FARMACOLOGÍA INTRODUCCIÓN | GuiaMed

Introduction to Pharmacology

Overview of the Class

• The session is led by Christian Poos, focusing on an introduction to pharmacology.

• Key topics include definitions of pharmacology and drugs, branches of pharmacology, types of pharmacological actions, classifications, and adverse effects.

Definition of Pharmacology

• Pharmacology derives from Greek: "pharmakon" (drug) and "logos" (study), defining it as the study or treatise on drugs.

• A comprehensive definition includes studying drug history, properties, biochemical effects, mechanisms of action, absorption, distribution, biotransformation, elimination, and therapeutic use.

Understanding Drugs

• A drug is defined as any chemical substance that alters the functioning of living organisms through molecular interactions.

Branches and Disciplines in Pharmacology

• Nine important branches are identified:

• Pharmacognosy: Studies natural drug origins and characteristics.

• Pharmacokinetics: Examines absorption, distribution, biotransformation, and elimination—what the body does to drugs.

• Pharmacodynamics: Focuses on biochemical effects and mechanisms—what drugs do to the body.

Further Branches Explained

• Pharmaceutical Technology: Involves preparation and distribution methods for drugs.

• Pharmacotherapy: Concerns using drugs to prevent or treat diseases.

• Clinical Pharmacology: Studies drug actions in healthy vs. sick individuals.

• Molecular Pharmacology: Investigates drug interactions at a molecular level.

• Toxicology: Focuses on poisons and adverse medication effects.

• Pharmacometrics: Analyzes dose-response relationships.

Key Concepts in Pharmacological Actions

Action vs. Effect in Pharmacology

• The pharmacological action refers to changes induced by a drug in various bodily functions; it's crucial for classifying different types of actions.

Types of Pharmacological Actions

• Five major types include:

• Stimulation: Enhances cellular function; e.g., caffeine increases activity levels.

• Depression: Reduces cellular function; specific examples will be discussed later.

Pharmacological Actions and Classifications

Types of Pharmacological Actions

• Anesthetic Action: An example of anesthetic action is the use of acepar, which serves to numb or reduce sensation in a specific area.

• Excitation and Irritation: This refers to violent stimulation of cells, organs, and systems that can lead to hypertrophy or atrophy. For instance, topical iodine or silver nitrate can cause skin irritation.

• Replacement Action: Replacement involves substituting a missing secretion in the body with its corresponding hormone. A clear example is insulin for patients with diabetes mellitus who have insufficient insulin production.

• Anti-infectious Action: This action aims to attenuate or destroy microorganisms causing infections in humans. Antibiotics, antivirals, antifungals, and antiparasitics are key examples.

Classification by Mode of Action

Local Action Drugs

• These drugs act at the site of application without entering circulation. Examples include topical medications applied directly on mucous membranes.

General/Systemic Action Drugs

• These drugs affect the entire organism as they penetrate circulation. Common forms include intramuscular or intravenous applications.

Remote/Indirect Action Drugs

• Administered at one site but produce effects far from that location. For example, applying a drug topically may irritate the skin but elevate heart rate indirectly.

Adverse Effects of Medications

Side Effects

• Side effects are non-therapeutic effects that appear after therapeutic doses; they are often undesirable but can sometimes be beneficial (e.g., diarrhea, headache).

Secondary Effects

Adverse Drug Reactions and Their Mechanisms

Understanding Toxic Reactions

• Adverse reactions in clinical settings are often difficult to differentiate, typically requiring conceptual understanding rather than straightforward identification.

• Toxic reactions occur when drug doses exceed the therapeutic margin for a specific patient, leading to severe effects such as hemorrhage from anticoagulants or seizures from high doses of local anesthetics.

Intolerance vs. Tolerance

• Intolerance is characterized by exaggerated toxic responses to normal therapeutic doses, which is relatively rare.

• For instance, carbamazepine, used for seizures, may cause ataxia even at minimal doses in patients with intolerance.

Idiosyncrasy and Allergic Reactions

• Idiosyncrasy refers to abnormal responses seen in a small percentage of patients due to genetic factors; these reactions are unique and infrequent.

• Allergic reactions involve abnormal immune responses after normal drug administration; unlike idiosyncratic reactions, they stem from immune system interactions rather than genetic predispositions.

Pharmacological Interactions

• Adverse pharmacological interactions occur when two or more drugs are taken together, resulting in one drug enhancing or diminishing the effect of another.

• Such interactions can lead to synergistic effects or antagonism between drugs, potentially causing toxic adverse reactions if one drug amplifies the other's action.

Conclusion and Future Topics

• Understanding these adverse effects is crucial for safe pharmacological practices. The discussion will continue with topics on pharmacokinetics and dynamics in future videos.