Term
| Define transdermal drug delivery |
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Definition
| Transdermal drug delivery facilitates the passage of therapeutic quantities of drug substances through the skin and into the general circulation for their systemic effects. |
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Term
| List five drug examples available transdermally |
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Definition
| Scopolamine, Nitroglycerin, Clonidine, Nicotine, Estradiol |
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Term
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Definition
A drug used for nausea, motion sickness
A patch applied to the back of the ear |
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Term
| Define clonidine and why it can be given transdermally |
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Definition
| An anti-hypertensive given transdermally because it has adverse effects when taken orally |
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Term
| Define nitroglycerin and why it can be given transdermally |
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Definition
| A vasodilator given transdermally (but usally SL) because it has poor oral absorption |
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Term
| Define nicotine and why it can be given transdermally |
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Definition
| Used for smoking cessation, used transdermally because it breaks a habit and has a long release |
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Term
| Define estradiol and why it can be given transdermally |
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Definition
| Used as a female hormone, used transdermally usually for convenience |
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Term
| Are transdermal, percutaneous, and dermatologic synonymous? |
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Definition
Transdermal=percutaneous
But dermatologic is different |
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Term
| Does transdermal avoid first pass metabolism? |
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Definition
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Term
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Definition
The skin is the most extensive and readily accessible organ of the human body.
In an average adult, it covers a surface area of over 2 m^2 and receives about one-third of the blood circulation |
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Term
| List the three anatomical layers of skin |
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Definition
1. epidermis (stratum corneum & stratum germinativum)
2. dermis
3. subcutaneous tissue/hypodermic area |
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Term
| How small do drugs have to be to qualify for transdermal drug delivery |
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Definition
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Term
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Definition
A layer in the epidermis which behaves as a semipermeable membrane
Drug molecules can penetrate by passive diffusion |
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Term
| What physico-chemical properties of the drug influence percutaneous absorption |
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Definition
Molecular weight
Solubility
Partition coefficient (LogP)
Dissociation constant (pKa)
Nature of the carrier |
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Term
| How does drug concentration affect transdermal drug absorption? |
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Definition
Generally, the higher the concentration of drug applied, the higher will be the drug absorption.
Additionally, the more surface area a drug is applied to, the more will be the absorption. |
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Term
| How does the location of the skin on the body affect transdermal drug absorption? |
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Definition
A thin skin layer is more suitable for absorption than a thick layer.
However, absorption also varies with the site of application (eg hydrocortisone) |
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Term
How is hydrocortisone often given transdermally?
Why? |
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Definition
| Hydrocortisone penetrates the scrotum 40 times more rapidly than the forearm and back |
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Term
| How does hydration status affect transdermal drug absorption? |
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Definition
Hydration favors percutaneous absorption.
The delivery system may also act as an occlusive barrier increasing skin hydration. |
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Term
| How does time of contact affect transdermal drug absorption? |
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Definition
| The longer the medicated application is allowed to stay in contact with the skin, the greater is the drug absorption. |
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Term
| How does race/ethnicity affect transdermal drug absorption? |
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Definition
| Generally, dark skin (African) stratum corneum has more layers in it than that of Caucasian, making the drug less permeable to a small extent |
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Term
| Give two synonyms of chemical enhancers (of transdermal drug) |
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Definition
| Permeation enhancers; absorption enhancers |
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Term
| How do transdermal chemical enhancers work? |
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Definition
| Chemical enhancers increase skin permeability by reversibly damaging or altering the physicochemical nature of the stratum corneum thereby reducing its resistance for paracellular drugs only |
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Term
| Give examples of transdermal chemical enhancers |
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Definition
Dimethyl sulfoxide (DMSO),
azone,
acetone,
oleic acid,
propylene glycol,
sodium dodecyl sulfate
etc |
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Term
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Definition
