Iontophoresis-A Review

Iontophoresis is a non-invasive method of propelling high concentrations of a charged substance, normally

medication or bioactive agents, transdermally by

repulsive electromotive force using a small electrical

charge approximately (0.5 mA/cm2) applied to an

iontophoretic chamber containing a similarly charged

active agent and its vehicle.

Iontophoresis is a method of active transdermal drug delivery and isdefined as the introduction of a chosen ion into the tissues by meansof an electrical current. It is either administered in clinic with DUPELB.L.U.E., or using Action Patch. Insurance coverage and reimbursementfor iontophoresis varies by state. Clinicians can increase the likelihood ofreimbursement by ensuring the patient’s medical record includes specificitems. Among these items is a description of the condition(s) that justifymedical necessity for iontophoresis

The objective of delivery system is to achieve optimum therapeutic management.But, it still remains a challenge in the field of pharmaceuticals for deliveryof ionic species such as proteins and peptides.

Development of iontophoretic system is a breakthrough in this field designedto improve the delivery rate of ionic compounds. This technique generates anelectrical potential gradient that facilitates the movement of solute ions acrossthe membrane. Moreover with the advent of more sophisticated techniques available

for the production of recombinant proteins and peptides, there is an ever-increasingdemand of novel delivery systems that could effectively deliver these ionicspecies at the specific site.

Iontophoresis seems to be an ideal candidate to sort out the limitations associatedwith the delivery of ionic drugs. In this review, efforts have been made tosummarize all the aspects of iontophoretic delivery including history, typesand various factors affecting the drug delivery.

Introduction

There has been a growing awareness in recent years of potential therapeuticimportance of achieving true controlled drug delivery where the rate of drugoutput may be modulated in a precisely controlled manner1. Transdermaldrug delivery has usefulness in achieving the controlled delivery of pharmaceuticals,which are relatively small in molecular size and rather lipophilic in nature,however, these systems are rather limited in their capability of achieving thetransdermal systemic delivery of peptides, proteins and drugs which is oftencharged and highly hydrophilic in nature2. In order to deliver anionic drug, peptide/protein molecule through transdermal delivery to attaina systemic effect, chemical and/or physical methods are required to enhancethe rate of penetration of therapeutic agent through the main diffusion barrier3,

4. The intophoratic technique is highly desirable to improve the transdermaldelivery of peptide and proteins using a lower current intensity with a shorttime period4. The idea of applying electric current to increase thepenetration of electrically charged drugs into surface tissues was probablyorganized by Veratti in 19475,6. Leduc did the first well-documentedexperiments at the beginning of the 20th century7,8. Leduc demonstratedthe introduction of strychnine and cyanide ions into the rabbits when the correctpolarities were applied.

Inchley also carried out similar experiments in 19219. The application of iontophoresis to the treatment of hyperhydrosis could be reduced by ion transfer of certain applied solutions by electro-phoretic technique. Today, the treatment of hyperhydrosis is the most successful and popular applications of iontophoresis in dermatological medication10. The transdermal delivery of many ionized drugs at therapeutic levels is precluded by their slow rate of diffusion under a concentration gradient alone are now application with the help of iontophoretic technique and devices11.

Iontophoresis can be defined as the process in which the flux or rate of absorptionof ionic solutes into or through skin is enhanced by applying a voltage drop/electricfield across the skin12, 13. Transdermal iontophoretic techniqueis capable of administering drugs in a pulsatile pattern by alternately applyingand terminating the current input at programmed rate14. In addition,delivery rate can be controlled by the intensity of applied electric currentor Electro-chemical potential gradient15. It can also be define asa means of enhancing the flux of ionic drugs across skin by the applicationof an electrochemical potential gradient16.

Types

Voltage drop across a membrane driving force for the flux of ions through it opens up new type of approaches to mode transport of ionic drugs across skin. Iontophoresis is usually defined as either anodal (+) in which the positive anode is placed in the solution applied to the epidermis and negative cathode is placed in the solution applied to the epidermis and negative cathode is placed in the dermal receptor solution, or cathodal (-), in which the electrode location are reserved. Anodal (+) introphoresis is facilitated by the movement of a caution from the donor to the receptor, whereas cathodal iontophoresis implies the movement of an anion from the donor to receptor17. Gangaross et.al.18 reported that the penetration of antiviral compound 5-iodo-2-deoxyuridine can be increased by both anodal (+) and cathodal (-)  iontophoresis. It was hypothetized that anodal (+) iontophoresis of iodourine may be due to hydrokinesis. It is known that, under the driving force of a potential gradient, manovalent cations cross the skin more easily than manovalent anions19.

