Know! How are drugs used in Medicines?

Drugs play a pivotal role in the field of medicine, acting as both a boon and a potential threat. The intricate balance between their therapeutic benefits


Shubham Kumar

1/29/20245 min read

Drugs play a pivotal role in the field of medicine, acting as both a boon and a potential threat. The intricate balance between their therapeutic benefits and harmful consequences is delicately governed by a concept known as the drug responsive curve. This curve establishes the relationship between drug exposure and potential health effects, critically essential in determining the toxicity of a desired drug.

The heart of this analysis lies the crucial understanding that there exists a fine line between a drug acting as a life-saving medicine and transforming into a deadly poison. The dose responsive curve, a fundamental concept in pharmacology, sheds light on this balance. It signifies that the higher the dose, the more intense the response or effect, which can be both curative and, paradoxically, fatal.

To navigate this delicate balance, researchers employ the concept of the therapeutic index. This index is calculated using the ratio of the lethal dose (LD50) to the effective dose (ED50). LD50 represents the amount of drug needed to cause the death of 50% of a tested population, while ED50 is the dose required to cure 50% of the recipients with minimal side effects. The therapeutic index provides a crucial metric, ensuring that drugs are administered within safe limits, maximizing therapeutic outcomes while minimizing adverse effects.

With the therapeutic index in hand, the concept of the therapeutic dose comes into play. This dose signifies the amount of drug necessary to trigger a therapeutic response in an individual, effectively treating illness, disease, or complications. The determination of the therapeutic dose involves meticulous analysis of the therapeutic index and the dose responsive curve. For example, consider the case of Paracetamol, a commonly used drug. The specified therapeutic dose ensures that the disease is treated with minimal side effects. Deviating from this recommended dose can lead to toxic effects, underscoring the importance of precise administration.

In the realm of drug safety, the concept of the threshold dose is also vital. This dose represents the exposure level below which harmful or adverse effects of a substance are not observed in a population. It provides a safety benchmark, guiding healthcare professionals and pharmaceutical manufacturers in setting dosage levels to avoid detrimental outcomes.

Moreover, the combined effect of drugs introduces another layer of complexity. When multiple drugs are administered simultaneously, they can either synergize, enhancing each other’s effects, or antagonize, counteracting one another. Understanding these interactions is pivotal in creating effective and safe drug combinations, ensuring that patients receive optimal treatment without compromising their well-being.

The world of medicine relies heavily on the intricate understanding of drug responsive curves, therapeutic indices, therapeutic doses, and threshold doses. This knowledge forms the bedrock of safe and effective drug administration, ensuring that medications provide the intended benefits while minimizing risks. It is through this meticulous balancing act that healthcare professionals continue to harness the power of drugs, transforming them from potential poisons into life-saving medicines, thereby improving the quality of life for countless individuals around the world.

Parameters which you should know to understand the process and manufacture of drugs in medicines. These are Drug Responsive curve, Therapeutic Curve, Therapeutic index, Lethal dose 50 and Lethal Concentration 50.

Drug Responsive Curve: The drug responsive curve is the relationship between the exposer and potential health effects, that can be established by measuring the response relative to an increasing dose. The analysis of this relationship is important to determine the toxicity of a desired drug. Since, there is a very fine line between the usage of drug as both poison and medicine.

Therefore, dose responsive curve of any drug is monitored very precisely to obtain recommended outcome. Moreover, this curve also suggests that, if a dose makes the poisons, it means the larger or more intense the dose, the greater the response or the effect. On of the most important fact of the dose responsive curve is that "Dose is directly proportional to response." Therefore, higher the dose, higher the fatal circumstances and response and vice-versa.

The dose responsive curve only determines the toxicity of the desired drugs. In order to create a medicine, the manufacturer must know the concentration to used, so that drug can act as medicine instead of poison. Therefore, several techniques like Therapeutic index, therapeutic dose and threshold dose is determined.

Therapeutic index: The term therapeutic dose refers to the ration of the dose that produces a toxic lethal effect to the desired therapeutic effect

Therapeutic Index = Lethal Dose\Effective Dose = LD50/ED50

LD50 (Lethal Dose): The LD50 represents the amount of drug required to kill the 50% of a population of the tested subjects (Usually animals). In simpler terms, the dose which kills 50% recipients. Dose refers to the actual amount of chemical consumed by the live biological system.

ED50 (Effective Dose): The ED50 represents the amount of drug required to cure the 50% of a population of the tested subjects (usually animals). Furthermore, the ED50 is specified in curing the 50% of the recipients. Moreover, it creates maximum curing effect on minimum side effects.

The therapeutic index is determined to confirm the amount of drug to be used in the medicines for the maximum output with bare minimum side effects.

After determining the therapeutic index, the therapeutic dose if operated.

Therapeutic Dose: Therapeutic dose refers to the amount of dose required to trigger the therapeutic response in an individual to treat the illness, disease or any complications. The concentration is determined by the analysis of therapeutic index and dose responsive cure.

For example, lets take example of Paracetamol. Paracetamol is also a drug, therefore, its therapeutic dose of paracetamol is specified to cure the disease with bare minimum side effects.

The usual dose of paracetamol of 500mg is taken at every 4 to 6 hrs as required. For effective results, doctors recommend taking paracetamol dose immediately the moment you realize about your fever or illness.

However, paracetamol should be taken only up to 400mg, if you take dose of paracetamol higher than 400mg, then it may leads to toxic effects in your body.

Threshold Dose: A dose or exposure level below which the harmful or adverse effects of a substance are not seen in a population. That dose is referred to as the threshold dose.

The dose is also referred to as the NOAEL i.e., No observed adverse effect level or NEL i.e., no effect level.


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