Lecture 6+7 - Pharmacology Basics

What determines bioavailability physical proper3es

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Unformatted text preview: binding, and other characteris3cs. (hydroxyl group) (amine group) Distribu&on: Depends on Blood Flow and Blood Brain Barrier •  Excludes ionized substances; •  Ac3ve transport mechanisms; •  Not uniform – leaky (circumventricular areas) Bioavailability •  The frac3on of an administered dose of drug that reaches the blood stream. •  What determines bioavailability? –  –  –  –  –  –  –  –  –  –  Physical proper3es of the drug (hydrophobicity, pKa, solubility) The drug formula3on (immediate release, delayed release, etc.) If the drug is administered in a fed or fasted state Gastric emptying rate Circadian differences Interac3ons with other drugs Age Diet Gender Disease state Depot Binding (accumula&on in faCy &ssue) •  Drugs bind to “depot sites” or “silent receptors” (fat, muscle, organs, bones, etc) •  Depot binding reduces bioavailability, slows elimina3on, can increase drug detec3on window •  Depot ­bound drugs can be released during sudden weight loss – may account for flashback experiences? Degrada&on & Excre&on •  Liver –  Enzymes(cytochrome P ­450) transform drugs into more water ­ soluble metabolites –  Repeated drug exposure increases efficiency tolerance •  Kidneys –  Traps water ­soluble (ionized) compounds for elimina3on via urine (primarily), feces, air, sweat Excre&on: Other routes •  Lungs...
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This note was uploaded on 03/21/2014 for the course COGS 174 taught by Professor Pineda during the Winter '11 term at UCSD.

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