| The use of electric current applied to the skin to drive drugs through the epithelium. |
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Term
| How does iontophoresis work? |
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Definition
Either by adding a counterion, creating ion-electric field interaction which provides a directional force to drive drug ions through the skin
Or by simply increasing the permeability of the skin |
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Term
| What is the difference between a cation and an anion? |
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Definition
Cation: positively charged
Anion: negatively charged |
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Term
| Give an example of iontophoresis has been proven to affect drug absorption |
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Definition
| lidocaine (local anesthetic) demonstrated a penetration depth of 10-20 mm using iontophoresis compared to 5 mm using direct topical application |
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Term
| List five types of drugs being investigated for iontophoresis |
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Definition
Dexamethasone,
amino acids,
peptides,
verapamil,
propranolol |
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Term
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Definition
The application of high-frequency ultrasound to enhance drug permeation across the skin
This process influences the integrity of stratum corneum and thus affects drugs’ permeability |
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Term
| How are drugs prepared for sonophoresis |
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Definition
| Drugs are mixed with a coupling agent (gel, cream, ointment) that transfers ultrasonic energy from the ultrasound transducer to the skin. |
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Term
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Definition
| Electroporation is the creation of aqueous pores in lipid bilayers by the application of short (micro- to milli-seconds) high voltage (200-1000V) electric pulse. |
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Term
| How has electroporation been proven effective? |
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Definition
It has been used to deliver a wide range of drugs with MWs up to several thousand Daltons (proteins, DNA).
Electroporation also leads to an increase in skin permeability up to 4 orders of magnitude. |
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Term
| What is the difference between iontophoresis (I) and electroporation (E)? |
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Definition
I requires low voltage, while E requires a high voltage.
Ionized (charged) drug passes through the skin in I, while intact (neutral) drug passes through in E. |
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Term
| How are percutaneous absorption methods tested in vivo? |
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Definition
| human and animal models e.g. pig, rhesus monkey, mouse. Biologic samples collection includes sections of skin, venous blood from application site, blood from systemic circulation and urine. |
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Term
How are percutaneous absorption methods tested in vitro?
What are the testing systems used? |
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Definition
Includes cadaver skin and excised animal skin.
Drug permeation testing systems include side-by-side diffusion cell and Franz diffusion cell (top-to-bottom diffusion). |
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Term
| Define Transdermal drug delivery systems |
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Definition
| (aka Transdermal patches) are designed to support the passage of drug substances from the surface of skin into the systemic circulation. |
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Term
| What are the two categories of transdermal patches? |
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Definition
| Monolithic and membrane-controlled systems. |
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Term
| Define Monolithic/Matrix system transdermal patches and explain how they work |
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Definition
A polymeric drug matrix layer is between the backing and frontal layers.
The polymer matrix controls the rate at which the drug is released for absorption. |
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Term
| Give three examples of Monolithic system transdermal patches |
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Definition
Nitro-Dur (Key),
Vivelle (Novartis),
Testoderm (Alza)
(He says we don't need to know for exam) |
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Term
| How are monolithic system transdermal patches prepared? |
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Definition
Drug and polymer are blended together, then casted as a matrix.
The gelled matrix is cut into individual dosage units and assembled between the backing and frontal layers. |
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Term
| Define membrane-controlled transdermal systems. What are they composed of? |
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Definition
| They contain a drug reservoir or pouch, usually in liquid or gel form, rate controlling membrane, contact adhesive, protective frontal layer, and a backing layer. |
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Term
| Give two examples of membrane-controlled transdermal systems |
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Definition
Nitro (Summit) and Transderm-Scop (Baxter)
(He says we don't need to know for exam) |
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Term
| List advantages of transdermal drug delivery |
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Definition
-Avoidance of first-pass metabolism,
-Less drug-food interaction
-Less degradation in the GI tract
-Good if patient can't take po
-Easy ER therapy
-Easy therapy termination
-Patient compliance because non-invasive |
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Term
| List disadvantages of transdermal drug delivery |
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Definition
-Only relatively potent drugs
-development of contact dermatitis
-irritation of skin,
-often uneconomical |
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