Transdermal Drug Delivery Systems Overview

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Questions and Answers

What is the primary purpose of excess drug in transdermal delivery systems (TDDS)?

To decrease the rate of drug absorption.

To minimize skin irritation from the adhesive.

To replace the drug more frequently than recommended.

To ensure continuous drug availability and absorption. (correct)

Which feature distinguishes reservoir systems from other transdermal delivery systems?

They use a solid drug form for storage.

They provide an immediate burst of drug upon application.

They contain multiple small reservoirs of drug. (correct)

They include a single large reservoir for the drug.

In what way do reservoir systems typically deliver drugs compared to monolithic systems?

They have a simpler design and construction process.

They provide an inconsistent drug release.

They involve a non-controlled rate of release.

They result in a more consistent drug delivery. (correct)

How are most reservoir systems constructed?

Through a lamination process or pre-constructed units. Signup and view all the answers

What is one characteristic of micro-reservoir systems in reservoir TDDS?

They feature numerous small reservoirs between the backing and membrane. Signup and view all the answers

What is one of the main advantages of iontophoresis as a delivery method?

Allows delivery of large, charged molecules Signup and view all the answers

Which of the following is a disadvantage of iontophoresis?

Potential skin irritation at high current densities Signup and view all the answers

How can iontophoresis enhance patient compliance?

By allowing non-invasive therapeutic regimens Signup and view all the answers

What can help minimize the skin irritation caused by iontophoresis?

Lowering the current used during treatment Signup and view all the answers

What is a significant drawback of the iontophoresis delivery method regarding drug absorption?

Delayed time before drug reaches bloodstream Signup and view all the answers

What is the primary indication for transdermal nicotine products?

Smoking cessation Signup and view all the answers

Which of the following transdermal systems uses a reservoir type?

Lidoderm Signup and view all the answers

What is a common dosing frequency for transdermal oxybutynin?

Twice weekly Signup and view all the answers

Which product is indicated for the treatment of moderate to severe restless legs syndrome?

Neupro Signup and view all the answers

What advantage does transdermal drug delivery systems (TDDS) offer in terms of drug compliance?

Improves compliance by providing a consistent release. Signup and view all the answers

Which transdermal product is currently in development?

Medherent's TEPI patch Signup and view all the answers

What is a significant disadvantage of transdermal drug delivery systems?

Only relatively potent drugs may be used. Signup and view all the answers

For which condition is transdermal selegiline indicated?

Major depressive disorder Signup and view all the answers

What is the primary indication for the fentanyl iontophoretic transdermal system (IONSYS)?

Short term management of acute post-operative pain Signup and view all the answers

What must be done before initiating treatment with the iontophoretic transdermal system?

Titrate drug to the minimum effective dose on IV fentanyl Signup and view all the answers

Which of the following is a common use for iontophoresis in veterinary medicine?

Delivery of NSAIDs Signup and view all the answers

What is an important formulation factor for sonophoresis?

Smooth and non-gritty vehicle Signup and view all the answers

Which agent is commonly delivered using iontophoresis for inflammation treatment?

Dexamethasone Signup and view all the answers

What is the mechanism of action of sonophoresis?

High frequency ultrasound to disrupt skin lipids Signup and view all the answers

What type of drug formulation is typically used with sonophoresis?

Gel, ointment, or cream Signup and view all the answers

Which one of the following statements about pilocarpine iontophoresis is accurate?

It induces sweating for cystic fibrosis diagnosis Signup and view all the answers

What is a primary benefit of photodynamic therapy?

It avoids the first pass effect. Signup and view all the answers

What is a major limitation of the laser light used in photodynamic therapy?

It can only pass through about 3 cm of tissue. Signup and view all the answers

Which of the following is an adverse effect of photodynamic therapy?

Skin and eye sensitivity to light. Signup and view all the answers

Which of the following is a non-cancer use for photodynamic therapy?

Psoriasis. Signup and view all the answers

What is the primary mode of cancer identification in photodynamic therapy?

Differential uptake of photoinactive agents by abnormal cells. Signup and view all the answers

How is Aminolevulinic acid administered when used for actinic keratosis?

