Pharmacology Chapter on Drug Absorption
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Questions and Answers

What is drug allergy characterized by?

  • Hypersensitive reaction to a drug (correct)
  • Biochemical changes in the body
  • Emotional reliance on a drug
  • Improper use of medications

    • Which combination illustrates a drug interaction that results in no effect?

  • Caffeine + Alprazolam (correct)
  • Caffeine + Alcohol
  • Penicillin + Morphine
  • Tetracycline + Aspirin

    • What term describes the inappropriate intake of substances, either periodically or continually?

  • Drug habituation
  • Drug tolerance
  • Drug abuse (correct)
  • Drug misuse

    • What type of dependence is characterized by biochemical changes requiring a substance for normal function?

    <p>Physiological dependence</p> Signup and view all the answers

    What is the term for drugs that are sold illegally?

    <p>Illicit drugs</p> Signup and view all the answers

    What is the primary route of drug administration for drugs such as adrenaline and naloxone when using an endo-tracheal tube?

    <p>Diluted via endo-tracheal route</p> Signup and view all the answers

    Which factor does NOT influence drug absorption in the body?

    <p>Weather conditions</p> Signup and view all the answers

    Which statement about the absorption of weak basic drugs is correct?

    <p>They are best absorbed in the intestine.</p> Signup and view all the answers

    Which of the following drugs is most affected by the first pass effect?

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

    Which food item is known to enhance the bioavailability of all drugs?

    <p>Grape juice</p> Signup and view all the answers

    To increase the absorption of iron, which of the following can be used?

    <p>Vitamin C</p> Signup and view all the answers

    Which pharmaceutical form of a drug is generally absorbed the fastest?

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

    What happens to drugs that are gastric irritants or are destroyed by gastric mucosa?

    <p>They should be enteric coated.</p> Signup and view all the answers

    Which of the following is not a mineral source of drugs?

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

    What is a significant disadvantage of the oral route of drug administration?

    <p>Onset of drug action is slow</p> Signup and view all the answers

    Which drug source utilizes the Genetic Engineering technique?

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

    Which of the following routes of administration is primarily used for local effects?

    <p>Local application</p> Signup and view all the answers

    Which of the following drugs is destroyed by digestive juices and therefore cannot be administered orally?

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

    What is a common characteristic of enteric-coated pills and tablets?

    <p>They resist being broken down by gastric acid</p> Signup and view all the answers

    The hybridoma technique is used to produce which of the following?

    <p>Monoclonal Antibodies</p> Signup and view all the answers

    Which method of administration is used for drugs in emergencies and unconscious patients?

    <p>Intravenous administration</p> Signup and view all the answers

    Which of the following methods of drug administration can lead to rapid effects?

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

    What is a disadvantage of self-medication mentioned in the content?

    <p>It is difficult for patients to manage.</p> Signup and view all the answers

    Which of the following drugs can be administered sublingually?

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

    Which method uses a galvanic current to facilitate drug absorption?

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

    What is a potential risk associated with inhalation drug administration?

    <p>Direct cardiac tissue effects</p> Signup and view all the answers

    Which of the following drugs is known to actively pass through the fetal barrier?

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

    What does pharmacodynamics primarily study?

    <p>Biological and therapeutic effects of drugs</p> Signup and view all the answers

    What is the likely effect of enzymes when inhibited by irreversible antagonists?

    <p>Permanent inactivation of the enzymes</p> Signup and view all the answers

    How is the plasma half-life of a drug defined?

    <p>The time required for the drug concentration to reduce by half</p> Signup and view all the answers

    Which formula is used to calculate drug dosage for children based on age?

    <p>Young's formula</p> Signup and view all the answers

    What is the primary concern when administering drugs to elderly patients?

    <p>Reduced renal function affecting drug clearance</p> Signup and view all the answers

    What is the consequence of tolerance in drug administration?

    <p>Increased dosage to achieve the same effect</p> Signup and view all the answers

    Which type of drug reaction is characterized by an exaggerated immune response?

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

    What effect does the administration route have on a drug such as magnesium sulfate?

    <p>Effects vary significantly based on the administration route</p> Signup and view all the answers

    Which type of drug reaction is characterized as being predictable and dose-dependent?

