Dosage Regiments/Intervals

When would we use a drug free interval?

When the drug toxicity is related to length of it being in the system and not concentration

What is the therapeutic goal when dosing?

Maintain antibiotic above the bacterial MIC for the entire dosing interval

What happens to Cmax when you give the same daily dose but over multiple administrations?

The Cmax decreases

Do you want a high or a low CMAX?

It depends on the drug. Some are more efficacious after reaching a certain CMAX and some or toxic if the CMAX is too high

What happens to Cmin when you have a constant total daily dose and split the dose into multiple administrations?

It increases

Do you want a small Cmin or a large Cmin?

Depends. Some drugs needs the concentration to be above a certain minimum and some drugs have toxic effects based on maintaining concentrations over a certain Cmin

What is a major consideration when doing multiple doses?

What is the accumulation of the drug at that moment

How can you estimate the accumulation of a drug if using multiple dosing?

Is dosing interval and T1/2 is known

What determines the extent of accumulation from first dose to steady state?

Half-life

At what point is there going to be double accumulation when giving multiple doses?

When the next dose is after 1 half life

How long does it take to get to Css (steady state) without a loading dose?

5 half lives

What is the Css determined by?

Clearance

How can we control the Css?

Dose

What are Cmax and Cmin based on?

Volume of distribution, absorption, elimination

How can we control Cmax and Cmin?

Dose and dose interval

What is extent of accumulation determined by?

T1/2

How can we control the extent of accumulation?

Dose interval