CPT1: Absorption Flashcards
What is pharmacokinetics?
The study of the rate and extent of absorption. So the Absorption, distibution, metabolism and excretion of the drug
What is pharmacodynamics?
What the drug does to the body
What does pharmaokinetics tell us?
- What dose to give
- How often to give it
- Some drug interactions
- How to changre the dose in certain medical conditions
What is absorption?
The movement of the drug from the site of admiinistation to the blood stream (across membrane)
What are factors effecting the rate of absorption?
- Route of administration
- Dose
- Lipid solubility
- Weak acid/ base
Give examples of different routes of administrations and their corresponding sites of absorption
- IV - directly into venous blood
- IM - muscles
- Subcutaneous - into blood from skin layers
- Epidural - epidural space
- oral - mouth —> GI tract
- Sublingual - under tounge into blood stream
- buccal - oral muscosa to blood stream
- intra-octular - eye
- topical - skin
- respiratory tract - nasal passage way or lungs
What is ionisation?
The additional/ removal of an electron
process where an atom/ molecule aquired a +ve or -ve charge
- What is the henderson - hasselbalch equatoin?
- Referring to the equation, when does pKa = pH?
- what is the equation for pH?
- pH = pka + log( [A-]/ [HA])
- When A- = HA then pH = pKA and the drug is 50% ionised
- pH = -log[H+]
What is the equation used to determine %ionisation?
%ionisation = 100/ 1+ AL(pKa-pH)
What are the mechanisms for crossing membranes?
- Passive
- Active
- Facilitated
What are the requirements for passive diffusion?
- lipid solubilty
- water solubility
Describe facilitated diffusion
A selective gate way allowing entery of one group of molecules
Describe active transport
- Requires ATP
- Moves against conc gradient
- What are P-glycoproteins
- What do they do?
- Proteins with a carbohydrate attached
- P-Glycoproteins sit on apical membranes and when substances cross the apical membrane the P-Glycoprotein causes it to be activately effluxed back into the gut. ATP dependent
Where are G-glycoproteins located and what is there function there?
- intestine - prevent absorption
- liver - excretion into bile
- kidney - excretion into urine
- brain - prevent entery from blood to brain
