👨⚕️ FARMACOLOGÍA. FARMACOCINETICA
Introduction to Pharmacokinetics
Overview of Pharmacology
- Raúl Izquierdo introduces the topic of pharmacokinetics, emphasizing its importance in understanding drug interactions within the body.
- He defines pharmacology as the science that studies drugs, including their therapeutic and toxic properties.
Key Concepts in Pharmacokinetics
- The focus shifts to pharmacokinetics, which examines how the body affects a drug.
- Introduction of the acronym "UPME" representing key processes: Liberation, Absorption, Distribution, Metabolism, and Excretion.
Understanding Drugs and Their Forms
Definitions
- A drug or active ingredient is defined as any substance that has a therapeutic effect on the body.
- An excipient is described as a substance accompanying an active ingredient that aids in its release at the target site.
Pharmaceutical Forms
- Pharmaceutical forms are combinations of active ingredients and excipients; they can be solid (tablets), semi-solid (ointments), or liquid (solutions).
Pharmacokinetic Processes
Liberation Process
- Liberation refers to how a drug is released from its pharmaceutical form to its site of action.
Absorption Factors
- Absorption involves processes through which a drug moves from its release site into systemic circulation.
- Key factors affecting absorption include:
- Liposolubility: More liposoluble drugs have better absorption.
- Formulation: Solid drugs absorb slower than semi-solid or liquid forms.
- Perfusion and Surface Area: Higher perfusion rates and larger surface areas enhance absorption.
Administration Routes
Types of Administration
- Two main categories of administration routes are discussed:
- Enteral: Involving the digestive system (oral, sublingual, rectal).
- Parenteral: Bypassing the digestive system (intravenous, intramuscular, subcutaneous).
Distribution Mechanisms
Drug Distribution
- Distribution describes how drugs move from systemic circulation to target organs. Not all circulating drugs are therapeutically active due to protein binding.
Protein Binding Impact
- Proteins like albumin bind with drugs; only unbound fractions exert therapeutic effects. For example, if a drug has 90% protein binding, only 10% remains active.
Metabolism Insights
Metabolic Phases
- Metabolism transforms drugs for easier elimination. It consists of two phases:
- Phase I: Activation/Inactivation where many drugs become inactive metabolites.
- Phase II: Conjugation phase where substances are linked for easier excretion.
Importance of Prodrugs
- Some prodrugs require metabolic activation to produce therapeutic effects after administration.
Excretion Processes
Elimination Pathways
- Excretion encompasses processes by which drugs are removed from the body. Major pathways include:
- Renal excretion (kidneys)
- Biliary excretion (liver)
This structured overview provides insights into pharmacokinetics while linking back to specific timestamps for further exploration.
Understanding Drug Concentrations and Their Effects
Key Concepts of Drug Concentration
- The minimum effective concentration (MEC) of a drug is defined as the smallest amount required to achieve a therapeutic effect. This is crucial for determining the appropriate dosage for treatment.
- Conversely, the minimum toxic concentration (MTC) refers to the least amount of a drug that can cause toxic effects. Understanding this threshold helps in avoiding adverse reactions during treatment.
- The range between MEC and MTC is known as the therapeutic window, which indicates where a drug can be effective without causing toxicity. This concept is vital for safe medication administration.
- Any concentration below the MEC is considered ineffective, meaning it will not produce any therapeutic benefits. This highlights the importance of proper dosing in pharmacotherapy.
- Similarly, concentrations above the MTC are deemed toxic, emphasizing the need for careful monitoring of drug levels in patients to prevent harmful side effects.