04 Drug Elimination

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Zero Order

• for each unit of time (horizontal line), eliminate 5 units
• rate is constant x drug concentration to 0th power
• know the drugs

First order

• unit change is varying, percent change same
• time it takes to fall from 4 to 2 is same as time takes from 2 to 1

Elimination

• more blood flow = more elimination

• at high concentration of drug, drug operating at Vmax rate = zero order operation

Urine pH

• A- and B+ excreted

• acidic urine: favors HA form and reabsorption
• alkaline urine: favors BOH and reabsorption

Metabolism

Phase 1

• active, not ready for excretion
• prodrug to drug

Phase 2

• very polar inactive to kidney for excretion