FINALS TRANSDERMAL Flashcards
_______________________________ are formulations that are
applied to the body surface and are designed to deliver the active
drug across the skin, into the systemic circulation
Transdermal drug delivery system are formulations that are
applied to the body surface and are designed to deliver the active
drug across the skin, into the systemic circulation
________________________________ of a drug generally results from direct
penetration of the drug through the stratum corneum , a 10-15 µm
thick layer of flat, partially desiccated non-living tissue
Percutaneous absorption of a drug generally results from direct
penetration of the drug through the stratum corneum , a 10-15 µm
thick layer of flat, partially desiccated non-living tissue
The _______________________, being keratinized tissue, behaves as a
semi-permeable artificial membrane, and drug molecules
penetrate by passive diffusion. (Major rate-limiting barrier to
transdermal transport)
The stratum corneum, being keratinized tissue, behaves as a
semi-permeable artificial membrane, and drug molecules
penetrate by passive diffusion. (Major rate-limiting barrier to
transdermal transport)
Over most of the body, the stratum corneum has ____________ of
flattened corneocytes with an overall thickness of about 10 mm (6).
Over most of the body, the stratum corneum has 15 to 25 layers of
flattened corneocytes with an overall thickness of about 10 mm (6).
Substances with both _______ and ___________________________
are good candidates for diffusion through the stratum corneum,
epidermis, and dermis.
Substances with both aqueous and lipid solubility characteristics
are good candidates for diffusion through the stratum corneum,
epidermis, and dermis.
- Increases skin permeability by reversibly damaging or altering the
physicochemical nature of the stratum corneum to reduce its diffusional
resistance. - Among the alterations are increased hydration of the stratum
corneum, a change in the structure of the lipids and lipoproteins in the intercellular channels through solvent action or denaturation, or
both
Chemical Enhancers
Example of chemical enhacers:
Example: Acetone, Dimethylacetamide, Ethanol, Oleic acid, SLS
______________ is delivery of a charged chemical compound across the skin
membrane using an electrical field.
Iontophoresis
_____________________, or high-frequency ultrasound, is also being
studied as a means to enhance transdermal drug delivery.
Among the agents examined are hydrocortisone, lidocaine, and
salicylic acid in such formulations as gels, creams, and lotions.
It is thought that high-frequency ultrasound can influence the
integrity of the stratum corneum and thus affect its penetrability.
Sonophoresis
_______________________ are designed to
support the passage of drug substances from the surface of the
skin through its various layers and into the systemic
circulation.
TDDSs (also often called transdermal patches)
Incorporate a drug matrix layer between the backing and the
frontal layers.
The drug matrix layer is composed of a polymeric material in which the drug is dispersed.
❑The polymer matrix controls the rate at which the drug is released for percutaneous absorption.
Monolithic System
❑Designed to contain a drug reservoir, or pouch (liquid/gel form), a rate
controlling membrane, backing adhesive, protecting layer.
❑Advantage: As long as drug solution in the reservoir remains saturated, the
release rate of drug through controlling membrane remains constant.
❑In membrane system: the small quantity of drug is frequently placed in the
adhesive layer to initiate prompt drug absorption and pharmacotherapeutic
effects on skin placement
Membrane-controlled
Transdermal System
(protect the system from environmental entry and from loss of drug from the system)
occlusive backing membrane
(store and release the drug at the
skin site)
drug reservoir or matrix system
which is removed before application and enables drug release
release liner
maintain contact with the skin after application
adhesive layer
a belladonna alkaloid, is used to prevent travel-related motion sickness and the nausea and vomiting that result from the use of
certain anesthetics and analgesics used in surgery.
Transdermal Scopolamine
is a circular flat patch 0.2 mm thick and 2.5 cm2 in area. (4 layer system),
*The TDDS contains 1.5 mg of scopolamine and is designed to deliver approximately 1 mg of scopolamine at an approximately constant rate to the systemic circulation over the 3-day lifetime of the system.
*Priming dose in the adhesive layer: 200mg (to saturate the skin binding site and rapidly brings the plasma concentration to the required steady
state)
Transdermal Scopolamine
Patch is worn in a hairless area behind the ear
*Applied at least 4h before the antinausea effect is required
*1 disk worn at a time and may be kept in place for 3 days
*Continued treatment: fresh disk is placed behind the other ear and the
other removed
*Side effect: dryness of the mouth and drowsiness
Transdermal Scopolamine
❑Example: Minitran, Nitro-dur, Transderm-Nitro, Nitrodisc
❑Delivers NTG for 24H after application
❑Tolerance is a major factor limiting effectiveness of these systems when used continuously for more than 12H per day
hence an appropriate dosing schedule would include a daily patch on period of 12-14h and a patch off period of 10-12hours.
❑Used in the prophylactic treatment of angina
❑It has a relatively low dose, short plasma half-life, high peak plasma levels, and inherent side effects when taken sublingually, a popular route.
❑It is rapidly metabolized by the liver when taken orally; this first-pass effect is bypassed by the transdermal route.
Transdermal Nitroglycerin
❑When a TDDS is applied to the skin, nitroglycerin is absorbed continuously, resulting in active drug reaching the target organs (heart, extremities) before inactivation by the liver.
❑Only a portion of the total nitroglycerin in the system is delivered over the usual 24-hour use period; the remainder serves as the thermodynamic energy source to release the drug and remains in the system.
❑Placed on the chest, back, upper arms or shoulders; free from hair, clean and dry
❑The use of extremities below the knee or elbow is discourages as are the areas that are
abraded or have lesions or cuts
❑Patients should also understand that exercise, sauna (may elevate body temp) increase absorption of NTG
Transdermal Nitroglycerin
*For Hypertension
* lends itself to transdermal delivery because of its lipid solubility, high volume of distribution, and therapeutic effectiveness in low plasma concentrations
*The TDDS provides controlled release of clonidine for 7 days. (4 layered patch)
*The system is applied to a hairless area of intact skin on the upper outer arm or chest.
*After application, clonidine in the adhesive layer saturates the skin site.
*Then from the reservoir begins to flow through the rate-controlling membrane and the skin to the systemic circulation.
Transdermal Clonidine
*Therapeutic plasma clonidine levels are achieved 2 to 3 days after initial application.
*Application of a new system to a fresh skin site at weekly intervals maintains
therapeutic plasma concentrations.
*If the patch is removed and not replaced with a new system, therapeutic plasma
clonidine levels will persist for about 8 hours and then decline slowly over several
days.
*If the patient has local skin irritation before 7 days of use, the system may be removed
and replaced with a new one applied on a fresh skin site
Transdermal Clonidine
Adjuncts in smoking cessation programs (effective aid in quitting smoking)
Example: Nicoderm CQ, Nicotrol, Prostep
oThe TDDSs provide sustained blood levels
replacement therapy to help the patient establish and sustain remission from
smoking.
oMotivation to quit smoking is enhanced through the reduction of withdrawal
symptoms and by partially satisfying the nicotine craving and desired sensory
feelings provided by smoking
oThe commercially available patches contain 7 to 21 mg of nicotine for daily
application during the course of treatment ranging from about 6 to 12 weeks.
Used TDDSs should be discarded properly because the retained nicotine is
poisonous to children and pets.
Transdermal Nicotine