Merits

01. It is a non-invasive technique could serve as a substitute for chemical enhancers20.

02. It eliminates problems like toxicity problem, adverse reaction formulationproblems associated with presence of chemical enhancers in pharmaceuticals21.

03. It may permit lower quantities of drug compared to use in TDDS, this maylead to fewer side effects.

04. TDDS of many ionized drug at therapeutic levels was precluded by theirslow rate of diffusion under a concentration graduation, but iontophoresis enhancedflux of ionic drugs across skin under electrical potential gradient20.

05. Iontophoresis prevent variation in the absorption of TDDS.

06. Eliminate the chance of over or under dosing by continuous delivery ofdrug programmed at the required therapeutic rate.

07. Provide simplified therapeutic regimen, leading to better compliance.

08. Permit a rapid termination of the modification, if needed, by simply bystopping drug input from the iontophoretic delivery system22.

09. It is important in systemic delivery of peptide/protein based pharmaceuticals,which are very potent, extremely short acting and often require delivery ina circadian pattern to simulate physiological rhythm, eg. Thyrotropin releasinghormone, somatotropine, tissue plasminogen activates, inter ferons, enkaphaline,etc23.

10. Provide predictable and extended duration of action.

11. Reduce frequency of dosage.

12. Self-administration is possible.

13. A constant current iontophoretic system automatically adjust the magnitudeof the electric potential across skin which is directly proportional to rateof drug delivery and therefore, intra and inter-subject variability in drugdelivery rate is substantially reduced. Thus, minimize inter and intra-patientvariation24.

14. An iontophoretic system also consists of a electronic control module whichwould allow for time varying of free-back controlled drug delivery24.

15. Iontophoresis turned over control of local anesthesia delivery in reducingthe pain of needle insertion for local anesthesia25.

16. By minimizing the side effects, lowering the complexity of treatment andremoving the need for a care to action, iontophoretic delivery improve adherenceto therapy for the control of hypertension26.

17. Iontophoretic delivery prevents contamination of drugs reservoir for extendedperiod of time27.

Demerits      

01. Iontophoretic delivery is limited clinically to those applications forwhich a brief drug delivery period is adequate28.

02. An excessive current density usually results in pain.

03. Burns are caused by electrolyte changes within the tissues.

04. The safe current density varies with the size of electrodes29.

05. The high current density and time of application would generate extremepH, resulting in a chemical burn17.

06. This change in pH may cause the sweat duct plugging perhaps precipitateprotein in the ducts, themselves or cosmetically hyperhydrate the tissue surroundingthe ducts28.

07. Electric shocks may cause by high current density at the skin surface.

08. Possibility of cardiac arrest due to excessive current passing throughheart.

09. Ionic form of drug in sufficient concentration is necessary for iontophoreticdelivery.

10. High molecular weight 8000-12000 results in a very uncertain rate of delivery.

Physico-chemical parameters

The movement of drug ions across the skin is dependent not only the magnitudeof apparent electric field, but also upon the concentration of solution, themolecular size of drug to be passed, as well as charge and valence of ion.

(i) pH:

The iontophoretic drug delivery rate is dependent on the ionic form of drugdelivery, which is extremely effected by the pH of the system, when the skinis maintained at a negative charge by exposing the solution with pH 4 or higher,it facilitate the transdermal delivery of cationic drugs30,31. Sandersonet. al.,23 suggested that the control of pH offers advantage of polarizationeffects on skin and enhance the perm selectivity of skin for catecholemine drugduring iontophoretic delivery. Several authors reported the pH dependent penetrationenhancement of lidocaine32, thyrotropin releasing hormone33

enalaprilate34 insulin4, acetate ions35.

(ii) Species variation: 

The vide differences in physical characteristics such as appendages per unitarea, thickness and structural changes between human and laboratory rodent displaya variation in penetration of drugs36,37. The average penetrationof drugs is in order of rabbit > rat > guineas pig > human. Human skinis very much less permeable than other rodents but iontophoretic delivery ofdrug is 7-fold greater in human skin consists of greater negative charge/orgreater area fraction of negative pores38. Siddique et. al.,4

observed that idiosyncrasy in hairless rats during the iontophoretic deliveryof insulin.

