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
explain how solutions given by parenteral route can vary
-vegetable oil or water
-vegetable oil is likely to be more slowly absorbed than a solution with water
–control of absorption
Name 4 routes of administration for the parenteral route
-intravenous
-subcutaneous (administered to fat layer)
-intramuscular
-intradermal (administered to dermis)
What are the 2 types of intravenous injections and explain them
bolus —- single, small volume injection
infusion — slow, large volume
Intravenous injections are _____ solutions. WHY
aqueous.
there can be NO PRECIPITATION within the circulatory system. this could produce emboli (blocked artery)
Why might a fat emulsion be used in an intravenous injection?
for caloric sources. Glucose doesn’t cut it for some patients
Can a suspension be used for an intravenous injection? Why or why not
NO
The particle size of the drug CANNOT BE BIGGER THAN AN RBC. (7 micrometers). They are larger than that in a suspension
Subcutaneous injections are injected into…..
and what volume
loose subcutaneous tissue at a volume of 2mL or less
what are some sites of subcutaneous injection
forearm, upper arm, thigh
Do subcutaneous injections HAVE to be aqueous solutions?
no!
they can also be suspensions or pellets
Where are intramuscular injections given? Why?
DEEP INTO SKELETAL MUSCLES such as gluteal or lumbar muscles
This is done to avoid hitting a nerve or a blood vessel
Do intramuscular injections HAVE to be aqueous solutions?
no—-
they can be aqueous or oleaginous solutions
or
suspensions
What does oleaginous mean
oil based
What is an advantage of intramuscular injections
Certain drugs, because of their low solubility, provide sustained drug action after an intramuscular injection
ex: penicillin G benzathine provides 7-10 days of effect
is dissolution slower in aqueous or oleaginous solutions
oleaginous
where are intradermal injections given and at what volume
in the corium (dermis) of the skin
given at VERY SMALL VOLUMES (~0.1mL)
sites: arms and back
when are intradermal injections given?
tuberculin or allergy testing
does the epicutaneous route of administration give local or systemic effects?
both
Drug absorption via the skin is enhanced if…
-it is in solution
-if it has a favorable lipid/water partition coefficient
-if it is a nonelectrolyte
Drugs that are applied by the epicutaneous route (on the surface of the skin) are absorbed by….
-pores
-sweat glands
-hair follicles
-sebaceous glands
Name some drugs applied to the skin surface for percutaneous absorption and systemic action (disk or patch)
-nitroglyicerin
-estradiol
-clonidine
-scopolamine
-Fentanyl
-nicotine
Are pharmaceutical preparations applied to the skin usually for systemic or local effects?
usually local (antiseptic, antifungal, antinflammatory, etc)
what are local applications used for
antiseptics
antifungal
anti-inflammatory
local anesthetic
skin emollients
protectants
What are the potential dosage forms for LOCAL applications via the epicutaneous route
Semisolid dosage form (ointment, cream, paste)
solid dry powder (aerosol sprays)
liquid dosage form (solutions and lotions)
Ointments are a _____ dosage form
semisolid
The ointment base is either…
hydrophobic or hydrophilic
is there a universal ointment base for all drugs?
NO
Are ointments greasy or non greasy
greasy
Creams are a ______ dosage form
semisolid
creams are _______, meaning they contain oil and water
emulsions
differentiate between creams and ointments
creams are less viscid (sticky), are lighter than ointments, and are nongreasy
Pastes are a _____ dosage form
semisolid
Which has the MOST solid substance —- creams, ointments, or pastes?
pastes
Since pastes are more solid than ointments, what can you say about their action
pastes are stiffer and less penetrating. Therefore, they are not so much used for therapeutic effect as for protective action (absorbing discharge from skin lesions)
if therapeutic effect is the main concern which will be the preference —- creams, ointments, or pastes
creams or ointments – NOT PASTES
Powders are a _____ dosage form
solid
powders can be used ___ or ___
orally or locally
What can you say about the particle size of the powder
the powder should NOT BE GRITTY AND CAUSE IRRITATION ON THE SKIN
Give examples of when a local topical powder would be prescribed
for diaper rash, chafing, and athlete’s foot
Lotions are a ____ dosage form
liquid
–suspension of solid drug (VERY SMALL PARTICLES) in an aqueous vehicle
are lotions greasy or nongreasy
nongreasy
lotions are mainly used for…..
large skin applications
why is lotion the choice when a large skin area is concerned?
because lotions are less viscous than the other options (after all, it’s a liquid dosage form) and is thus easier to spread
name 4 dosage forms for the ocular route
-sterile solutions
-sterile suspensions
-sterile ointments
-delivery systems
between optic ointments, suspensions, and solutions, rank them according to how long they stay on the surface of the eye
longest — ointments
second — suspensions
shortest —– solutions
for both the ocular route and nasal route, the solutions must be ___. why?
ISOTONIC to reduce irritation to the local tissue
Name 4 dosage forms via the nasal route
solutions — decongestants
sprays
inhalers —– decongestants
delivery systems
Does the rectal route have predictable drug release and absorption?
NO — parenteral route does
is there an intranasal route for nitroglycerin
NO
there is….
sublingual
buccal
oral
ointment
transdermal infusion
does passive transport mean that the drug is highly lipid soluble?
no
