PT1020: Introduction to Pharmacology

Learning Outcomes

Upon completi

on of the course, students will be able to:

1. Distinguish between pharmacodynamics (how drugs affect the body) and pharmacokinetics (how the body affects drugs).

2. Describe the effects of drugs binding to various receptors and the resulting physiological responses.

3. Identify pharmacological effects elicited by agonists and antagonists, understanding their clinical implications.

4. Design and interpret a pharmacological dose response curve, recognizing the significance of key parameters such as EC50 and EMAX.

Drug Properties

Desirable Attributes

• Specific Action: Targeting specific physiological pathways without affecting unrelated functions.

• Potent: Eliciting a significant response at low concentrations.

• Minimal Side-effects: Reducing unintended adverse effects to improve patient outcomes.

• Easy to Administer: Ensuring accessibility and compliance through various routes of administration.

• Low-cost, Readily Available: Facilitating widespread access to medications.

Undesirable Attributes

• Adverse Effects: Unfavorable reactions that can limit a drug's use.

• Organ Toxicity: The potential for drugs to cause damage to vital organs.

• Teratogenic Effects: Risks associated with drug use during pregnancy leading to birth defects.

• Costly: Economic factors that can affect medication availability.

Principles of Pharmacology

Pharmacology encompasses various subfields:

• Medicinal Pharmacology: Focusing on the therapeutic use of drugs to alleviate symptoms and treat diseases.

• Toxicology: Investigating adverse effects of chemicals and substances, including drug overdoses and poisonings.

Mechanism of Action

Drugs function through several primary mechanisms:

• Alter activity of cells: Modifying the functions of different cell types within the body.

• Replace deficient substances: Supplementing substances lacking in certain medical conditions.

• Neutralize excessive substances: Mitigating the effects of an overabundance of hormones or neurotransmitters.

• Destroy harmful cells/organisms: Targeting pathogens or cancerous cells for elimination.

Drug Naming Conventions

1. Chemical Name: Specifies the chemical structure (e.g., 2-Acetoxybenzoic acid).

2. Generic Name: The non-proprietary name used universally (e.g., Acetylsalicylic acid).

3. Brand Name: A trademarked name assigned by a manufacturer (e.g., Aspirin).

Drug-Receptor Interaction

Understanding drug-receptor interactions is crucial for predicting physiological effects, including absorption, distribution, metabolism, and excretion (ADME).

Drug Specificity

Drugs ideally bind selectively to target proteins, though no drug is completely specific, which can lead to unintended side effects at higher doses.

Drug-Receptor Complex

Drugs and their receptors form complex three-dimensional structures where ligands bind, characterized by strength of binding known as affinity.

Entities Binding to Receptors

Drugs can interact with:

• Endogenous molecules: Naturally occurring substances in the body (e.g., hormones).

• Exogenous drugs: Imports designed with pharmacological properties (e.g., Endorphins and Morphine).

Agonists vs. Antagonists

• Agonists: Compounds that bind to receptors and activate them, leading to a biological response (e.g., Salbutamol).

• Antagonists: Compounds that bind to receptors but do not activate them, blocking the action of agonists (e.g., Atenolol).

Dose Response Curves

Key Concepts:

• Hyperbolic and sigmoidal curves illustrate drug responses.

• Maximal response (EMAX): The greatest response achievable from a drug.

• Concentration needed for 50% maximal response (EC50): A critical value in determining drug potency.

Characteristics of Agonists

• Full Agonist: Produces the maximum possible response.

• Partial Agonist: Produces a response less than the maximum even at full concentration.

• Inverse Agonist: Induces a response that is opposite to that of a typical agonist, leading to reduced activity below baseline.

Summary of Pharmacodynamics

Pharmacodynamics involves the interaction between drugs and living systems, influencing the strength (potency) and effectiveness (efficacy) of drugs. It involves two primary processes: agonism (eliciting a response) and antagonism (preventing a response to endogenous ligands).

Key Definitions

• Pharmacodynamics: Refers to what a drug does to the body.

• Pharmacokinetics: Refers to what the body does to a drug, including how it is absorbed, distributed, metabolized, and excreted.