How do drugs exert their effects in the body?

Definition

Drugs exert their effects in the body primarily by interacting with specific biological molecules called receptors. These interactions can either activate (agonists) or inhibit (antagonists) normal cellular processes. Drugs may also affect enzymes, ion channels, or transporters, altering physiological functions.

Worked Example

Example:
A common pain reliever, ibuprofen, reduces inflammation and pain.

• Mechanism: Ibuprofen inhibits the enzyme cyclooxygenase (COX).
• Effect: COX is necessary for the synthesis of prostaglandins, which mediate pain and inflammation.
• Result: By blocking COX, ibuprofen decreases prostaglandin production, thus reducing pain and swelling.

Mathematically, the inhibition can be represented as:

$$ \text{COX} + \text{Ibuprofen} \rightarrow \text{Inactive Complex} $$

This reduces the rate of the reaction:

$$ \text{Arachidonic Acid} xrightarrow{\text{COX}} \text{Prostaglandins} $$

With ibuprofen:

$$ \text{Arachidonic Acid} xrightarrow{\text{COX (inhibited)}} \text{Less Prostaglandins} $$

Key Takeaways

• Drugs act mainly by binding to receptors, enzymes, or other targets, altering normal biological activity.
• The effect depends on the drug's action (activation or inhibition) and the target's role in the body.
• Understanding drug mechanisms helps predict therapeutic effects and potential side effects.