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Posts Tagged ‘Transdermal Drug Delivery System’


Human Factor Engineering: New Regulations Impact Drug Delivery, Device Design And Human Interaction

Curator: Stephen J. Williams, Ph.D.

Institute of Medicine report brought medical errors to the forefront of healthcare and the American public (Kohn, Corrigan, & Donaldson, 1999) and  estimated that between

44,000 and 98,000 Americans die each year as a result of medical errors

An obstetric nurse connects a bag of pain medication intended for an epidural catheter to the mother’s intravenous (IV) line, resulting in a fatal cardiac arrest. Newborns in a neonatal intensive care unit are given full-dose heparin instead of low-dose flushes, leading to threedeaths from intracranial bleeding. An elderly man experiences cardiac arrest while hospitalized, but when the code blue team arrives, they are unable to administer a potentially life-saving shock because the defibrillator pads and the defibrillator itself cannot be physically connected.

Human factors engineering is the discipline that attempts to identify and address these issues. It is the discipline that takes into account human strengths and limitations in the design of interactive systems that involve people, tools and technology, and work environments to ensure safety, effectiveness, and ease of use.

 

FDA says drug delivery devices need human factors validation testing

Several drug delivery devices are on a draft list of med tech that will be subject to a final guidance calling for the application of human factors and usability engineering to medical devices. The guidance calls called for validation testing of devices, to be collected through interviews, observation, knowledge testing, and in some cases, usability testing of a device under actual conditions of use. The drug delivery devices on the list include anesthesia machines, autoinjectors, dialysis systems, infusion pumps (including implanted ones), hemodialysis systems, insulin pumps and negative pressure wound therapy devices intended for home use. Studieshave consistently shown that patients struggle to properly use drug delivery devices such as autoinjectors, which are becoming increasingly prevalent due to the rise of self-administered injectable biologics. The trend toward home healthcare is another driver of usability issues on the patient side, while professionals sometimes struggle with unclear interfaces or instructions for use.

 

Humanfactors engineering, also called ergonomics, or human engineering, science dealing with the application of information on physical and psychological characteristics to the design of devices and systems for human use. ( for more detail see source@ Britannica.com)

The term human-factors engineering is used to designate equally a body of knowledge, a process, and a profession. As a body of knowledge, human-factors engineering is a collection of data and principles about human characteristics, capabilities, and limitations in relation to machines, jobs, and environments. As a process, it refers to the design of machines, machine systems, work methods, and environments to take into account the safety, comfort, and productiveness of human users and operators. As a profession, human-factors engineering includes a range of scientists and engineers from several disciplines that are concerned with individuals and small groups at work.

The terms human-factors engineering and human engineering are used interchangeably on the North American continent. In Europe, Japan, and most of the rest of the world the prevalent term is ergonomics, a word made up of the Greek words, ergon, meaning “work,” and nomos, meaning “law.” Despite minor differences in emphasis, the terms human-factors engineering and ergonomics may be considered synonymous. Human factors and human engineering were used in the 1920s and ’30s to refer to problems of human relations in industry, an older connotation that has gradually dropped out of use. Some small specialized groups prefer such labels as bioastronautics, biodynamics, bioengineering, and manned-systems technology; these represent special emphases whose differences are much smaller than the similarities in their aims and goals.

The data and principles of human-factors engineering are concerned with human performance, behaviour, and training in man-machine systems; the design and development of man-machine systems; and systems-related biological or medical research. Because of its broad scope, human-factors engineering draws upon parts of such social or physiological sciences as anatomy, anthropometry, applied physiology, environmental medicine, psychology, sociology, and toxicology, as well as parts of engineering, industrial design, and operations research.

source@ Britannica.com

The human-factors approach to design

Two general premises characterize the approach of the human-factors engineer in practical design work. The first is that the engineer must solve the problems of integrating humans into machine systems by rigorous scientific methods and not rely on logic, intuition, or common sense. In the past the typical engineer tended either to ignore the complex and unpredictable nature of human behaviour or to deal with it summarily with educated guesses. Human-factors engineers have tried to show that with appropriate techniques it is possible to identify man-machine mismatches and that it is usually possible to find workable solutions to these mismatches through the use of methods developed in the behavioral sciences.

