Solid Dosage Forms Flashcards
What does GRAS stand for and what does it describe?
Generally Regarded as Safe, refers to excipients that have been used for a long time safely even if they haven’t been tested by the FDA
GRAS refers only to what kind of doses?
Oral doses
What does PCID stand for?
Physico-chemical Identifiers
These would allow you to accurately identify that the drug you have is correct and would prevent counterfeiting of the drug
PCIDs
Elimination is the sum of which two processes?
Metabolism and excretion
Buccal tablets are meant to be used where?
Between the cheek and the gum
Certain drugs are very highly 1st pass metabolized; what are three oral dosage forms designed to get around that?
Orally disintegrating tablets, Sublingual tablets, Buccal tablets
Why does it take 25 minutes for conventional tablets to reach the minimum effective concentration in the blood?
There is a 3-step process to release: Disintegration of the tablet to granules, Dissolution of the tablet into solution (rate determining step) and absorption of the drug into the bloodstream so it can be circulated.
What is the ONLY WAY for a drug to pass through a biological membrane?
In a solution
Should tablets be kept in the bathroom cabinet?
No, because the tablets absorbs moisture from the air and starts to break apart
What should you tell your pt who is receiving tablets?
Take them with water (necessary for disintegration/dissolution) and keep them away from excessive moisture
What are some concerns about oral delivery of drug products?
If molecule too big or poorly soluble, it may not be able to be absorbed by the GI tract; there are often side effects from having the drug in the blood, because there is no way to control which tissues the blood w/ drug travels too; not all drugs can handle the acidity and enzymes of the stomach/intestines; it can take drugs a long time to dissolve and permeate the body
This solid dosage form is geared toward children, the elderly, and the infirm…
Chewable tablets
Why do chewable tablets need to be highly flavored?
Because most drugs have a bad taste, and since the pt is chewing the tablets, the taste must be improved so the pt will be willing to take it
What do you need to tell a patient receiving chewable tablets?
Make sure to chew the whole tablet and swallow, do not swallow whole (can affect drug action in some cases)
At what pH will enteric-coated tablets start to break apart?
Around pH 4
What is the difference between enteric-coated and conventional tablets?
Enteric-coated tablets are coated so that at low pH (ie, in the stomach) the pills will not dissolve, while conventional tablets do not have any protection from the acidity of the stomach
What do you need to tell a patient receiving enteric-coated tablets?
Do not take the tablet with antacids (it would raise the pH of the stomach and make the tablet dissolve too quickly)
What do you need to tell a person receiving sublingual or buccal tablets?
Don’t take the tablet with liquid or drink for about 10 minutes after taking (will wash drug into stomach and defeat the plan to avoid 1st pass metabolism as much as possible)
What are effervescent tablets?
Tablets designed to be dissolved into a solution and then drunk
What are some advantages of effervescent tablets?
Helps mask the taste of the drug, helps solubize some drugs (ie aspirin)
What do you need to tell a pt receiving effervescent tablets?
Wait til the entire tablet has dissolved before drinking (tablets themselves usually quite large, so would be difficult to swallow)
What are some differences between tablets and capsules?
Capsules have their drug product encases in a thin gelatin shell, while tablets have their drug and excipients compressed together; capsules have fewer ingredients (less need for excipients to add bulk)
What few excipients do capsules contain?
Diluents (increase capsule volume), Lubricants (make powders flow in filling machines easier), Colors (to make capsule shell easier to identify)
Why would a capsule be preferable to a tablet in some cases?
Easy to handle/swallow, tasteless and odorless so no need for extra coating, fewer ingredients so can be cheaper to make
What are some problems with capsules?
They cannot be “split” to change the dose, are sensitive to too much moisture, are 1st pass metabolized, might be poorly absorbed by GI tract
Instead of a disintegration step, what is the first step in the activation of a capsule?
The capsule rupture step (water softens the shell so enzymes can act to break open the capsule)
Is the capture rupture step or the disintegration step slower?
The capsule rupture step is slower than the disintegration step for tablets
What promotes cross-linking of gelatin in capsules?
Moisture and age of the proteins (as proteins age they cross link)
What does cross-linking affect (on the concentration-time graph)
Tmax, Cmax, and AUC (area under the curve)
What are some advantages of modified release drugs?
Patient compliance increases when fewer doses must be taken, constant blood levels are important for therapy of some conditions, and for SOME drugs bioavailability better for slowly-released drug
What are different ways to create extended-release drugs?
Matrix diffusion, matrix erosion, encapsulation, and encapsulation (osmotic system)
Where is the drug located in matrix diffusion and what is the rate determining step?
