Understanding Pharmacology: From Basic Principles to Nature of Drugs


Pharmacology is a multidisciplinary field that explores the interactions between chemicals and biological systems. It encompasses various sub-disciplines, including medical pharmacology, toxicology, pharmacokinetics, and pharmacodynamics. This article aims to provide an overview of these areas and delve into the nature of drugs, their molecular characteristics, and how they interact with biological receptors.

The Scope of Pharmacology

Medical Pharmacology

Medical pharmacology focuses on the use of chemicals in the prevention, diagnosis, and treatment of diseases, particularly in humans. It aims to understand how drugs can be effectively used to alleviate symptoms, cure diseases, or even prevent them altogether.


Toxicology, on the other hand, studies the adverse or undesirable effects of chemicals on biological systems. This area is crucial for assessing the safety profile of drugs and understanding their limitations.


Pharmacokinetics deals with how the body affects drugs, including processes like absorption, distribution, metabolism, and excretion. Understanding pharmacokinetics is essential for determining the appropriate dosage and administration route for drugs.


Pharmacodynamics explores the actions of drugs on the body, including their mechanisms of action and their therapeutic and toxic effects. This knowledge is vital for predicting how drugs will interact with biological systems and for developing new therapeutic agents.

The Nature of Drugs

Types of Drugs

Drugs can be classified based on their origin and chemical structure. They may include:

  • Inorganic ions
  • Nonpeptide organic molecules
  • Small peptides and proteins
  • Nucleic acids
  • Lipids
  • Carbohydrates

Some drugs are derived from plants or animals, while others are partially or entirely synthetic. Alkaloids, which are often found in nature, are molecules with a basic pH, usually due to amine groups in their structure.

Optical Activity and Enantiomers

Many biologically important molecules and drugs are optically active, meaning they contain one or more asymmetric centers and can exist as enantiomers. These enantiomers often differ significantly in their affinity for biological receptors and may also be metabolized at different rates, leading to varying clinical outcomes.

Size and Molecular Weight

The molecular weight of drugs can range from as low as 7 (e.g., lithium) to over 50,000 (e.g., thrombolytic enzymes, antibodies). Most drugs have molecular weights between 100 and 1000. Drugs smaller than 100 are usually not selective enough, while those larger than 1000 are often poorly absorbed and distributed.

Drug-Receptor Bonds

Drugs can bind to receptors through various types of chemical bonds, including:

  • Strong covalent bonds (usually irreversible)
  • Weaker electrostatic bonds
  • Even weaker interactions like hydrogen, van der Waals, and hydrophobic bonds


Pharmacology is a complex field that integrates various disciplines to understand the interaction between drugs and biological systems. From the basic principles of pharmacokinetics and pharmacodynamics to the intricate nature of drugs and their development, pharmacology continues to be a cornerstone in the advancement of medical science.

Bibliography: Katzung & Trevor’s Pharmacology: Examination & Board Review, 10e Trevor AJ, Katzung BG, Kruidering-Hall MM, Masters SB. Trevor A.J., & Katzung B.G., & Kruidering-Hall M.M., & Masters S.B.(Eds.),Eds. Anthony J. Trevor, et al.

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Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always seek the advice of a healthcare provider with any questions regarding a medical condition.

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