Pharmacology and Toxicology: Excretion and Clearance
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Questions and Answers

Which of the following substances are secreted in breast milk?

  • Lithium and Tetracycline
  • Benzodiazepines and Nicotine (correct)
  • Salicylic acid and Benzoic acid
  • Chloramphenicol and Heavy metals

    • What is the sum of all clearances from the drug-metabolizing and drug-eliminating organs?

  • Rate of elimination
  • Dosage
  • Half-life
  • Total body clearance (correct)

    • What is the rate of elimination in first-order kinetics?

  • Independent of drug concentration
  • Constant, regardless of drug concentration
  • Proportional to the square of the drug concentration
  • Proportional to the drug concentration (correct)

    • What is the characteristic of zero-order kinetics?

    <p>The rate of elimination is constant, regardless of drug concentration</p> Signup and view all the answers

    What is the relationship between half-life and administration of a drug?

    <p>A low half-life requires frequent administration</p> Signup and view all the answers

    What determines the duration of action of a drug?

    <p>Rate of elimination and dosage</p> Signup and view all the answers

    What is the equation for the rate of elimination in first-order kinetics?

    <p>Elimination rate = k.C1</p> Signup and view all the answers

    Which of the following drugs follows zero-order kinetics?

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

    What is the characteristic feature of fibrinoid necrosis in arterial walls?

    <p>Deposition of bright-pink amorphous material</p> Signup and view all the answers

    What is the mechanism of enzymatic fat necrosis?

    <p>Lipase activation from injured pancreatic cells or macrophages</p> Signup and view all the answers

    What is the characteristic gross appearance of fat necrosis?

    <p>White, chalky areas</p> Signup and view all the answers

    What is the result of lipase activation in enzymatic fat necrosis?

    <p>Release of fatty acids from triglycerides</p> Signup and view all the answers

    What is the characteristic histological feature of fat necrosis?

    <p>Vague cell outlines and calcium deposition</p> Signup and view all the answers

    What is the characteristic feature of tuberculosis-specific granulomatous inflammation?

    <p>Involvement of epiteloid histiocytes and Langhans type giant cells</p> Signup and view all the answers

    What is the field of study concerned with the actions, interactions, and mechanism of action of drugs?

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

    What is the result of the complexation of fatty acids with calcium in enzymatic fat necrosis?

    <p>Formation of soaps</p> Signup and view all the answers

    What is the primary function of lysosomes in intracellular killing of microorganisms?

    <p>To fuse with phagosomes and form phagolysosomes</p> Signup and view all the answers

    What type of microbicidal agents are produced by neutrophils through oxygen-dependent mechanisms?

    <p>Hydrogen peroxide and myeloperoxidase</p> Signup and view all the answers

    What is the role of mast cells in acute inflammation?

    <p>To release preformed inflammatory mediators and synthesise new ones</p> Signup and view all the answers

    What type of inflammation is characterized by the presence of a fibrinous exudate and dilated blood vessels?

    <p>Serous inflammation</p> Signup and view all the answers

    What is the byproduct of oxygen reduction that contributes to the killing of microorganisms?

    <p>Peroxide anions and hydroxyl radicals</p> Signup and view all the answers

    What is the function of lactoferrin in oxygen-independent mechanisms of microbicidal activity?

    <p>To chelate iron required for bacterial growth</p> Signup and view all the answers

    What type of inflammation is characterized by the presence of pus?

    <p>Suppurative inflammation</p> Signup and view all the answers

    What is the role of myeloperoxidase in oxygen-dependent microbicidal mechanisms?

    <p>To react with hydrogen peroxide to produce a potent microbicidal agent</p> Signup and view all the answers

    Which chemical mediator is NOT involved in vascular dilatation during acute inflammation?

    <p>IL-1</p> Signup and view all the answers

    Which of the following chemical mediators is involved in the transient phase of increased vascular permeability?

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

    Which chemical mediator is involved in neutrophil polymorph chemotaxis?

    <p>IL-8</p> Signup and view all the answers

    What is the function of tissue macrophages during acute inflammation?

    <p>To secrete numerous chemical mediators</p> Signup and view all the answers

    Which chemical mediator is involved in both vascular dilatation and increased vascular permeability?

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

    What is the role of leucotriene B4 in acute inflammation?

    <p>It is involved in neutrophil polymorph chemotaxis</p> Signup and view all the answers

    Which chemical mediator is involved in the upregulation of adhesion molecules on endothelium?

    <p>All of the above</p> Signup and view all the answers

    What is the role of prostaglandins in increased vascular permeability?

    <p>They potentiate the action of other chemical mediators</p> Signup and view all the answers

    What is the primary mechanism of action of Rifampin in regards to mycobacterial cell walls?

    <p>Inhibition of mycolic acid synthesis</p> Signup and view all the answers

    Which of the following adverse effects is unique to Ethambutol?

    <p>Optic neuritis</p> Signup and view all the answers

    What is the primary mechanism of resistance to Rifampin?

    <p>Mutations in the embB gene</p> Signup and view all the answers

    What is the effect of Ethambutol on bacterial growth?

    <p>Slowed growth and replication</p> Signup and view all the answers

    Which of the following is a common adverse effect of Rifampin?

    <p>Red-orange discoloration of body secretions</p> Signup and view all the answers

    What is the target enzyme of Ethambutol?