    <p>Type A</p> Signup and view all the answers

    What best describes the action of a partial agonist at a receptor site?

    <p>Simultaneously stimulates and blocks receptor activity</p> Signup and view all the answers

    Which of the following drugs is most likely to cause cummulation?

    <p>Digitalis with continuous administration</p> Signup and view all the answers

    What is the most appropriate response when a drug is causing drug intolerance due to increased sensitivity?

    <p>Decrease the dose</p> Signup and view all the answers

    Study Notes

    Endo-tracheal Route

    • Drugs administered through the endo-tracheal route should be diluted before administration.
    • Examples of such drugs include adrenaline, atropine, lignocaine, and naloxone.

    Absorption

    • Absorption is the process of drug entry from the administration site into the systemic circulation.

    Factors Influencing Absorption

    • Physico-chemical properties: Ferrous salts are absorbed better than ferric salts. Vitamin C enhances iron absorption.
    • Pharmaceutical form of the drug: Solutions are absorbed faster than suspensions or tablets.
      • Drugs are absorbed faster through the lungs than sublingually, through the intestine than the gastric mucosa, and by the intramuscular route than the subcutaneous route.
    • pH within the gut: Weak acidic drugs are absorbed from the stomach, while weak basic drugs are absorbed from the intestine.
    • Gastric irritants and drug destruction: Drugs that irritate the gastric mucosa (like salicylates) and are destroyed by it (like insulin) are enteric-coated.
    • Rate of dissolution and gut motility: A faster rate of dissolution leads to faster absorption. Sustained-release formulations prolong the duration of action.
    • Presence of other substances in the lumen: Food, calcium, and iron decrease tetracycline absorption. Fatty meals enhance griseofulvin absorption. Grape juice increases the bioavailability of all drugs.

    First Pass Effect (Pre-Systemic Metabolism)

    • Some drugs are metabolized in the liver during their first pass through it, reducing their bioavailability. Examples include benzyl penicillin, insulin, and paracetamol.
    • Strategies to overcome first-pass metabolism include:
      • Increasing the oral dose: e.g., propranolol.
      • Using alternative routes: e.g., intravenous lidocaine, sublingual nitroglycerine.

    Bioavailability

    • The percentage of the drug that reaches systemic circulation unchanged and becomes available for biological effects after administration by any route. IV administration has 100% bioavailability.

    Distribution

    • Drugs move from the systemic circulation to various tissues and organs.
    • Penicillin has limited passage through the normal blood-brain barrier, but penetrates readily in acute bacterial meningitis.
    • Drugs cross the fetal barrier actively, including thalidomide, diphenylhydantoin, tetracyclines, corticosteroids, anti-thyroid drugs, and aspirin.

    Pharmacodynamics

    • The study of biological and therapeutic effects of drugs, including their mechanisms of action.

    Mechanisms of Action

    • Physical Action: e.g., kaolin adsorbs toxins during diarrhea.
    • Chemical Action: e.g., sodium bicarbonate neutralizes hydrochloric acid in gastritis.
    • Action on enzymes: Drugs can stimulate or inhibit enzymes, with effects varying in duration and reversibility.

    Drug-Receptor Interactions

    • Affinity: The tendency of a drug to bind to a receptor.
    • Potency: The amount of drug required to elicit a response.
    • Efficacy: The magnitude of biological response.
    • Competitive Antagonism: An agonist can displace a competitive antagonist from a receptor with increased agonist concentration.
    • Non-Competitive Antagonism: An agonist cannot displace a non-competitive antagonist from a receptor.
    • Partial Agonist: Partially stimulates and blocks receptors.
    • Inverse Agonist: Produces effects opposite to that of an agonist.

    Elimination Half-Life (t½)

    • The time it takes for the plasma concentration of a drug to decrease by half. For example, a drug with a t½ of 4 hours will have its concentration halved every four hours.
    • It depends on drug clearance.
    • Important for determining the time required to reach a steady-state concentration in the body.