(iii) Characteristics of Penetrants:         

The rate of penetration of substances through the intact skin depends on thesize, charge, and configuration of molecules and relative solubility of thecompound in lipid, water, in the Horney layer and on the vehicle in which thecompound is presented to the skin39. The iontophoresis gives uncertaindrug delivery rate for an ionic solute of molecular weight 8000 to 12,00040.Fora negatively charged species, the size dependent flux enhancement neutralizesthe influence of electric field. Conversely, positive charged species becomesincreasingly important to effect the electric field as the size of permeantincreases. Pickal37 reported that the flux enhancement ration forcations and neutral species in negative pores increases as the size of Penetrantsincreases.

(iv)Concentration:

The concentration dependent iontophoretic delivery has not been fully investigated,some of the authors reported that as the concentration of drugs viz. hydromorphones41

and acetate ions36 increase in reservoir system then permeation ofdrug also increases. The iontopheric delivery of insulin does not effected bythe reservoir concentration at the current range of 0.2 – 0.8 MA42.O’malley and Oester43 showed the flux of solute was non-linearlyproportional to its concentration.

(v) Buffer Systems:

Buffer systems also affect the permeation of drugs by iontophoresis. It isimportant to optimize the concentration of buffer species in the system andshould be sufficiently high to maintain good buffer capacity but should notreach an extent such that the current is mostly carried by the buffer speciesinstead of drug special which may result the low efficiency of iontophoreticpermeation20.

(vi) Ionic Strength:   

The ionic strength of a drug delivery system is directly related to the iontophoreticpermeation of drugs. Some authors reported that increasingly the ionic strengthof the system decreases the permeation rate of drug20,44, and hasno significant effect on penetration up to the 0.5 V45.

(vii) Electrodes: 

The electrode materials used for iontophoretic delivery are to be harmlessto the body and sufficiently flexible to apply closely to the body surface.

The most common electrodes are aluminum foil, platinum and silver/silver chlorideelectrodes used for iontophoretic drug delivery. A better choice of electrodeis silver/silver chloride because it minimizes electrolysis of water duringdrug delivery.The positioning of electrodes in reservoir depends on the charge of the activedrug. The distribution of drug within the skin depends on the size and positionof electrodes. They are usually selected according to individuals needs. Largerelectrode areas introduce the greater amounts of drug but lesser current densityis tolerated to the skin in a non-linear manner. Metal electrodes touching tothe skin produce burns with much lower current in composition to padded electrodes.A loose contact between the padded electrode and skin also produce burn dueto uneven distribution of current. The safe current density varies with thesize of electrodes46,47.

(viii) Temperature:

The penetration of drug through skin is affected by dual effect of both humidityand temperature1. The iontophoretic delivery follows the Arheniousequation and enhances drug permeation with temperature48.

Electrical parameters

(I) Current:         

The extent of charged molecules, which may penetrate through the skin, aretheoretically proportional to the intensity of current and the duration of treatmentfor a transdermal iontophoretic delivery3,49. The relationship betweenthe drug delivery rate (D) and current (I) follows the given question:

D = It M/Zf

Where, t is the fraction of current carried by drug ions or transference number,M is the molecular weight of drug ion, Z is the molecular charge per drug ionand F is Faraday’s constant.Srinivasan et. al.20 suggested that increase in permeability ofdrug through skin may be more gradual than the increase in the current. Lelawogset. al.15 reported the permeability rate of arginine-vassopressinwas dependent not only upon the current density applied but also on the deliverymode of applied current.

(ii)Voltage:

The ionic flux due to an applied voltage drop across a membrane is based onthe fundamental thermodynamic properties of the system. The diffusion of drugduring iontophoresis follows Nerst-Plank equation. It states that the flux ofthe ionic drug due to applied electric filed is directly proportional to the

voltage drop and charge of the ion50. Masada et. al.,12

demonstrated ionic flux of Tetraethyl ammonium bromide (TEAB) with varying voltagedrop (0.125, 0.250, 0.250, 1.000). The enhancement factor for hairless mouseskin showed good agreement up to 0.5 volts and significantly higher at 1.0 voltdue to skin damage but it is up to 0.25 V.

(iii)Resistance:

The electrical resistance of the skin varies widely with iontophoretic drugdelivery. The resistance of the skin during iontophoretic application was muchlower on sweat pores, especially when they discharge sweat51. A slightfall in resistance occurs when electrode was interested in to the epidermis.

