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Introduction to Pharmacology- Definition, Historical Landmarks and Scope of Pharmacology

The term "pharmacology" comes from two Greek words: pharmakon (drugs) and logos (science).

Introduction to the pharmacy – definition

The term "pharmacology" comes from two Greek words: pharmakon (drugs) and logos (science). It is the study of chemicals that interact with biological systems through chemical processes, particularly through binding to regulatory molecules and activating or suppressing normal physiological activities. These compounds may be chemicals that are supplied to create a favorable therapeutic impact on a process within the patient or to have a harmful effect on regulatory mechanisms in parasites that infect the patient.

Many plant and animal elements were probably known by early man for their therapeutic or poisonous properties. Belief in these materials' healing properties was based only on conventional knowledge, that is, empirical facts that had not been subjected to rigorous investigation. Generation after generation has passed these abilities down. Superstition, primitive material medica, herbal remedies, traditional medicine, and witchcrafts used since the dawn of time have all now metamorphosed into pharmacology, an incredibly structured science.

Pharmacology is divided into two primary branches:
Pharmacokinetics - This term refers to the activities or actions of a medication as it passes through the body. Absorption, distribution, metabolism, and excretion of drugs are examples of these activities. A drug's onset of action, peak concentration, duration, and peak concentration level are also included in this branch of pharmacology.

Pharmacodynamics - The study of drugs' molecular, biochemical, and physiological effects, as well as pharmacological mechanism of action, is known as pharmacodynamics. In its most basic form, it is what medication does to the body.

Clinical pharmacology, psychopharmacology, pharmacotherapeutics, pharmacogenetics, pharmacogenomics, toxicology, chemotherapy, posology, pharmaco-economics, pharmacoepidemiology, molecular pharmacology, neuropharmacology, immunopharmacology, pharmacometrics, and other branches of pharmacology are also included.

Historical landmarks of pharmacology

Pharmacology originated as a separate study in the nineteenth century, splitting off from studies in disciplines like organic chemistry and physiology. A Latvian born in 1838, Oswald Schmiedeberg is often considered the father of modern pharmacology. A pharmacologist at the University of Strasburg, he oversaw a laboratory dedicated to determining the levels of chloroform in blood following his PhD research. Amanita muscaria is a fungus derived from the genus Ascomycota that has been used to treat conditions such as glaucoma and a number of sedatives, including chloral hydrate and chloral anhydride. Muscarine is derived from the fungus and stimulates the parasympathetic nervous system.

At the University of Michigan, John Jacob Abel became the first American to hold a pharmacology chair in 1890. Abel later moved to the Baltimore campus of Johns Hopkins University. It was Alexander who was the first to isolate the hormone adrenaline and the histamine from the pituitary gland, as well as to isolate pure crystallized insulin. Researchers studied pharmacological substances in animals such as pigeons, cats, dogs, and frogs. Testing was also conducted on humans. They experienced serious bad effects from these drugs at times, such as when the German pharmacist Friedrich Serturner and three of his associates were poisoned for many days by an alkaloid extracted from opium. Morpheus, the Ancient Greek deity of sleep, inspired the name morphine for this alkaloid.

Scope of pharmacology

The study of the properties of drugs, medicines, and poisons is a centuries-old practice previously carried out by druggists and professional poisoners. Until the end of the nineteenth century, medicines were naturally occurring organic or inorganic substances, most usually obtained from plants; hence, the art of material medica (the collecting and fabrication of such pharmaceuticals) was inextricably linked to botany. A large number of formularies and standards for such medications were created (pharmacopoeias). However, the explosive growth of the chemical industry during the last century has resulted in the development of pharmaceuticals that much outweigh those mentioned in ancient pharmacopoeias.


A drug's molecular structure can provide details regarding its mode of action, pharmacokinetics, stability, and metabolic destiny.

Structure-Activity Interaction - A change in a medicine's molecular structure can increase or worsen its pharmacological effects, frequently exposing the mechanism of action. An image of the biological reactive spot (the receptor) may be constructed as a result of such a study. Drugs are also metabolised by biological systems, which might result in a more active or less active form of the parent drug. The structure of the drug can be changed to increase or decrease the rate of metabolic conversion.

Sites of Action - A medication's organ or cellular site of action.

Drug Receptors are macromolecules in cells or cell membranes that interact with medications to elicit their effects. Although covalent bonds can form, the interacting forces are mostly low-energy reversible ionic and Van der Waals interactions (e.g., organophosphate insecticides).


The substance's effect on the body. The study of the link between medicine concentration and biologic effect is known as pharmacodynamics (physiological or biochemical). Most drugs need knowledge of the organ, functional system, or tissue level site of action and mechanism of action. As an example, the drug's action may only be constrained to the brain, to the neuromuscular junction, to the heart, to kidneys, etc. Biochemistry or molecular biology are frequently used to describe the mechanism of action. Most medications have an influence on several organs or tissues, and their effects can be both harmful and good. Both desired and undesired (toxic) results have a dose-response relationship. Age, weight, obesity, edoema, concomitant conditions, other drugs (various interactions including effects on protein binding or metabolic rate), food, dosage interval and mode of administration, and genetic differences in elimination rate are also considerations to consider.


For a drug to be effective, it must be absorbed and reach the site of action at an appropriate concentration. After a drug is administered to the surface of the body (e.g., the GI tract, the skin, etc.), the absorption rate dictates how long it takes for the drug's concentration to reach its maximal level in plasma and at the receptor.

