What is Pharmacology?: Definition | Basic Concept | Branches |

Pharmacology is said to be the corner stone and one of the most important subjects in the modern pharmacy and medical practice.

In this article, you will learn what is Pharmacology, Its basic concept, definition, what is a drug and how it works, what are the different branches of pharmacology.

Let’s have a look;

Pharmacology

What is Pharmacology?

The word pharmacology is derived from two Greek words, pharmacon meaning a “drug” and logy meaning “study.”

  • It is the study of how medicinal substances interact with living systems.
  • Pharmacology is the branch of medical and pharmaceutical science that deals with the study of drugs, their nature, their sources, and their properties, absorption, distribution, biotransformation, elimination, interactions, toxicology, and therapeutic applications.
  • Or, Pharmacology is the study of the body’s reaction to drugs.
  • It is the study of Pharmacokinetics and Pharmacodynamics of a drug. These are also the two main areas of this subject.

The field of pharmacology is concerned with drugs and how they interact within our bodies. Pharmacologists study the different types, uses for each drug type as well their interactions on normal or abnormal cell function in living organisms

Pharmacology looks at how medicinal substances work, their adverse effects, and their interaction with other medications or foods.

This subject is at the center of biomedical science, combining chemistry, physiology, and pathology.

The person who is an expert in this field is known as Pharmacologist. They work closely with several other fields that make modern biomedical sciences, including neuroscience, molecular and cellular biology, immunology, and cancer biology.

This subject explains what the drugs are, what they do for physiological functions, and what the body does with the drug.

Pharmacology also explains each drug’s dosage,  why a person may experience side effects when consuming drugs, and why there is such a broad view of the difference between drug actions among different people.

Pharmacology provides the research to understand the safety and efficacy of these drugs.

Pharmacology vs Pharmacy

As we have discussed above it is actually the branch of medical science in which we study the drugs research, discovery, the function of cellular and organic functions of these chemical products.

While Pharmacy is a health care professional and is the application of the principles learned from pharmacology.

Pharmacology vs Pharmacist

It is a subject and discipline while Pharmacist is a person who formulates and dispenses medicine. Pharmacists study this in the doctor of pharmacy degree as a subject, and this is the basic and cornerstone of modern pharmacy practice.

To know what exactly is pharmacology, you need to understand the drug first.

What is a Drug?

Any chemical substance that is used for the diagnosis, prevention, and treatment of diseases.

A drug is any chemical entity that causes a change in biological function in a living organism.

Some drugs are formed naturally inside the body, such as insulin and noradrenaline, etc. Drugs that are human-made or natural and introduced into the body from outside are called Xenobiotics. For example, are all those medicines such as paracetamol and all other drugs we take orally or on other routes?

How do drugs work?

Drugs generally work by interacting with receptors on the surface of cells or enzymes within cells. Drugs binding sites and enzyme molecules have a specific 3 dimensional structure that allows only medicines or other molecules that precisely attach to them.

What is a Receptor?

A drug receptor is a specific target area that binds to a drug and mediates its pharmacological process. These receptors can be present in enzymes, nucleic acids, or proteins that are restrained to particular membranes.

When the receptors and the drugs combined they form drug-receptor complexes leads to biological reactions. The strength of the reaction is proportional to the amount of drug-receptor complexes. A common way to show the relationship between drug concentration and the biological response is to use a concentration or a dose-response curve.

The Protein present in our body in different shapes/structures/forms and has many different functions. Each protein has a particular function and is specific to the type of cell on which it operates.

For example, there are certain types of proteins called receptors. Receptors embed in cell surfaces; there are different receptors for different types of cells. The receptors present in Liver cells are different than those present on heart cells. The receptor binds to other proteins and chemicals outside the cell, which, in turn, changes how the cell functions.

Proteins also work on drug targets. For a drug/medicine to show effects, it must be bind with protein just like a lock and key system. Once it is attached to the receptor, it can have two very crucial  effects on the cell. It may produce a change in the response or stop a normal response from the cell.

If it produces a change in the response, this will be called an agonist, and if it stops, it will be known as antagonists.

Dose-Response Curve

The concept of the dose-response curve is one of the most important concepts of pharmacology. A dose-response curve refers to the relationship between a drug’s effect and the amount of drug given.

The dose-response curves relationship is important for understanding the drug’s safe and dangerous levels. The treatment index can be determined and dosing guidelines established.

The dose-response curves are drawn on a simple x/y-axis, the drug dose is usually on the x-axis, and the drug response is usually on the y axis. Most are presented on a logometric scale as opposed to the curvature of the drug response. The Y-axis is often represented by a percentage to indicate the percentage of people who will respond to the drug. When reviewing dose-response curves, an important feature of curves is that it is a graduated relationship. This means that the response of drug increase with the amount of drug administered. This classification of dose-response curves allows your doctor to adapt the person taking the drug to the prescription.