Admixed immediately prior to use. Signup and view all the answers

What role do micropores play in drug delivery techniques?

They allow drugs to bypass the stratum corneum. Signup and view all the answers

What type of drug delivery method uses tiny needles to pierce the skin?

Microneedle devices. Signup and view all the answers

What type of light is primarily used in photodynamic therapy?

Visible light spectrum. Signup and view all the answers

Which of the following is a potential side effect of treatment with Visudyne®?

Sensitivity to light. Signup and view all the answers

How is Cysview® administered for bladder cancer detection?

Instilled into the bladder. Signup and view all the answers

What is electroporation primarily used for?

To enhance skin permeability. Signup and view all the answers

Which condition is treated with Photofrin®?

Barrett’s esophagus. Signup and view all the answers

Which of the following is a disadvantage of photodynamic therapy?

It may cause nausea and vomiting. Signup and view all the answers

Study Notes

Transdermal Drug Delivery Systems (TDDS)

TDDS contain an excess of drug within the system to ensure continued drug saturation in the stratum corneum
TDDS allow for a slower decrease in drug delivery rate compared to systems without excess drug
Most TDDS designs include a drug-releasing capacity exceeding the recommended replacement timeframe
Fresh TDDS are used to replace used ones on a schedule

Types of TDDS: Reservoir

Reservoir systems (membrane-controlled systems) contain a drug reservoir (pouch, typically in liquid or gel form), a rate-controlling membrane, backing, adhesive, and protective layers
A small amount of drug in the adhesive layer is frequently used to initiate prompt absorption
Reservoir systems offer a more-consistent drug release profile compared to monolithic systems
Reservoir systems can be manufactured by pre-constructing the delivery unit, filling the reservoir, and sealing; or by a lamination process (continuous construction, dosing, and sealing)
Micro-reservoir systems are a subcategory of reservoir systems containing several small reservoirs of drug enclosed between backing and a rate-controlling membrane

Membrane-Controlled Transdermal Systems (Reservoir Systems)

Can result in contact dermatitis after application to the skin
Can contain some drug within the adhesive layer for “immediate” delivery
Often result in a more consistent drug delivery as compared to monolithic systems

Examples of Transdermal Drug Delivery Systems

Transderm-Nitro (TDDS): Reservoir system, used for the delivery of Nitroglycerin
Nicoderm: Reservoir system, used for nicotine replacement therapy
Exelon: Matrix system, used for the delivery of rivastigmine (treatment of Alzheimer's disease)
Emsam: Matrix system, used for the delivery of selegiline (treatment of major depressive disorder)
Oxytrol: Matrix system, used for the delivery of oxybutynin (treatment of urge incontinence)
Lidoderm: Reservoir system, used for the delivery of lidocaine (relief of pain associated with postherpetic neuralgia)
Neupro: Matrix system, used for the delivery of rotigotine (moderate to severe restless legs syndrome and Parkinson's disease)
TEP: (Transferred Epithelial Patch): Matrix system, used for the delivery of ibuprofen

Advantages of TDDS

Produce more uniform blood levels than conventional oral products
Can maintain plasma levels over a longer duration
Reduces adverse effects
Extends the activity of drugs having short half-lives
Improves compliance
Avoids GI absorption problems (not affected by food interaction, GI tract pH)
Avoids the first pass effect
Provides an alternative to oral administration (for patients experiencing nausea/vomiting)
Non-invasive, convenient, and user-friendly
Easy to identify medication in emergencies
Drug therapy may be terminated rapidly by removing the TDDS

Disadvantages of TDDS

Only relatively potent drugs may be used due to skin impermeability
Biological factors such as skin thickness, skin permeability, and the presence of pores on skin surfaces can affect drug delivery.

