Chapter 14 14.8 Importance of Rates of diffusion of Medicines in Human Body (Keynotes, lesson planner and mcqs)
Importance of diffusion rates of medicines in human body
🧫 cell membrane – lipid-soluble drugs diffuse faster
Animation shows drug molecules moving in bloodstream – rate controls absorption.
14.8 Importance of Rates of diffusion of Medicines in Human Body
The tendency of the molecules contained in a medicine to move from a region of higher concentration to one of lower concentration is called diffusion. The diffusion rates of medicines control how rapidly and effectively they can be absorbed, distributed and eliminated from the body.
When the medicines are taken orally, the rates of their diffusion between the stomach and intestine control how quickly they are absorbed in the blood. A faster diffusion rate means early absorption and hence a faster onset of action.
Once the drug molecules are absorbed by the blood, they start diffusing into various tissues and organs. The rate of diffusion here determines how quickly the drug becomes effective. For example, lipid-soluble drugs diffuse more easily through cell membranes, making them more effective in shorter time. Generally, a faster rate of diffusion leads to higher drug concentration at its target organ which means a more effective response.
In short, rates of diffusion play a crucial role in the delivery and movement of drugs throughout the body. This process of diffusion ensures that essential substances reach their target locations quickly which eventually helps in the treatment of diseases.
💡 Quick Check – Medicines & Diffusion
Q: Why do lipid-soluble drugs act faster?
A: Because they diffuse more easily through the lipid bilayer of cell membranes → faster target concentration.
Q: What happens if diffusion rate is very slow?
A: Delayed absorption, slower onset of action, lower effectiveness.
📘 memorization trick
“Lipid‑soluble = fast & soluble”
Faster diffusion → faster relief. Think: oil-based drugs pass membranes easily.
⚡ short tips
• Oral drugs: diffusion in gut → blood.
• Blood → tissues depends on concentration gradient.
• Larger gradient = faster diffusion.
🧪 quick activity
Drop a tea bag into cold vs hot water – observe diffusion speed. Relate to medicine solubility & temperature effect.
⏳ 35‑minute lesson planner
00-05 min: recall diffusion definition (high→low).
05-12 min: read 14.8 – role in stomach/intestine absorption.
12-18 min: discuss lipid-soluble drugs & cell membrane.
18-25 min: activity – tea bag demo (temp effect).
25-35 min: 10 MCQs quiz & review.
📝 10 MCQs – Diffusion of Medicines (submit & see result)
📌 good guidelines for students
• Diffusion rate controls drug absorption, distribution, elimination.
• Faster diffusion → faster onset of action.
• Lipid‑soluble drugs cross membranes easily.
• Concentration gradient drives diffusion (high → low).
• Always consider how drug properties affect diffusion.
