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55 Cards in this Set

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What is TDDS?
Transdermal Drug Delivery System.
Define TDDS?
Facilitates the passage of the therapeutic quantities of the drug substance through the SKIN to the general circulation for SYSTEMIC effects.
TDDS is usually only suitable for drugs of what level of potency?
Typically only for drugs of high potency.
Drugs used in TDDS have to be a ? ? ? skin.
They have to be a good penetrant of skin. Or they need a penetration enhancer.
In the use of TDDS for drug application ? size has to be considered reasonable?
Patch size has to be reasonable.
How fast is the requirement for the onset of action for a drug before it is considered for application through the use of TDDS?
It needs to be clinically prompt in its onset of action.
A patch has to be ?-? and ? acceptable.
Has to be non-irritating and aesthetically acceptable.
List 6 advantages of the TDDS method of drug application?
1. Avoidance of the First pass effect

2. A stable and controlled blood level

3. Termination at any time is conceivable

4. Long-term duration, ranging from a few hours to one week.

5. No interference with gastric and intestinal fluids or enzymes

6. Aids in the administration of drugs with:
A very short half-life;
A narrow therapeutic window;
Poor oral absorption
List 2 disadvantages of the TDDS method of drug application?
1. Limited to ONLY potent drugs

2. Some pts. develop contact dermatitis at site of application
What is the largest organ of the body?
Skin
Anatomically the skin is a ? organ with ? distinct layers.
It is a stratified organ with 3 distinct layers.
List the 3 distinct layers of the skin?
1. Epidermis

2. Dermis

3. Subcutaneous Fat Layer
What is the slowest step of a drug permeating through the skin?
The passing of the drug through the STRATUM CORNEUM is the RATE-LIMITING STEP.
The stratum corneum is a ?-? membrane.
It is a semi-permeable membrane.
List 3 things that affect the passive diffusion of a drug through the stratum corneum.
1. Concentration of the drug

2. Aqueous solubility

3. Oil-water partition coefficient
Which drugs are good candidates for diffusion through the stratum corneum?
Drugs with both aqueous and lipid solubility are good candidates.
Drugs that pass through the stratum corneum may also pass through what else?
May pass through the deeper dermis layers or to the blood.
What is the term that describes "the absorption of substances from outside the skin to positions beneath the skin, including entrance to the blood stream"
Percutaneous absorption.
List the 4 components of TDDSs? Which 3 are the most important?
1. Polymer matrix or matrices

2. The drug

3. Permeation enhancers

4. Other excipients

(1-3 are the most important)
Give an example of an excipient seen in TDDSs?
Adhesives
What is the purpose of the polymer matrix in a TDDS?
It controls the release of a drug from the device.
What 2 types of polymers are used to make polymer matrices for TDDSs?
1. Natural polymers

2. Synthetic polymers
Give 5 examples of natural polymers?
1. Cellulose derivatives

2. Gelatin

3. Shellac

4. Waxes

5. Gums and their derivatives
Give 3 examples of sythetic polymers?
1. Polyvinyl alcohol

2. Polyvinyl chloride

3. Polyrurea
Describe 5 desirable PHYSIOCHEMICAL properties of a drug for transdermal delivery?
1. mw <1000 daltons

2. The drug should have affinity for both lipophilic and hydrophilic phases, because the skin is composed of both of these

3. The drug should have a low melting point

4. Drug should be potent, should have a short half life.

5. Non-irritating
What do permeation enhancers do?
They help the drug penetrate the skin.
List 5 ways that permeation enhancers increase skin permeation.
1. Causing reversible damage to the stratum corneum

2. Optimizing the thermodynamic activity of the drug in the vehicle and/or skin

3. Increasing the drug diffusivity in the stratum corneum

4. Establishing a drug reservoir within the stratum corneum

5. Increasing the solubility of the active
What are the 2 types of permeation enhancers?
1. Chemical

2. Physical
Describe how chemical permeation enhancers achieve increased skin permeation of a drug?
These are compounds that promote skin permeability by altering the skin as a barrier to the flux of a desired penetrant.
They increase the skin permeability by reversibly damaging or altering the physiochemical nature of the stratum corneum.
List the 3 groups that chemical permeation enhancers are classified by?
1. Solvents

2. Surfactants

3. Misc. chemicals
What are some examples of chemical permeation enhancers that fall under the classification of solvents?
Water alcohols, like methanol and ethanol
What are some examples of chem. perm. enh.s that fall under the classification of surfactants?
1. Anionic surfactants (eg Sodium lauryl sulfate)

2. Nonionic surfactants (eg, Pluronic F127, Pluronic F68)
Give an example of a chem. perm. enh. that falls under the classification of Miscellaneous chemicals?
Urea (A hydrating and keratolytic agent)
What are the two different physical methods of permeation enhancement?
1. Iontophoresis

2. Sonophoresis
What is Iontophoresis?
A method of permeation enhancement that involves the use of charged chemical components across the skin membrane using an electric field.
What is sonophoresis?
A physical method of permeation enhancement that involves the use of high frequency ultrasound. It is thought to influence the integrity of the SC and thus affect its penetrability.
List 2 miscellaneous excipients that may be observed in TDDSs?
1. Adhesives

2. Backing membrane
What is an adhesive?
An exipient in TDDSs. The fastening of all TDDSs to the skin has so far been done by using a pressure sensitive adhesive.
Four requirements of an adhesive that is going to be used as an excipient in a TDDS?
1. Should adhere to the skin aggressively yet be easily removed.

2. Should not leave an unwashable residue on the skin

3. Should not irritate or desensitize skin

4. Phys. and chemical compatibility with the drug, excipients and enhancers of the device
What is a backing membrane?
It is an excipient seen in TDDSs. It is flexible and provides a good bond to the drug reservoir. They prevent drug from leaving the dosage form through the top, and accept printing.
What are the two potential TDDS designs?
1. Monolithic

2. Membrane-controlled systems
How many layers are seen in monolithic TDDS designs?
Three
How many layers are seen in Membrane-controlled systems?
Four
List 5 characteristics of a monolithic TDDS design?
1. Drug is incorporated into the MATRIX

2. Backing

3. Adhesive layer

4. Drug may or may not be added in excess

5. Excess drug maintains steady state of the drug for a long time.
List 5 characteristics of a Membrane-controlled system?
1. Drug RESERVOIR in liquid or gel form.

2. Backing

3. Adhesive layer

4. A RATE CONTROLLING MEMBRANE (THIS IS THE 4TH LAYER THAT REALLY DISTINGUISHES THIS FROM THE MONOLITHIC DESIGN)

5. Includes Transderm Nitro, Transderm Scop
What controls the release of a drug in a membrane-controlled TDDS?
Semi-permeable membrane.
What controls the release of the drug from a monolithic TDDS design?
Polymer
The patch is ?.
Occlusive
List 6 marketed TDDSs?
1. Scopolamine

2. Nitroglycerin

3. Clonidine

4. Estradiol

5. Nicotine

6. Fentanyl
What is Scopolamine used to treat?
For prevention of motion sickness.
What is Nitroglycerin used to treat?
Angina
What is Clonidine used to treat?
HTN
What is Estradiol used to treat?
Hormone Deficiency (Osteoporosis in postmenopausal women)
What is Nicotine used to treat?
Smoking cessation
What is Fentanyl used to treat?
For the mgmt of chronic pain in patients requiring opioid analgesia