Pharmacology administration Flashcards
What does absorption mean?
Can you name 2 factors that affect absorption in general?
(Hint think about IV drug)
It is the TRANSFER of the drug from the site of administration (e.g. orally/intravenous/topical) to the SYSTEMIC CIRCULATION
The SITE of absorption -> where and how it is administered.
The drug FORMULATION -> what is it made of, is it coated/not coated?
What does BIOAVAILABILITY mean?
The FRACTION of the drug that actually reaches the SYSTEMIC CIRCULATION.
The calculation is this:
F = Amount reached to the systemic circulation/Amount administered
Can you explain the effect of pH in the stomach to a medication?
The stomach has a low pH. A low pH means that it has a high concentration of hydrogen ions. Drugs can be weak acids.
When the hydrogen reacts with the drug (a weak acid) (A), the system will favour the forward reaction to reduce the number of hydrogen ions present. This will favour the reaction that produces the non-ionic product. The product will therefore be able to cross the cell membrane and therefore can be absorbed.
Describe the mechanisms underlying passive diffusion
and active transport of drugs
Passive diffusion
→ small molecules faster
→solubility in the lipid bilayer
Facilitated Transport ( = carrier-mediated) is
* passive
* bidirectional
* relies upon concentration gradient
e.g. SLC (solute carrier) Superfamily
* Organic Anion Transporters
* Organic Cation Transporters
If drug is a substrate for transporter/carrier
which pumps drugs back into lumen
* ATP-driven pumps
* ABC Superfamily e.g MDR1 (P-glycoprotein)
What is the therapeutic range?
What factors affect this?
This is the concentration of the drug in plasma where it is high enough for it to be therapeutic, but low enough to avoid toxicity.
The RATE OF THE RISE affects how quickly it gets to the therapeutic window, and how it stays there.
The WAY the drug is administered and the RATE it is absorbed impact whether the drug can get into the therapeutic window.
What is bioequivalence?
They have the SAME ACTIVE INGREDIENTS, and have SIMILAR BIOAVAILABILITY
Describe the absorption of a medication after oral intake?
- Medication is taken orally
- The medication is dissolved - the drug might be coated, to make sure that it is not broken down by the stomach acid/enzymes, or to protect the stomach
- It is mainly absorbed in the intestines because of the villi and microvilli. Factors such as the type of medication affects absorption (e.g. hydrophobic or polarity).
- Enters the portal vein
- Enters the vein in the liver
- Enters the circulatory system.
Meaning of “first pass”?
When the drug is metabolised by the enzyme in the liver and the gut
What are the 8 actors affecting absorption of medication taken orally?
GASTRIC EMPTYING - if you had food, the medication stays in the gut for longer, if not, it will pass through and it is not absorbed well;
GASTROINTESTINAL MOTILITY - peristalsis (how your IG walls move)
BLOOD FLOW
PARTICLE SIZE - how big is it and it’s molecular weight
PARTICLE FORMULATION - is it extended-release made, does it have an enteric coating?
PHYSIOCHEMICAL FACTORS - soluble, binds to calcium like milk (problem - it wont be absorbed well)
METABOLISM - is it metabolised by enzymes in the intestines?
What does the metabolism of a drug in the intestines or liver do?
Either activate it or inactivate it
What are 3 ways to administer through the GI system (ENTERAL administration)?
Orally through SUBLINGUAL and BUCCAL - under the tongue and on the cheeks
DUODENAL - by tube
RECTAL - if people are vomiting can cause irritation
AVOIDS FIRST PASS
Name the 7 routes of administration with examples
Sublingual - angina medication
Intramuscular - contraceptive
Subcutaneous - local anesthetics
Rectal - antiepileptic drug
Inhalation - for COPD
Topical - Ibuprofen, corticosteroids
Interarticular - anti-inflammatory - corticosteroids
What is the difference between pharmacokinetics and pharmacodynamics?
Pharmacokinetics - how drug it reaches the blood stream
Pharmacodynamics - whether it is toxic or not and therapeutic or not
What stops drugs from entering the interstitial fluid (from the blood vessel) or being broken down in the cell
The drug is BOUND to a protein.
What is drug elimination and how does it differ from drug clearance?
Drug elimination is the removal of the drug from the bloodstream.
