Introduction to Pharmacology

Introduction and General Pharmacology

• Pharmacology is the study of drugs, particularly their actions on animals, organs, and tissues
• Treatments in early times involved flesh, blood, excreta of animals, plant, and metal preparations
• A drug is any substance or product used to modify or explore physiological systems or pathological states for the recipient's benefit (WHO definition)
• Drugs are derived from the word "drogue," meaning herb.

Types of Medications

• Medication: A substance used for diagnosis, cure, treatment, mitigation, or prevention.
• Prescription: Written directions for drug preparation and administration.
• Therapeutic effect: Intended primary effect of a drug. (e.g., morphine sulfate is analgesia)
• Side effect: Unintended secondary effect of a drug. (e.g., diarrhea with Mg-Antacids)

Pharmacokinetics

• Pharmacokinetics: The study of absorption, distribution, metabolism, and excretion of drugs, and their relation to the pharmacologic response.
• Pharmacodynamics: A quantitative study of biological and therapeutic effects of drugs (how the drug impacts the body).
• Poisons: Substances that cause harm, danger, or death in animals or humans.
• Chemotherapy: The effect of drugs on microorganisms and parasites, including cancer treatment.

Drug Codes and Information Sources

• Pharmacopoeia: An official code with a selected list of established drugs and preparations, describing physical properties, purity, and potency.
• Formulary: Provides information on available drugs based on sources and expert recommendations.

Drug Toxicity, Allergy, and Interactions

• Drug toxicity: Deleterious effect on an organism or tissue due to overdose or external use.
• Drug allergy: Immunological reaction or hypersensitivity to a drug (e.g., penicillin hypersensitivity).
• Drug interaction: Effects of administering one drug before or after another, sometimes altering their effects. (e.g., caffeine and Alprazolam show no interaction)

Drug Abuse and Dependence

• Drug abuse: Inappropriate intake of a substance, occasional or continual. (e.g., alcohol abuse).
• Drug dependence: A person's reliance or need to take a drug or substance.
  • Physiological dependence: Due to biochemical changes in the body tissue, needing the substance for normal function (e.g., heroin dependence)
  • Psychological dependence: Emotional reliance on a drug to maintain well-being with a feeling of need (e.g., nicotine dependence)

Drug Tolerance, Habituation, and Illicit Drugs

• Drug tolerance: Body tissue changes causing the body to require increasing doses for normal function. (e.g., Marijuana usage may cause tolerance).
• Drug habituation: A mild form of psychological dependence. (e.g., habituation to cigarettes).
• Illicit drugs: Drugs sold illegally (e.g., cocaine)

Various Names of Drugs

• Generic name: A shortened version of a drug's chemical name, structure, or formula.
• Official name: Name used in official publications.
• Chemical name: Name used by chemists.
• Trade name: Name given by the manufacturer (e.g., Esidrex).

The Nature and Sources of Drugs

• Mineral sources: Liquid paraffin, magnesium sulfate, magnesium trisilicate, kaolin
• Animal sources: Insulin, thyroid extract, heparin, gonadotropins, anti-toxic sera
• Plant sources: Morphine, digoxin, quinine, atropine, reserpine
• Micro-organism sources: Antibiotics like penicillin, Polymixin B
• Synthetic sources: Analgesics, hypnotics, anti-cancer agents, antimicrobials
• Genetic engineering: Insulin, growth hormone
• Hybridoma Technique: Monoclonal antibodies

