Pharmacology

What is a drug?

Any chemical that affects living processes by modifying existing functions, not creating new ones (exception: supplements like calcium).

What are the two types of drug effects?

• Wanted/therapeutic effect (e.g., paracetamol relieves pain).

• Side effects (e.g., hepatotoxicity, gastric irritation from ibuprofen).

What is pharmacology?

The science of drugs, including history, sources, physical/chemical properties, absorption, distribution, metabolism, excretion, actions, therapeutic uses, and toxic effects.

What is medical (clinical) pharmacology?

The use of drugs for diagnosis, prevention, and treatment of human diseases; includes clinical trials and human interaction studies.

What is pharmacy?

The branch of health sciences dealing with preparation, dispensing, and proper utilization of drugs.

What is toxicology?

The branch of pharmacology that studies adverse and toxic effects of drugs, chemicals, and poisons (e.g., pesticides, sarin gas).

What is clinical toxicology?

Study of toxic/adverse effects of toxins on humans, including diagnosis and treatment of poisoning.

What is analytical toxicology?

Measurement of toxic chemicals in biological and environmental samples.

What is forensic toxicology?

Study of medico-legal aspects of toxicity; links health conditions/death to a poison.

What is environmental toxicology?

Study of how toxins move into the environment/food chain; includes industrial toxicology (workplace exposure).

What is pharmacokinetics (PK)?

Study of how the body handles drugs (ADME: absorption, distribution, metabolism, excretion).

What is pharmacodynamics (PD)?

Study of biochemical and physiological effects of drugs and their mechanism of action (what the drug does to the body).

Difference between PK and PD?

• PK = "What the body does to the drug" (ADME).

• PD = "What the drug does to the body" (mechanism, targets, effects).

What are the major drug targets?

Receptors, enzymes, ion channels, and transporters.

How do drugs act on receptors?

By stimulating or inhibiting them, thereby modifying existing cellular functions.

How do drugs act on enzymes?

By inhibiting or stimulating enzyme activity, altering metabolic pathways.

How do drugs act on ion channels?

By blocking or opening channels, altering ion flow across membranes.

How do drugs act on transporters?

By inhibiting or modulating the movement of molecules across membranes.

What is paracetamol’s scientific name?

Acetaminophen.

What are some brand names for paracetamol?

Panadol, Tylenol, Panda.

What are the pharmacological actions of paracetamol?

• Analgesic (relieves pain).

• Antipyretic (reduces fever).

• Weak anti-inflammatory effect compared to NSAIDs.

How does paracetamol work?

Inhibits COX enzymes, reducing prostaglandin production (↓ fever, pain, inflammation).

What are the effects of prostaglandins in the stomach?

• Increase mucus and bicarbonate production (protective).
• Decrease acid secretion.
• If prostaglandins ↓ → increased acid, less mucus → gastric irritation.

Why should ibuprofen (Brufen) be taken with food?

To reduce gastric irritation caused by prostaglandin inhibition.

What is an indication?

The condition or reason for which a drug is prescribed.

What is a contraindication?

A situation where a drug should not be used due to risk of harm.

What is toxicity?

Harmful or adverse effects of a drug at certain doses.

What is the mechanism of action?

the specific biochemical interaction through which a drug produces its therapeutic effect, usually by binding to a target such as a receptor, enzyme, or ion channel.

What does pharmacology study?

Pharmacology studies how drugs interact with living systems and how they produce effects within the body.

What are the two effects of a drug?

1. Desired (therapeutic) effect – the intended benefit, e.g., paracetamol relieving pain. 2. Side effect – an unintended effect, e.g., paracetamol causing liver toxicity.

Define pharmacology.

The science of drugs, including their source, properties, absorption, distribution, metabolism, excretion, actions, and therapeutic or toxic effects.

Define medical (clinical) pharmacology.

The study of drug use in diagnosing, preventing, and treating human diseases.

Define pharmacy.

The branch of health sciences concerned with preparing, dispensing, and properly using drugs.