The second important premise of the human-factors approach is that, typically, design decisions cannot be made without a great deal of trial and error. There are only a few thousand human-factors engineers out of the thousands of thousands of engineers in the world who are designing novel machines, machine systems, and environments much faster than behavioral scientists can accumulate data on how humans will respond to them. More problems, therefore, are created than there are ready answers for them, and the human-factors specialist is almost invariably forced to resort to trying things out with various degrees of rigour to find solutions. Thus, while human-factors engineering aims at substituting scientific method for guesswork, its specific techniques are usually empirical rather than theoretical.

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The Man-Machine Model: Human-factors engineers regard humans as an element in systems

The simple man-machine model provides a convenient way for organizing some of the major concerns of human engineering: the selection and design of machine displays and controls; the layout and design of workplaces; design for maintainability; and the work environment.

Components of the Man-Machine Model

  1. human operator first has to sense what is referred to as a machine display, a signal that tells him something about the condition or the functioning of the machine
  2. Having sensed the display, the operator interprets it, perhaps performs some computation, and reaches a decision. In so doing, the worker may use a number of human abilities, Psychologists commonly refer to these activities as higher mental functions; human-factors engineers generally refer to them as information processing.
  3. Having reached a decision, the human operator normally takes some action. This action is usually exercised on some kind of a control—a pushbutton, lever, crank, pedal, switch, or handle.
  4. action upon one or more of these controls exerts an influence on the machine and on its output, which in turn changes the display, so that the cycle is continuously repeated

 

Driving an automobile is a familiar example of a simple man-machine system. In driving, the operator receives inputs from outside the vehicle (sounds and visual cues from traffic, obstructions, and signals) and from displays inside the vehicle (such as the speedometer, fuel indicator, and temperature gauge). The driver continually evaluates this information, decides on courses of action, and translates those decisions into actions upon the vehicle’s controls—principally the accelerator, steering wheel, and brake. Finally, the driver is influenced by such environmental factors as noise, fumes, and temperature.

 

hfactorconsideroutcomes

How BD Uses Human Factors to Design Drug-Delivery Systems

Posted in Design Services by Jamie Hartford on August 30, 2013

 Human factors testing has been vital to the success of the company’s BD Physioject Disposable Autoinjector.

Improving the administration and compliance of drug delivery is a common lifecycle strategy employed to enhance short- and long-term product adoption in the biotechnology and pharmaceutical industries. With increased competition in the industry and heightened regulatory requirements for end-user safety, significant advances in product improvements have been achieved in the injectable market, for both healthcare professionals and patients. Injection devices that facilitate preparation, ease administration, and ensure safety are increasingly prevalent in the marketplace.

Traditionally, human factors engineering addresses individualized aspects of development for each self-injection device, including the following:

  • Task analysis and design.
  • Device evaluation and usability.
  • Patient acceptance, compliance, and concurrence.
  • Anticipated training and education requirements.
  • System resilience and failure.

To achieve this, human factors scientists and engineers study the disease, patient, and desired outcome across multiple domains, including cognitive and organizational psychology, industrial and systems engineering, human performance, and economic theory—including formative usability testing that starts with the exploratory stage of the device and continues through all stages of conceptual design. Validation testing performed with real users is conducted as the final stage of the process.

To design the BD Physioject Disposable Autoinjector System , BD conducted multiple human factors studies and clinical studies to assess all aspects of performance safety, efficiency, patient acceptance, and ease of use, including pain perception compared with prefilled syringes.5 The studies provided essential insights regarding the overall user-product interface and highlighted that patients had a strong and positive response to both the product design and the user experience.