Routes of Drug Administration

• Local application: For topical use (e.g., ointments)
• Oral route: Administration through the mouth (e.g., pills, tablets).
• Parenteral route: Administration other than through the mouth via injection (intramuscular, intravenous etc).
• Intradermal: Into the layers of the skin (e.g., BCG vaccine).
• Subcutaneous: Under the skin (e.g., Insulin, sex hormone implants).
• Intramuscular: Into muscle tissue (e.g., diazepam).
• Intravenous: Into veins (e.g., large volume fluids).
• Intra-arterial: Into arteries (Used in diagnostic studies)
• Intra-thecal: Drugs directly into the spinal cord membranes (e.g., spinal anesthesia.)
• Intra-peritoneal: Into peritoneal cavities (e.g., infant saline administration).
• Intraosseous cannulation: Into the bone, often used in shock cases (e.g., adrenaline).
• Inhalations: Administration via vapors or aerosol (e.g., pressurized metered dose aerosols, dry powders, or nebulized solutions).
• Transcutaneous: Across the skin (e.g., iontophoresis).
• Sublingual: Under the tongue (e.g., nitroglycerin).
• Trans nasal: Through the nose (e.g., vasopressin).
• Trans rectal: Into the rectum (e.g., aminophylline).
• Endo-tracheal: Into the trachea (after dilution) (e.g., adrenaline).

Enteric Coated Pills and Tablets

• Enteric-coated tablets dissolve in the intestine, not the stomach, to avoid stomach irritation.

Pharmacokinetics (ADME)

• Absorption: Drugs moving from administration site to systemic circulation
• Factors influencing absorption: Physico-chemical properties of drugs, pharmaceutical form of the drug, pH of the gut, rate of dissolution, presence of other substances, first pass effect
• First pass effect: Drugs metabolized by the liver during initial passage, thus reducing bioavailability (e.g., Proponolol)
• Oral bioavailability: Percentage of the drug that reaches the systemic circulation after oral administration.

Factors Modifying Dosage and Action of Drugs

• Age: Infants are more susceptible to drug effects due to underdeveloped enzyme systems. Lower dose required according to age and weight.

• Sex/Gender: Women generally need lower doses than men (Fat content and hormone differences).

• Women may have greater sensitivity or different reactions to certain drug types. Prescriptions should be individualized.

Routes of Administration and Their Impacts

• Administration routes affect the drug's action. Magnesium sulfate is a purgative when administered orally, and dehydrating agent when administered rectally.

Drug Intolerance and Tolerance

• Drug Intolerance: Decrease drug dose due to super-sensitivity.
• Drug Tolerance: Failure to respond to a drug.
• Can be congenital (genetic) or acquired (due to repetitive use).

Types of Tolerance, Hypersensitivity, and Idiosyncrasy

• Tachyphylaxis:Rapidly diminishing response to successive doses of a drug.
• Cross-tolerance: Tolerance between related drugs.
• Hypersensitivity: Exaggerated immune response to a drug (Allergic reaction).
• Idiosyncrasy: Abnormal response to a drug due to genetic or enzyme factors (e.g., peripheral neuritis)

Drug Dependence and Addiction

• Habituation/dependence: Emotional or psychological dependence on the drug, emotional distress if stopped.
• Addiction: A state of psychic craving for or physiological dependence on a drug. Intense withdrawal symptoms if stopped.

Pathological State Affecting Drug Effects

• Patient's condition affects drug actions. Aspirin lowers temperature to normal, but not below normal.

Drug Accumulation and Adverse Drug Reactions

• Drug accumulation: When drug administration rate exceeds elimination, leading to adverse reactions.
• Adverse Drug Reactions: Unwanted medical responses to a drug.
  • Predictable (Type A): Dose dependent, related to drug action.
  • Unpredictable (Type B): Dose independent, due to genetic or enzyme factors.
  • Continuous (Type C): Long-term use leading to cell or organ damage.
  • Delayed (Type D): Effects showing up after prolonged use.
  • Withdrawal (Type E): Effects when drug use is stopped suddenly.

Drug Combinations

• Combining different drugs may affect their actions
• Addition/Summation (1+1=2)
• Synergism (1+1=3)
• Potentiation (1+1=2)
• Antagonism (1+1=0)

Drug Classification: Adverse Effects

• Provides a useful way to classify drug effects, recognizing the different types of adverse reactions and how they manifest based on dose, timing and origin.

This quiz covers the fundamentals of pharmacology, including the definition of drugs, types of medications, and an overview of pharmacokinetics. Understand the therapeutic effects, side effects, and historical context of drug use. Test your knowledge in this essential field of study.