Define toxicology.

The study of harmful effects of drugs and chemicals on organisms, including poisons, pesticides, and industrial substances.

What are the two universal pharmacological principles?

1. Any substance can be toxic under certain conditions. 2. All health supplements should meet the same safety and efficacy standards as drugs.

Define prescription.

A written direction for preparing and administering a drug.

Define therapeutic effect.

The primary intended effect of a drug — the reason it’s prescribed (e.g., morphine → analgesia).

Define side effect.

A secondary, unintended effect that may be predictable and harmless or undesirable (e.g., sedation from antihistamines).

Define drug toxicity.

A harmful effect resulting from excessive dosage, incorrect use, or genetic sensitivity.

Define drug interaction.

Occurs when the effect of one drug is altered by the presence of another, either enhancing or reducing its action.

Define drug misuse.

Improper use of medications (like laxatives or vitamins), causing acute or chronic toxicity.

Define drug abuse.

Inappropriate, repeated intake of a substance for non-medical purposes, leading to dependence (e.g., opioids).

Define pharmacotherapeutics.

The use of drugs to prevent or treat diseases.

Define chemotherapeutics.

Use of drugs to kill or inhibit microorganisms or cancer cells.

Define pharmacogenomics.

The study of how an individual’s entire genome affects drug response.

Define pharmacogenetics.

The study of how specific genes cause differences in drug response between individuals.

Define idiosyncratic drug response.

An unusual, unpredictable drug reaction often caused by genetic or immunologic factors.

Define tolerance.

A reduced response to a drug after repeated use, requiring higher doses for the same effect.

Define tachyphylaxis.

A rapid form of tolerance developing within hours or a day of repeated drug administration.

Define pharmacodynamics.

“What the drug does to the body” — including biochemical and physiological effects, receptor interactions, and mechanisms of action.

Define pharmacokinetics.

“What the body does to the drug” — involving absorption, distribution, metabolism (biotransformation), and excretion.

Explain absorption.

The movement of drug molecules from the administration site into the bloodstream.

Explain distribution.

Movement of drug molecules from the circulation into body tissues and fluids.

Explain biotransformation.

Metabolic conversion of a drug into a different chemical form, usually for easier excretion.

Explain excretion.

Elimination of drug molecules from the body through organs such as the kidneys or liver.

What is the difference between disintegration and dissolution?

Disintegration – tablet breaks into smaller particles. Dissolution – particles dissolve to allow absorption into circulation.

What is the relationship between pharmacokinetics and pharmacodynamics?

Pharmacokinetics influences how much drug reaches the site of action; pharmacodynamics determines the effect produced.

What are the main natural sources of drugs?

• Plants: morphine, cocaine, atropine * Microbes: penicillin, streptomycin * Animals: insulin, thyroid hormones * Minerals: lithium compounds

What are synthetic drugs?

Drugs created in laboratories (e.g., aspirin, barbiturates) or modified from natural compounds (e.g., oxycodone from morphine).

What are serendipitous discoveries in pharmacology?

Drugs found accidentally while testing for another use, e.g., salicylic acid (aspirin).

What is drug variability?

Differences in drug response due to factors like age, sex, and genetics.

What does “poisons are also drugs” mean?

Because both poisons and drugs are chemicals that interact with biological systems — the dose determines whether it’s therapeutic or toxic.

What happens with too much paracetamol?

Leads to hepatotoxicity (liver damage) and potentially death within 24 hours if overdosed.

What is the difference between misuse and abuse?

• Misuse: improper medical use (e.g., overusing vitamins). * Abuse: psychological dependence and repeated nonmedical use (e.g., opioids).

What is the effect of tolerance and dependence in opioids?

Tolerance requires higher doses; dependence leads to addiction and withdrawal symptoms upon stopping.

What are examples of drug discovery approaches?

1. Serendipity – accidental discovery. 2. Conventional synthesis – creating new or modified chemical entities.

What are antibacterial and antiviral agents?

