Penetration Enhancers in Transdermal Drug Delivery System Permeation enhancers are substances that reduce the skin barrier's ability to make skin more permeable and allow drug molecules to cross the skin at a faster rate advantages and disadvantages types of penetration enhancers techniques physical and chemical enhancers

1. Penetration Enhancers in
Transdermal Drug Delivery System
Presented by
Simran
M. Pharmacy 1st year
GGSCOP, YNR

2. TRANSDERMAL DRUG DELIVERY SYSTEM
Transdermal drug delivery has been accepted as a potential non-invasive route of drug
administration, with advantages of prolonged therapeutic action, decreased side effect, easy use
and better patient compliance.
Transdermal drug delivery system (TDDS) also known as “patches” are dosage form design to
deliver a therapeutically effective amount of drug across a patient skin.
Transdermal delivery not only provides controlled, constant administration of the drug, but also
allows continuous input of drugs with short biological half-lives and eliminates pulsed entry into
systemic circulation, which often causes undesirable side effects.

3. The principal barrier to most transdermal drug delivery is the stratum corneum, the outermost
layer of the skin comprising keratin-rich cells embedded in multiple lipid bilayers. Many
strategies have been suggested in order to overcome the low permeability of drugs through the
skin.
A popular approach is the use of penetration enhancers, which enhance the permeability of the
stratum corneum.
These agents partition into, and interact with, the stratum corneum constituents to induce
reversible increase in skin permeability.
Permeation enhancers are the substances that reduce the skin barrier ability make skin more
permeable and allow drug molecules to cross the skin at a faster rate.

4. PENETRATION ENHANCERS
Permeation enhancers are defined as substances that are capable of promoting penetration of
drugs into skin and transdermal therapeutic systems offers a more reliable mean of administering
drug through the skin.
Ideal properties of penetration enhancers
1. They should have no pharmacological activity within the body. i.e. should not bind to receptor
sites.
2. It should be nontoxic, non-irritating, and non-allergenic.
3. Onset of action should be rapid, and duration of activity should be predictable and suitable for
the drug used.
4. Upon removal of the enhancer, the horny layer should be immediately and fully recover its
normal barrier property.

5. 5. When removed from the skin, barrier properties should return both rapidly and fully.
6. The accelerant should be chemically and physically compatible with all drugs and adjuvants to
be formulated in topical preparations and devices.
7. If liquid and to be used at high volume fractions, it should be suitable solvent for drugs.
8. It should spread well on the skin, with a suitable skin “feel”.
9. It should readily formulate into dermatological preparations, transdermal devices, and skin
adhesives.

6. ADVANTAGES
1. Penetration rate of drug sufficiently high for therapeutic efficiency by using penetration
enhancers.
2. It is useful for unabsorbable drugs to facilitate their absorption through skin.
3. It can improve transdermal absorption of topical preparation.
4. It is penetration rate determining factor in transdermal drug delivery system.
5. The terpenes like limonene in propylene glycol solution are effective penetration enhancer for
cytotoxic drugs.
6. It also acts as rate limiting factor.

7. DISADVANTAGES
1. The effective concentration varies from drug to drug.
2. The uses of different penetration enhancer with various concentrations are restricted
completely.
3. Physicochemical properties of enhancers are also affecting the side effects in the body.

8. BASIC PRINCIPLE OF TRANSDERMAL PERMEATION
Transdermal permeation is based on passive diffusion. Skin is the most intensive and readily
accessible organ of the body as only a fraction of millimeter of tissue separates its surface from
the underlying capillary network. The release of a therapeutic agent from a formulation
applied to the skin surface and its transport to the systemic circulation is a multistep process,
which includes:
1) Diffusion of drug from drug to the rate controlling membrane.
2) Dissolution within and release from the formulation.
3) Sorption by stratum corneum and penetration through viable epidermis.
4) Uptake of drug by capillary network in the dermal papillary layer.
5) Effect on the target organ.
6) Partitioning into the skin’s outermost layer, the stratum corneum.
7) Diffusion through the stratum corneum, principal via a lipidic intercellular pathway.

