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?

Physiological dependence Signup and view all the answers

What is the term for drugs that are sold illegally?

Illicit drugs 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?

Diluted via endo-tracheal route Signup and view all the answers

Which factor does NOT influence drug absorption in the body?

Weather conditions Signup and view all the answers

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

They are best absorbed in the intestine. Signup and view all the answers

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

Paracetamol Signup and view all the answers

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

Grape juice Signup and view all the answers

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

Vitamin C Signup and view all the answers

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

Solutions Signup and view all the answers

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

They should be enteric coated. Signup and view all the answers

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

Morphine Signup and view all the answers

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

Onset of drug action is slow Signup and view all the answers

Which drug source utilizes the Genetic Engineering technique?

Insulin Signup and view all the answers

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

Local application Signup and view all the answers

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

Insulin Signup and view all the answers

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

They resist being broken down by gastric acid Signup and view all the answers

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

Monoclonal Antibodies Signup and view all the answers

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

Intravenous administration Signup and view all the answers

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

Inhalations Signup and view all the answers

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

It is difficult for patients to manage. Signup and view all the answers

Which of the following drugs can be administered sublingually?

Nitroglycerin Signup and view all the answers

Which method uses a galvanic current to facilitate drug absorption?

Iontophoresis Signup and view all the answers

What is a potential risk associated with inhalation drug administration?

Direct cardiac tissue effects Signup and view all the answers

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

Thalidomide Signup and view all the answers

What does pharmacodynamics primarily study?

Biological and therapeutic effects of drugs Signup and view all the answers

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

Permanent inactivation of the enzymes Signup and view all the answers

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

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

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

Young's formula Signup and view all the answers

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

Reduced renal function affecting drug clearance Signup and view all the answers

What is the consequence of tolerance in drug administration?

Increased dosage to achieve the same effect Signup and view all the answers

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

Hypersensitivity Signup and view all the answers

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

Effects vary significantly based on the administration route Signup and view all the answers

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

Type A Signup and view all the answers

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

Simultaneously stimulates and blocks receptor activity Signup and view all the answers

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

Digitalis with continuous administration Signup and view all the answers

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

Decrease the dose 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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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.