PM2B In-Class Test Revison
- Created by: odionj01
- Created on: 13-03-20 10:53
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- PM2: Med Design
- Therapeutic Index: Measurement of the safety of a drug (lethal dose for 50% of the population divided by effective dose for 50%)
- Definitions
- Bioavailability:The fraction (F) of an orally administered dose that reaches systemic circulation.
- pKa: A measure of how strong or weak an acid FG within a molecule is.
- pKa= -log(Ka)
- The lower the pKa value indicates a stronger acid. Thus, would be fully ionised
- Only unionised drug molecules are able to cross plasma membranes
- LogP: The log of the partition coefficient of octane/water.
- P: The Partition coefficient measures the partitioning of API between octanol phase and water phase.
- Octanol phase= hydrophobic/lipophili. More positive value= likes lipid environment
- Water phase=hydrophilic. More negative value= likes aqueous environment.
- P= [organic]/[aqueous]
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- LogP=0means that there is equal partition between octanol and water
- P: The Partition coefficient measures the partitioning of API between octanol phase and water phase.
- Vd: The volume that would contain the total body content of the drug (Q) at the concentration equal to that present in the plasma (Cp).
- Vd= Q/Cp
- Half-life: The time it takes for drug from maximum concentration (Cmax) to reach half the maximum concentration in the body.
- The longer the half-life, the longer the drug will last in the body after dosing is discontinued.
- Bioavailability
- For a drug to reach systemic circulation (lumen of small intestine). It must penetrate local barriers and experience first pass metabolism.
- The fraction (F) of orally administered dose is calculated by by a plasma concentration time curve
- The areas under the plasma concentration-time curve (AUC) are used to estimate F.
- F= AUC oral/AUC intravenous
- The areas under the plasma concentration-time curve (AUC) are used to estimate F.
- The fraction absorbed following intravenous admin. is 1(100%)
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