Pharmacokinetics vs Pharmacodynamics—Why It Matters

MBBS
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Pharmacokinetics is ‘What does the body do to the drug’ which includes Absorption, Distribution, Metabolism, Excretion.

Pharmacodynamic is ‘What does the drug do to the body’ which include Receptor action, intensity of effect, therapeutic vs toxic response.

Let’s take a drug as an example, Paracetamol

◇Absorption: Asorbed from the stomach & intestine

◇ Distribution: Reaches blood and tissues
◇ Metabolism: Metabolized in the liver
◇Excretion: Excreted via kidneys (urine)

This journey is Pharmacokinetic of a drug

  • Action: Inhibits prostaglandin synthesis
  • Effect: Reduce Pain and Fever

This effect is Pharmacodynamic of a drug.

As for insulin PK explains why insulin must be injected as there absorption is destroyed by stomach acid and never reaches the bloodstream

PK VS PD
PK VS PD1536×1024 713 KB

Most of the adverse events occurs when PK changes are ignored which leads to accumulation and toxicity. PD variability is overlooked leads to poor response.

Which creates more impact PK or PD? Whats your opinion?

MBH/AB

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Nice breakdown—it makes the PK vs PD difference very clear. Your insulin point is especially important: pharmacokinetics explains why oral insulin doesn’t work, since it would be degraded in the GI tract before reaching the bloodstream.

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Nice breakdown of the content nicely explained

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PK changes often have a bigger impact on safety due to toxicity risks, while PD variability mainly affects how well a drug works. Both are important, but monitoring PK is usually more urgent to prevent harm.

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It is very clear and concise.

Understanding pharmacokinetics vs pharmacodynamics is key to safe, effective, and patient-centered therapy.

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