Understanding Pharmacokinetics: How Drugs Work in Our Bodies

Pharmacokinetics, or PK for short, is really important when it comes to how we classify drugs. This involves looking at how drugs are absorbed, how they move around in our bodies, how they are broken down, and how they are removed. We often refer to these steps as ADME: Absorption, Distribution, Metabolism, and Excretion. Each of these steps helps us understand how a drug can be used and what the risks might be.

Let’s break these down:

1. Absorption:

   • This tells us how a drug gets into the body.
   • For example, drugs can be taken in different ways, like by mouth (oral) or through a needle (intravenous).
   • The term “bioavailability” means how much of the drug actually enters the bloodstream. This can be anywhere from 0% (like with IV drugs) to 100% (like with oral drugs).

2. Distribution:

   • This is about how drugs spread out to different parts of the body.
   • A key idea here is the “volume of distribution” (Vd). This shows how well a drug moves into different tissues and can range from 0.1 to 60 liters for each kilogram of body weight.

3. Metabolism:

   • This describes how long a drug works and how strong its effect is.
   • Some drugs go through what’s called “first-pass metabolism.” This can make the drug less effective, and around 75% of drugs taken by mouth go through this process.

4. Excretion:

   • This is how our body gets rid of drugs.
   • Renal clearance is one way we measure this. It shows how quickly our kidneys can remove a drug and can vary quite a bit, from 100 to 1500 milliliters per minute for different people. This can affect how much of a drug we need to take.

Pharmacokinetics helps us sort drugs into different groups, such as:

• Fast vs. Slow Metabolizers: Some people process drugs quickly, while others take their time.
• Drugs with Narrow Therapeutic Index (NTI): These drugs need to be watched closely because small changes can be risky.

In short, understanding pharmacokinetics helps us categorize drugs better. This helps doctors decide:

• How much medicine to give.
• Which form of the drug is best to use.
• How to predict what will happen when different drugs are combined.

Knowing about pharmacokinetics is key for safe and effective treatment!