NRSG 540 Module 3 .pdf

MODULE 3: PHAMACOKINETICS and PHARMACODYNAMICS Pharmacokinetics The study of drug movement throughout the body and how the body deals with medications There are 4 processes of pharmacokinetics 4 Processes of Pharmacokinetics Absorption Distribution Loading… Metabolism Excretion...

MODULE 3: PHAMACOKINETICS and PHARMACODYNAMICS Pharmacokinetics The study of drug movement throughout the body and how the body deals with medications There are 4 processes of pharmacokinetics 4 Processes of Pharmacokinetics Absorption Distribution Loading… Metabolism Excretion Absorption Process involving movement of a substance from its site of administration, across body membranes, to circulating fluid Most drugs must be absorbed to produce an effect Absorption is the primary pharmacokinetic factor determining factor determining the length of time it takes for a drug to produce its effect Factors that Influence Absorption Drug formulation Dose Route of administration Size of drug molecule Loading… Surface area of absorption site Digestive motility Blood flow Lipid solubility Ionization Certain foods Distribution Transport of drugs t/o the body after being absorbed or injected Simplest factor determining distribution is blood supply Some tissues have ability to accumulate and store drugs after absorbed Not all drug molecules in plasma reach target cells due to protein binding Distribution Drug-drug interactions effect distribution: Addition Synergism Antagonism Displacement Distribution Blood brain barrier- Some medications cross the blood brain barrier to produce action in the CNS, some do not which makes treatment hard Fetal placental barrier- Mother barrier with placental to fetus Metabolism Process of chemically converting a drug to a form that is more easily removed by the body Liver is the primary site of drug metabolism, however kidneys and cells of the intestinal tract also have high metabolic rates Most metabolism in the liver is accomplished by the hepatic microsomal enzyme system Metabolism Hepatic microsomal enzyme system CYP enzymes primary actions are to inactivate drugs and accelerate their excretion Metabolism CYP enzymes may produce a metabolite that produces a greater therapeutic action that the original drug Loading… Some drugs have the ability to increase metabolic activity- enzyme induction Some drugs have the ability to reduce metabolic activity in the liver- enzyme inhibitors Metabolism After oral administration, drugs cross directly into the hepatic portal circulation, which carries blood to the liver before distributing to other parts of the body As blood passes through liver circulation and are some drugs are completely metabolized to an inactive form– this is called first pass effect Excretion Process of how drugs are removed from the body Primary site of excretion is the kidneys, although excretion also occurs in the respiratory system, gallbladder, biliary tract Biliary excretion leads back to liver excretion– enterohepatic recirculation Excretion Factors that can affect drug excretion Liver and kidney impairment Blood flow Degree of ionization of the drug Lipid solubility of the drug Protein-drug complexes Metabolic activity Acidity or alkalinity Respiratory, glandular or biliary action Drug Plasma Concentration and Therapeutic Response Therapeutic response of most drugs is related to their plasma levels Minimum effective concentration– amount of drug required to produce a therapeutic effect Toxic concentration– amount of drug that will results in serious adverse reactions Onset, Peak Levels, and Duration of Drug Action Onset- amount of time it takes a drug to produce a therapeutic effect after administration Peak plasma level- when medication has reached its highest concentration in the blood stream Duration of action- amount of time a drug maintains its therapeutic effect  Plasma half life- time it takes for T Loading Doses and Maintenance Doses Loading dose- higher amount of drug given to quickly increase blood plasma levels Maintenance dose- given to keep plasma drug concentration in a therapeutic range Pharmacodynamics How medications change the body Frequency distribution curve Median effective dose Therapeutic Index and Drug Safety Median lethal dose Therapeutic index Median toxicity dose Graded Dose Response and Therapeutic Response Phase 1– lowest doses; few target cells hit Phase 2- shows increase in dose = increased response Phase 3- plateau where increasing the drug provides no additional therapeutic response Potency and Efficacy Potency- Indicates the strength of a Efficacy- Ability of a drug to drug in eliciting a therapeutic produce a desired therapeutic effect effect; A highly potent drug when administered at a sufficient requires a lower dose to achieve the dose desired effect compared to a less potent drug Cellular Receptors Types of Drug-Receptor Interactions Agonist Partial agonist Antagonist Pharmacokinetics or Pharmacodynamics??? Metabolites excreted in urine Pharmacokinetics or Pharmacodynamics??? Reduced blood clotting Pharmacokinetics or Pharmacodynamics??? Increases intracellular calcium in cardiac cells by inhibiting the Na+/K+ ATPase pump Pharmacokinetics or Pharmacodynamics??? Bioavailability of around 70-80% when taken orally Pharmacokinetics or Pharmacodynamics??? Renal clearance is the primary route of elimination Pharmacokinetics or Pharmacodynamics??? Loading… The therapeutic effect is pain relief and reduction of inflammation  Questions, comments, concerns