Lesson 2 Pharmacokinetics PDF

Lesson 2 Pharmacokinetics 3° Medicine Professor: Vittoria Carrabs PhD Academic year: 2024/25  Summary 1. INTRODUCTION. 2. TRANSPORT ACROSS BIOLOGICAL MEMBRANES 3. LIBERATION 4. ADME: Ø Absorption Ø Distribution Ø Metabolism Ø Excretion 2...

Lesson 2 Pharmacokinetics 3° Medicine Professor: Vittoria Carrabs PhD Academic year: 2024/25  Summary 1. INTRODUCTION. 2. TRANSPORT ACROSS BIOLOGICAL MEMBRANES 3. LIBERATION 4. ADME: Ø Absorption Ø Distribution Ø Metabolism Ø Excretion 2  PHARMACOKINETICS Biological system Drug PHARMACODYNAMICS Pharmacokinetics: is a branch of pharmacology that studies the fate of the drug in the organism as a function of time and dose (LADME). *what body does to the administered drug (how the body absorbs, distributes, metabolises and eliminates the drug) 3  iberation is the process of release of drug 1 from the formulation. Absorption bsorption: is the process of a substance Liberation entering the blood circulation. istribución: is the dispersion or 2 dissemination of substances throughout the fluids and tissues of the body 3 Metabolism Distribution etabolism: is the irreversible transformation of compounds into metabolites. xcretion: is the elimination of the substances from the body. 4 Excretion  iberation Process in which the drug is separated from the other components of the pharmaceutical specialty. ü The release ends with the drug dissolving (ready to be absorbed) ü All dosage forms, except those in which the drug is administered as a solution, undergo the release process.. UNIT 2: Pharmacokinetics 6  bsorption Absorption is the process of a substance entering from the administration site to the blood circulation. Passage into RELEASE of the Dissolution of the drug the drug bloodstream -the drug must cross biological membranes It´s affected by : Solubility. Concentration. Absorption surface. Blood flow at absorption surface. Administration route. 7  bsorption ü FACTORS THAT MODIFY THE ABSORPTION OF DRUGS: → Drug Concentration: Passive Diffusion Concentrated solution >> Diluted solution 9  bsorption ü FACTORS THAT MODIFY THE ABSORPTION OF DRUGS: → Dosage form: - Liquid forms are usually absorbed more quickly than solid forms. - small particles=better absorption Solution > Capsule > Tablet 10  bsorption ü FACTORS THAT MODIFY THE ABSORPTION OF DRUGS: → Routes of administration: – Your choice will depend on the type of treatment, the pharmacokinetic characteristics of the drug and the patient's conditions. – Drugs administered by IV have no absorption process. IV > IM > Oral 11  bsorption ü FACTORS THAT MODIFY THE ABSORPTION OF DRUGS: → Routes of administration: - IMMEDIATE OR DIRECT: Drugs do not undergo alterations before reaching their action site. - MEDIATE OR INDIRECT: The drug must pass through the skin or mucous membranes and may suffer alterations.  bsorption ü FACTORS THAT MODIFY THE ABSORPTION OF DRUGS: ü → Routes of administration: Route Start of action Examples Subcutaneous Several minutes Insulin, heparin IMMEDIATE Intramuscular Several minutes Antibiotics, narcotics OR DIRECT Intravenous 1 minute An t i can cer Intraarterial 1 minute An t i can cer Or al 30-60 minutes Most medications MEDIATE O Sublingual Several minutes Nitroglycerin in angina pectoris INDIRECT Rectal 15-30 minutes Analgesics, laxatives Topical 1 hour Creams and oils bsorption Types of route of administration: » ORAL Administration route. – Barrier : digestive tract – Most drugs use this route of administration – Less predictable route of administration – The absorption is better when: Lipidic or non-ionised molecules The stomach is empty Acid drugs (stomach) particle size (small ones) UNIT 2: Pharmacokinetics 14 bsorption PARENTERAL Administration route. IV: avoids the absorption process. – SC an IM: Place the drug close to capillary vessels. – SC and IM: are faster than oral. – SC is slower than IM administration (more vascularization) UNIT 2: Pharmacokinetics 15 bsorption PARENTERAL Administration route. Disadvantages of the parenteral route: Ø Requires instruments for its realization, which must be properly sterilized. Ø Requires a qualified person to use it. Ø Promotes local infection Ø In case of an adverse reaction to the drug, the intensity of the reaction is usually greater, and the reaction time is shorter compared to the oral route. 16 bsorption » TOPICAL Administration route (Dermal, …) The systemic absorption depends on drug lipophility. Damaged skin allows the easy entrance of compounds. When topical effects are desired, systemic absorption can be a disadvantage. Transdermal patch 17  bsorption »BIOAVAILABILITY Bioavailability represents absorption. Bioavailability (F): represents the fraction of the administered dose of a drug that enters into the systemic circulation in its active form, and the rapidity at which this occurs. IV: Bioavailability of 100%. Other routes: lower bioavailability 18  bsorption Bioavailability must be considered when calculating dosages for non-IV routes. F is affected by factors that modify absorption, distribution and metabolism (accelerated intestinal transit, hepatic first pass effect, age, sex, genetic phenotype, existence of diseases, etc.). The bioavailability is measured by calculating the AUC (Area Under Curve) 19 bsorption Area Under the Curve (AUC): A measure of the total amount of plasma drug over time after IV or extravascular administration of the drug 20  bsorption »ABSOLUTE BIOAVAILABILITY Absolute bioavailability compares the bioavailability of non-IV WITH IV administration. The comparison must be dose normalized. The absolute bioavailability for an oral administered drug: IV: (F=1). 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