Part 6 Flashcards
Explain why suspensions have a higher dissolution and absorption rate than powders
suspensions are FINE particles suspended in a liquid vehicle. Therefore, the surface area is higher increasing the dissolution rate
POWDERS are GRANULES. They are larger and have a smaller surface area than fine particles
rank the following according to dissolution rate:
tablet
capsule
suspension
powder
highest: suspension>powder>cap>tab
IN ORDER FOR ABSORPTION TO TAKE PLACE….
the drug must be in solution
What is the term for a tablet becoming granules
disintegration
what is the term for granules becoming fine particles
deaggragation
Absorption of drugs via oral route can occur anywhere between….
the mouth and the rectum
The highest absorption occurs in…..
the alimentary tract (small intestine)
What are the parameters affecting absorption
-gastric emptying time
-large volume of water
-degree of drug ionization
-drug’s interaction
-controlled release
explain how gastric emptying time affects absorption via the oral route
-the presence of fatty foods SLOWS gastric emptying. fatty foods have the most slowing effect, then proteins, then carbohydrates
-if you lie on the right side when bedridden, the pylorus will sit right on top of the stomach, raising gastric emptying time
-some drugs such as morphine have a quieting effect on the GI tract and can slow movement, increasing gastric emptying time
the higher the gastric emptying time, the _____ the absorption
slower
Explain how large volume of water affects the absorption rate
If a medicine is taken with a large volume of water (8 oz = 1 glass), gastric emptying is facilitated and absorption is increased
explain how the degree of ionization affects absorption
the pH of the GI tract increases progressively along its length from pH 1 in the stomach to pH 8 at the far end of the intestines.
pH has a definite bearing on the degree of ionization of most drugs, and this affects:
-lipid solubility
-membrane permeability
-absorption
As a general rule, weak acids are largely ________ (ionized or unionized) in the stomach
unionized
Since weak acids are largely unionized in the stomach, what can you say about their absorption here?
weak acids are absorbed fairly well from here
Are weak bases ionized in the stomach? what can you conclude about the absorption of weak bases in the stomach?
weak bases ionize in the stomach, and are NOT readily absorbed there
if an antacid drug is taken, what would occur?
alkalinization would occur.
this would decrease the gastric absorption of weak acids and increase the gastric absorption of weak bases
Do strong acids and strong bases readily absorb? explain
NO — due to their high degree of ionization
WHY does the small intestine serve as the major absorption pathway for drugs?
because of the suitable pH and the large surface area available along its 20 foot length
pH is about 6.5, thus weak acids and weak bases are well absorbed from the intestinal surface
most drugs are…
weak acids or weak bases
Explain how the drug’s interaction can affect absorption
if a tetracycline is taken with milk, a complex will be formed. this will reduce solubility of the drug and bioavailability
What is the measure of a degree of ionization
the hendersen hasselbach equation
A drug has to be (ionized or unionized) to cross the cell membrane
UNIONIZED
What can you say about the solubility of sublingual drugs
they are EXTREMELY SOLUBLE and rapidly dissolving
what can you say about the concentration of sublingual drugs
they have a HIGH drug concentration and avoid the first pass effectr
Does swallowing have to occur for a sublingual drug
no
What is a major advantage of the rectal route
~50% avoids the first pass effect (bypasses hepatic vein and the liver enzymes — metabolization) liver enzymes destroy the drug before it reaches circulation
are drugs given rectally for their local effects or systemic effects?
both
ointments for local effect
suppositories for systemic effect or local effect (hemrrhoids)
soluble drugs given rectally are usually absorbed by…
rectum and the colon
What are some advantaged of the parenteral route
-rapid absorption in case of emergency
-more predictable
-smaller doses – bc it’s put directly into circulation
-useful for uncooperative or unconscious patients
-pts who are unable to take oral meds
What are some disadvantages of the parenteral route
-once injected, there is no retreat (concern if toxic, overdose)
-frequent dosing
-more expensive (must be sterile, trained personnel usually do it)
Name 3 dosage forms for parenteral route
MUST BE STERILE (no bacteria):
solutions
suspensions
pellets