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Distribution NURS 1060: Exam 2 1 Review of Pharmacokinetics Four Basic Processes Absorption Distribution Metabolism Excretion 2 OUTCOME  Discuss critical thinking and clinical reasoning to provide quality patie...

Distribution NURS 1060: Exam 2 1 Review of Pharmacokinetics Four Basic Processes Absorption Distribution Metabolism Excretion 2 OUTCOME  Discuss critical thinking and clinical reasoning to provide quality patient care 3 COMPETENCY  Discuss critical thinking and clinical judgment used to provide accurate and safe medication administration. 4 CONCEPT  Clinical Decision Making: A process used to examine and determine the best actions to meet desired goals; requires anticipating, recognizing and organizing patient problems to respond with urgency and/or importance in a preferential order to avoid or minimize adverse changes in a patient’s condition.  Acid-Base Balance: The physiological mechanisms that maintain blood pH critical to homeostasis and optimal cell function. 5 Unit Outcomes  Discuss the phase of drug distribution.  Explain the concept of drug protein binding on distribution.  Contrast loading and maintenance doses.  Explain concepts related to plasma drug level.  Discuss concepts related to time course of a drug response 6  Movement of the drug from Distribution the blood to the site of action or storage area 7  Blood flow to tissues Drug Distribution Exiting the vascular Determined system by Three Factors Entering cells 8 Blood Flow to Tissues  Drugs are carried by the blood to tissues and organs of the body.  Blood flow determines the rate of delivery.  Abscesses and tumors  Low regional blood flow impacts therapy.  Pus-filled pockets, not internal blood vessels  Solid tumors have limited blood supply.  This is one reason treatment of abscesses and tumors can be difficult – the amount of drug to the site is reduced 9 Blood Flow to Tissues High blood flow regions: Slower blood flow regions: Heart, liver, kidney, brain Muscle ,bone, skin 10 Exiting the Vascular System  Capillary walls:  Ionized drugs pass between capillary cells.  Non ionized or lipid soluble drugs pass between and also directly through the lipid membrane of cells of the capillary wall. 11 Protein Binding  Drugs can form reversible bonds with protein.  Plasma albumin is the most important protein drugs bind with.  Albumin is a LARGE molecule that always remains in the bloodstream  Protein binding maintains a consistent level of drug in the blood  Prolongs drug action and constantly maintains drug levels 12 Protein Binding Bound Drug Drugs attached to protein/albumin in the blood Free Drug Drug not attached to protein/albumin in the blood 13 Protein Binding  Only free drug can travel to the site of action or a cell  Bound drug stays in the blood stream  Competing for protein binding sites will occur when the client is taking two drugs that are protein bound. Both drugs have an increase in the amount of free drug and a decrease in the amount of bound drug. Adverse reaction of toxicity can occur. 14 Protein Binding  Albumin is the most prevalent protein in plasma and the most important of the proteins to which drugs bind.  Only unbound (free) drug molecules can leave the vascular system. Bound molecules are too large to fit through the pores in the capillary wall. 15 Entering Cells  Drugs can enter cells to:  reach the site of action  undergo metabolism and excretion  Many drugs produce their effects by binding with receptors on the external surface of the cell membrane.  Key and Lock fit  Do not need to cross the cell membrane to act Time and Drug Responses Plasma Drug  Promote patient safety of Levels maximum benefit with minimum harm.  Individualize dosage for THIS Clinical patient. Significance 18 Plasma Drug Levels  Two plasma drug levels:  Minimum effective concentration (MEC) – lowest therapeutic level  Toxic concentration – above the therapeutic range  Therapeutic range is between MEC and toxic concentration 19 Minimum Effective Concentration  The amount of drug needed for the effects to start appearing.  Once the level falls below the minimum effective concentration, the effect is over. 20   The objective of drug dosing Therapeutic is to maintain plasma drug Range levels within the therapeutic range. 21 Half-Life  Time required for the concentration of a drug to reduce to half of its initial dose after reaching its peak.  Decrease by 50%  Often determines the dosing interval  When the amount of drug eliminated = the next dose administered the drug levels should be constant and plateau will be reached 22 Administer 2 grams of a drug daily Half – life is ??? What day is plateau reached? 23 Half Life Apply Your Knowledge Question Administer 16 mg of a drug with a half life of 2 hours: After 2 hours, how many mg will remain in the body? 24 Small Group Activity  Divide into groups of 2-3 students  Example Drug Information  Dose Given = 100 mg (one time dose) (% of maximum) Concentration  Drug Half Life = 60 minutes  Draw your own version of the example drug on a graph  How many half-lives were needed before most the drug(>95%) was removed from the body? Time  Explain your answer. Show your work! 25 Half-Life and Clearance 26 Risks of a Drug with Long Half-life  The longer the half-life, the longer it takes for the drug to leave the body.  Some drugs take days due to long half-life  Risk for toxicity is a safety concern  Example: digitoxin was replaced by digoxin because it has a shorter half-life  What if the patient is allergic to the drug with a long half- life? 27  Loading dose large initial dose or doses of Loading and a long-acting drug given to quickly reach the MEC Maintenance Doses Maintenance doses smaller doses used to keep the drug above the MEC 28  Patient is experiencing irregular heart rate  Loading and Administer a loading dose to reduce heart rate NOW Maintenance  Digoxin 0.5 mg STAT Doses  Administer daily at a lower dose to MAINTAIN heart rate  Digoxin 0.125 mg daily Example 29 Case Study A nurse is caring for a 75-year-old female who recently was admitted to the surgical floor for a total knee replacement. He is prescribed tramadol 50 mg every 6 hours for moderate pain. The patient complains of pain in the knee, rating it at a “6.” 1. When does the nurse anticipate the medication will peak in action? 2. When does the nurse anticipate another dose will be needed due to the duration of this drug? 30