Exam 1 Flashcards
Do oral or IV administration dosage forms directly enter the systemic circulation?
IV
The drug is considered _________ until it enters the blood stream
Outside the body
For a PK curve describe Tmax and To for an IV bolus
Tmax = To
For a PK curve describe Tmax and To for an oral dose
Tmax does not equal To
For oral doses what causes the Cmax delay?
Absorption: access of the drug to the systemic circulation
All extravascular delivery routes rely on what process?
Absorption
Kinetically, the absorption of most drugs follow what order process?
First order
What are the 3 key steps in drug absorption?
- Disintegration (for solid dosage forms)
- Dissolution (for solid dosage forms)
- Diffusion across the GI membrane
Compare the stomach to the small intestine
Stomach: relatively smooth (low SA)
Small intestine: numerous folds and projections (high SA)
How many L’s are secreted by the GI tract?
8-10L
When going from the stomach to the duodenum what happens to pH and enzymes?
Rapid change (pH 5-8)
More enzymes are introduced
In the GI tract what areas are the most efficient for drug absorption?
Duodenum, jejunum, and upper illeum
Where do drugs have longer residence time in the GI tract?
Duodenum
What is the typical range of absorption half-lives for oral solutions and rapidly disintegrating DF?
From 15 min to 1 hour
What are the underlying one-compartment model assumptions?
- Passive diffusion is operative at all times
- Both absorption and elimination of a drug follow a first order process
- Drug is eliminated in an unchanged form (i.e. no metabolism occured)
Elimination half-life, elimination rate constant, the apparent volume of drug distribution, and system clearance are _______ of ROA
Independent
Absorption of a drug from a tablet dosage form includes the following steps?
Disintegration to disssolution to diffusion through the membranes
Which PK parameters are independent of ROA?
Volume of distribution, elimination half-life, clearance, and elimination rate constant
Ka = what order constant?
First-order
What is the value that shows the fraction of drug available at the absorption site (GIT) that is absorbed per unit of time?
Ka
A high Ka = what
Rapid absorption
At Tmax
Ka = what
Ke
Elimination phase
Ke __ Ka
> >
Absorption phase
Ke __ Ka
«
When does the elimination process begin after the drug is administered?
Almost immediately
What is affect by both absorption and elimination during the absorption phase?
Cp
The amount of drug in the body (Db) ______ if the rate of drug absorption larger than the elimination rate
Increases
Drug Y (150mg) is given as an oral solution and has the following PK parameters: t1/2 = 8 h, ka = 0.25 h-1, Vd = 10 L, F = 1. What will be the plasma concentration at 12 hours after the dose is administered?
7 mg/L
Manini et al (2005) reported a case of adverse drug reaction in a previously healthy young man who ingested a recommended dose of an over-the-counter (OTC) cold remedy containing pseudoephedrine. Forty-five minutes later, he had an acute myocardial infarction (MI). Elevations of cardiac-specific creatinine kinase and cardiac troponin I confirmed the diagnosis. Cardiac magnetic resonance imaging (MRI) confirmed a regional MI. Cardiac catheterization 8 hours later revealed normal coronary arteries, suggesting a mechanism of vasospasm.
Why the patient developed a sever adverse reaction at a therapeutic dose?
The elimination process in the patient is not as fast as expected
For an oral dosage form, which expression correctly describes the relationship between Ka and Ke at the absorption phase?
Ke = Ka
Ke > Ka
Ka > Ke
Ka»_space; Ke
Ka»_space; Ke