have Zero Risk

Few medical interventions are completely risk-free.

The goal is an acceptable:

benefit-risk balance

Thinking Computer Models Prove a Drug Works

Computer modelling can guide research, but experimental and clinical evidence is still required.

Assuming Similar Structures Mean Identical Effects

Small structural changes can sometimes cause major differences in biological activity.

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Key Terms

Medicine — A substance or preparation used to prevent, diagnose, treat, or manage a medical condition.

Pharmaceutical — A substance developed or used for a medical purpose.

Active pharmaceutical ingredient (API) — The component responsible for a medicine's intended biological effect.

Excipient — An additional component of a pharmaceutical formulation other than the active ingredient.

Drug target — A biological molecule or structure with which a drug interacts to produce an effect.

Receptor — Usually a protein that responds to specific signalling molecules or drugs.

Agonist — A substance that activates a receptor.

Antagonist — A substance that blocks or reduces receptor activation.

Enzyme inhibitor — A substance that reduces the activity of an enzyme.

Binding site — A region of a biological molecule where another molecule can interact.

Functional group — A group of atoms responsible for characteristic chemical properties and reactions.

Polarity — Uneven distribution of electrical charge within a molecule.

Solubility — The extent to which a substance dissolves in a solvent.

Lipophilicity — The tendency of a substance to interact with or dissolve in lipid-like environments.

Chirality — A structural property in which a molecule may exist in non-superimposable mirror-image forms.

Enantiomer — One of two non-superimposable mirror-image forms of a chiral molecule.

Dose — The quantity of a medicine administered.

Therapeutic effect — The intended beneficial effect of a treatment.

Side effect — An unintended effect associated with a medicine.

Toxicity — The ability of a substance to cause harmful biological effects.

Drug interaction — A situation in which another substance changes the effects of a medicine.

Metabolism — Chemical modification of substances by the body.

Drug metabolism — Chemical transformation of pharmaceutical molecules within the body.

Lead compound — A promising molecule selected for further investigation during drug development.

Lead optimization — Modification of a lead compound to improve desirable pharmaceutical properties.

Structure–activity relationship (SAR) — The relationship between molecular structure and biological activity.

Medicinal chemistry — The field applying chemistry to the discovery and development of medicines.

Pharmacology — The study of drugs and their interactions with biological systems.

Toxicology — The study of harmful effects of substances on living organisms.

Clinical trial — A controlled research study involving human participants to investigate a medical intervention.

Placebo — An inactive treatment used as a comparison in some research studies.

Antibiotic — A medicine used to treat susceptible bacterial infections.

Antibiotic resistance — The ability of bacteria to survive or reproduce despite exposure to an antibiotic that would normally inhibit them.

Benefit-risk balance — Comparison of the expected benefits of a treatment with its potential harms.

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Key Takeaways

• Many medicines are organic compounds.
• Carbon's bonding versatility allows pharmaceutical molecules to have enormous structural diversity.
• Organic chemistry is fundamental to pharmaceutical development.
• Functional groups strongly influence drug properties.
• Drug molecules can contain hydroxyl, carboxyl, amino, ester, amide, and many other groups.
• Molecular shape can strongly influence biological activity.
• Drugs often work by interacting with specific biological targets.
• Important drug targets include receptors, enzymes, proteins, and ion channels.
• Drug-target interactions depend on molecular structure.
• Hydrogen bonding, ionic attraction, hydrophobic interactions, and other forces can contribute to drug binding.
• Paracetamol is an organic pharmaceutical used for pain relief and fever reduction.
• Aspirin is an organic pharmaceutical containing carboxyl and ester functional groups.
• Ibuprofen is an organic pharmaceutical containing a carboxyl group.
• Penicillins contain an important β-lactam ring.
• Antibiotics treat bacterial infections, not viral infections.
• Antibiotic resistance can evolve in bacterial populations.
• Some medicines activate receptors.
• Other medicines block receptors.
• Some pharmaceuticals inhibit enzymes.
• Solubility affects how medicines behave in the body.
• Polarity and charge can affect membrane crossing.
• Acid-base chemistry is important in pharmaceutical science.
• Three-dimensional molecular arrangement can matter as much as molecular formula.
• Enantiomers can interact differently with biological targets.
• Drug dose strongly influences both benefits and risks.
• More medicine is not necessarily better.
• Drugs can produce therapeutic effects and side effects.
• The body chemically modifies many drugs through metabolism.
• Scientists can modify molecular structures to improve potential medicines.
• Structure–activity relationships help scientists understand which parts of a molecule are important.
• Computer modelling can assist drug discovery but does not replace experimental testing.
• New medicines require extensive testing.
• Clinical trials provide evidence about safety and effectiveness.
• Medicines can provide enormous benefits while still carrying risks.
• Pharmaceutical decisions require consideration of benefit versus risk.
• "Natural" does not automatically mean safe.
• "Synthetic" does not automatically mean dangerous.
• Organic chemistry, biochemistry, biology, pharmacology, and medicine work together in pharmaceutical development.

