Pharmacokinetics: Linear vs Non-linear
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Questions and Answers

What must be balanced with the economic cost of obtaining patient data?

  • Benefits to patient outcomes (correct)
  • Training of laboratory personnel
  • Availability of resources
  • The complexity of testing procedures

    • Which of the following factors can contribute to variations in normal values in laboratory tests?

  • Geographical location of the patient
  • Laboratory techniques and reagents used (correct)
  • Type of specimen collected
  • Patient's medical history

    • Which area of the clinical lab focuses on the analysis of blood cells?

  • Hematology (correct)
  • Bacteriology
  • Clinical chemistry
  • Molecular diagnostics

    • What type of test is a Complete Blood Count (CBC) classified as?

    <p>The most common laboratory test</p> Signup and view all the answers

    What characterizes linear pharmacokinetics?

    <p>The rate of elimination is proportional to the amount of drug present.</p> Signup and view all the answers

    In non-linear pharmacokinetics, what happens to the rate of elimination as drug concentration changes?

    <p>It remains constant regardless of drug concentration.</p> Signup and view all the answers

    Which factor is NOT a potential cause of laboratory errors?

    <p>Laboratory personnel's education level</p> Signup and view all the answers

    The analysis of serum, urine, and body fluids is typically done in which of the following areas?

    <p>Clinical chemistry</p> Signup and view all the answers

    What is one possible explanation for unexpected steady-state concentrations after a dosage change in non-linear kinetics?

    <p>Saturated plasma protein binding sites.</p> Signup and view all the answers

    Which of the following medical terminologies refers to 'water'?

    <p>Hydr/o</p> Signup and view all the answers

    Which of the following drugs is known to exhibit non-linear pharmacokinetics due to autoinduction of drug metabolism?

    <p>Carbamazepine.</p> Signup and view all the answers

    Which laboratory division is responsible for DNA testing?

    <p>Molecular diagnostics</p> Signup and view all the answers

    Which condition explains the transition from linear to non-linear kinetics observed in drugs?

    <p>Enzyme saturation.</p> Signup and view all the answers

    Which of the following statements is true about drugs following Michaelis-Menten kinetics?

    <p>Their metabolism becomes non-proportional after enzyme saturation.</p> Signup and view all the answers

    What is meant by 'saturable pharmacokinetics'?

    <p>It describes a situation where metabolic enzymes are fully utilized.</p> Signup and view all the answers

    Which of the following best describes the impact of increasing dosage on plasma drug levels in linear pharmacokinetics?

    <p>It results in a proportionate increase in plasma drug levels.</p> Signup and view all the answers

    What could indicate an increased white blood cell (WBC) count?

    <p>Corticosteroid use</p> Signup and view all the answers

    What does a 'shift to the left' indicate in a WBC differential count?

    <p>An increase in immature neutrophils (bands)</p> Signup and view all the answers

    Which of the following conditions could lead to neutropenia?

    <p>Use of chemotherapy drugs</p> Signup and view all the answers

    What is the primary function of neutrophils?

    <p>Fight bacterial and fungal infections</p> Signup and view all the answers

    What percentage of circulating WBCs is typically comprised of lymphocytes?

    <p>20%-40%</p> Signup and view all the answers

    Which scenario is most likely to lead to leukopenia?

    <p>Viral infections like mononucleosis</p> Signup and view all the answers

    What is the clinical significance of a WBC count exceeding 50,000 cells/mm3?

    <p>May cause false elevations in hemoglobin and MCH</p> Signup and view all the answers

    What condition might result from drug-induced bone marrow suppression?

    <p>Decreased WBC count</p> Signup and view all the answers

    What is the significant platelet count threshold below which the risk of bleeding increases?

    <p>50,000/μL</p> Signup and view all the answers

    Which laboratory value indicates potential acute myocardial infarction when elevated above 4-5% of total CK?

    <p>CK-MB</p> Signup and view all the answers

    What could cause an elevation in total CK levels?

    <p>Seizures</p> Signup and view all the answers

    What is the normal range for CK-MB levels?

    <p>Less than 12 IU/L</p> Signup and view all the answers

    What is the primary location of Troponin I?

    <p>Cardiac muscle</p> Signup and view all the answers

    How soon do CK-MB levels typically rise after the onset of an acute myocardial infarction?

