Nature of disease and the purpose of therapy

WHO definition of health

Complete physical, mental and social wellbeing—not merely the absence of sickness or infirmity.

Health as a dynamic state

Wellbeing and potential that meet life's demands in a way suited to age, culture and personal responsibility.

Why is health/disease context-dependent?

Environment, age and culture matter: a trait may help in one setting but harm or limit function in another.

Naturalistic view of disease

Disease is abnormal functioning of an organism's systems, parts or organs.

Normative view of disease

A condition judged disagreeable or harmful by an individual or society.

Three key factors used to describe disease

Disvalue (harm or undesirability), phenomenology (signs/symptoms or manifestation), and aetiology (cause).

Disease: broad definition

Physiological or psychological processes that typically cause disability, pain or deformity and fall below accepted norms.

Does deviation from normality alone define disease?

No. Atypical or common changes do not by themselves establish disease; function, harm and context matter.

Medicalisation: possible effects

Labelling a condition as a disease can have both beneficial and adverse effects.

Aim of therapeutic intervention

Minimise the disvalue associated with disease.

Morbidity vs prognosis

Morbidity = current symptoms and disabilities; prognosis = likelihood of increased morbidity or premature death.

Who is considered healthy in the lecture's framework?

Someone without abnormal symptoms or disabilities whose prognosis is average for a person of the same age.

Lifestyle drugs

Medicines taken without a medical need to improve perceived quality of life or meet a psychosocial ideal.

What does drug therapy commonly do?

It often prevents or alleviates disease; cures are uncommon, especially in infectious and malignant disorders.

Patient treatment vs societal causes

Drug therapy treats the patient; it may not address the wider societal causes of disease.

How can drug therapy be understood from cell to population?

Molecular targets (often receptors) produce pharmacological effects; effects are assessed in patients and, at scale, as population benefit.

Most common drug target

Receptors.

Pharmacological effect

A measurable drug action, such as a change in plasma cholesterol.

Efficacy vs effectiveness

Efficacy = desired effect under controlled conditions; effectiveness = effect in real-life conditions.

Benefit (in the lecture's outcome framework)

Effectiveness expressed in monetary terms.

Main categories of chemical therapeutic agents

Small-molecule drugs; peptides/proteins; antibodies; enzymes; vaccines; DNA products.

Small-molecule drug sources

Synthetic organic, natural-product or semisynthetic drugs; examples include morphine and penicillin derivatives.

Peptide/protein drug sources

Made synthetically, obtained from natural sources or produced using recombinant DNA; examples include vasopressin and insulin.

Other therapeutic-agent examples

Antibodies (e.g. rituximab), enzymes, vaccines and DNA products.

Advantages of conventional drug therapy

Patient acceptability, wide application, oral delivery and strong industry involvement/choice.

Disadvantages of conventional drug therapy

Side effects and a diminishing development pipeline.

Properties of an ideal drug

Desired effect; easy to administer; low dose/frequency; few side effects; timely elimination; accessible source; inexpensive manufacture; stable.

What does the aspirin example show about ideal-drug properties?

A real drug can meet some ideals but not all: aspirin is easy to use and inexpensive, yet may cause side effects and has mixed performance on some criteria.

Pharmacophore

The part of a drug molecule that interacts with the target protein or receptor.

Carrier groups in a drug molecule

Groups that control ionisation and lipophilicity, influencing drug-likeness.

Vulnerable groups in a drug molecule

Groups susceptible to enzymatic degradation that can strongly affect metabolism.

Drug-likeness

Physicochemical properties that help predict whether a new compound can perform through liberation, absorption, distribution, metabolism and excretion.

Why does drug-likeness matter in development?

Poor drug-like properties can prevent a lead compound from reaching clinical testing.

Toxicity

The degree to which a substance can damage an organism; drug toxicity may appear as side effects, adverse reactions or death.

How can drug toxicity occur?

Overdose, accumulation, poor elimination, or off-target effects—especially concerning when the therapeutic index is low.

Why are drugs regulated?

To ensure an acceptable balance of risk and benefit, including safety and efficacy.