Drug dosing and elimination

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I'M_THE_TRADER_ (v3 - 23.05) (1)

luonut Carlos Perez

principles of Pharmacology

luonut Mashaal M Alghamdi

Stanley Cup Elimination Tree

luonut Garet Arsenault

Drugs In the body

luonut Shayla Tremblay

Drug dosing and elimination

Multiple dosing

Loading dose

Administering a larger initial dose followed by smaller maintenance dose

In instances where waiting for steady state is not reasonable

Maitinance dose

Practically, a steady state is reached after 3-5 half lives

Can be solved for if you have:

Max concentration

Drug swing

Peak dose minus trough dose when at plateau state

plateau state

After giving the same dose over the same interval for an amount of time, there will be a maximum dose that additional doses will not peak above

Dosing interval

a consistent time period between drug doses

adding additional dose before the origonal dose is excreted is cumulative and leads to a new peak of dose

compartment models

Multicompartment model

For many drugs 2 compartments is sufficient

Second compartment is the rest of the body

Can group together key organs

Used to account for distribution phase

modeling every organ is unrerasonable

One compartment model

Used for:

Aminoglycosides

Antibacterial drugs

Assumes drug is freely distributed and eliminated

A method of approximating drug distribution

Pharmacokinetics

Half life

Rate constant can be calculated for a drug

Does not apply to second order drugs

Plasma half life does not always equal pharmacological half life

Some things that can cause discrepency

DNA damaging drugs

Irreversible receptor binding

Amount of time for half of initial concentration to be cleared

Constant time irrespective of initial concentration

Zero order

Zero order drugs

Phenytoin

salicylate

Alcohol

Elimination of drug is constant

Some first order drugs at high concentrations function as zero order drugs

irrespective of drug concentration

First order

Drug elimination dependent on concentration

Constant percentage of drug eliminated

Accounts for most drugs

Bioavailability

Bioequivilence

Two drugs with varying concentration of the same therapeutic ingredient and different routes of administration, but same bioavailability

Can be used to compare drugs

Drugs with the same route of administration and mechanism can compare efficiency by bioavailability

Intravenous administration is 100% bioavailable

dependent upon routes of administration

Ammount of drug that reaches circulation