Pharmacokinetics 1 Flashcards
List the 6 rights of prescribing
Right patient
Right drug
Right route
Right dose
Right time
Right outcome
What is pharmacokinetics?
What the body does to the drug
Facilitates safe and effective use of medicines
Determines optimal dosage regimen (dose, route, dose interval, duration of treatment)
Predicts potential drug interactions
What is pharmacodynamics?
What the drug does to the body
What 4 processes are involved in pharmacokinetics?
Absorption
Distribution
Metabolism
Excretion
What is absorption in terms of pharmacokinetics?
Drug transfer from its site of administration to the systemic circulation (blood).
What are some routes of drug administration?
Enteral- Oral, Rectal, Sublingual, Buccal
Parenteral- injections, creams and patches
What are some factors which influence enteral absorption?
Gastrointestinal (GI) motility
GI blood flow
Drug particle size and formulation
Drug physicochemical properties
At what drug concentration is the ideal drug dose?
Between the minimum toxic concentration level and the minimum effective concentration
What are some concepts which must be considered when thinking about pharmacokinetics?
Absorption First-pass (pre-systemic metabolism) Bioavailability Volume of distribution Cytochrome P450 enzyme system Half-life Steady state Clearance
What is bioavailability?
Fraction of the oral dose of a drug that reaches the systemic circulation.
Bioavailability =Oral AUC/IV AUC
If a drug has an oral bioavailability of 20%, the oral dose needed for therapeutic effectiveness will need to be … times higher than the corresponding IV dose
5
What is the AUC?
The total amount of the drug found in the systemic circulation
Why are patients asked to take some tablets a certain time before food?
To increase the absorption and bioavailability of the drug
Why is sublingual method used in some nitrates to treat angina?
Fast absorption
The liver removes so much of the drug that not much leaves the liver into the blood
What is the first pass (pre-systemic) metabolism?
This refers to metabolism of the drug prior to reaching systemic circulation.
The bigger the first pass effect the smaller the bioavailability and vice versa