As a result of human factors testing, the BD Physioject Disposable Autoinjector System provides multiple features designed to aide in patient safety and ease of use, allowing the patient to control the start of the injection once the autoinjector is placed on the skin and the cap is removed. Specific design features included in the BD Physioject Disposable Autoinjector System include the following:

  • Ergonomic design that is easy to handle and use, especially in patients with limited dexterity.
  • A 360° view of the drug and injection process, allowing the patient to confirm full dose delivery.
  • A simple, one-touch injection button for activation.
  • A hidden needle before and during injection to reduce needle-stick anxiety.
  • A protected needle before and after injection to reduce the risk of needle stick injury.

 

YouTube VIDEO: Integrating Human Factors Engineering (HFE) into Drug Delivery

 

Notes:

 

 

The following is a slideshare presentation on Parental Drug Delivery Issues in the Future

 The Dangers of Medical Devices

The FDA receives on average 100,000 medical device incident reports per year, and more than a third involve user error.

In an FDA recall study, 44% of medical device recalls are due to design problems, and user error is often linked to the poor design of a product.

Drug developers need to take safe drug dosage into consideration, and this consideration requires the application of thorough processes for Risk Management and Human Factors Engineering (HFE).

Although unintended, medical devices can sometimes harm patients or the people administering the healthcare. The potential harm arises from two main sources:

  1. failure of the device and
  2. actions of the user or user-related errors. A number of factors can lead to these user-induced errors, including medical devices are often used under stressful conditions and users may think differently than the device designer.

Human Factors: Identifying the Root Causes of Use Errors

Instead of blaming test participants for use errors, look more carefully at your device’s design.

Great posting on reasons typical design flaws creep up in medical devices and where a company should integrate fixes in product design.
Posted in Design Services by Jamie Hartford on July 8, 2013

 

 

YouTube VIDEO: Integrating Human Factors Engineering into Medical Devices

 

 

Notes:

 

 Regulatory Considerations

  • Unlike other medication dosage forms, combination products require user interaction
  •  Combination products are unique in that their safety profile and product efficacy depends on user interaction
Human Factors Review: FDA Outlines Highest Priority Devices

Posted 02 February 2016By Zachary Brennan on http://www.raps.org/Regulatory-Focus/News/2016/02/02/24233/Human-Factors-Review-FDA-Outlines-Highest-Priority-Devices/ 

The US Food and Drug Administration (FDA) on Tuesday released new draft guidance to inform medical device manufacturers which device types should have human factors data included in premarket submissions, as well final guidance from 2011 on applying human factors and usability engineering to medical devices.

FDA said it believes these device types have “clear potential for serious harm resulting from use error and that review of human factors data in premarket submissions will help FDA evaluate the safety and effectiveness and substantial equivalence of these devices.”

Manufacturers should provide FDA with a report that summarizes the human factors or usability engineering processes they have followed, including any preliminary analyses and evaluations and human factors validation testing, results and conclusions, FDA says.

The list was based on knowledge obtained through Medical Device Reporting (MDRs) and recall data, and includes:

  • Ablation generators (associated with ablation systems, e.g., LPB, OAD, OAE, OCM, OCL)
  • Anesthesia machines (e.g., BSZ)
  • Artificial pancreas systems (e.g., OZO, OZP, OZQ)
  • Auto injectors (when CDRH is lead Center; e.g., KZE, KZH, NSC )
  • Automated external defibrillators
  • Duodenoscopes (on the reprocessing; e.g., FDT) with elevator channels
  • Gastroenterology-urology endoscopic ultrasound systems (on the reprocessing; e.g., ODG) with elevator channels
  • Hemodialysis and peritoneal dialysis systems (e.g., FKP, FKT, FKX, KDI, KPF ODX, ONW)
  • Implanted infusion pumps (e.g., LKK, MDY)
  • Infusion pumps (e.g., FRN, LZH, MEA, MRZ )
  • Insulin delivery systems (e.g., LZG, OPP)
  • Negative-pressure wound therapy (e.g., OKO, OMP) intended for home use
  • Robotic catheter manipulation systems (e.g., DXX)
  • Robotic surgery devices (e.g., NAY)
  • Ventilators (e.g., CBK, NOU, ONZ)
  • Ventricular assist devices (e.g., DSQ, PCK)

Final Guidance

In addition to the draft list, FDA finalized guidance from 2011 on applying human factors and usability engineering to medical devices.

