Drugs & Toxin are mainly excreted by which process `:-`

Options

A. Ultra filtration
B. Digestion in the form of excreta
C. Tubular secretion
D. Diffusion

Answer

To determine the process by which drugs and toxins are mainly excreted, let's analyze the options provided:

1. **Ultrafiltration**: This process occurs in the glomerulus of the nephron where blood is filtered under high pressure. During ultrafiltration, blood cells and large macromolecules are removed from the blood, leaving behind a filtrate that contains water, ions, and small molecules. However, drugs and toxins are usually absorbed quickly by the epithelial cells of the gut and do not reach the nephron in significant amounts. Therefore, ultrafiltration is not the correct answer.

2. **Digestion in the form of excreta**: In digestion, macromolecules are broken down and absorbed stepwise. Drugs, however, are rapidly absorbed as soon as they come into contact with the mouth epithelium or the stomach, meaning they do not reach the intestines to be excreted in the form of excreta. Thus, this option is also not correct.

3. **Tubular secretion**: This process occurs in the distal convoluted tubule (DCT) of the nephron. Here, certain substances, including ions and some drugs, are secreted from the blood into the tubular fluid. For example, drugs like penicillin are actively secreted into the nephron and subsequently excreted in urine. This makes tubular secretion a likely candidate for the excretion of drugs and toxins.

4. **Diffusion**: While some drugs may be absorbed through diffusion, this process does not apply to the excretion of drugs and toxins from the body. Therefore, diffusion is not the correct answer.

After analyzing all the options, the correct answer is **tubular secretion**.

### Summary of Steps:
1. **Evaluate ultrafiltration**: Understand that it filters blood but does not effectively excrete drugs and toxins.
2. **Consider digestion**: Recognize that drugs are absorbed quickly and do not reach excreta.
3. **Analyze tubular secretion**: Identify that this process actively secretes drugs into the nephron for excretion.
4. **Review diffusion**: Acknowledge that while drugs can be absorbed this way, it does not pertain to excretion.

### Correct Answer:
**Tubular secretion**