Pharmaceutical factors Flashcards
What is a double blind clinical trial?
Neither the participants nor the experimenters know who is receiving treatment
What is the MCC?
Medicine controls council
What is triptorelin?
An LHRH agonist
What is rifapentine?
Anti-TB drug
Name obstacles in the international pharmaceutical industry
Patents Payor pressure Generic competition Safety concerns Reputation Earnings pressure
Which experimental heart pill created by Pfizer failed?
Torcetrapib
What is torcetrapib?
Cholesteryl ester transfer protein (CETP) inhibitor
What are pharmacokinetics?
Study of time course of drug concentration in the body
“What body does to the drug”
Name the aspects of drug input and output
LADMET Liberation Absorption Distribution Metabolism Excretion Toxicity
Which pharmacokinetic factors are most important to determine dose?
Volume of distribution (Vd)
Half life (t1/2)
Clearance (CL)
What is absorption?
Movement of drug from site of administration to target site
What is distribution?
Diffusion/transport of drug from intravascular space to extravascular space
What is metabolism?
Chemical conversion/transformation of drugs into compounds for easier elimination
What is excretion?
Elimination of unchanged drug/metabolite from body via excretory system
What is bioavailability?
The fraction of administered dug that reaches the systemic circulation unchanged
What is the formula for bioavailability and why?
AUCoral/AUCIV
Because IV is always 100% bioavailable
Which factors affect bioavailability and how?
All ADME processes
Poor absorption = low bioavailability
High first-pass metabolism = low bioavailability
When is steady state achieved?
Rate of drug absorption = drug elimination
Cp plateaus
Which drugs will a missed dose affect?
Narrow therapeutic index drugs
How do you calculate Vd?
Total amount of drug in body (mg)/drug Cp (mg/L)
What is Vd an indication of?
Lipophilicity
Plasma protein binding
What is the relationship between Vd and Cp?
Inverse
What is the relationship between Vd and half life?
Direct
As Cp increases, what happens to Vd?
Decrease
As Cp decreases, what happens to Vd?
Increases
As half life increases, what happens to Vd?
Increases
As half life decreases, what happens to Vd?
Decreases
What if half life?
The time necessary for the drug’s plasma concentration to decrease by 1/2
What is the therapeutic range?
Above minimum therapeutic concentration
Below minimum toxic concentration
What does half life provide an index for?
Time-course of drug accumulation
Time-course of drug elimination
Dosing interval
Which factors influence half life?
Elimination rate
Vd
Patient factors
What effect does a higher clearance have on half life?
Decreased half life
What is the effect of a short half life on duration of action, dosing frequency, compliance, steady state and side effects
Short duration Increased dosing Lower compliance Earlier steady state Quicker side effects
What is the effect of a short long life on duration of action, dosing frequency, compliance, steady state and side effects
Long duration Decreased dosing Higher compliance Later steady state Longer side effects
What are first order kinetics?
The constant fraction of drug eliminated per unit of time
In first order-kinetics, half life is constant/variable?
Constant
In first-order kinetics, half life is concentration dependent/independent
Concentration independent
What are zero order kinetics?
The constant amount of drug eliminated per unit of time
In zero-order kinetics, half life is constant/variable?
Variable
In zero-order kinetics, half life is concentration dependent/independent?
Independent
Name drugs that undergo zero-order kinetics
Phenytoin
Warfarin
Alcohol
Name rate-limiting factors
Absorption
Distribution
Metabolism
Excretion
What is clearance (CL)?
Volume of plasma cleared of drug per unit time
What is the equation for clearance?
Rate of elimination/drug Cp
How do you determine clearance in IV dosing?
dose/AUC
How do you determine clearance in oral dosing?
bioavailability x dose/AUC
How do you determine clearance in with Vd and half life?
0.693 x Vd/half life
How do you calculate maintenance dose rate?
CL x Css
When is steady state reached with every single drug?
4-5 x t1/2
A drug with a Vd <15L is likely…?
Hydrophilic
A drug with a Vd >40L is likely…?
Lipophilic
Name reasons for polypharmacy
Multiple diseases
Combination therapy
Complementary therapy
What does terfenadine interact with and why was it withdrawn?
Macrolides
Grapefruit juice
-> fatal arrythmias
What is terfenadine?
An antihistamine
What does astemizole interact with and why was it withdrawn?
Macrolides
Grapefruit juice
-> fatal arrythmias
What is astemizole?
An antihistamine
What does mibefradil interact with and why was it withdrawn?
Beta blockers
-> cardiogenic shock
What is mibefradil?
Non-selective calcium channel blocker
What does it mean if a drug has a narrow therapeutic index?
Therapeutic effects is close to the adverse effect threshold