(iv) Frequency/Impedance:

The frequency of the applied current charges especially in man5,variability of frequency dependent impedance of human skin ranges from 10 KHzsto 100 Khzs. The impedance of the skin decreases at higher frequencies lesstime is available to accumulate the charge on the skin surface during an appliedpulse7.The iontophoretic delivery of insulin decreases with increasingthe frequency in the range of 50-2000 Hzs3 but Bagniefski and Burnettobserved decrease in sodium ion flux with increase in frequency (10 Khzs)52.The theoretical relationship between impedance of skin and frequency followsthis equation:

1/ZT = 1/ZR + 1/ZC

(v) On/Off Ratio3:

The on/off ratio of electricity effects the relative proportion of polarizationand depolarization of skin, which results the efficiency of transdermal iontophoreticdrug delivery. The number of on/off cycles in each second is shown as frequency.For example the on/off ration 1 : 1 at frequency 2000 Hzs (0.5 ms/cycle) provides0.25 ms depolarization period and same time for the polarization.Liu et. al.,3

suggested that the on /off ration of 1 : 1 at 2000 Hzs yields better glucosecontrol for iontophoretic insulin delivery than 4:1, 8:1 on/off ration. Apparently,1:4 and 8:1 rations, results a residue polarization the skin from the previouscycle which reduce the efficiency of insulin delivery.

(vi)Wave Form:

The waveform also affects the iontophoretic delivery of drug. The insulin deliverywas highest at sinusoidal waveform than square and triangular waveform3.

Operational parameters

(i)Duration of Application:

The transport of drug delivery depends on the duration of current applied53 in iontophoretic drug delivery. The iontophoretic penetration of drug linearly increased with increasing application time15. The skin permeation of arginine vasopressin54 achieves higher plateau rate and in case of insulin delivery, 2-3 fold reduced the blood glucose levels with increase in duration of iontophoretic application.

(ii)Mode of Current:

Direct current (DC) iontophoretic dosing of drug inevitably develops a skinpolarization potential, which reduce the efficiency of iontophoretic deliveryand cause skin irritation, burning and redness.But pulsed DC dosing patternis effective for drug transport, the same time average voltage because it faceslower skin resistance in comparison to simple DC application in flux enhancement.Lelawong et. al.15 reported that the skin permeation rate of argininevaspressine revealed no difference in the flux enhancement by simple DC andpulsed DC technique. But, blood glucose level was markedly reduced by pulsedDC in comparison to simple Dc in insulin3 delivery at the same currentdensity. It also maintained at much lower levels for a longer period of time.

Efficiency of drug delivery

The efficiency of iontophoretic drug delivery can be defined as that fractionof all ions which cross the skin are drug ions which cross the skin for eachmole of electrons flowing through the external circuit. This can be calculatedfrom the slope of the plot of drug delivery rate ® versus current (I), whichflows the given equation:

R = Ro + Fi. I

Where, Ro is the positive drug delivery using iontophoresis and Fi is the iontophoreticconstant defined as the amount of drug (on a weight basis) delivered per uni-timeper unit current.Synergistic manner of drug delivery

The penetration of drug through transdermal route can be achieved via theapplication of a combination of penetration enhancement technique.Several authors28,55

demonstrated the penetration of drugs (e.g. debutamine hydrochloride, azidothi-amidine)with the use of chemical enhancer (e.g. sod.  Lauryl sulfate, decylmethylsulfoxide) in combination of iontophoresis. The enhancement of drug throughskin is greater with a combination technique, when the single technique is used.Srinivasan et. al.56 explored the feasibility of synergism betweenthe ethanol  treated iontophoretic delivery of leuprolide and cholystokininanalogue. The penetration of tetracycline into tissue subject by the use ofboth Electro and phonophoresis were high than those obtained by the use of eitherElectro or phonophoresis57.

From Our Print Archives

Ease of Use Makes Iontophoresis Popular Modality

Ease of Use Makes

Iontophoresis Popular Modality

By Lisa Dress

Iontophoresis is a modern day alternative to the traditional delivery of medicine. This noninvasive modality uses electricity to "push" medications, such as steroids, into tissue.

According to the physical therapists who spoke withADVANCE, the result is a controlled, time efficient delivery of medication that has substantial benefits over other methods of drug delivery, such as injections.

Using this method wasn't always this simple, though. Iontophoresis has evolved from more primitive methods. Before the mass marketing of the units used for iontophoresis, which occurred around the mid- to late 1980s, PTs would stuff aluminum foil and cotton into bottle caps, put medicine on the cotton and run an electrode through a hole in the cap to try and produce the same effects seen today.

This hand-made modality captured the essence of the modern day iontophoresis, but was unsafe. Patients often were burned or developed skin reactions resulting from the treatment.

