Exam 3 Flashcards
What are the two types of controlled drug delivery?
Temporal -
- Sustained release (delayed or extended)
- Pulsatile release
Spatial -
- Systemic, local (ex. transdermal trying to target the skin, and targeted release.
- We want the drug to be fully released at that target organ.
What are the 5 advantages of controlled release?
- Can maintain optimum drug concentrations
- Improves efficiency of treatment with less amount of the drug
- Minimizes side effects
- Less frequent administration
- Increases patient convenience and compliance with the dosing regimen
What are the 5 disadvantages of controlled release?
- Relatively high production costs
- Dose dumping (leakage of drug mass)
- Difficult to stop drug release
- Maybe issue of biocompatability of the delivery systems (irritation at site)
- Potential necessity of surgical operation (ex. implant)
What are the 5 disadvantages of controlled release?
- Relatively high production costs
- Dose dumping (leakage of drug mass)
- Difficult to stop drug release
- Maybe issue of biocompatability of the delivery systems (irritation at site)
- Potential necessity of surgical operation (ex. implant)
When is temporal control of drug delivery needed (3) and not needed (3)?
Needed:
- Having the best drug conc.-time profiles at the site of action
- Reducing the # of administration frequency
- Simulating multiple dosing
Not needed:
- Drugs with a long half-life
- Drugs that have undesirable long-term effects
- Drugs that require immediate effect
What are the mechanisms of the two diffusion-controlled systems (Reservoir and matrix)?
Diffusion-controlled: The drug diffusion through the polymer network is the rate-limiting step.
Reservoir - The membrane controls the release rate. The drug reservoir is in the middle and the membrane surrounds it. Ex. Ocusert
Matrix - The drug and matrix are mixed together. The drug slowly diffuses out of the matrix. The drug in the middle takes the longest to diffuse out.
What is the mechanism of dissolution-controlled systems?
Dissolution systems are either encapsulated with a polymer membrane or are a drug+polymer matrix. The drug is dissolved over time.
You can use the Hixson-Crowell cube-root law to find the cube-root dissolution rate constant
What is the mechanism of erosion-controlled systems?
The initial release phase is controlled by the diffusion of drug molecules that are on the surface or have access to the surface via pores in the microsphere matrix.
The sustained-release phase is determined by the erosion of the polymer. As the polymer erodes, the entrapped drug molecules are released.
What is the mechanism of osmotic systems?
Osmotic systems have a film coating that is permeable for water, but not permeable for the drug or excipients. It also is rigid enough that it resists the hydrostatic pressure & pushes out the drug. There are one and two chamber devices.
Ex. Concerta
What is the mechanism of swelling systems?
As the length of the diffusion pathway is larger, the drug-conc gradient is decreased, which decreases the drug-release rate.
As the mesh size of the polymer network increases, the drug is better able to diffuse out of the polymer network, which increases the drug release rate.
What are the differences between membrane-modulated, adhesive dispersion, and matrix dispersion diffusion systems?
Membrane-modulated: Reservoir, has 4 clear components (adhesive, rate-controlling membrane, reservoir, and backing membrane)
Adhesive dispersion: Reservoir, 3 clear components (rate-controlling adhesive, reservoir, backing membrane; This one is a little more like a matrix
Matrix dispersion: Matrix, 2 components (drug + adhesive layer, backing membrane)
What is the Gliadel wafer?
It is a wafer that is placed in the cranium after the tumor gets resected. It displays erosion diffusion. There’s no need to remove it once it’s fully eroded.
What is the Lupron depot?
It is an IM injection that is used against prostate cancer. The drug is released over a 1-4 month period. This displays erosion diffusion.
What is Ocusert?
- Reservoir drug release system
- The device sits in the eye and as the drug slowly saturates the membrane, it releases at a very constant rate.
- Poly(ethylene-co-vinyl acetate)
What are Tetracycline Periodontal Fibers?
It’s a reservoir release system with a cap at either end of the cylinder.
- Cellulose membrane
What is Norplant?
Non-Erodible subdermal implant that is a reservoir with a constant release rate.
- Silicone capsules containing Levonorgestrel.
What are NicoDerm patches?
Reservoir release system with a rate controlling membrane, occulsive backing, and adhesive layer
What type of dissolution do Habitrol patches have?
Matrix release system
What type of dissolution is Nexplanon/Implanon NXT?
Matrix release system
What type of release is the Sustol extended-release injection?
Erosion release system
What are biologics?
Medications derived from or produced by living organisms.
Ex. Recombinant proteins, peptides, blood factors, vaccines, etc.
What % of the Top 200 drugs were biologics in 2018?
37% of top 200 drugs were biologics.
There are more than 100 biologics on the market. There has been a dramatic increase of importance.
What is the most important type of biologics? What are some important features?
Monoclonal antibodies (MAb)
- Large molecules (~150,000 daltons)
- Antigen binding site determines how the antibody complementarity determining region (CDR) interacts with the antigen
- Made of largely beta ribbons (not a-helix)
- There is a sugar part that is important for how the antibody will be processed in the body.
Ex. Humira, Herceptin, Avastin
What are the 4 main types of MAb derivatives?
Chimeric monoclonal antibody - The variable region is mouse, the rest is human. Ex. Remicade
Humanized monoclonal antibody - Mostly human, a little bit mouse.
Human recombinant - Fully human. Ex. Humira, Simponi.
What are antibody drug conjugates (ADCs)?
These combine target specificity of the MAb with efficacy of the small molecule drug.
Components: Antibody, linker, and cytotoxic agent.
Ex. The Ab may recognize cancer cells, then the small molecule can kill the cell.
What is the structure of a cytokine like and what are some examples of cytokine biologics?
4-helix bundle with molecular weight of ~30,000 daltons.
Ex. Neulasta, Epogen
What is the structure of insulin? Why is long-acting insulin “long-acting”?
The A-chain and B-chain of amino acids are linked together by a disulfide bond. Around 5800 daltons (small). Insulin takes on an alpha helical structure and it readily associates to form dimers and hexamers.
Long-acting insulin is long acting because it forms microcrystals upon injection, slowly releasing the drug.
Ex. Insulin Lispro (Humalog), Insulin Aspart (Novolog), Insulin Glargine (Lantus).
What are two examples of peptide biologics and what is the peptide structure like? What is a peptide analog?
Victoza & Sandostatin
These are short proteins, usually less than 50 amino acids. These have some secondary structure, but no higher order of structure.
Peptidomimetic is a peptide analog. They look like peptide structure, but the side chains aren’t from the 20 amino acids.
What are the 5 types of vaccines?
- Inactivated
- Conjugate
- Attenuated
- Toxoid
- Subunit
These can be much wider than other biologics.
What is CART-cell therapy?
CART-cell therapy are the first living drugs.
Immune cells (T cells) are removed from the patient’s blood then are genetically programmed to fight cancer cells. Then, those cells are multiplied and infused back into the patient. These newly programmed CAR-T cells kill the cancer cells.
Ex. Kymriah
What are the 3 types of coronavirus vaccines in development?
Protein based - Spike protein is purified and injected, immune system produces the antibody
Viral vector - Spike protein gene is purified, adenoviral vector is injected, body produces spike protein, immune system produces the antibody
mRNA - mRNA that codes for spike protein is purified and injected, then the body produces that spike protein, and immune system produces the antibody