The central relationship is:

MOLECULAR STRUCTURE → CHEMICAL PROPERTIES → BIOLOGICAL INTERACTIONS → DRUG EFFECT

And pharmaceutical development attempts to optimize:

effectiveness + selectivity + absorption + stability + safety

while minimizing:

toxicity + harmful interactions + unwanted effects

Check Your Understanding

1. What is a pharmaceutical?

2. What is an active pharmaceutical ingredient?

3. Why is organic chemistry important in medicine?

4. Give three examples of familiar medicines containing organic compounds.

5. Explain why molecular shape can influence drug activity.

6. What is a drug target?

7. Give three examples of biological drug targets.

8. Name three types of intermolecular interaction that can contribute to drug binding.

9. How can functional groups affect a drug's properties?

10. Identify two functional groups found in aspirin.

11. What class of medicine is ibuprofen?

12. What is an antibiotic?

13. Why should antibiotics not be used to treat ordinary viral infections?

14. What is antibiotic resistance?

15. What is a receptor?

16. Distinguish between an agonist and an antagonist.

17. What is an enzyme inhibitor?

18. Explain why water solubility can be important for a medicine.

19. Explain why lipid solubility can influence membrane crossing.

20. Why are acidic and basic functional groups important in pharmaceuticals?

21. What is chirality?

22. What is an enantiomer?

23. Why can two enantiomers behave differently in the body?

24. Explain why dose is important.

25. Distinguish between a therapeutic effect and a side effect.

26. What is drug metabolism?

27. What is a lead compound?

28. What is meant by a structure–activity relationship?

29. Why are clinical trials necessary?

30. Challenge: A pharmaceutical company discovers an organic molecule that blocks an enzyme involved in a disease.

a. What would the enzyme be called in relation to the drug?
b. Explain why the three-dimensional shape of the drug is important.
c. Explain how hydrogen bonding could contribute to drug binding.
d. Explain how an amine group might influence the drug's acid-base behaviour.
e. Explain how a carboxyl group might influence its behaviour.
f. Explain why polarity could affect water solubility.
g. Explain why polarity could also affect membrane crossing.
h. The molecule exists as two enantiomers. Explain why both should be investigated separately.
i. Scientists modify one functional group and the new molecule binds more strongly. What does this suggest about structure–activity relationships?
j. Explain why stronger binding does not automatically make the new molecule a better medicine.
k. Name three other properties scientists should investigate.
l. Explain why laboratory success does not prove that the compound will work safely in humans.
m. Explain the purpose of clinical trials.
n. Explain why researchers investigate both therapeutic effects and side effects.
o. Explain why increasing the dose may increase risk.
p. Explain why a medicine can be beneficial even if it has some side effects.
q. Explain why a natural origin would not prove that the drug is safe.
r. Explain why a synthetic origin would not prove that the drug is dangerous.
s. Describe how organic chemistry contributes to improving the molecule.
t. Use the example to explain:

structure → properties → biological interactions → pharmaceutical effect.