    <p>Arabinosyl transferase</p> Signup and view all the answers

    What is the primary effect of Ethambutol on mycobacterial cell walls?

    <p>Increased permeability</p> Signup and view all the answers

    Which of the following antibiotics can be used in combination with Ethambutol?

    <p>All of the above</p> Signup and view all the answers

    Study Notes

    Mammary Excretion

    • Benzoic acid, salicylic acid, alcohol, and heavy metals like lead, mercury, and arsenic can be excreted into milk
    • Chloramphenicol, lithium, tetracycline, benzodiazepines, and nicotine can also be excreted into milk

    Total Body Clearance

    • Total body clearance (CLtotal) is the sum of all clearances from the drug-metabolizing and drug-eliminating organs
    • Clearance is the proportionality factor used to determine the rate of elimination
    • Rate of elimination = CL x Concentration

    Half-Life (t1/2) of a Drug

    • Half-life (t1/2) refers to the time required for plasma concentration of a drug to decrease by 50%
    • Low half-life: Frequent administration
    • High half-life: Should be given once or twice daily

    Elimination Kinetics

    • Rate of elimination is the rate of disappearance of active molecules from the bloodstream or body
    • Rate of elimination and dosage determine the duration of action of a drug
    • There are two types of elimination kinetics:
      • First-order kinetics (linear): rate of elimination is proportional to drug concentration
      • Zero-order kinetics (non-linear): rate of elimination is constant, regardless of drug concentration

    First-Order Kinetics

    • Rate of elimination = k.C1
    • Plasma drug concentration (Cp) decreases exponentially with time
    • Half-life is constant

    Zero-Order Kinetics

    • Elimination rate = k
    • Drug concentration in plasma (Cp) decreases linearly with time
    • Examples: phenytoin, alcohol, heparin, aspirin at high dose

    Fat Necrosis

    • Fat necrosis is seen in adipose tissue
    • Types of fat necrosis:
      • Enzymatic fat necrosis: occurs in the surrounding adipose tissue under the action of pancreatic lipases
      • Traumatic fat necrosis: occurs in breast and subcutaneous fat tissues
    • Grossly, fat necrosis appears as white, chalky areas (fat saponification)
    • Histologically, there are vague cell outlines and calcium deposition

    Fibrinoid Necrosis

    • Fibrinoid necrosis is a pathologic pattern resulting from antigen-antibody (immune complex) deposition in blood vessels
    • Microscopically, there is bright-pink amorphous material (protein deposition) in arterial walls, often with associated inflammation and thrombosis
    • Example: polyarteritis nodosa

    Pharmacodynamics

    • Pharmacodynamics is concerned with the actions, interactions, and mechanisms of action of drugs
    • Table 9.2 summarizes the chemical mediators involved in the three main stages of acute inflammation:
      • Vascular dilatation: histamine, prostaglandins, PGE2/I2, VIP, nitric oxide, PAF
      • Increased vascular permeability: transient phase—histamine, prolonged phase—bradykinin, nitric oxide, C5a, leucotriene B4, PAF, potentiated by prostaglandins
      • Adhesion of leucocytes to endothelium: upregulation of adhesion molecules on endothelium, principally by IL-8, C5a, leucotriene B4, PAF, IL-1, and TNF-alpha

    Role of Tissue Macrophages

    • Macrophages secrete numerous chemical mediators when stimulated by local infection or injury
    • Lysosomes (membrane-bound packets containing toxic compounds) fuse with phagosomes to form phagolysosomes
    • Intracellular killing of microorganisms occurs

    Role of Neutrophils

    • Neutrophils are highly specialized cells, containing microbicidal agents
    • Microbicidal agents may be classified as:
      • Oxygen-dependent mechanisms: hydrogen peroxide, myeloperoxidase, halide, Cl-, peroxide anions, hydroxyl radicals, singlet oxygen
      • Oxygen-independent mechanisms: lysozyme, lactoferrin, cationic proteins, low pH inside phagocytic vacuoles

    Role of Mast Cells

    • Mast cells have an important role in acute inflammation
    • On stimulation by the C3a/C5a complement components, they release preformed inflammatory mediators stored in their granules and metabolize arachidonic acid into newly synthesized inflammatory mediators

    Adverse Effects of Rifampin

    • Red-orange discoloration of body secretions (urine, sweat, tears)
    • Hepatotoxicity (hepatitis most serious) (mainly in patients having preexisting liver disease)
    • Allergic reactions (fever, skin rash)
    • Gastrointestinal upset; nausea, vomiting, and diarrhea
    • Hematologic effects; hemolytic anemia, thrombocytopenia

    Ethambutol

    • Inhibits arabinosyl transferase (gene names = embA, embB, and embC)—important for the synthesis of the mycobacterial arabinogalactan cell wall
    • Bacteriostatic
    • Targets the enzyme arabinosyl transferase, leading to incomplete and defective cell wall formation
    • Can be used in combination with other anti-TB drugs

    Mechanisms of Resistance to Rifampin

    • Mutations in the embB gene, reducing its affinity for ethambutol

    Adverse Effects of Ethambutol

    • Optic neuritis; causing loss of visual acuity and red-green color blindness

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    Description

    This quiz covers the excretion of pharmacological substances, including antibiotics and heavy metals, via milk and other routes, as well as the concept of total body clearance in pharmacokinetics.

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