    <p>Within 4 - 6 hours</p> Signup and view all the answers

    Which of the following best describes the MCV value mentioned in the laboratory data?

    <p>It indicates the size of red blood cells.</p> Signup and view all the answers

    Which of the following conditions would NOT typically lead to an elevation in total CK levels?

    <p>Hypotension</p> Signup and view all the answers

    What does a high INR indicate during Warfarin treatment?

    <p>Blood is too thin, risk of excessive bleeding</p> Signup and view all the answers

    What is the typical target range for INR in patients on Warfarin?

    <p>2.0 - 3.0</p> Signup and view all the answers

    Which substance can interfere with INR levels by promoting blood clotting?

    <p>Vitamin K-rich foods</p> Signup and view all the answers

    What does a low aPTT indicate in patients undergoing heparin therapy?

    <p>Increase the heparin infusion rate</p> Signup and view all the answers

    Which of the following measures may be taken for patients with elevated INR and bleeding?

    <p>Administer vitamin K</p> Signup and view all the answers

    What is the normal range for activated Partial Thromboplastin Time (aPTT)?

    <p>20 - 35 seconds</p> Signup and view all the answers

    How is aPTT primarily used in clinical practice?

    <p>To monitor HEPARIN therapy</p> Signup and view all the answers

    What intervention should be taken when aPTT is found to be high?

    <p>Hold or reduce the heparin dose</p> Signup and view all the answers

    Study Notes

    Pharmacokinetics: Linear vs Non-linear

    • Linear kinetics: Drug elimination rate is proportional to the amount of drug present.
    • Non-linear kinetics: Drug elimination rate is constant regardless of drug amount.
    • Michaelis-Menten Kinetics: Follows linear kinetics until enzymes become saturated.

    Examples of Non-linear Pharmacokinetics

    • Valproic Acid: Saturated plasma protein binding sites
    • Carbamazepine: Autoinduction of drug metabolism

    Key Factors Influencing Pharmacokinetics

    • Saturation of enzymes responsible for drug metabolism: Causes a non-proportional increase in drug levels.

    Examples of Drugs Exhibiting Non-linear Kinetics

    • Phenytoin
    • Salicylic Acid

    Importance of Lab Tests in Patient Care

    • Necessary for clinical decision-making
    • Used to monitor treatment effectiveness
    • Serum, urine, and bodily fluid samples are analyzed
    • Consider the cost-benefit analysis of lab testing
    • Be mindful of potential false-positive and false-negative results.

    Normal Values in Laboratory Tests

    • Vary between laboratories depending on techniques and reagents
    • Fluctuate based on patient age, gender, weight, height, and other factors.

    Clinical Microbiology

    • Includes bacteriology, virology, parasitology, immunology, and mycology

    Clinical Chemistry

    • Analyzes blood specimens like enzymology, toxicology, and endocrinology

    Hematology

    • Analyzes blood cells, including coagulation

    Blood Bank

    • Conducts blood specimen testing for transfusions

    Molecular Diagnostics

    • Performs DNA testing, including cytogenetics.

    Common Laboratory Tests in Clinical Practice

    • Complete Blood Count (CBC)
    • Electrolytes
    • Blood Chemistries
    • Urinalysis (UA)
    • Disease-Specific Tests

    Laboratory Errors

    • Occur rarely but can happen
    • Potential causes: Technical error, improper calculation, inadequate specimen, incorrect sampling timing, improper sample preservation, food substances affecting specimen, or medication interference with laboratory tests.

    White Blood Cells (WBCs)

    • Normal Range: 3,200–11,300 cells/mm3
    • WBC count with differential: Provides a breakdown of the percentage of each type of WBC.

