A REVIEW ARTICLE ON TRANSDERMAL DRUG DELIVERY SYSTEM

About Author:
Mohit Dangwal
DIT Faculty of Pharmacy
Dehradun, Uttarakhand
dangwal_mohit@yahoo.in

Abstract
Transdermal drug delivery system (TDDS) is topically administered dosage form in the form of patches which deliver drugs for systemic effects at a predetermined and controlled rate. This review focuses towards the basic facts about the transdermal drug delivery system including the methods of their preparation and some of the recent advancements that have in achieved in this field.

REFERENCE ID: PHARMATUTOR-ART-2015

INTRODUCTION
Transdermal drug delivery system (TDDS) is the dosage forms which deliver a therapeutically effective amount of drug across a patient’s skin [1].  Transdermal drug delivery offers controlled release of the drug into the patient, it enables a steady blood-level profile resulting in reduced systemic side effects and sometimes, painless and offer multi-day dosing. Since the first transdermal patch was approved in 1981 to prevent the nausea and vomiting associated with motion sickness, the FDA has approved, throughout the past 22 years, more than 35 transdermal patch products, spanning 13 molecules[2].

Advantages [3]

  • This approach to drug delivery offers many advantages over traditional methods
  • Transdermal drug delivery enables the avoidance of gastrointestinal absorption, with its associated pitfalls of enzymatic and pH associated deactivation
  • This method also allows for reduced pharmacological dosaging due to the shortened metabolization pathway of the transdermal route versus the gastrointestinal pathway.
  • The simplified medication regimen leads to improved patient compliance and reduced inter & intra – patient variability.
  • Self administration is possible with these systems.
  • The drug input can be terminated at any point of time by removing transdermal patch.

Disadvantages [4]

  • The drug that requires high blood levels cannot be administered and may even cause irritation or sensitization of the skin
  • Only relatively potent drugs are suitable candidates for TDDS because of the natural limits of drug entry imposed by the skin’s impermeability.
  • High cost of the product is also a major drawback for the wide acceptance of this product
  • Contact dermatitis is another drawback reported in TDDS
  • Barrier function of skin varies from site to site during application in same person

HUMAN SKIN[5]


Fig: SKIN COMPONENTS AND FUNCTIONS PERFORMED ROUTES FOR DRUG PENETRATION THROUGH SKIN –

There are macro and micro routes for drug penetration through the skin

1. Macro route -


FIGURE : DRUG PERMEATION THROUGH THE SKIN

2.Microroute –


FIGURE : MECHANISAM OF SKIN PERMEATION

Components of TDDS

  • Polymer matrix / Drug reservoir
  • Drug
  • Permeation enhancers
  • Pressure sensitive adhesive (PSA)
  • Backing laminates
  • Release liner
  • Other excipients

1:Polymer matrix / Drug reservoir:[6]
These control the release rate of the drug from the device and are hence considered as the backbone of the system.These are generally prepared by dispersing the drug in liquid or solid state synthetic polymeric base.

Possible useful polymers for transdermal devices are: [7,8,9,10,11]

(a).Natural Polymers: e.g., cellulose derivatives, Zein, Gelatin, Shellac, Waxes, Proteins, Gums and their derivatives, Natural rubber, Starch etc.

(b).Synthetic Elastomers: e.g. polybutadiene, hydrin rubber, polyisobutylene, silicon rubber, nitrile, acrylonitrile, neoprene, butylrubber etc.

(c).Synthetic Polymers: e.g. polyvinyl alcohol, polyvinylchloride, polyethylene, polypropylene, polyacrylate, polyamide, polyurea, polyvinylpyrrolidone, polymethylmethacrylate etc.

2:Drug:[12,13]

Ideal Properties of a Transdermal Drug Delivery System are as follows

S.no

Properties

Comments

1


Shelf life

Up to 2 yrs

2


Particle size

<40cm2

3


Dosing frequency

Once in a day or once in week

4


Aesthetic appeal

Clear or white colour

5


Packaging

Easy removal of release liner & min. no. of steps required to apply

6


Skin irritation

Easy removal of release liner & min. no. of steps required to apply

7


Release

Consistent pharmacokinetic & pharmacodynamic profile over time.

Permeation enhancers[14,15,16,17]
The chemical compounds that increase permeability of stratum corneum so as to attain higher therapeutic levels of the drug candidate are called permeation enhancers. These interact with structural components of stratum corneum i.e.,proteins or lipids and alter the protein and lipid packaging of stratum corneum and modifying chemically the barrier functions which increases permeability

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