Introduction
Definition
Pharmacology is the branch of science that deals with the study of drugs, including their origin, composition, pharmacokinetics, therapeutic use, and potential side effects.
Pharmacology has several branches, including:
1. **Pharmacokinetics:** Examines how the body absorbs, distributes, metabolizes, and excretes drugs.
2. **Pharmacodynamics:** Focuses on the mechanisms of drug action and the physiological effects within the body.
3. **Pharmacogenetics/Pharmacogenomics:** Explores the role of genetics in individual responses to drugs.
4. **Toxicology:** Studies the adverse effects of drugs and other chemicals on living organisms.
5. **Clinical Pharmacology:** Involves the application of pharmacological principles in clinical settings, optimizing drug therapy.
6. **Neuropharmacology:** Concentrates on drugs affecting the nervous system.
7. **Cardiovascular Pharmacology:** Studies drugs related to the heart and circulatory system.
8. **Immunopharmacology:** Examines the interactions between drugs and the immune system.
9. **Chemotherapy:** Focuses on drugs used in the treatment of cancer.
**Natural Sources of Drugs:**
1. **Plants:** Many drugs originate from plant sources. Examples include aspirin from willow bark and morphine from the opium poppy.
2. **Animals:** Some drugs, like insulin, are derived from animal tissues.
3. **Microorganisms:** Antibiotics like penicillin are produced by certain bacteria and fungi.
4. **Minerals:** Substances like lithium and magnesium are used as therapeutic agents.
**Synthetic Sources of Drugs:**
1. **Laboratory Synthesis:** Many drugs are created through chemical synthesis in laboratories, allowing for precise control over their composition.
2. **Biotechnological Production:** Advances in biotechnology enable the production of drugs using genetically modified organisms or cell cultures.
3. **Semisynthetic Drugs:** These are partially synthesized from natural sources and modified to enhance their therapeutic properties.
Dosage forms and routes of drug administration
**Dosage Forms:**
1. **Tablets and Capsules:** Solid forms containing the drug, often with added ingredients for stability.
2. **Liquid Preparations:** Including solutions, suspensions, and syrups.
3. **Topical Formulations:** Creams, ointments, patches applied to the skin for localized effects.
4. **Injections:** Intravenous (IV), intramuscular (IM), and subcutaneous (SC) injections for rapid drug delivery.
5. **Suppositories:** Solid dosage forms inserted into body cavities, often rectally.
6. **Inhalants:** Gases or aerosols for respiratory absorption, such as inhalers.
**Routes of Drug Administration:**
1. **Oral:** Through the mouth, either swallowed or sublingual (under the tongue).
2. **Intravenous (IV):** Directly into the bloodstream, ensuring rapid onset.
3. **Intramuscular (IM):** Injected into a muscle, providing a slower release than IV.
4. **Subcutaneous (SC):** Injection under the skin, suitable for certain medications.
5. **Topical:** Applied to the skin or mucous membranes for localized effects.
6. **Inhalation:** Administered through the respiratory system for rapid absorption.
7. **Rectal:** Suppositories or enemas for absorption through the rectum.
**Terminology Used in Pharmacology:**
1. **Drug:** Any substance used for the diagnosis, treatment, or prevention of a disease.
2. **Pharmacokinetics:** The study of how the body absorbs, distributes, metabolizes, and excretes drugs.
3. **Pharmacodynamics:** The study of the biochemical and physiological effects of drugs and their mechanisms of action.
4. **Bioavailability:** The fraction of a drug that reaches the systemic circulation unchanged and the rate at which this occurs.
5. **Half-life:** The time it takes for half of the drug to be eliminated from the body.
6. **Adverse Effect:** Undesirable and potentially harmful effect of a drug.
7. **Placebo:** A substance with no therapeutic effect, used in clinical trials to assess the efficacy of a drug.
8. **Therapeutic Index (TI):** The ratio of the dose that produces toxicity to the dose that produces a therapeutic response.
9. **Generic Name:** The non-proprietary name of a drug, often derived from its chemical name.
10. **Brand Name:** The proprietary name given to a drug by a pharmaceutical company.