    Factors Modifying Dosage and Drug Action

    • Age:
      • Newborns: More susceptible to drug effects due to underdevelopment of microsomal enzymes, reduced excretion, and an underdeveloped blood-brain barrier.
      • Infants: Clark's formula for dosage: (Adult dose X Weight in Kgs) / 70
      • Children: Young's formula for dosage: (Adult dose X Age in years) / (Age +12)
      • Elderly:
        • 60-70 years: ¾ of adult dose
        • Above 70 years: ½ of adult dose.
    • Sex/Gender: Women typically require smaller doses of drugs than men due to differences in fat content and enzyme activity influenced by sex hormones.
    • Routes of Administration: - IV > Sublingual & Inhalation > IM > SC > Oral - The route of administration affects the drug's action. For example, magnesium sulfate is a purgative when given orally, a dehydrating agent rectally, and an anticonvulsant and calcium antagonist intravenously.
    • Drug Intolerance: Decreased dose required due to hypersensitivity.
    • Tolerance: Decreased response to the usual drug dose.
      • Congenital: Due to racial, species, or individual variations.
      • Acquired: Due to repeated drug administration.
    • Special Types of Tolerance:
      • Tachyphylaxis: Rapidly diminishing response to successive doses. e.g., ephedrine in blood pressure.
      • Cross Tolerance: Tolerance between related drugs. e.g., ethyl alcohol and general anesthetics.
    • Hypersensitivity (Allergic Reactions): Exaggerated immune response. May not occur on the first dose but does on subsequent doses. Not dose-dependent.
    • Idiosyncrasy (Pharmacogenetics): Abnormal effect due to genetic or enzyme differences. e.g., peripheral neuritis with slow isoniazid metabolizers.
    • Drug Dependence:
      • Habituation: Emotional or psychological dependence. Withdrawal leads to emotional distress. e.g., cigarette smoking.
      • Addiction: Psychic craving or physiological dependence. Withdrawal leads to severe reactions. e.g., marijuana, amphetamine.
    • Pathological State: e.g., Aspirin lowers body temperature to normal but not below normal.
    • Cummulation: Drug accumulation occurs when administration exceeds elimination, leading to adverse reactions and interactions. e.g., digitalis.
    • Emotional State (Placebo Effect): Inert dosage forms produce psychological effects. Used in drug testing.
    • Drug Combinations:
      • Addition or Summation: 1 + 1 = 2
      • Synergism: 1 + 1 = 3
      • Potentiation: 1 + 1 = 2
      • Antagonism: 1 + 1 = 0

    Toxicity of Drugs (Adverse Drug Reactions)

    • Unpredictable:
      • Idiosyncrasy
      • Allergic reactions (Hypersensitivity reactions).
    • Predictable:
      • Overdose toxicity
      • Teratogenic effect
      • Long-acting sulfonamides can induce jaundice in babies.
      • Chloramphenicol can lead to blood complications.
      • Smoking and radiation can cause cancer.
      • Streptomycin can damage the 8th cranial nerve.
      • Prolonged antibiotic use can lead to superinfection and vitamin B and K deficiencies.

    Type A Adverse Drug Reactions (Augmented)

    • Predictable and dose-dependent.
    • Extension of the drug's pharmacological action.
    • Examples:
      • Hypoglycemia by insulin.
      • Excess bleeding by warfarin.
      • Bronchoconstriction by propranolol.
      • Pupil constriction by prazosin.

    Type B Adverse Drug Reactions (Bizarre)

    • Unpredicted and dose-dependent.
    • Often opposite reactions occurring due to genetic abnormalities.
    • Examples:
      • Benzodiazepines causing excitement in females.
      • Isoniazid inducing peripheral neuritis.
      • Succinylcholine causing apnea.
      • Primaquine causing hemolysis.
      • Anaphylactic reactions with penicillin.

    Type C Adverse Drug Reactions

    • Continuous, leading to cell damage.
    • Examples:
      • Bleomycin causing pulmonary fibrosis.
      • Cyclosporine causing nephrotoxicity.
      • Paracetamol causing hepatotoxicity.
      • Anticancer agents causing decreased sexual characteristics.

    Type D Adverse Drug Reactions

    • Delayed reactions occurring after prolonged drug use.
    • Examples:
      • Thalidomide causing phocomelia.
      • Phenytoin causing cleft lip and cleft palate.
      • Valproate causing spina bifida.
      • Warfarin causing microcephali.

    Drug Allergy

    • Immunological or hypersensitive reaction to a drug. Example: Penicillin drug hypersensitivity.

