| facilitate the passage of therapeutic quantities of drug substances through the skin and into the general circulation for their systemic effect | Transdermal drug delivery systems (TDDSs) |
| 1 first conceived of the percutaneous absorption of drug substances.
2 First transdermal system approved by FDA | 1) 1965: Stoughton
2) 1979: Scopolamine (TRANSDERM SCOP) |
| 1 For transdermal drug delivery, it is considered ideal if the drug penetrates through the skin to the underlying blood supply without __ | 1 without drug buildup in the dermal layers. |
| Routes of Skin Permeation | 1 Transcellular route (within the lipid bilayer)
2 Intercellular route (between the lipid bilayer - polar) |
| Benefits of TDDS | 1 Eliminates potential pain associated with injections
2 No first pass metabolism in liver
3 Eliminates gastrointestinal side effect
4 Improves patient compliance due to simpler, pain free delivery
5 Potential for home administration |
| Factors affecting percutaneous absorption | 1) Drug concentration
2) The larger the area of application(larger TDDS), the more drug is absorbed
3 Aqueous solubility of a drug and Partition coefficient
- Drugs penetrate the skin better in their un-ionized form
- Nonpolar drugs penetrate lipid rich regions
- Polar drugs favor transport between cells
4 Drugs with molecular weights of 100 to 800 and adequate lipid and aqueous solubility can permeate skin.
The ideal molecular weight of a drug for transdermal drug delivery is believed to be 400 or less
5 Hydration of the skin generally favors percutaneous absorption.
6 Percutaneous absorption greater when thin horny layer
7 longer the medicated application contact - greater total absorption |
| 1 Drugs with molecular weights of __ and adequate lipid and aqueous solubility can permeate skin.
2 The ideal molecular weight of a drug for transdermal drug delivery is believed to be __ | 1) 100 to 800
2) 400 or less |
| 1 increase percutaneous absorption of therapeutic agents.
2 increases skin permeability by reversibly damaging or altering the physicochemical nature of the stratum corneum to reduce its diffusional resistance | 1 Percutaneous absorption enhancers
2 Chemical enhancers |
| What are the alterations of Chemical Enhancers? | 1 INCREASED HYDRATION of the stratum corneum
2 A CHANGE IN TEH STRUCTURE of the lipids and lipoproteins in the intercellular channels |
| LIST OF skin penetration enhancers | acetone, azone,
dimethyl acetamide, dimethyl formamide, dimethyl sulfoxide (DMSO)
ethanol,
oleic acid,
polyethylene glycol, propylene glycol,
sodium lauryl sulfate |
| The selection of a permeation enhancer should be based on: | 1 its efficacy in enhancing skin permeation
2 its dermal toxicity (low)
3 its physicochemical and biologic compatibility with the system’s other components. |
| is a delivery of a charged chemical compound across the skin membrane using an electrical field. | iontophoresis |
| 1 Iontophoresis-enhanced transdermal delivery has shown some promise as a means of __ administration.
2 thru IV- rapid metabolism and poor absorption after oral delivery, poor in transdermal route (large molecular size and ionic in character) | 1 peptide and protein
2 Active peptides |
| A number of drugs have been the subject of iontophoretic studies, they include | lidocaine
dexamethasone
amino acids,
peptides
insulin
Verapamil
Propranolol |
| a process that exponentially increases the absorption of topical compounds (transdermal delivery) with HIGH-FREQUENCY ULTRASOUND.
occurs because ultrasound waves stimulate micro-vibrations within the skin epidermis and increase the overall kinetic energy of molecules making up topical agents. | Sonophoresis |
| It is thought that high-frequency ultrasound can influence the integrity of the stratum corneum and thus affect its penetrability.
Among the agents examined are: | 1 hydrocortisone,
2 lidocaine,
3 salicylic acid
in such formulations as gels, creams, and lotions |