If you increase the dose, the response will also be increased, but at a certain level, the effect and the curve plateau at the top will stop even if you further increase the dose.  This is the point where your body’s ability to detoxify a drug or repair toxic injury has been exceeded.

Effective Dose Vs Lethal Dose

The effective dose (ED50) is the amount of drug that shows a biological response in the body while the Lethal dose (LD50) is the amount of a drug or toxin that causes death in 50% of the test animals. [1]

What are potency and efficacy?

The drug’s potency means the dose of a drug that shows 50% of the effect, while the efficacy is the dose of a drug by which it shows a response.

  • The potency is the concentration or dose of a drug required to produce 50% of that drug’s maximal effect.
  • Efficacy is the maximum effect expected from a drug (i.e., when this magnitude of the effect is reached, increasing the dose will not produce a greater effect).
  • For example, one medication (med A) treats disease at a dose of 10 mg. A subsequent medication (Med B) treats that disease at a dose of 20 mg. In this manner, the two medications have similar efficacy, yet “Med A” is more potent than drug B. It takes less medication A to create a similar impact.

What is a first-pass effect?

This is one of the most commonly used terms among pharmacists and pharmacy students, and many Pharmacy students are confused about this terminology.

Your liver is actually a metabolic machine, and it often inactivates drugs on their way from the gastric Intestinal tract to the body. This is called the first-pass effect.

History Of Pharmacology

The earliest recorded efforts to study and categorize drugs date back thousands of years. The ancient Egyptians are known for their pharmaceuticals based on simple ingredients like herbs or animal parts.

Early work in this field focused on natural substances like herbs which early doctors used for their treatments until they could find better alternatives using more modern techniques. However, some crude drugs have remained constant all these years, such as acupuncture, due to their effectiveness at relieving pain without any side effects or risks associated in addition to that.

In the 1st century AD, the Greek physician Dioscorides wrote one of history’s first Western pharmacological treatises. This book listed herbal plants used in classical medicine and their appropriate uses to cure various ailments such as headaches and insomnia. It also provided instructions on how much each plant should be dried until consumption would relieve symptoms like nausea caused by morning sickness during pregnancy. Today, the medical discipline is known as “pharmacology,” originally developed from medieval apothecaries who prepared drugs but prescribed them too.

Many different types of traditional medicine vary by culture and may have unique uses. For example, the Chinese use herbs while Tibetans utilize dance therapy for healing from physical ailments and entheogens such as DMT which has religious significance in certain religions like Christianity or Judaism. Other cultures rely on ” entheogens ” pharmacological substances for spiritual purposes with substantial historical implications.

Pharmacology was developed into modern science until a doctor and herbalist, Nicholas Culpeper, translated ancient pharmacological texts on healing plants. Until the 18th century, much of clinical pharmacology was established by William Withering. However, the early 19th century was when medicine found itself in an exciting and unique position. The biomedical resurgence and new knowledge about plants, thanks to Nicholas Culpeper’s work, enabled scientists like Withering, who had been studying this field for years with great success, to finally put their expertise together into one cohesive subject they called clinical pharmacology.

By the early 19th century, chemists in France and Germany had isolated many active drugs like morphine, strychnine, etc., from their crude plant sources. Pharmacology was firmly established by Oswald Schmeiderberg (a German), who lived from 1838 to 1921. He helped found the first pharmacological journal, wrote a book on Pharmacology, and headed an institution in Strasbourg that would become one of Europe’s leading centers for studying medicine.

In the 20th century, pharmacological research developed a broad range of new drugs. One crucial example is penicillin which has been used to cure many infections since its discovery in 1928 by Sir Alexander Fleming (1881-1955).

Pharmacology these days involves the design and manufacture of new drugs from chemical synthesis in the laboratories. In addition to this, there has been an increased focus on how best to administer these medications through clinical research studies with large patient populations.


Pharmacology
Pharmacology

Branches of Pharmacology

Pharmacology has 2 main branches.

  • Pharmacodynamics
  • Pharmacokinetics

Other branches of pharmacology include

  • Therapeutics
  • Clinical Pharmacology
  • Pharmacogenetics
  • Pharmacognosy
  • Toxicology
  • Pharmacoepidemiology
  • Animal Pharmacology
  • Posology
  • Pharmacoeconomics
  • Chemotherapy
  • Comparative Pharmacology
  • Neuropharmacology
  • Psychopharmacology
  • Cardiovascular pharmacology
  • Pharmacovigilance


1. Pharmacokinetics

Pharmacokinetics refers to the movement of drugs inside, through, and on the body. The nature of an individual’s response to a particular drug depends on the drug’s intrinsic pharmacological properties at its site of action.

Pharmacokinetics investigates how the body absorbs, metabolizes, and excretes drugs.

