Volume : 2, Issue : 11, NOV 2016

POSOLOGICAL DOSE OF THERAPEUTICS OVER PROPHYLAXIS IN TOXICOLOGICAL SERENDIPITY

Kinsuk Sarker, Apurbo Sarker, Arittra Ghosh, Prof. Dr. Dhrubo Jyoti Sen

Abstract

Drug, any chemical substance that affects the functioning of living things and the organisms (such as bacteria, fungi and viruses) that infect them. Pharmacology, the science of drugs, deals with all aspects of drugs in medicine, including their mode of action, physical and chemical properties, metabolism, therapeutics and toxicity. The therapeutic index of a drug is the ratio between the dosage that causes a toxic/lethal effect and the dosage that causes a therapeutic effect. The term pharmacotherapy refers to the use of drugs for treating diseases, whereas pharmacology is the study of drug action on living systems. It is the interaction of the drug molecules and drug receptors that brings about a therapeutic effect. However, it is extremely essential to administer the drug in the right dose to achieve such an effect. If taken in large doses, certain drugs could cause adverse effects. Thus, in order to reap the benefits, it is essential to assess the right dose. Therapeutic drug monitoring (TDM) becomes essential to determine the dose at which a drug will be safe and effective, especially with those with a narrow therapeutic index (NTI). Also, monitoring might be required when the patient is affected by a medical condition that has an adverse effect on the clearance of NTI drugs. There's no denying the fact that drug metabolism could vary from person to person. Thus, the key to avoid drug-related problems is to consider the drug's therapeutic index and other relevant factors for ensuring safety. Therapeutic index (TI) refers to any of the several indices that are used for measuring a drug's safety. The most common TI is the ratio of the median lethal dose to the median effective dose of a drug. The formula for TI is: LD50/ED50. LD50 stands for median lethal dose and ED50 stands for median effective dose (therapeutic dose). LD50 refers to the dose that would produce a lethal effect in 50% of the population, whereas ED50 refers to the dose that will produce the desired therapeutic effect in 50% of the population. This index is commonly used to measure a drug's safety. The therapeutic index formula is: TD50/ED50. TD50 stands for the median toxic dose, whereas ED50 stands for the median effective dose. TD50 refers to the minimum drug dose that would produce a toxic effect in 50% of the population, whereas ED50 refers to the minimum drug dose that will produce the desired therapeutic effect in 50% of the population. Another related concept is that of therapeutic range (TR). TR is the range of doses/concentrations at which a therapeutic agent or drug produces a therapeutic response without causing any significant adverse effect in patients. It can be measured by: MEC/MTC. MEC stands for minimum effective concentration, whereas MTC stands for minimum toxic concentration. MEC is the minimum concentration of the drug that is required for achieving the therapeutic effect, whereas MTC is the minimum concentration at which toxicity occurs. Basically, if at a particular dosage, a drug is above MTC, it would cause adverse effects. Similarly, a drug below MEC will not produce the desired therapeutic response.

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