    Clinical Significance of WBCs

    • Increased WBCs (leukocytosis): Infection, leukemia, trauma, thyroid storm, corticosteroid use
    • Decreased WBCs (leukopenia): Viral infection, aplastic anemia, bone marrow suppression due to chemotherapy or immunosuppressants

    Neutrophils

    • Most common type of WBCs
    • Fight bacterial and fungal infections
    • Involved in the pathogenesis of some inflammatory disorders

    Clinical Significance of Neutrophils

    • Increased Neutrophils (Neutrocytosis or Neutrophilia): Infection, metabolic disorders, uremia, response to stress, emotional disturbances, burns, acute inflammation, use of medications such as corticosteroids
    • Decreased Neutrophils (Neutropenia): Viral infections, septicemia, use of chemotherapy drugs

    Absolute Neutrophil Count (ANC)

    • Total number of circulating segments and bands
    • Increased risk of infection as ANC decreases
    • Normal Range: 20%-40%

    Lymphocytes

    • Second most common type of circulating WBCs
    • Normal Range: 20%-40%

    Platelets

    • Important for blood clotting
    • Low platelets can result in bleeding, especially below 50,000/μL

    Case Study: Olympic Bicyclist

    • RBC: 4.2 × 106 cells/mm3
    • Hgb: 14 g/dL
    • Hct: 42%
    • MCV: 90 μm3/cell
    • MCH: 31 pg/cell
    • MCHC: 36 g/dL
    • WBC differential:
      • Segs: 65%
      • Bands: 10%
      • Lymphocytes: 17%
      • Monocytes: 5%
      • Eosinophils: 2%
      • Basophils: 0.5 %

    Cardiac Tests: Creatine Kinase (CK)

    • Enzyme found in skeletal and cardiac muscle
    • Three isoenzymes: CK-MM (skeletal muscle), CK-BB (brain), CK-MB (cardiac tissue)
    • CK-MB: Important marker for acute myocardial infarction (AMI)

    Clinical Significance of Total CK

    • Trauma
    • Surgery
    • Shock
    • Seizures
    • Muscular dystrophy
    • Cerebrovascular accident
    • Polymyositis
    • Dermatomyositis
    • Chronic alcoholism
    • Reye’s syndrome
    • Malignant hyperthermia

    Clinical Significance of CK-MB

    • Normal Range: Less than 12 IU/L or less than 4% of total CK
    • Serial CK-MB tests are useful in diagnosing AMI
    • Elevation greater than 4%-5% of total CK suggests acute MI
    • Levels rise 4-6 hours after MI onset, peak at 12-24 hours, and return to normal in 2-3 days

    Troponin

    • Family of proteins found in skeletal and cardiac muscle fibers
    • Troponin I: Found solely in cardiac muscle
    • Troponin T: Found in both cardiac and skeletal muscle
    • Troponin I and T: Sensitive markers of cardiac injury

    International Normalized Ratio (INR)

    • Ratio of patient's prothrombin time (PT) to international reference thromboplastin
    • Used to monitor warfarin treatment
    • High INR: Blood is too thin, risk of excessive bleeding
    • Low INR: Blood is too thick, risk of clotting or thrombosis
    • Target INR: Usually 2.0-3.0 depending on patient condition

    Clinical Significance of INR

    • INR below desired range: Suboptimal anticoagulation, need to increase warfarin dosage
    • INR above desired range: Need to omit or reduce warfarin dosage
    • Treatment for elevated INR or bleeding: Vitamin K, fresh frozen plasma, or clotting factors

    Factors Affecting INR

    • Ingestion of vitamin K-rich foods
    • Alcoholism
    • Diarrhea and vomiting
    • Technique of blood draw
    • Medications

    Activated Partial Thromboplastin Time (aPTT)

    • Normal Range: 20-35 seconds
    • Useful for detecting bleeding disorders caused by deficient or defective coagulation factors
    • Used to monitor heparin therapy
    • Not typically monitored for low-molecular-weight heparin (LMWH)

    Clinical Significance of aPTT

    • Elevated aPTT: Patient on heparin therapy
    • Therapeutic range depends on the laboratory's reagent
    • Low aPTT: Need to increase heparin infusion rate
    • High aPTT: Need to hold or reduce heparin dosage

    Key Differences Between PT and aPTT

    • PT: Evaluates the extrinsic pathway of coagulation, uses thromboplastin and calcium.
    • aPTT: Evaluates the intrinsic pathway of coagulation, employs partial thromboplastin and calcium.

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    Pharmacotherapy I PDF

    Description

    Explore the differences between linear and non-linear pharmacokinetics, including key concepts like Michaelis-Menten kinetics. Learn about various drugs that exhibit these pharmacokinetic properties and the significance of lab tests in patient care. Assess how saturation of enzymes affects drug metabolism and treatment effectiveness.

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