A drug can be administered orally (by mouth), parenterally (by injection), or intravenously (through veins). There are are other drug administration routes like rectal route, vaginal route, through inhalation and subcutaneous.

The kidney is the main organ that filters drugs out of the body, but also the lungs and sweat glands play a minor role.

However, the rate of occurrence, intensity, and duration of the response generally depends on the following parameters:

  • The rate and extent of drug absorption.
  • The rate and extent of distribution of the drug in different tissues, including the site of action;
  • The rate of excretion of the drug from the body.
2. Pharmacodynamics

Pharmacodynamics is defined as the body’s response to the drug. It refers to the relationship between the drug concentration at the site of action and any effect, namely the intensity and the time course of the effect and the side effects.

Pharmacodynamics is influenced by receptor binding and sensitivity, post-receptor effects, and chemical interactions.

Pharmacodynamics and pharmacokinetics explain the effects of the drug, such as the relationship between dose and response.

The pharmacological response depends on the binding of the drug to its target molecule. The concentration of the drug at the receptor site influences its effect.

The pharmacodynamics of a drug may be influenced by physiological changes due to diseases, genetic mutations, aging, or other drugs. These changes are due to the disorders’ ability to modify receptor binding, alter the number of binding proteins, or decrease the receptor’s sensitivity.

3. Chemotherapy

Chemotherapy is another pharma field that deals with the medicines used to treat cancer and malignancies with cytotoxic and other drugs. It is a type of treatment with medicines that block or slow down cell growth, most often for cancer.

Depending on the type of most cancers, their size, and whether or not it has spread, chemotherapy can also additionally treat most cancers, slow or save their spread, or make their signs and symptoms better. Chemotherapy is regularly used with different cancer treatments, including radiation or surgical procedure. For instance, an affected person can be given chemotherapy to shrink a tumor before surgical procedure or radiation or to help kill most cancer cells that can be left afterward.

Chemotherapy is occasionally administered with different nonchemotherapy agents including antibodies that also block or sluggish tumor growth.

4.  Therapeutics

Therapeutics is the branch that specializes in treating diseases and in the art and science of healing. Therefore, in pharmacology, the treatments refer to drugs and their administration method to treat diseases.

5. Clinical Pharmacology

Clinical pharma promotes the rational use of drugs in humans by examining their corrective effects to increase the drug’s effect and reduce side effects. In short, it is the science of drugs and their clinical use.

This is pharmacology with an added emphasis on applying pharmacological principles and methods in the real world. This ranges from the discovery of new target molecules to the effects of drug use in the population.

Clinical Pharmacology has a broad scope from the discovery of new target molecules, to the effects of drugs used on the whole population.

Clinical Pharmacology links the gap between the modern medical practice and laboratory science.  The main purpose is to promote the safety of medications, maximize the drug effects, and reduce the side effects.

A clinical Pharmacologist is a medical expert that collects and produces new data through well-designed studies. Clinical pharmacologists work under the supervision of medical specialists and must have access to enough outpatients for clinical care, education, teaching, and research.

A clinical pharmacist is responsible for the improvement of patient care through the safe, economic, and effective use of medications. This person is also responsible for the development and assistance of clinical trial services especially fundamental pharmacodynamic studies, studies of pharmacokinetics and drug metabolism, to pharmacogenetics. The roles of clinical pharmacologists can vary from country to country.

6. Pharmacogenetics

Pharmacogenetics is the study of how individuals respond to medical therapy based on their genes or you can say it is the study of the role of the genome in drug response.

It is the study of the role of the genome in drug response. Pharmacogenomics analyzes how the genetic composition of an individual influences their response to medication.

This is relatively a new field in the medical world because this field combines pharmacology & genomics to develop safer, more effective drugs and doses that will be adjusted to a person’s genetic makeup.

7. Pharmacognosy

Pharmacognosy is the study of drugs derived from natural sources. This deals with the pharmacodynamics and the mechanisms by which substances, mainly from natural sources, directly or indirectly influence living systems changes.

Pharmacognosy deals with the natural drugs received from organisms together with most plants, microbes, and animals. Till now, many essential drugs consisting of morphine, atropine, galanthamine, etc. have been derived from natural sources which continue to be appropriate model molecules in drug discovery. Traditional medicine is also part of pharmacognosy and most third-world nations still rely upon the usage of natural medicines.

8. Toxicology

Toxicology is another branch that is devoted to the scientific study of the harmful effects of drugs on living organisms. This involves observing and reporting the symptoms, mechanisms, detection, and treatment of toxic substances, particularly in human poisoning.

Includes environmental agents and natural chemical compounds, as well as synthesized pharmaceutical compounds for medical use. These substances can have toxic effects on living organisms, including growth disorders, discomfort, illness, and death.