Among the fluids that help to distribute medications in the body are blood, body water, extracellular fluid, lymphatic fluid, and brain fluid. According to the medication's chemical and physical properties, it can be bound to plasma proteins or dissolved in body fat, allowing it to reach its action sites or excretory mechanisms but not transit through them.

Metabolism - This is how the body prepares some pharmaceuticals for excretion, and it involves drug fate-biotransformation (e.g., hydrolysis, conjugation, oxidation-reduction).

Excretion - Drug clearance is mediated primarily by the kidney, but other organs such as the liver, lungs, and skin also play a role. Pharmaceuticals excreted in faeces are often derived from unabsorbed orally administered pharmaceuticals or bile metabolites that are not reabsorbed by the stomach.

Biological Factors Influencing Pharmacokinetic Aspects - Variations in population pharmacokinetic constants (absorption rates, elimination rates) are normal. Age, weight, obesity, edoema, concomitant conditions, other drugs (various interactions including effects on protein binding or metabolic rate), food, dosage interval and mode of administration, and genetic differences in elimination rate are also considerations to consider.

Clinical pharmacology and therapeutics

Indications and Therapeutic Uses - The therapeutic use of drugs in pharmacology, internal medicine, and therapeutics can all be seen as clinical pharmacology, internal medicine, and therapeutics. A certain medicine may be prescribed for specific clinic illnesses or disease entities, and the physician must assess the possible benefit of drug use against the risks of unwanted effects.

Where detoxification of the medication by the liver is relevant, contraindications and factors (e.g., liver disease) may modify pharmacological action. It is crucial to recognize that the presence of sickness or organ failure may have an impact on how a drug works. Age, pregnancy, concurrent use of other drugs, and sickness can all have an impact on a patient's response to a particular therapy.

Posology - An old name for dose regimens. Pharmacokinetics includes the consideration of dose regimens.

Bioavailability - A measure of how much of a drug is actually absorbed and is circulated in the body after oral administration. The bioavailability of the same drug may fluctuate depending on the manufacturer.

Prescription writing - Both the patient and the medicine provider (pharmacist) must receive clear, error-free instructions from the physician. Physicians must exercise caution when providing too many medications or ineffective preparations. Unproven clinical value drugs, as well as potentially harmful chemicals, should be avoided if less risky therapies are available. An assessment of cost-benefit ratios and risk-benefit ratios is necessary. Drugs may be delivered by generic name since it is typically possible to receive a less expensive prescription medicine in this method. The physician may mention a manufacturer if he or she believes the product is superior or more reliable.

Medication Nomenclature - A new drug is frequently given a code name in addition to its formal chemical name by the pharmaceutical producer. If the medicine seems promising and the firm intends to commercialize it, the USAN Council, which is funded by American Pharmacists Association


Pharmacology is concerned with the unfavorable effects of chemical compounds. Toxicology is concerned not only with therapeutic drugs, but also with other substances that may cause intoxication in the home, environment, or business.

Forensic Toxicology - Deals with the medicolegal consequences of using substances that are toxic to animals or humans. To support this aspect of toxicology, analytical chemistry and fundamental toxicological concepts are combined. Almost half of all poisonings and more than a quarter of all deaths among children under the age of five occur in this age group. Household products that are dangerous for children should be kept away from them, and pets should not be exposed to poisonous rodenticides or insecticides.

Clinical Toxicology is concerned with dangerous occurrences that are caused by or are associated with pharmaceuticals or other chemicals in a specific way.


Pharmacovigilance is the branch of pharmacology concerned with the impact of medications on patient safety. It comprises the characterization, identification, and comprehension of adverse drug reactions, toxicities, and side effects that occur as a result of short- or long-term drug use. Adverse medication responses, particularly drug-drug interactions, are believed to be a primary cause of inpatient death, as well as a large increase in hospitalization duration. No medication is without risky side effects. Some adverse drug reactions are modest, while others are severe and can be fatal. Side effects are commonly predicted based on knowledge of a drug's pharmacology. The following are some examples of chemical or drug-induced toxicity:

Allergic responses -
Although the occurrence of major allergic reactions to medications involving antigen-antibody interactions is limited, when they do occur, the physician must be prepared to handle the situation.

Blood dyscrasias are serious and sometimes fatal adverse effects of drug therapy. Among these are agranulocytosis, aplastic anaemia, hemolytic anaemia, thrombocytopenia, and clotting factor deficits.

Several chemicals and drugs can damage the liver and kidneys. This is because the liver and kidney extract and process these substances.

Teratogenic consequences -
The thalidomide tragedy highlighted the fact that medications might have a negative impact on foetal development.

Behavioral toxicity - This phrase refers to the suppression of natural anxiety, the lowering of motivation, the impairment of memory and learning, the distortion of judgement, the impairment of reflexes, the detrimental effects on mood, and so on.

Drug dependency and abuse - Some chemicals, when used repeatedly, can lead to drug dependency. Numerous psychopharmacological substances, including opiates, barbiturates, amphetamines, nicotine, and ethanol, are prone to abuse and addiction. Tobacco (nicotine) addiction is very well recognized.

Carcinogenesis - Carcinogenesis is a form of delayed toxicity with a long latency period.

Pharmacogenetic toxicities occur when some genetically predisposed people experience a strikingly harmful response to usually safe medications. Prolonged apnea following succinylcholine, for example, or malignant hyperthermia linked with anaesthetics are examples.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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