Factors Modifying Drug Action

Factors Modifying Drug Action include age, body weight, genetics, sex, disease, diet, and drug interactions that influence a drug’s effects.

Factors Modifying Drug Action

Several factors can influence how a drug acts in the body:

1. Age

   • Neonates: Immature liver/kidneys → slower metabolism and excretion.
   • Elderly: Reduced organ function → altered drug response.

2. Body Weight & Composition

   • Doses often adjusted by weight (mg/kg).
   • Fat-soluble drugs distribute more in obese individuals.

3. Sex

   • Hormonal differences affect metabolism.
   • Some drugs act differently in males vs. females.

4. Genetic Factors

   • Genetic variation (pharmacogenetics) influences metabolism (e.g., CYP450 enzymes).
   • Example: Slow acetylators metabolize isoniazid slowly.

5. Route of Administration

   • Affects onset, intensity, and duration (e.g., oral vs. IV).

6. Time of Administration

   • Circadian rhythms influence drug effects.
   • Example: Cortisol-like drugs work better in the morning.

7. Tolerance & Resistance

   • Tolerance: Reduced effect over time (e.g., opioids).
   • Resistance: Microbes become less sensitive to drugs.

8. Pathological States

   • Liver/kidney disease → impaired metabolism/excretion.
   • GI disorders → altered absorption.

9. Psychological Factors

   • Belief and expectation (placebo effect) can influence drug response.

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