9. Pharmacoepidemiology

Pharmacoepidemiology is the branch of pharmacology that deals with studying the use and effects of drugs in many people. It provides an estimate of the likelihood of a drug’s beneficial effects on a population and its adverse effects. This can be called a bridge science that encompasses both clinical pharmacology and epidemiology.

10. Animal Pharmacology

This one deals with the different properties of drugs in animals. A wide variety of animals are used, including rabbits, mice, guinea pigs, etc. The drugs are administered to the animals, and all the parameters (behavior, activity, vital signs, etc.) are recorded. Each change is noted below. If it is useful in animals, the drug is tested in humans.

11. Posology

This branch is concerned with determining the doses of the drugs– It is the science of dosage. For example, ibuprofen’s usual dose in adults and adolescents over 12 years is 200 mg to 400 mg three to four times a day.

Like Pharmacology it is also a greek word that is made from “Posos” which means “how much” and “logos” means “science”. So it is a branch of the medical field that deals with the dose and quantity of drugs that can be given to patients to get the desired pharmacological effects.

The portion of medication can’t be fixed rigidly on the grounds that different elements are responsible i.e age, sex, the seriousness of the sickness, and so forth. The official doses in pharmacopeia address the normal range of quantity.

Some of the important factors that influence the doses of drugs are;

  • Age
  • Sex
  • Bodyweight
  • Route of administration
  • Time of administration
  • The severity of the disease etc.

12 Pharmacoeconomics

Pharmacoeconomics is the scientific discipline that concerns the cost and value of drugs, often intending to optimize health resource allocation. For example, pharmacoeconomic studies can compare the costs of various drugs with results, such as the benefits for patients receiving drugs and the savings made by health systems through effective treatment or disease prevention.

13. Comparative pharmacology

It is a pharmacology branch that compares one drug to another, belonging to the same group or the other.

Comparative pharmacology today deals with the process of identical compounds on different cell systems of different organisms with the aim of uncovering the molecular basis of this process and analyzing the processes involved.

14. Neuropharmacology

Neuropharmacology is a branch of neuroscience that studies the effects of drugs on the nervous system, including the brain, spinal cord, and nerves that carry information to and from different parts of the body. The goal of neuropharmacology, in general, is to understand the basic function of impulses and signals in the brain to determine the effects of drugs on the treatment of neurological disorders and dependence.

Neuropharmacology is the study of drugs that affect the nervous system. It focuses on developing compounds that may be beneficial for people with neurological or psychiatric conditions.

Therefore, Neuropharmacology requires a deep knowledge of how the nervous system works, as well as the way each drug acts on neural circuits, altering cellular behavior and ultimately the behavior of living beings.

Neuropharmacology itself only emerged five decades ago, there were only four drugs for neurological disorders: morphine, caffeine, nitrous oxide, and aspirin.

With the molecular basis of many drug processes and modern insights into the availability of existing research methods, work is underway to understand how the brain works at the molecular and cellular levels. It involves understanding the role of genetic variation in the effects of drugs on individual patients to deliver drugs to the brain and seek personalized treatment for a disease of the nervous system.

15. Psychopharmacology

Psychopharmacology is the scientific study of the effects of drugs on mood, sensation, reflection, and behavior. It is distinct from neuropsychopharmacology, which focuses on the correlation between drug-induced nervous system function changes and changes in consciousness and behavior.

Psychopharmacology is the study of the use of drugs in the treatment of mental illness. The complexity of this field needs constant study to stay up to date with new developments.

You can learn more about Psychopharmacology here.

16. Cardiovascular pharmacology

Cardiovascular is the study of the effects of drugs on the entire cardiovascular system. Cardiovascular relative to the circulatory system, which includes the heart and blood vessels, transports nutrients and oxygen to body tissues and removes carbon dioxide and other wastes.

Cardiovascular diseases are disorders of the heart and blood vessels. They include arteriosclerosis, coronary artery disease, heart valve arrhythmia, arrhythmia, heart failure, hypertension, orthostatic hypotension, shock, endocarditis, diseases of the aorta and its branches, disorders of the peripheral vascular system, and congenital heart disease.

Some of the common drugs used in cardiovascular pharmacology are antihypertensive drugs such as sympathetic nervous system blockers, direct vasodilators, diuretics, and ACE inhibitors.

17. Pharmacovigilance

According to the World Health Organization,  “Science and activities related to the identification, evaluation, understanding, and prevention of adverse effects or any other possible problem related to drugs.”

Pharmacovigilance is a science and activity related to the detection, diagnosis, understanding, and prevention of adverse effects or any other drug-related problem.


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This Article is Written By A Registered Pharmacist: Manzoor Ahmad And Medically Reviewed By Dr Sajid (Pharm-D, Mphil, PhD Pharmacognosy.

 

Please Feel free to ask any questions related to this topic in the comments section. Also, Like, Comment, And Share to Reach more People. 



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