DRUG ADMINISTRATION & ABSORPTION Flashcards
Wh at are the 4 main processes of pharmacokinetics?
Absorption, distribution, metabolism, elimination/excretion
What are the 3 routes of drug administration?
Topical, parenteral, enteral
Examples of topicals:
- skin
-inhalers
-eye and ear drops
Examples of enteral:
-oral
-rectal
Examples of parenteral:
-intravenous (in the vein, quicker, bypasses absorption)
-subcutaneous (under the skin)
-intramuscular (into muscle)
-transdermal (through skin)
-intrathecal( into spine)
-sublingual (under tongue)
Medication goes straight into the bloodstream
Process of oral drug administration:
Stomach, portal vein, liver, systemic circulation, target tissue, target cell
What is drug absorption?
Movement of a drug from its site of administration body across membranes, and circulating fluids (bloodstream).
Drugs must first dissolve (seperate from the excipient) in stomach and/or intestinal fluids which are largely composed of water
What must happen for a drug to dissolve?
MUST be in water!!!
What must happen for a drug to get in the bloodstream?
MUST dissolve in lipids (fat)!!!
All drugs must be ________, although they can be ________ IF they are taken with food.
- SOLUBLE
- NON-SOLUBLE
What do biological fluids consist mainly of?
Water, polar environment
Orally administered drugs are bound to excipients that add bulk to the tablet, but also can:
- enhance the rate of dissolution
- slow the rate of dissolution
- alter hepatic enzymes (first pass effect)
A drug cannot be absorbed until it is:
Free of excipients, it must be dissolved first
If a drug is water soluble (polar), can it be administered IV ?
YES
- since IV administration skips the process of absorption, a fast onset of action is expected
What is passive diffusion?
- most common mechanism
- movement is dictated by the concentration gradient
- move from a high to low concentration gradient until equilibrium is reached
- drugs must be small in size an lipid soluble to pass through biological membrane via diffusion
What is carrier-mediated transport?
- this process requires energy
- drugs can move against the concentration gradient
- drugs that are large in size and highly water soluble must be actively transported across biological membrane in order to reach their target site
Stomach:
- distensible, we’ll vascularized area
- stomach fluids are highly acidic (pH of 2)
- contains powerful hydrolytic enzymes
Small Intestines:
- Highly vascularized area
- greater SA than the stomach
- highly basic (pH=8)
Acids:
- compound that ionizes in water to produce a protein
- most acidic drugs used in pharm are weak acids
- when dissolved in water these drugs dissociate into a negatively charged anion and proton
AH is the neutral or non polar form of the drug (can be absorbed)
Bases:
- a compound that accepts (protons) in water
- most basic drugs used in pharm are weak bases
- when dissolved in water these drugs associate with a proton an becomes positively charged
B is the neutral or non polar form of the drug (can be absorbed)
In acidic environments, are weakly acidic drugs non polar or polar?
Remain in their non polar form
In basic environments, are weakly acidic drugs polar or non polar?
They become polar
What happens when the pH of a solution decreases?
Becomes more acidic, the concentration of the AH increases
Absorption of weakly acidic drug in the stomach:
Weakly acidic drug is absorbed
- passes through biological membrane an into plasma