The agency said it received over 600 comments on the draft guidance, which deals mostly with design and user interface, “which were generally supportive of the draft guidance document, but requested clarification in a number of areas. The most frequent types of comments requested revisions to the language or structure of the document, or clarification on risk mitigation and human factors testing methods, user populations for testing, training of test participants, determining the appropriate sample size in human factors testing, reporting of testing results in premarket submissions, and collecting human factors data as part of a clinical study.”

In response to these comments, FDA said it revised the guidance, which supersedes guidance from 2000 entitled “Medical Device Use-Safety: Incorporating Human Factors Engineering into Risk Management,” to clarify “the points identified and restructured the information for better readability and comprehension.”

Details

The goal of the guidance, according to FDA, is to ensure that the device user interface has been designed such that use errors that occur during use of the device that could cause harm or degrade medical treatment are either eliminated or reduced to the extent possible.

FDA said the most effective strategies to employ during device design to reduce or eliminate use-related hazards involve modifications to the device user interface, which should be logical and intuitive.

In its conclusion, FDA also outlined the ways that device manufacturers were able to save money through the use of human factors engineering (HFE) and usability engineering (UE).

– See more at: http://www.raps.org/Regulatory-Focus/News/2016/02/02/24233/Human-Factors-Review-FDA-Outlines-Highest-Priority-Devices/#sthash.cDTr9INl.dpuf

 

Please see an FDA PowerPoint on Human Factors Regulatory Issues for Combination Drug/Device Products here: MFStory_RAPS 2011 – HF of ComboProds_v4

 

 

 

 

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Author, Editor: Tilda Barliya PhD

We previously started a discussion on Transdermal Drug Delivery system (TDDS), see: https://pharmaceuticalintelligence.com/2013/01/28/introduction-to-transdermal-delivery-tdd-system-and-nanotechnology/

We introduced the main aspects of the anatomy of the skin, the advantages and disadvantages of TDDS and the main factors that affect the efficacy of a TDDS and their different types. In this followup, will try to dig a little bit deeper and analyze some examples of TDDS already made it to public use. The first TDD patch to be introduced to the US market was scopolamine in 1979 (1a,1b) for prevention of nausea and vomiting associated with motion sickness and recovery from anesthesia and surgery. But the TDDS that revolutionized the transdermal market was the nicotine patch, which was first introduced in 1991 as a treatment for smoking cessation (1c). Since then there has been development of a number of different patches, including a testosterone patch for hypogonadism in males and combination patches of estradiol and norethindrone or levonorgestrel for menopausal symptoms. Figure 1 shows the global sales of TDDS products by segments.

However, there are many disease applications that are treated with peptide or protein preparations (ranging from 900 Da molecular mass to > 150,000 Da molecular mass), usually by means of injection, as they cannot be delivered via topical application at present. Dermal and transdermal delivery of large molecules such as peptides, proteins, and DNA has remained a significant challenge.

Several attempts have been made to develop topical formulations for macromolecules using a wide variety of tools such as using delivery enhancers, delivery vehicles, and different penetration methods. For instance, the chemical enhancers such as alcohols, fatty acids, surfactants, and physical enhancers such as microneedles, ultrasonic waves and low electrical current (iontophoresis) methods  have been examined to improve topical delivery of macromolecules. These techniques however, suffer from different obstacles, ranging from inverse correlation between size and transdermal transport up to variably due to solvent ions, cargo charge and pH.  Poorly water-soluble peptides and proteins, which can be more readily solubilized by the dual water/oil formulation may offset some of these disadvantages.