Today, due to technological advances and manufactured devices, iontophoresis is safer and much more comfortable for patients, resulting in greater acceptance and increased use, said Donna Pendleton, PT, CHT.

The battery or electrically powered device is the size of two packs of cigarettes together, and includes features such as electrodes, an on-off switch, a timer and wire leads. The device is unique because it uses a direct current as a vehicle to drive the medication. Most other modalities, such as TENS and high-volt, use an alternating current.

Iontophoresis relies on basic chemistry to deliver drugs through the skin for a very local, topical application. A direct current, which is always positive or negative, as opposed to an alternating current which changes its polarity, will propel similarly charged drug molecules away from the electrode and into the underlying tissue, Pendelton said. "The skin absorbs the medication because it is porous and acts as a sponge."

She added that there is some therapeutic benefit of the direct current. "It increases healing and blood flow, but the electrical current doesn't provide a significant benefit by itself."

Iontophoresis is used for conditions such as bursitis, carpal tunnel syndrome, gout, neuroma, sprains and strains. These conditions generally result in inflammation and pain. Pendleton added that it is also a good treatment option for synovial cysts and low back pain.

The most commonly used medications are cortisones and steroids, specifically dexamethasone. Although there is the potential to use a variety of medications in the treatment process, PTs generally opt to use only what is supported in

the documentation, Pendleton said.

There are many advantages to using iontophoresis in comparison to other well-known methods of drug delivery, such as injections, said Jim Smith, PT, clinic supervisor at NovaCare, a corporate physical therapy company, headquartered in King of Prussia, PA. Smith said because the elect-rical modality delivers medication through the skin pores, without breaking intact skin as with an injection, there is no risk of infection. He added that many people also have aversions to needles, making iontophoresis a preferred treatment option.

Pendleton concurred that the electrical modality is an efficient and effective treatment. A cortisone or steroid injection for inflammation is generally given by the physician in one large dose and can cause side effects, she said. "An injection of a steroidal medication, besides getting into the bloodstream, is over and beyond what is necessary to improve the local problem," she noted. "Usually between the first 24 to 48 hours after a bolus injection of a steroid, patients often report that they feel worse and have a post-injection burning. This doesn't happen with iontophoresis."

Smith said iontophoresis has a much more immediate effect in relieving pain and decreasing inflammation, while it is also an easily monitored treatment. "The good thing about iontophoresis is that the PT can start out applying small doses of medication and, over the course of treatment, re-evaluate the patient's condition as far as pain and inflammation."

Treatments generally take five to 20 minutes and are done every other day for one to two weeks to allow time for the accumulation of medication in the inflamed area and evaluation of the patient's progress.

Pendleton noted that working in this time frame is beneficial since it allows PTs ample opportunity to start treatments on other patients. Iontophoresis, like most other modalities, is done in conjunction with other rehabilitation activities.

"This is just one of the many tools PTs will use to get their patient better," he noted. "It's not a cure-all. PTs also perform other therapy techniques such as exercises, icing and massage, in conjunction with the treatment." Smith added that iontophoresis is widely recognized by managed care and third party payers.

Side effects such as a temporary reddening of the skin are minimal, he said, although some patients are electrically sensitive. "Most patients are tolerant of the treatment, although they may not like the feeling of the electrical current."

Code Description*97033 Application of modality one or more areas; Iontophoresis each 15 minutes*Note: It is recommended to verify patient’s policy guidelines to insurance coverage for this procedure.Some states will allow for 99070 (miscellaneous code for supplies) – Check policy in your state

GUIDELINES TO CPT® CODES

IontophoresisThe following documentation is recommended:• Diagnosis that describes the patients condition(s)• Documentation of how treatment is benefiting patient (improvedoutcomes, functional gains, reduced medication)• Other treatments that have been tried and failed• A prescription specifying iontophoresis and compound written by thetreating physician1 Current Procedural Terminology© 2005 American Medical Association. All Rights Reserved.2 Ingenix (2004), HCPCS Level II, 2005 Expert. Salt Lake City, St. Anthony Publishing/Medicode.3 The National Medicare allowable is determined by multiplying the physician fee schedule conversionfactor [for year 2005, $37.89750 by the total non-facility RVU. 69 Fed Reg (November 15, 2004)]

