Introduction to Pharmacology

Introduction to Pharmacology

• Pharmacology is the science of drugs.
• It examines how chemical agents, including drugs, hormones, neurotransmitters, and toxins, affect living processes.
• Pharmacology also studies how drugs interact with biological systems to change function.
• It encompasses the study of drug origin, physical and chemical properties, mechanisms of action, effects, and uses.

What is a Drug?

• A drug is any substance or product intended to alter or explore physiological or pathological states for the recipient's benefit.
• Drugs are used for diagnosis, prevention, and treatment of diseases.
• A drug is any chemical or biological substance, synthetic or not, that, when introduced into an organism's body, alters its functions.
• Drugs are distinguished from endogenous biochemicals by being introduced from outside the organism. Insulin, for example, is a hormone when produced within the body, but a drug when administered externally.

Drug vs. Medicine

• A drug is any substance designed to create a specific reaction in the body.
• A medicine is any substance designed to prevent or treat diseases.
• Drugs can have positive or negative effects, while medicines' effects are always beneficial.
• Some drugs are addictive, while medicines are not.

Sources of Drugs

• Drugs can originate from animals (oil, steroids, hormones like thyroxine and insulin)
• Minerals (inorganic sources like magnesium trisilicate, MgSO4, CaCO3)
• Plants (alkaloids, glycosides, tannins, anthraquinones like yohimbine, atropine, vincristine)

Drug Nomenclature

• There are four types of drug names:
  • Chemical name: describes the chemical structure (e.g., propan-2-ol). It's often complex and hard to use.
  • Code name: used during early research to hide the drug (e.g., R015-1788/Flumazenil).
  • Generic name: accepted by a scientific body like USAN (United States Adopted Name Council). It's also called the non-proprietary name.
  • Proprietary name: assigned by the manufacturer (e.g., ciprotab, spardium, sparflux). It's also called the brand name.

Effects of Drug Actions

• Adverse effects: Unwanted effects that can occur at therapeutic doses. They may be predictable or unpredictable, and their frequency often increases with dosage.
  • Idiosyncrasy: Genetically based abnormal reactions to drugs.
• Overdosage/Toxicity: Excessive drug intake. This may stem from a single high dose, or repeated moderate doses. Examples of drug toxicity include hemorrhage from anticoagulant overdose.
• Hypersensitivity/Allergy: Reactions based on previous exposure involving an antigen-antibody reaction.
• Tolerance: decreased responsiveness to a drug. It might be acute (short-lasting) or chronic (long-lasting).

Combined Effect of Drugs

• Antagonism: Drugs that counteract each other's effects.
• Synergism: The combined effect is greater than the sum of individual effects.
• Additivity: The combined effect is equivalent to the sum of individual effects.
• Potentiation: One drug strengthens the effect of a second drug.

Pharmacology Sub-divisions/Branches

• Pharmacokinetics: How the body handles drugs—absorption, distribution, metabolism, and excretion.

• Pharmacodynamics: How drugs affect the body—mechanism of action, drug–receptor interactions, dose–response relationships.

• Toxicology: Study of harmful effects of chemicals on living systems.

• Pharmacotherapeutics: Study of using drugs in treatment of disease (clinical management of diseases).

• Pharmacogenetics: Variations in drug response due to genetics.

• Pharmacoepidemiology: Effects of drugs on populations.

• Pharmacogenomics: Use of genetic information to guide drug choices.

• Chemotherapy: Treatment using drugs to fight microorganisms.

• Behavioral pharmacology: Studies of drugs' effects on behavior.

• Biochemical and Cellular pharmacology: The mechanisms of action of drugs at a cellular level.

• Clinical pharmacology: the study of pharmacodynamics and pharmacokinetics in humans.

• Psychopharmacology: The effects of drugs on mood, behavior and other responses

• Veterinary pharmacology: The use of drugs in animals

• Molecular pharmacology: the biophysical and biochemical interactions of drug molecules with cells.

• Systems Pharmacology: Drug effects and toxicity in whole organisms.

• Neuropharmacology: The nervous system's responses to drugs.

• Endocrine Pharmacology: Hormone-related responses to drugs.

• Cardiovascular pharmacology: Study on the heart, vascular system and endocrine systems that regulate cardiovascular function.

• Relationships among various subdisciplines are complex; The field continues to advance*