    Drug Interaction

    • Occurs when the administration of one drug alters the effect of another drug, either before or after administration. Examples:
      • Caffeine + Alprazolam = No effect.
      • Tetracycline + Calcium = No effect.

    Drug Misuse

    • The improper use of common medications. Example: Vitamin B complex is one of the most abused drugs globally.

    Drug Abuse

    • Inappropriate intake of a substance, either continually or periodically. Example: Alcohol is the most abused drug worldwide.

    Drug Dependence

    • Reliance on or a need to take a drug or substance.
    • Physiological Dependence: Biochemical changes in tissues require the substance for normal function. Example: Drug addiction to morphine, amphetamine.
    • Psychological Dependence: Emotional reliance on a drug for well-being, accompanied by a feeling of need. Example: Cigarette smoking.

    Drug Tolerance

    • Biochemical changes in tissues require increasing drug doses for the same effect. Example: Marijuana use can cause tolerance.

    Drug Habituation

    • A mild form of psychological dependence. Examples: Habituation to coca leaves, cigarette and hookah smoking.

    Illicit Drugs

    • Drugs sold illegally. Example: Amphetamine, Cocaine.

    Various Names of Drugs

    • Generic name: A shorthand version of the drug's chemical name, structure, or formula.
    • Official name: The name listed in official publications.
    • Chemical name: The name known by chemists.
    • Trade mark or brand name (proprietary name): The name given by the drug manufacturer.
    • Example: Hydrochlorothiazide (official name), Esidrex (brand name)

    The Nature and Sources of Drugs

    • Mineral Source: Liquid Paraffin, Magnesium Sulphate, Magnesium Trisilicate, Kaolin.
    • Animal Source: Insulin, Thyroid extract, Heparin, Gonadotropins, Anti toxic sera.
    • Plant Source: Morphine, Digoxin, Quinine, Atropine, Reserpine.
    • Micro-organisms Source: Antibiotics like Penicillin, Polymixin B.
    • Synthetic Source: Analgesics, Hypnotics, Anticancer agents and antimicrobials.
    • Genetic Engineering: Insulin and growth hormone, Genes.
    • Hybridoma Technique: Monoclonal Antibodies.

    Routes of Drug Administration

    • Local Application (Local Route): Action at site of application. Examples: Dusting Powder, Paste, Lotions, Drops, Ointments, Plasters, Bougie for urethra, Pessary for vagina, Suppository for vagina and rectum.
    • Oral or Enteral Route: Drugs administered through the mouth. Examples: Tablets, Pills, Capsules.
      • Advantages: Most common route, safe, convenient, economical.
      • Disadvantages: Slow onset of action, irritant and unpalatable drugs cannot be administered, not suitable for vomiting/diarrhea, not for unconscious patients, drugs destroyed by digestive juices cannot be administered.
    • Parenteral Route:
      • Advantages: Rapid onset, useful for unconscious patients, suitable for irritant/unpalatable drugs.
      • Disadvantages: Inconvenient, less safe, risk of infection, potential for vein/nerve injury, more expensive.
    • Enteric Coated Pills and Tablets: Coated to prevent breakdown in the stomach, for drugs sensitive to gastric acids.
    • Inhalations: Rapid effects. Examples: Pressurized metered dose aerosols (salbutamol, beclomethasone), dry powder inhalers (salmeterol), nebulized solutions (salbutamol).
    • Transcutaneous Drug Administration:
      • Iontophoresis: Galvanic current facilitates drug absorption to deeper tissues.
      • Inunction: Drugs rubbed into the skin. Example: Nitroglycerin.
      • Jet injection: High-velocity drug injection through the skin. Example: Insulin.
      • Adhesive Units: Nicotine patches, scopolamine for motion sickness.
    • Transmucosal:
      • Sublingual Administration: Example: Nitroglycerin.
      • Trans Nasal Route: Example: Vasopressin, Calcitonin.
    • Trans Rectal Route: Rectum has a rich blood and lymph supply. Examples: Aminophylline, diazepam.

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    Lecture 1, General Pharmacology PDF

    Description

    Explore the concepts of drug administration, particularly through the endo-tracheal route, and understand the factors influencing drug absorption. This quiz covers examples of drugs, their absorption mechanisms, and how various properties affect their entry into systemic circulation.

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