Particles of the drug are dispersed throughout an insoluble polymer matrix, and the diffusion of the drug out of the matrix is the rate-determining step
What are some factors that affect the rate in matrix diffusion?
Molecular weight of polymer and cross linking of the matrix
Where is the drug located in matrix erosion and what is the rate-determining step?
Particles of the drug are dispersed in the polymer matrix, and the erosion of the polymer is the rate-determining step
Where is the drug located in encapsulation and what is the rate-determining step?
The drug is the core and coated with insoluble polymer, and the slow diffusion of the drug through the polymer shell is the rate-determining step
How is the rate modified in encapsulation?
Controlling the thickness of the shell
Where is the drug located in osmotic system encapsulation and what is the rate-determining step?
The drug is the core surrounded by a semi-permeable polymer with a laser-formed hole in the film, and the rate-determining step is the diffusion of the water into the film that dissolves the drug
What does semi-permeable mean?
Only water can pass through but nothing else
What does “zero order” release mean?
It means there is a constant rate of release
Which of the modified release technologies have a zero-order release?
Osmotic system encapsulation
What is dose-dumping?
When the controlled release mechanism fails for some reason and most or all of the drug is released quickly
How should you counsel patients to lower risk of dose-dumping?
Tell patients not to chew capsules or take the drug with alcohol
Divided powders are also called what?
Chartules
What are target populations for divided powders?
Small children and those who have trouble swallowing
What is the difference between bulk powders and divided powders?
Divided powders are packaged in “unit of use” envelopes while bulk powders are packaged in multi-dose containers
Do divided powders or tablets/capsules enter the blood faster? Why?
Divided powders are slightly faster because there is only one step before absorption (dissolution) as opposed to the two-step process for tablets/capsules
What are some concerns of divided powders?
They are expensive and must be protected from moisture
What are some advantages of “gum” dosage forms?
They avoid 1st pass metabolism, although some drugs can be absorbed both orally and by the GI tract
Why would a drug be made into gum form (like nicotine gum)?
The drugs tend to be highly first-pass metabolized
Are troches and lozenges the same?
No, troches have a stick and are meant to be left between the gum and cheek to dissolve over 10-15 minutes
What should you tell a patient receiving a lozenge or troche?
Do not drink for about 10 minutes after taking the lozenge (will wash the drug into the stomach and defeat the purpose)
What is the Cmax value?
The highest concentration of drug acheived
What is the Tmax value?
Time necessary to attain peak concentration in blood
The area under the curve (AUC) is proportional to the amount of ____ absorbed in body
drug
What are the four steps of ADME?
Absorption, distribution, metabolism, excretion
What is a xenobiotic?
Something foreign to the body
Which organ usually changes the chemical structure of a xenobiotic to make excretion easier?
Liver
Are the four ADME steps sequential (one after another) or all they all going on at the same time?
All happening at same time (at different speeds)
Why are the absorption and distribution steps initially faster than metabolism and excretion steps?
Because when the drug first enters the body, there is very little circulating in the blood to be metabolized; most of it still must be broken down and absorbed into the blood
Define First-Pass metabolism
When drug passes through the portal vein into the liver, the vast majority is metabolized and sent to be excreted; the remaining amount is distributed throughout the body
Which vein drains the intestine and will have the highest concentration of drug ever seen in the body?
The portal vein
What makes up a drug product?
Drug + dosage form
What is a dosage form?
System designed to deliver a well-defined amount of medicine to a specific location in the body at a certain time and in a way to maximize the therapeutic effect and minimize side effects
What are five required features of dosage forms?
Delivers proper amount of medicine at proper rate at action site, provides reproducible dose in each unit, maintains drug in chemically stable state (avoids incompatibilities between drug and excipients), has acceptable pharmaceutical qualities (smell, taste, etc.), and is suitable for large scale manufacturing
What are four ways to classify dosage forms?
Physical state, Point of Application/Delivery Route, Delivery mode, Technology of Release
What are the two delivery modes?
Systemic (whole body) or local (usually not going to blood first, delivery to specific place)
What is the difference between conventional and modified technology of release?
In conventional, release rate is rapid and limited only by rate at which drug substance dissolves; in modified, release rate designed to be controlled and slower than rate of drug dissolution would normally be
What are the excipients in a tablet?
diluents, binding agent, disintegrating agents, lubricants, colors/coatings
What is the purpose of a diluent in a tablet?
To give bulk to the tablet
What do disintegrating agent excipients in tablets do?
Attract water from the GI tract to swell/disintegrate tablet
