Transdermal Drug Delivery Systems

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Author:
ANVigil
ID:
117904
Filename:
Transdermal Drug Delivery Systems
Updated:
2011-11-19 14:37:39
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Test Dose Form TDDS
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Description:
Dose Form Test 3
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  1. What are some factors that influence percutaneous absorption?
    • Physical and chemical properties of drugs
    • Pharmaceutical vehicle
    • Condition of the skin
  2. What is percutaneous absorption?
    Absorption of substances from outside the skin to underneath the skin, including enterance into the blood stream
  3. What are the layers of the skin from outer to inner most?
    • Epidermis: Stratum Corneum, Stratum Lucidum, Stratum Germinativum
    • Dermis
    • Subcutaneous
  4. What is another name for the stratum conreum?
    • Horny layer.
    • This is where Keratin is contained
  5. The stratum lucidum is also called?
    Stratum granulosum
  6. Describe the stratum corneum?
    • Outer layer composed of partially desiccated nonliving cells and film (sevum and sweat) and keratin
    • 15-25 layers of cells over most of the body
    • Lacks continuity; not significant factor in drug penetration
    • Behaves as a semipermeable artificial membrane to drug penetration by passive diffusion
    • Major rate-limieting barrier to transdermal drug transport
  7. Are there several layers of epithelia cells?
    Yes and they are at different stages of differentiation
  8. T/F
    The skin is covered by an emulsified film of sebum, sweat, and dead celss that are constantl desquamating (peeling)
    True
  9. Describe the statum lucidium
    • aka Stratum Granulosum
    • Barrier layer with living cells at several differentiated levels
    • Living epidermis
  10. Describe the Statum Germinativum
    • Living epidermis
    • Has basal layer separating from dermis
  11. Describe the dermis
    Vascularized tissue that drug must reach
  12. What is transdermal absorption?
    From skin into circulation
  13. Define transcellular
    • across
    • Lipid-rich, non-polar drugs
  14. Define intercellular
    • between
    • Channels are the major route of drug penetration; polar drugs
  15. Define trans-appendegeal
    • Across skin appendages
    • Hair follicles, sweat glands, sebaceous glands, minor drug absorption
  16. What are factors affecting absoprtion through the skin related to the drug?
    Concentration of drug, particle size, molecular weight (100-800), solubility in oil and water, attraction to skin
  17. What are factors affecting absorption through the skin related to the vehicle?
    • Adherence to skin
    • miscibility with sebum
    • action as a moisture barrier (hydration of skin)
  18. What are the factors affecting absoption through the skin related to the skin?
    • Intact vs broken skin
    • surface area applied
    • site of application (thin horny layer)
  19. What are the factors affecting absorption through the skin related to the physical factors?
    • Rubbing (inunction or exercise lead to vasodilation
    • Time of contact with skin
    • Multiple application (Saturation)
  20. Percutaneous absorption can be enhanced through what two methods?
    • Chemical
    • Physical
  21. Chemical methods work by?
    • Reduction of Stratum Corneum's resistance
    • Modification of Stratum Corneum's hydration
    • Modification of lipids in intercellular channels
    • Through carrier mechanisms
  22. What solvents are exmaples of chemical percutaneous enhancers?
    • Water
    • Alcohols (methanol, ethanol, 2-propanol)
    • Alkyl methyl sulfoxides (DMSO, decyl methyl sulfoxide, others)
    • Pyrrolidones (2-pyrrolidone, n-methyl-2-pyrrolidone, others)
    • Laurocapram (Azone)
    • Urea
    • N,N-diethyl-m-toluamide
    • Miscellaneous (acetone, dimethyl acetamide, dimethyl formamide, etc)
