1: Intro Flashcards
What is a drug?
A chemical entity of known structure, other than a nutrient/dietary supplement, which causes a biological effect in a living organism.
What is a medicine?
A preparation of one or more drug, alongside other substances (stabilisers, solvents, etc.), which is used therapeutically - i.e. to treat, cure, prevent or diagnose disease.
How are drugs classified?
Molecular Structure: catecholamines, tricyclics…
Mode of Action: cetylcholinesterase inhibitors, β-blockers…
Therapeutic Use: bronchodilators, antihypertensives…
How are drugs named?
Drugs are named in three ways: 1) chemical name by molecular composition, 2) generic drug name, always written with a lower-case, and 3) proprietary / trade name, always written with an upper-case.
When discussing drugs in pharmacology, the generic name is used. Several proprietary drug names may refer to the same generic drug, as a drug can have several effects: i.e. the drug liraglutide, which is marketed for both type 2 diabetes (‘Victoza’) and obesity (‘Saxenda’).
An example of drug naming: the bronchodilating drug ‘salbutamol’:
Chemical name: 4-[2-(tertiary butylamino)-1-hydroxyethyl]-2-(hydroxymethyl) phenol
Generic name: salbutamol
Proprietary / trade name: Ventolin
What is pharmacology?
Pharmacology is the science-oriented study of drug action. It involves the following sub-fields:
- Physiology
- Neurobiology
- Microbiology
- Biochemistry and cell biology
- Chemistry
- Structural biology
- Molecular biology
- Genetics
- Pathology
The two main branches of pharmacology are pharmacodynamics (i.e. what a drug does to a body, such as drug effects and response), and pharmacokinetics (i.e. what a body does to a drug, such as transportation, absorption, and excretion).
In contrast, toxicology studies the adverse effects of chemicals on living organisms, and pharmacy is a patient-oriented health service licensed to dispense medicine.
What are pharmacodynamics?
One of the two main branches of pharmacology: what a drug does to the body, e.g.:
Does the drug work? How, and how well? What is the dose-response relationship? What is the molecular target? How strongly does the drug bind? What is the mechanism of action?
This is in contrast to pharmacokinetics, which deals what a body does with and to a drug (e.g. transportation, absorption, and excretion).
What are pharmacokinetics?
One of the two main branches of pharmacology: what a body does with and to a drug.
How is the drug administered? Why? How much is bioavailable? How much gets to the right place? How long does it stay at the target site? How much gets to the wrong place? How does the drug leave the body?
This is in contrast to pharmacodynamics, which deals with what a drug does to a body (e.g. drug effects and response).
What is “ADME” short for?
Absorption, Distribution, Metabolism, and Excretion
Drug absorption and distribution (A and D) contributes to a drug’s delivery to a target site.
Drug metabolism and excretion (M and E) contributes to a drug’s elimination.
Controlling ADME is vital for determining a drug’s onset, intensity, and duration.
What is absorption?
Absorption is the movement of the drug from the site of administration to the systemic circulation, i.e. blood.
Absorption is NOT the movement of the drug to its site of action (this is called distribution).
The route of administration (ROA) plays a crucial role in absorption:
Intravenous (IV) administration results in 100% bioavailability (100% of the drug reaches systemic circulation). All other routes (e.g. oral, rectal, or inhalation) are less bioavailable, but less unpleasant to a patient.
What does “enteral” mean in terms of route of administration (in contrast to parenteral)?
Enterally administered drugs pass through the gastrointestinal (G.I.) tract and must therefore cross a tight barrier composed of the epithelial cells.
Enteral routes of administration include oral (swallowed), sublingual (dissolved under the tongue), and rectal (crammed into the butthole).
What does “parenteral” mean in terms of route of administration (in contrast to enteral)?
Parenterally administered drugs refers to drugs that are not administered orally, and therefore do not go through the gastrointestinal (G.I.) tract.
As these drugs do not have to pass the barrier created by the epithelial cells of the G.I. tract, they have higher bioavailability and are absorbed quicker.
Parenteral routes of administration include I.V. (needle injections), subcutaneous (placed/injected under the skin), intramuscular (injected into a muscle), inhalation (breathed / smoked), intranasal (snorted), topical (placed on an outer surface of the body, like skin or eyes), and transdermal (placed on skin and absorbed through it).
What does oral drug administration entail?
Oral drug administration…
- is the most common route of drugs, as it is easy and comfortable for self-dosing and cost-effective to make
- has rapid onset (10-20 minutes), but only after drug has dissolved
- has a large capacity for absorption due to the large surface area of the small intestine
- is the most complicated route for a drug, as it must survive gastric acid, digestive enzymes, food, and gut bacteria before absorption
As drugs must dissolve before they can be absorbed, dissolution rate can be a limiting factor in oral drug delivery. This can be partly controlled, e.g. by changing the surface area of a tablet or covering it in a slowly or fast dissolving gel.
The small intestine is the major site of absorption from orally, sublingually, or rectally administered drugs, as it is the part of the gastrointestinal (G.I.) tract with the largest surface area (200 m2), has a thin membrane (one cell thick), and has a high blood flow.
What is the role of the small intestine during enteral drug absorption?
The small intestine is the major site of absorption from orally, sublingually, or rectally administered drugs, as it is the part of the gastrointestinal (G.I.) tract with the largest surface area (200 m2), has a thin membrane (one cell thick), and has a high blood flow.
