Minimum effective (and toxic) concentration of a drug

In the previous post (click), I explained that correctly accounting for the pharmacokinetics of a drug can help explain the concentration of the drug in the blood and in the target organ. The question that obviously follows this point is:

What is the desired concentration of the drug?

As we commonly notice, each drug we take has a certain amount associated with it and a certain frequency of administration. The purpose of this is to raise the concentration of the drug to a level that it effectively reaches the target organ to cause its effect. The minimum amount of drug required for the drug to have its intended effect is called the minimum effective concentration of a drug. While it is possible that higher concentrations of the drug show beneficial effect too, the drug must be at the minimum effective concentration to have its effect. Below this, the drug doesn't show efficacy.

If too little drug is a problem, too much is also a problem. The converse of the minimum effective concentration is called the minimum toxic concentration of a drug. It is the minimum level above which toxic side effects of the drug are observed.

So the desired concentration of the drug is such that it has its desired effect without being toxic. As a result, most drug delivery strategies are designed such that the drug concentration remains between the minimum effective and minimum toxic concentration of a drug. Once we know through experimentation the various body processes that impact the concentration of the drug, we can generate a virtual facsimile of the processes the drug undergoes using computer programs and mathematical equations, a process we know as mathematical modeling. Once a model is ready, countless scenarios of hypothetical and existing drug dosing can be tested and we can check if we are maintaining the drug concentration at the desired level. The presence of a model helps improve the drug development process by minimizing the number of experiments required.

Routine drug development processes in the pharmaceutical industry are increasingly adapting pharmacokinetic modeling to propose drug doses, frequencies, and sometimes novel ways of drug administration to maintain drug concentration at the desired level. Applying pharmacokinetic models in Ayurveda can allow Ayurveda too to evolve at a similar pace as modern medicine. In the next post, we will see a sample pharmacokinetic model, important terms involved and possible applications for such models in the world of Ayurveda.