Multiple Dosage Regimens - Pre Lecture Flashcards
What is a good dosage regime?
Drug concentration is between MEC an MTC (therapeutic window)
How do you maintain drug concentrations within the therapeutic window?
- Magnitude of dose: increase or decrease dose
- Dosing intervals: increase or decrease dosing frequency
What is the frequency (dosing interval expressed as?
tau (τ)
How do we determine multiple dosing regimens?
PK parameters obtained from single dosing and use this information along with dose and dosing interval to predict the effects seen from a particular dosing regimen
Describe steady state of multiple oral dosage regimen?
- AUC of a single dose is equal to AUC of a single dosing interval
- Cmax and Cmin are constant and remain unchanged from dose to
dose
What is the equality of AUC mean?
That elimination is first order and that subsequent doses of a drug do no affect the PKs observed after a single dose
What is the principle of superposition?
Concentrations due to a second dose are additive to subsequent doses
Taking single dose data and assume that multiple doses will add to existing concentrations
What are the reasons for non-linearity?
- Changing pathophysiology in the patient
- Saturation of a drug carrier system
- Enzyme induction
- Enzyme inhibition
What occurs as the number of doses increases?
Cmax differences become small
What is Cmax used for?
Evaluate drug accumulation and to evaluate drug safety (MTC)
What is accumulation ratio?
- Ration of Cmax/Cmax of first dose
- Examines drug accululation after multiple doses
What happens when number of doses increase mathematically?
Describe the accumulation ratio after single IV bolus?
Describe the accumulation ratio for multiple IV injections before steady state?
Describe the accumulation ratio for multiple IV injections at steady state?
How do you find Cmax?
How do you find Cmin?
How do you find Cavg?
