Pharmacokinetics Flashcards
What is pharmacokinetics
what the body does to the drug
ADME;
absorption distribution, metabolism, excretion
How do drugs get administered?
Intral;po (orally), rectal, Intradermis, sub-Q, intra-muscle, topical, intravenous, inhaled, buccal(between teeth), sublingual.
how do drugs get absorbed?
Passive diffusion, facilitated diffusion, Active transport, endostosis.
REMEMBER: This is only when a drug is not taken in intravenously.
Passive diffusion
High to low concentration
Has to be small + hydroliphic
Can pass through cell membrane and through the basal lateral membrane into the blood
Facilitated diffusion
High to low concentration
Needs a protein to pass through the concentration
Large: or hydrophilic
Active transport
Low to high concentration
Large or hydrophillic drug
Needs to be pumped via ATP
Endocytosis
Too big to be transported.
Needs receptor mediated endocytosis
binds onto receptors on the outside of the membrane which will trigger endocytosis which is the drug being taken into the cell, and then exocytosed into the blood stream. Ex. B12
What can impact absorption?
Ph, Blood flow, TSA + contact time, P-glycoprotein
pH
Charged molecules are more difficult to be absorbed: want nonpolar elements which are easier to be moved.
Weak acids need to be put in an acidic environment in order for it to be absorbed
Weak bases needs you to shift the reaction; needing to make the environment more alkaline for the drugs to be absorbed
Blood flow
Need good blood flow;
less blood flow: less absorption
Diseases which decrease blood flow means any orally or rectally or through the skin cannot ensure that it can be absorbed
Total surface area and contact time
not enough time for it to absorb
Ex: diarrhea you are decreasing absorptioin because you’re decreasing the contact that the drug will have.
Ex. Constipated- tons of contact time with an increase of absorption
the intestines: increases the total surface area… any intestinal diseases decrease the TSA which means it decreases the absorption
p-Glycoprotein
Drug resistance… from
A special p-glycoprotein on the apical surface and it just spits it back out and then you will poop the drug out
So it decreases the absorption
Bioavailability (F)
Fraction of the drug that actually does enter into the systemic circulation
IV = 100% bioavailability
Any other way will have not 100% because of all of the factors
Orally: the concentration will rise but it will start to fall because of metabolism. 100Mg but possibly only 50Mg get into the system. F=Auc oral/Auc IV. F=50mg/100mg= 50% is the bioavailability
Solubility
Hydrophobic, small: easily pass and there can be more bioavailability and absorption
Hydrophilic, large drug: lower absorption, lower bioavailability