Iontophoresis is a method of active transdermal drug delivery and isdefined as the introduction of a chosen ion into the tissues by meansof an electrical current. It is either administered in clinic with DUPELB.L.U.E., or using Action Patch. Insurance coverage and reimbursementfor iontophoresis varies by state. Clinicians can increase the likelihood ofreimbursement by ensuring the patient’s medical record includes specificitems. Among these items is a description of the condition(s) that justifymedical necessity for iontophoresis.The Correct Coding Initiative (CCI) was developed by the Centers for Medicare & Medicaid Services(CMS) to prevent payments from being made due to inappropriate HCPCS (HealthcareCommonProcedure Coding System)code assignment.

www.empi.com and 1-800-328-2536802245A © Empi 7/05

GUIDELINES TO CPT® CODESFOR EMPI PRODUCTSEMPI has compiled this coding information for your convenience. Every reasonable efforthas been made to provide all commonly billed codes that may be applicable to proceduresinvolving the cleared uses of Empi’s products. It is ultimately the provider’s responsibility todetermine coverage, and submit appropriate codes, modifiers and charges for the servicesrendered. The clinician must use independent clinical judgment in choosing codes that mostaccurately describe the products and/or services provided. Empi makes no representation,guarantee or warranty, expressed or implied, that this compilation is error-free or that the use ofthis information will prevent differences of opinion or disputes with Medicare or other third-partypayers, and will bear no responsibility or liability for the results or consequences of its use.

The clinician should also be aware that codes can change over time and/or interpretationsof whether a code is properly used in a particular situation is often subject to medical policyinterpretation and judgment. There is no guarantee that a local carrier/payer will cover the codesor pay the reimbursement amounts stated in this document. Local carriers/payers frequentlychange their reimbursement policies and interpretations. Providers should contact the localcarriers/payers for their current interpretation of coverage and coding policies. The key in allcoding and billing to the federal government is to be truthful and not misleading and make fulldisclosures to the government in all attempts to seek reimbursement for a product and/or service.Documentation recommendations are only guidelines to help our customers to properlydocument for coverage of medically necessary treatments when using our products. Theclinician must use their own judgment when documenting treatment plans assessments.Empi’s customer service department will handle all insurance verification for you, and ourreimbursement department can answer any questions that may arise regarding coverage andcoding. Empi works with almost all insurance companies, covering approximately 110 millionlives.We hope the following information will assist you in getting the best outcomes andreimbursement when using the Empi product line.EmpiYour Partner In Rehabilitation and Pain Management1 Current Procedural Terminology© 2005 American Medical Association. All Rights Reserved.2 Ingenix (2004), HCPCS Level II, 2005 Expert. Salt Lake City, St. Anthony Publishing/Medicode.3 The National Medicare allowable is determined by multiplying the physician fee schedule conversion

factor [for year 2005, $37.89750 by the total non-facility RVU. 69 Fed Reg (November 15, 2004)]

Conclusion

From the literature cited and the personal experiences gained during developingiontophoretic system, this system seems to be a potential alternative deliverysystem for charged species. Iontophoretic drug delivery has developed a newapplication system for dermal and transdermal delivery of drugs that is electro-phoreticallyself-regulated device with electronic indicator58. The controlledor feed back iontophoretic drug delivery may include the use of polymeric systemresponsive to an oscillation magnetic field, temperature sensitive polymers59,60,polymers responsive to externally applied ultrasound and chemically sensitivepolymers. The iontophoretic delivery of macromolecules will open the doors tonon-invasive transdermal delivery of peptide-based pharmaceuticals, followingthe advances in recombinant DNA technology, which are the wonder drugs of tomorrow.

References

01. Kost, J., “Pulled and Self-Regulated Drug Delivery”. CRC Press, Boca Raton, FL, 1990.

02. Chien, Y.M., “Transdermal Controlled Systemic Medications”, Marcel Dekker Inc. Publication, 1987m Chapter 2.

03. Liu, J.C., Sun, Y., Siddique, O., Chien, Y.W., Shi, Wm., Li, J., Int. J. Pharm., 1988, 44, 197.

04. Siddiqui, O., Sun, Y., Liu, J.C., Chien, Y.W., J. Pharm. Sci., 1987, 76, 341.

05. Turnell, W.J., Proc. Royl Soc. Med., 1921, 14, 41-52.

06. Singh J, Maibach HI.,  Dermatology. 1993; 187(4): 235-8.

07. Leduc, S., Ann. D’electrobiol., 1900, 3, 545.

08. Leduc, S., “Electric Ions and their Uses in Medicine”, Rebman London, 1908.

09. Inchley, O.J., Pharmacol. Exp. Ther., 1921, 18, 241-256.