The majority of topically applied peptides and proteins cannot enter the circulation in the skin as there is no basal-to-apical transport of such molecules through the vascular endothelium, and as such they must travel in the lymphatics in order ultimately to reach the circulation.

In a recent paper, Dr. Gregory Russell-Jones and colleagues review the use of a microemulsion system to effectively deliver proteins through the skin (2).

Water-in-Oil microemulsions:

Microemulsions are  nanosized, clear, thermodynamically stable, isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a co-surfactant.  These droplets can ‘hide’ water-soluble molecules within a continuous oil phase and therefore enable the use of water-soluble therapeutic drugs for different diseases, that otherwise cannot be achieved by the transdermal route.

Microemulsion system may have the potential advantages in delivery because of their:

  • High solubilization capacity
  • Ease of preparation,
  • Transparency,
  • Thermodynamic stability,
  • High diffusion and absorption rates

Previous work, both in small animals and humans, has utilized microemulsions containing small hydrophobic molecules, or small ‘model’ hydrophilic molecules.  The validity of these models in measuring lateral movement of topically applied material is rather questionable. Whereas only few of the studies evaluated the efficacy of microemulsions as transdermal drug delivery systems and were shown for desmopressin, cyclosporine and folate analogue methotrexate ( ref 2). More notably are the advances in insulin delivery.

Diabetes for instance , is the most common endocrine disorder and by the year 2010, is estimated that more than 200 million people worldwide will have DM and 300 million will subsequently have the disease by 2025 (7). DM patients suffer from a defect in insulin secretion, insulin action, or both and therefore require a constant external administration of insulin to keep their sugar levels under control. Insulin is most commonly being administrated using a pen, a syringe, an automated pump and more recently using a patch to ensure a pain-free approach. Some of these patcesh are being evaluated in clinical trials.

As a different approach, the authors have evaluated the use of microemulsion to delivery different type of peptides such as IGF-1, GHRP-6 and Insulin in an obese mice model. Among the studies that were conducted they evaluated the effect of increasing the dose of topically administered insulin formulated in a water-in-oil microemulsion which was compared with subcutaneously administered insulin. It was possible to increase the dose of topically administered insulin from 10 to 100 µg as there was no reduction in serum glucose seen at this dose. By contrast, it was not possible to increase the dose of subcutaneously administered insulin owing to the potential of death through induction of hypoglycemia (2). These are very encouraging results!!!

The authors also noted changes in weight loss/gain of the mice upon treatment depending on the initial weight and which was consistent with the known anabolic effect of insulin. Presumably the greater effect seen with the topical insulin is due to the depot-like effect of this route of administration, leading to a longer stimulation of both adipocytes and muscle cells.

An exciting area of potential development is weight control management. The results using insulin, IGF-I and GHRP-6 given topically are particularly intriguing. Whether these results can be replicated in humans and whether the use of these drugs for potential treatment of obesity will be commercially viable will be particularly interesting to observe.

Summary:

Effective peptide and protein delivery to the skin has received much attention in the pharmaceutical industry, with many companies developing a variety of delivery devices to force peptides and proteins into and across the epithelium of the skin. Despite these many attempts, effective delivery of high-molecular-mass compounds has at best been poor. The water-in-oil microemulsion system may overcome the water-impermeable barrier of the epidermis and allows for effective delivery of highly water-soluble molecules such as peptides and proteins following topical application.