Physical Absorption Enhancers: Iontophoresis

Advantages:*
Control delivery rates by varying current density, pulsed voltage, drug concentration, and ionic strength
Allows large, charged molecules to be delivered to the patient
Avoids GI incompatibility, erratic absorption, and first-pass metabolism
Reduces adverse effects
Reduces inter-patient variability
Avoids continuous injection and infusion risks (infection, inflammation, fibrosis)
Enhances patient compliance with a convenient and non-invasive therapeutic regimen
Disadvantages:*
Can lead to skin irritation at high current densities (burns can result from improper placement)
Lag time between administration and drug reaching the bloodstream
Products:*
IONSYS: Fentanyl iontophoretic transdermal system, used for the short-term management of acute post-operative pain
Lidocaine IP products (LidoSite, NumbyStuff): topical anesthetic for the needle-phobic
Other Uses:*
Iontophoresis of pilocarpine: Induce sweating in the diagnosis of cystic fibrosis
Topical delivery of fluoride to teeth
Dexamethasone: delivered directly into joints
Delivery of NSAIDs, corticosteroids, anti-inflammatory agents, antibiotics, and local anesthetics for veterinary use
Being investigated for protein delivery

Physical Absorption Enhancers: Sonophoresis (Phonophoresis)

High-frequency ultrasound used to transport drug across the skin
Drug is mixed with a coupling agent (gel, ointment, cream)
Ultrasonic energy transferred from the phonophoresis device to the skin through the coupling agent
Thought to disrupt the lipids in the stratum corneum, increasing skin penetrability

Formulation Factors for Sonophoresis

Vehicle must be smooth and non-gritty
Vehicle should have relatively low viscosity
Avoid air incorporation

Photodynamic Therapy (PDT)

Light-activated drug is applied topically or injected intravenously
Drug accumulates in the affected tissue
Low power light delivered through a PDT device is focused on the affected tissue
Light activates the photo-reactive drug, releasing agents that destroy only affected cells
Most applications use light waves in the visible light spectrum (350-800 nm range)

Advantages of PDT:

Avoids first pass effect
Causes minimal damage to healthy tissues

Disadvantages of PDT:

Current laser light can only pass through ~3 cm of tissue
Makes skin and eyes sensitive to light for 6+ weeks following treatment
Other potential adverse effects: nausea, vomiting, metallic taste in the mouth

Uses of PDT :

Cancer diagnosis: Abnormal cells take up the compound differently than normal cells
Cancer therapy: Primarily used to treat tumors on or just under the skin, or on the lining of internal organs using endoscopes and fiber optic catheters
Non-cancer applications: Age-related macular degeneration, psoriasis, actinic keratoses, severe acne (in clinical trials)

Approved Photodynamic Therapy Products:

Levulan: Aminolevulinic acid, used to treat actinic keratosis
Kerastick: ALA, used to treat warty overgrowths of the skin
Photofrin: Porfimer sodium, used to treat esophageal cancer, endobronchial non-small cell lung cancer, and Barrett’s esophagus
Cysview: Hexaminolevulinate HCl, used to visualize bladder cancers during cystoscopy
Visudyne: Verteporfin, used to treat age-related macular degeneration, psoriasis, and rheumatoid arthritis (unlabeled use)

Other Techniques:

Microporation: Creation of micropores in the stratum corneum, achieved by electroporation, microneedles, ultrasound, radiofrequency, and lasers
Electroporation: High voltage pulse applied to the skin for a short period, leading to increased permeability of the stratum corneum and formation of pores
Microneedle or Microprojection-Based Devices: Tiny drug-coated projections or needles pierce the top layer of skin, creating superficial holes for drug transport
Transdermal Patches: Drug delivery system that provides controlled release of medication through the skin.

Summary

Transdermal drug delivery systems (TDDS) provide a convenient and non-invasive route for medication administration.
They offer advantages such as sustained drug release, reduced adverse effects, and improved patient compliance.
TDDS are particularly beneficial for drugs with short half-lives, those experiencing first pass effects, or those who have difficulty with oral absorption.
Techniques such as iontophoresis, sonophoresis, and photodynamic therapy employ physical absorption enhancers to facilitate drug penetration through the skin.
Microporation, using methods like electroporation and microneedles, disrupts the stratum corneum to enhance drug transport.
TDDS are continually evolving, with new products and techniques under development to address a wide range of medical conditions.

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Description

This quiz explores the principles and designs of Transdermal Drug Delivery Systems (TDDS), focusing on reservoir systems. Learn about the components, functionality, and advantages of these innovative drug delivery methods. Test your knowledge on TDDS and their importance in modern medicine.