Pharmacokinetics: Difference between revisions
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[[Image:DrugPk.png|600px|thumb|right|Diagram of Drug Concentration with key PK characteristics highlighted]] | [[Image:DrugPk.png|600px|thumb|right|Diagram of Drug Concentration with key PK characteristics highlighted]] | ||
[[Pharmacokinetics]] (PK) measures the variations of drug levels in the body with relation to how much compound you take and time since taking the [[Pharmaceutical Drugs|pharmaceutical compound]]. | [[Pharmacokinetics]] (PK) measures the variations of drug levels in the body with relation to how much compound you take and time since taking the [[Pharmaceutical Drugs|pharmaceutical compound]]. | ||
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===Bioavailability (F)=== | ===Bioavailability (F)=== | ||
This is the amount of a drug that actually makes it into your bloodstream as compared to the amount you put in your mouth, inhale, or inject. Since the body has dozens of defense mechanisms to keep foreign compounds out of your blood, simply getting the active compound into your bloodstream is pretty difficult. Drug compounds must pass through the hostile stomach, must avoid setting off an immune response, must avoid being metabolized by the liver and ultimately be absorbed by the small intestine in order to make it into the blood. | This is the amount of a drug that actually makes it into your bloodstream as compared to the amount you put in your mouth, inhale, or inject. Since the body has dozens of defense mechanisms to keep foreign compounds out of your blood, simply getting the active compound into your bloodstream is pretty difficult. Drug compounds must pass through the hostile stomach, must avoid setting off an immune response, must avoid being metabolized by the liver and ultimately be absorbed by the small intestine in order to make it into the blood. | ||
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===T<sub>max</sub>=== | ===T<sub>max</sub>=== | ||
How long after taking the drug does the drug hit its C<sub>max</sub>, typically measured in hours. It is a measure of how long you have to wait before the drug hits maximum effectiveness along with when you can expect short term side effects to reach their peak. | How long after taking the drug does the drug hit its C<sub>max</sub>, typically measured in hours. It is a measure of how long you have to wait before the drug hits maximum effectiveness along with when you can expect short term side effects to reach their peak. | ||
===Volume of Distribution (V<sub>d</sub>)=== | |||
The volume in which a drug is distributed after it has been injected intravenously and has equilibrated between the blood plasma and surrounding tissues. Although this value has no literal physiological meaning, V<sub>d</sub> is indicative of the extent of distribution of the drug. In general, highly plasma protein bound drugs will have a small V<sub>d</sub> while those drugs that are bound within tissues will have a large V<sub>d</sub>. As a rough approximation: | |||
{| class="wikitable" border="0px" width="400px" style="text-align:center" | |||
|- | |||
! colspan="2" align="center"| V<sub>d</sub> Distribution Extent Comparisons | |||
|- | |||
! V<sub>d</sub> (L) | |||
! Extent of Distribution | |||
|- | |||
! 5 | |||
! Only In Plasma | |||
|- | |||
! 5-20 | |||
! In Extracellular Fluids | |||
|- | |||
! 20-40 | |||
! In Total Body Fluids | |||
|- | |||
! >40 | |||
! In Deep tissues; Bound to Peripheral Tissues | |||
|} | |||
===Clearance (Cl)=== | ===Clearance (Cl)=== | ||
This is a measure of the volume of plasma cleared of the drug per unit of time. In other words, how much of your blood is rid of the drug per unit of time. | This is a measure of the volume of plasma cleared of the drug per unit of time. In other words, how much of your blood is rid of the drug per unit of time. | ||
===Area Under the Curve (AUC)=== | ===Area Under the Curve (AUC)=== | ||