Ref:

1a. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2995530/

1b. http://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=76671

1c. http://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=92761472-2bdb-4ef9-9c81-a39b1852d7e0

2. Gregory Russell-Jones and Roy Himes. “Water-in-oil microemulsions for effective transdermal delivery of proteins”. Expert Opin. Drug Delivery 2011 Invited review –  8, 537-546.

http://www.mentorconsulting.net/publications_files/Russell-Jones%202011%20WOW%20transdermal.pdf

3.  Ellen Jett Wilson. “Three Generations: The Past, Present, and Future of Transdermal Drug Delivery Systems”

http://www.freece.com/Files/Classroom/ProgramSlides/1be80281-23ef-4687-a334-c79b7200dd19/3%20Gen%20Homestudy%20(TV).pdf

4. http://www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2012/09/WC500132404.pdf

5. http://www.fda.gov/downloads/Drugs/…/Guidances/UCM220796.pdf

6. http://onlinelibrary.wiley.com/doi/10.1111/cbdd.12008/pdf

7. Salim Bastaki. Diabetes mellitus and its treatment. Int J Diabetes & Metabolism (2005) 13:111-134. http://ijod.uaeu.ac.ae/iss_1303/a.pdf

8. http://sphinxsai.com/Vol.3No.4/pharm/pdf/PT=39(2140-2148)OD11.pdf

9. Dhote V et al. Iontophoresis: A Potential Emergence of a Transdermal Drug Delivery System. Sci Pharm. 2012 March; 80(1): 1–28.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3293348/

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Author, Editor: Tilda Barliya PhD

Transdermal drug delivery is a very exciting and challenging research area. It is defined as the administration of therapeutic drugs through the skin.   The human skin is a readily accessible surface for drug  delivery (1). Skin of an average adult body covers a surface of approximately 2 m2 and receives about one-third of the  blood circulating through the body. Over the past decades,  developing controlled drug delivery has become  increasingly important in the pharmaceutical industry.

The potential of using the intact skin as the port of drug administration to the human body has been recognized for several decades, however the skin is a very difficult barrier to the ingress of materials allowing only small quantities of a drug to penetrate over a period of time. In order to design a drug delivery system, one must first understand the skin anatomy and it’s implication of drug-of choice and method of delivery.

The Anatomy of the skin

Human skin comprises of three distinct but mutually dependent tissues :

  •  The stratified, vascular, cellular epidermis (stratum corneum and viable epidermis),
  • Underlying dermis of connective tissues
  • Hypodermis

The Epidermis: This is the outermost layer of skin also called as horney layer. It is approximately 10mm thick when dry but swells to several times this thickness when fully hydrated. It contains 10 to 25 layers of dead, keratinized cells called corneocytes. It is flexible but relatively impermeable. The stratum corneum is the principal barrier for penetration of drug.

The Dermis : Dermis is 3 to 5mm thick layer and is composed of a matrix of connective tissue, which contains blood vessels, lymph vessels and nerves. Capillaries reach to within 0.2 mm of skin surface and provide sink conditions for most molecules penetrating the skin barrier. The blood supply thus keeps the dermal concentration of a permeant very low and the resulting concentration difference across the epidermis provides the essential concentration gradient for transdermal permeation.

The Hypodermis: The hypodermis or subcutaneous fat tissue supports the dermis and epidermis. It serves as a fat storage area. The cutaneous blood supply has essential function in regulation of body temperature.

For transdermal drug delivery, drug has to penetrate through all these three layers and reach into systemic circulation while in case of topical drug delivery only penetration through stratum corneum is essential and then retention of drug in skin layers is desired.

Transdermal drug delivery (TDD) offers many advantages over conventional delivery systems yet has several limitations (3).

Advantages:

  • avoidance of hepatic first pass metabolism,
  • The steady permeation of drug across the skin allows for more consistent serum drug levels
  • non-invasive nature of drug application
  • convenience
  • improved patient compliance and discontinuation of administration by removal of the system

Disadvantages:

  • Possibility of local irritation at the site of application (Erythema, itching, and local edema as well as severe allergic reaction).
  • Skin’s low permeability limits the number of drugs that can be delivered in this manner (Many drugs with a hydrophilic structure permeate the skin too slowly to be of therapeutic benefit. Drugs with a lipophillic character, however, are better suited for transdermal delivery).