    • Amphiphiles
  23. What are amphiphiles?
    • Both sides, polar and nonpolar
    • Anionic surfactants
    • Cationic surfactants
    • Amphoteric suractants
    • Nonionic surfactants
    • Fatty acids and alchols
  24. What are some examples of anionic surfactants?
    • Docusate sodium
    • SDS
  25. What are some examples of cationic surfactants?
    • Quaternary ammonium salts
    • Also preservative
  26. What are examples of amphoteric surfactants?
    • Lecithins
    • Cephalins
    • Alkyl bentamines
  27. What are examples of nonionic surfactants?
    mono, di and triglycerides
  28. What are some examples of alchols and fatty acids?
    • Lauryl
    • cetyl
    • stearyl alcohols
    • sorbitan
    • PEG
  29. What are some physcial methods that enhance percutaneous absorption?
    • Iontophoresis
    • Sonophoresis
  30. Define iontophoresis
    delivery of charge chemicals across the skin using electrical field
  31. Define sonophoresis
    High-frequency ultrasound facilitates drug penetration through the Stratum Corneum
  32. What are some advantages of TDDS?
    • Avoid GI difficulties
    • Substitute ORAL administration
    • Avoid first-pass effect
    • Substitute parenteral therapy
    • Provide multi-day therapy with single application because they act as a reservoir of drug (better compliance)
    • Drug effects can be terminated by removal of system
    • Fast identification during emergencies
  33. What are some disadvantages of TDDS?
    • Unsuitable for irritating and sensitizing drugs or highly sensitive persons, contact dermatitis
    • Only relatively potent drugs can be prepared as TDDS
    • Technical difficulties during preparations of TDDS
  34. What are the two different designs of TDDS?
    • Monolithic system
    • Membrane-controlled system
  35. What is the monolithic system?
    • Most have excess drug, continual drug avaliabilty
    • The skin controls the rate of absorption of drug
    • Maintains wide range of plasma concentration over which the drug is effective but not toxic
    • Drug and molymer matrix (mixture) are blended or dissolved
    • Drug-matrix layer is dried, gelled matrix (sheet or cylindrical form)
    • Assembling between backing and frontal layers (foil cover-strip)
  36. What is the membrane-controlled system?
    • The system controls the rate of drug delivery, rate -controlling membrane
    • Delivers uniform quantities of drug to the skin over a period of time
    • Drug in the reservoir (liquid or gell) remains saturated and the release rate of drug is constant
    • Adhesive layer contains an initial priming dose
    • Backing layer (water resistant) and drug reservior (liquid or gel) and Controlling semipermeable membrane and adhesive layer containing priming dose (holds the system onto the skin and protective peel strip
  37. Scopolamine
    • Transderm-SCOP
    • Used for motion sickness as antiemetic applied to the post-auricular area
  38. Nitroglycerine
    • Transderm-Nitro, Nitrodur, Nitrodisc, Deponit, Minitran
    • Used once a day in the prophylaxis of angina pecroris (not for attacks) applied to the chest or upper arm
  39. Clonidine
    • Catapress TTS
    • Used to treat hypertension
    • One patch maintains 7 days of constant blood levels
  40. Estrogen
    • Estraderm, Vivelle
    • Used for problems during menopause, ovary failure, hypogonadism, provides 4 days constant blood levels
  41. Fentanyl
    • Duragesic
    • Potent analgesic used in chronic pain such as cancer, 72 hours effective
  42. Lidocaine
    • Lidoderm
    • 5% surface anesthesia, 12 hour relief, 12 hour on-off use
  43. Nicotine
    • Several brand names available
    • Used for cessation of smoking
  44. What are rate controlling systems like transdermal patches intended to do?
    • Deliver drug at a controlled rate to intact skin without buildup in the dermal layers (skin is not target)
    • Rlease the drug promptly from the system into the S. Corneum for penetration into the general circulation (systemic effects)
    • Cause occlusion of the skin so there is only one way flux of drug, therapeutic advantage over other dosage forms (nothing is lost)
    • Cause no irritation or sensitization to the skin due to drug vehicle or adhesive
    • Increase patient compliance (size and color)
    • Design must avoid proliferation of bacteria under occluded skin
  45. What are some examples of drugs in a matrix system?
    • Estradiol
    • Fentanyl
    • Methylphenidate
    • Nicotine
    • Nitroglycerin
    • Oxybutynin
    • Rivastigmine
    • Ritigotine
  46. What are some examples of drugs in a reservoir system?
    • Clonidine
    • Estradiol
    • Fentanyl
    • Nicotine

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