Terminology of Pharmacology

Pharmacology: The term pharmacology comes from the two Greek words: pharmacon- a drug or medicine and logos- the truth about or a rational discussion. Pharmacology is a science of drug. It can also be defined as study the effects of drugs on the function of living systems. It deals with interaction of exogenously administered chemical molecules (drugs) with leaving system. Two important and interrelated areas of pharmacology are: pharmacokinetics and pharmacodynamics.

Pharmacokinetics: The term pharmacokinetics comes from a Greek word: kinesis- movement. Pharmacokinetics is what the body dose to the drug. This refers to movement of drug in and alteration of drugs by the body. This includes absorption, distribution, metabolism and excretion (ADME) of the drug. e.g. - Digoxin is 70% absorbed orally, 25% bound to plasma proteins, localized in heart, skeletal muscle, liver and kidney; small fraction is metabolized in liver and excreted in urine.

Pharmacodynamics: The term pharmacodynamics comes from a Greek word: dynamis- Power. Pharmacodynamics is what the drug dose to the body. This includes physiological and biochemical effects of drugs and their mechanisms of action at organ/system/subcellular/ macromolecular levels. e.g. Adrenaline – interact with β₁ adrenoceptors in heart, that is a G-protein coupled receptor, which stimulates adenylyl cyclase and increases intracellular cAMP which leads to cardiac stimulation.

Figure 1: Branches of Pharmacology

Drug: The word drug comes from French: Drogue- a dry herb. Drug is any substances or product that is used or intended to be used to modify or explore physiological systems or pathological states for the benefit of the recipient. Drug is the single active chemical entity present in a medicine that is used for diagnosis, prevention, treatment/cure of a disease.

Essential Drugs: As per the WHO, essential drugs or medicines can be defined as those drugs that satisfy the priority healthcare needs of the population. They are selected with due regard to public health relevance, evidence on efficacy and safety and comparative cost effectiveness. They are intended to be: Available within the context of functioning health systems at all times, available in adequate amounts, in appropriate dosage forms, with assured quality, contains adequate information about efficacy and safety, and at a price the individual and community can afford.

Orphan Drugs: The drugs or biological products developed for diagnosis, treatment or prevention of a rare disease or condition, or a more common endemic disease found in resource poor countries are known as orphan drugs. There is no reasonable expectation that the cost of developing and marketing those drugs will be recovered from the sale of the drug. e.g. sodium nitrite, fomepizole, miltefosine, rifabutin, digoxin immune Fab (digoxin antibody) etc.

Pharmacy: Pharmacy is the art and science of compounding and dispensing drugs or preparing suitable dosage forms for human and veterinary uses. It includes collection, identification, purification, isolation, synthesis, standardization and quality control of medicinal substances.

Pharmacotherapeutics: Application of pharmacological information together with knowledge of the disease for its prevention, mitigation or cure is known as pharmacotherapeutics. It includes selection of the most appropriate drug, dosage and duration of treatment for the specific features of a patient.

Toxicology: It is the study of poisonous effect of drugs and other chemicals with emphasis on detection, prevention and treatment of poisoning. It also includes the study of adverse effects of drugs.

Chemotherapy: It is the treatment of systemic infection or malignancy with specific drugs that have selective toxicity for the infecting organism or malignant cell with no/minimal effects on the host cells.

Preclinical Pharmacology: It is the scientific study which involves laboratory animals using wide‐ranging doses of the study drug to obtain preliminary efficacy, toxicity and pharmacokinetic information. Such tests assist pharmaceutical companies to decide whether a drug candidate has scientific merit for further development as an investigational new drug.

Clinical Pharmacology: It is the scientific study of drugs in human. It includes pharmacokinetic and pharmacodynamic investigation in healthy volunteers and in patients.

Pharmacogenetics: pharmacogenetics is a study of genetic variations that alters drug metabolism and drug response. Originally, pharmacogenetics focused on familial idiosyncratic drug reactions, where affected individuals show an abnormal-usually adverse-response to a class of drug.

Pharmacogenomics: This term overlaps with pharmacogenetics, describing the use of genetic information to guide the choice of drug therapy on an individual basis, i.e. the response to therapeutic drugs between individuals can be predicted from their genetic make-up. Ultimately, linking specific gene variations with variations in therapeutic or unwanted effects of a particular drug should enable the tailoring of therapeutic choices on the basis of an individual's genotype.

Pharmacoepidemiology: This is the study of drug effects at the population level. It is concerned with the variability of drug effects between individuals in a population, and between populations.

Pharmacoeconomics: This branch of health economics aims to quantify in economic terms, the cost and benefit of drugs used therapeutically. It arose from the concern of many governments to provide for healthcare from tax revenues, raising questions of what therapeutic procedures represent the best value for money.

Pharmacovigilance: It is a science and activities related to the detection, assessment, understanding and prevention of adverse effects or any other drug related problem. So this is a science of keeping a watch on adverse reactions. 

References:

Brunton, L., Lazo, J.S., Parker K.L., 2006. Goodman and Gilman’s, The Pharmacological Basis of Therapeutics. 11^th edition, The McGraw-Hill Medical Publishing, New Delhi, India.

Katzung B.G., Masters S.B., Trevor A.J., 2012. Basic & Clinical Pharmacology. 12th edition, The McGraw-Hill Companies, New Delhi, India.

Rang, H.P., Ritter, J.M., Flower, R.J., Henderson, G., 2016. Rang and Dale’s Pharmacology. 8^th edition, Churchill Livingstone, Philadelphia.

Satoskar, R.S., Bhandarkar, S.D., Rege, N.N., 2009.Pharmacology and Pharmacotherapeutics. Twentieth 1^st edition, Popular Prakashan Pvt. Ltd., Mumbai, India.

Tripathy, K.D., 2013. Essentials of Medical Pharmacology. 7^th edition, Jaypee Brothers Medical Publishers (P) Ltd, New Delhi, India.