Two main routes of Traditional Transdermal Drug Penetration (3):

  • Transcellular pathway – Drugs cross the skin by directly passing through both the phospholipid membranes and the cytoplasm of the dead keratinocytes that constitute the stratum corneum. Although this is the path of shortest distance, the drugs encounter significant resistance to permeation. This is because the drugs must cross the lipophilic membrane of each cell, then the hydrophilic cellular contents containing keratin, and then the phospholipid bilayer of the cell one more time. This series of steps is repeated numerous times to traverse the full thickness of the stratum corneum. Few drugs have the properties to cross via this method.
  • Intercellular (Paracellular) route – Drugs crossing the skin by this route must pass through the small spaces between the cells of the skin, making the route more tortuous. Although the thickness of the stratum corneum is only about 20 μm, the actual diffusional path of most molecules crossing the skin is on the order of 400 μm. The 20-fold increase in the actual path of permeating molecules greatly reduces the rate of drug penetration.
  • A less important pathway of drug penetration is the follicular route. Hair follicles penetrate through the stratum corneum, allowing more direct access to the dermal microcirculation. However, hair follicles occupy only 1/1,000 of the entire skin surface area. Consequently, very little drug actually crosses the skin via the follicular route.

For thransdermal delivery , the skin condition (pH and temp, age, blood supply, hydration etc) is of major impact on the efficiency.

The basic components of any transdermal delivery system include the drug dissolved or dispersed in an inert polymer matrix that provides support and platform for drug release. There are two basic designs of the patch system that dictate drug release characteristics and patch behavior (1) :

  1.  Matrix or Monolithic: The inert polymer matrix binds with the drug and controls it’s release from the device.
  2. Reservoir or Membrane: The polymer matrix does not control drug release. Instead, a rate-controlling membrane present between the drug matrix and the adhesive layer provides the rate-limiting barrier for drug release from the device.

Example of a TDD system is a systems in which, the drug reservoir is sandwiched between a drug-impermeable backing laminate and a rate controlling polymeric membrane.

Along the biological aspect of the skin condition (pH and temp, hydration etc) the chemical composition of the drug of choice and polyer martix are also of crucial nature.

  • Drug type (lipid, protein, macromolecule etc)/ Molecular size and shape
  • Drug concentration
  • Diffusion coefficient
  • Partition coefficient

To date, there are several approved TDD patches on the market (3) (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2995530/table/T2/) and several other ongoing clinical Trials:clinical trials see link  (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2995530/table/T3/)

As this topic is very complicated and requires a careful evaluation of the different products on the market, we’ll go dig deeper into the different TDD systems and analyze several examples, in the following post.

Ref:

1. Nilkhil Sharma., Geta Agrawal.,  A. C. Rana., Zulfiqar Ali Bahat., and Dinesh Kumar. ” A Review: Transdermal Drug Delivery System: A Tool For Novel Drug Delivery System”. Int. J. Drug Dev. & Res., Jul-Sep 2011, 3 (3): 70-84.

http://ijddr.in/old/Dacuments/1/File%20no%206%20Vol%203%20Issue%203.pdf

2. Yakov Frum – Bradford School of Pharmacy

http://www.gla.ac.uk/services/postgraduateresearch/scholarships/macrobertson/macrobertsonscholarshipreports/2005-6awards/yakovfrum-bradfordschoolofpharmacy/

3. Eseldin Keleb, Rakesh Kumar Sharma2, Esmaeil B Mosa, Abd-alkadar Z Aljahwi. “Transdermal Drug Delivery System- Design and Evaluation”. International Journal of Advances in Pharmaceutical Sciences 1 (2010) 201-211.

4. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2995530/

5. http://www.manufacturingchemist.com/technical/article_page/Liftoff_for_needlefree_delivery/39384.

6. http://www.ncbi.nlm.nih.gov/pubmed/21413905

7. Greg Russell Jones: http://www.mentorconsulting.net/News.htm

see detailed papers on this link no.7  with active PDF files.

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