Antibacterial agents kill or inhibit bacteria; antiviral agents target viruses without harming host cells.

What does pharmacodynamics study?

The biochemical and physiological effects of drugs and their mechanisms of action.

What relationship does pharmacodynamics examine?

The relationship between drug concentration and drug effect.

What are common drug targets?

Receptors or enzymes.

Why must a drug be potent?

To bind a sufficient number of target proteins at a reasonable dose.

How do most drugs exert their effects?

By interacting with receptors—specialized target macromolecules on or within cells.

What happens after a drug binds its receptor?

The receptor undergoes a conformational or biochemical change that triggers a response.

What are the key determinants of specificity in drug-receptor interactions?

Complementarity of shape and electrostatic/hydrophobic/hydrogen-bonding interactions.

What is the “lock-and-key” model?

Drug and receptor fit precisely, matching both shape and electrochemical structure.

Why do most drugs bind non-covalently?

Non-covalent binding allows reversible control of drug effects and avoids irreversible toxicity.

What type of bond leads to irreversible binding and long duration of action?

Covalent bonds.

What determines the specificity of a drug’s action?

The receptor type and its molecular recognition site.

Are all drug targets proteins?

Most are proteins, but some may be lipids or nucleic acids.

Do all drugs use receptors?

No—some act via physical, chemical, or enzymatic mechanisms.

What makes a receptor an excellent drug target?

Its ability to regulate cell function by precisely recognizing ligands with specificity, selectivity, and sensitivity.

Why are non-covalent interactions saturable?

Because receptor sites are finite—once all are occupied, no further binding can occur.

Why can one ligand produce different effects in different tissues?

Different receptor isoforms (e.g., β₁ vs β₂) are coupled to distinct signaling cascades.

What is an example of receptor isoform difference?

β₁ receptors in the heart increase contractility; β₂ in the lungs cause relaxation.

Why can non-selective β-blockers be dangerous in asthmatic patients?

They block both β₁ (heart) and β₂ (lungs) receptors—causing bronchoconstriction.

What do selective β-blockers aim to do?

Block β₁ receptors while sparing β₂ to reduce cardiac effects without airway constriction.

What property of receptors allows small drug doses to have large effects?

Signal amplification through intracellular cascades.

What are the four major receptor families?

Ligand-gated ion channels, G-protein-coupled receptors (GPCRs), enzyme-linked receptors, and intracellular receptors.

What is a ligand-gated ion channel?

A receptor that opens an ion channel upon ligand binding, allowing ion flow and cellular response.

Give an example of a ligand-gated ion channel.

The nicotinic acetylcholine receptor (nAChR).

What happens when ACh binds to a nicotinic receptor?

Sodium influx causes skeletal muscle depolarization and contraction.

Where are nicotinic receptors found?

At skeletal neuromuscular junctions and autonomic ganglia (sympathetic & parasympathetic).

What do skeletal muscle relaxants do?

Bind to nicotinic receptors and prevent ACh binding or Ca^{2+} release, leading to muscle relaxation.

How can pesticide toxicity affect nicotinic receptors?

By overstimulating or blocking them, altering neuromuscular transmission and causing paralysis.

What’s the difference between nicotinic and muscarinic receptors?

Nicotinic receptors bind nicotine; muscarinic receptors bind muscarine (a mushroom toxin).

How does nicotine affect the autonomic nervous system?

Activates both sympathetic and parasympathetic ganglia—effect depends on the dominant system.

What response does nicotine cause in the heart?

Sympathetic dominance → increased heart rate and contraction.

What are enzyme-linked receptors?

Receptors with an extracellular ligand-binding domain and an intracellular enzyme (usually kinase) that gets activated after ligand binding.

What happens when a ligand binds to a tyrosine kinase receptor?

• Receptor dimerization* Autophosphorylation of tyrosine residues* Activation of intracellular signaling proteins and pathways

What is autophosphorylation?

The receptor phosphorylates its own tyrosine residues to activate itself and downstream signaling proteins.