Bioavailability [Neurosurgery Wiki]

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====== Bioavailability ======

**Bioavailability** refers to the proportion of a drug or other substance that enters the bloodstream when it is introduced into the body and is thus able to have an active effect.

===== Key Points =====

  * **Absolute bioavailability** compares the bioavailability of the same drug given via a non-intravenous route (e.g., oral) to its bioavailability when given intravenously (IV). IV administration is considered 100% bioavailable.

    ^ Formula: ^
    | **Absolute Bioavailability** = ((AUC_non-IV / AUC_IV) × (Dose_IV / Dose_non-IV)) × 100 |

  * **Relative bioavailability** compares the bioavailability of two different formulations of the same drug.

===== Factors Affecting Bioavailability =====

  * First-pass metabolism
  * Drug formulation (e.g., tablet vs. liquid)
  * Solubility
  * Gastrointestinal pH and motility
  * Presence of food
  * Enzyme activity or transport proteins in the gut/liver

===== Clinical Relevance =====

  * Important in dosing decisions
  * Affects therapeutic equivalence of generic vs. brand-name drugs
  * Relevant in drug design and pharmacokinetics studies