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Questions and Answers
What is drug allergy characterized by?
Which combination illustrates a drug interaction that results in no effect?
What term describes the inappropriate intake of substances, either periodically or continually?
What type of dependence is characterized by biochemical changes requiring a substance for normal function?
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What is the term for drugs that are sold illegally?
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What is the primary route of drug administration for drugs such as adrenaline and naloxone when using an endo-tracheal tube?
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Which factor does NOT influence drug absorption in the body?
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Which statement about the absorption of weak basic drugs is correct?
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Which of the following drugs is most affected by the first pass effect?
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Which food item is known to enhance the bioavailability of all drugs?
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To increase the absorption of iron, which of the following can be used?
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Which pharmaceutical form of a drug is generally absorbed the fastest?
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What happens to drugs that are gastric irritants or are destroyed by gastric mucosa?
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Which of the following is not a mineral source of drugs?
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What is a significant disadvantage of the oral route of drug administration?
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Which drug source utilizes the Genetic Engineering technique?
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Which of the following routes of administration is primarily used for local effects?
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Which of the following drugs is destroyed by digestive juices and therefore cannot be administered orally?
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What is a common characteristic of enteric-coated pills and tablets?
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The hybridoma technique is used to produce which of the following?
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Which method of administration is used for drugs in emergencies and unconscious patients?
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Which of the following methods of drug administration can lead to rapid effects?
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What is a disadvantage of self-medication mentioned in the content?
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Which of the following drugs can be administered sublingually?
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Which method uses a galvanic current to facilitate drug absorption?
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What is a potential risk associated with inhalation drug administration?
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Which of the following drugs is known to actively pass through the fetal barrier?
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What does pharmacodynamics primarily study?
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What is the likely effect of enzymes when inhibited by irreversible antagonists?
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How is the plasma half-life of a drug defined?
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Which formula is used to calculate drug dosage for children based on age?
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What is the primary concern when administering drugs to elderly patients?
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What is the consequence of tolerance in drug administration?
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Which type of drug reaction is characterized by an exaggerated immune response?
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What effect does the administration route have on a drug such as magnesium sulfate?
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Which type of drug reaction is characterized as being predictable and dose-dependent?
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What best describes the action of a partial agonist at a receptor site?
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Which of the following drugs is most likely to cause cummulation?
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What is the most appropriate response when a drug is causing drug intolerance due to increased sensitivity?
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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.
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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
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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)
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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.
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Tolerance: Decreased response to the usual drug dose.
- Congenital: Due to racial, species, or individual variations.
- Acquired: Due to repeated drug administration.
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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.
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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.
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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)
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Unpredictable:
- Idiosyncrasy
- Allergic reactions (Hypersensitivity reactions).
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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.
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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.
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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).
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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.
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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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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.