9. CLASSIFICATION OF PENETRATION ENHANCERS
AND TECHNIQUES
Types/Techniques
of penetration
enhancers
Mechanism of action Examples
1. Chemical
enhancers
They act by three
mechanisms
1. By disruption of the
highly ordered structure
of stratum corneum lipid.
2. By interaction with
intercellular protein.
3. By improved partition of
the drug or solvent into
stratum corneum.
1. Sulphoxides -dimethyl
sulphoxide(DMSO),dimethyl
formamide(DMF)
2. Azones
3. Pyrrolidones
4. Fattyacids–Lauric acid, Myristic acid
5. oxizolidinones
6. Amine and Amides –Urea
7. Surface active agents–sodium lauryl
sulphate, Benzalkonium chloride 8.
cyclodextrins

10. Types/Techniques of
penetration enhancers
Mechanism of action Examples
2. Drug Vehicle Based Interaction of enhancers with stratum
corneum and development of SAR for
enhances with optimal characteristics
and minimal toxicity.
Ion pairs and complex Coacervates chemical
potential adjustment
3. Natural Penetration
enhancers
Mechanism for Terpenes It may
increase one or more of following
effects: 1. Partition coefficient
2. Diffusion coefficient
3. Lipid Extraction
4. Drug Solubility
5. Macroscopic Barrier Perturbation
1. Terpenes-Menthol, Linalool, Limonene,
Carvacrol.
2. Essential oil-Basil oil, Neem oil,
Eucalyptus,
4. Physical Enhancers These are variable techniques
available for increasing the
penetration by physical separation
and magnetic and ultrasonic.
1. Iontophoresis
2. Sonophoresis
3. Phonophoresis
4. Magnetophoresis
5. Electroporation
6. Thermophoresis
7. Radiofrequency

11. CHEMICAL PENETRATION ENHANCERS
Water - a) Free water with in the tissue can alter the permeant solubility in the stratum corneum
thereby modifying partitioning from the permeant vehicle into the membrane.
b) Hydration causes an increased permeability by aqueous solvation of the intercellular lipids, in
particular the glycosphingolipids and ceramides.
c) Increased hydration causes an increase in water binding to keratin in the cells thereby swelling
the corneocytes.
Sulphoxides and similar chemicals - Dimethyl sulfoxide (DMSO) is an effective penetration
enhancer that promotes permeation by reducing skin resistance to drug molecules or by
promotion of drug partitioning from the dosage form. In addition, DMSO may alter the physical
structure of the skin by elution of lipid, lipoprotein and nucleoprotein structures of the stratum
corneum.

12. Azones - Azone enhances the skin transport of a wide variety of drugs including steroids,
antibiotics and antiviral agents. Azone partitions into a bilayer lipid to disrupt their packing
arrangement but integration into the lipid is unlikely to be homogeneous. Azone molecules may
exist dispersed within the barrier lipoid or separate domains within the bilayer.
Pyrrolidones - Pyrrolidones are able to promote both the penetration of hydrophilic drugs (eg
mannitol) and 5- fluorouracil) and the penetration of lipophilic drug substances (eg progesterone).
N-Methyl-2- pyrrolidone (NMP) and 2-pyrrolidone (2P) as well as 2-pyrrolidone-5-carboxylic
acid are the most widely used enhancers of this group.
Fatty Acids - A large number of fatty acids and their esters have been used as permeation
enhancers. Fatty acids, alcohols, sulphoxides, surfactants, and amides are enhancers for
Naloxone.

13. Urea - Urea promotes transdermal permeation by facilitating hydration of the stratum corneum
and by the formation of hydrophilic diffusion channels within the barrier. Cyclic urea permeation
enhancers are biodegradable and non-toxic molecules consisting of a polar parent moiety and a
long chain alkyl ester group. As a result, enhancement mechanism may be a consequence of both
hydrophilic activity and lipid disruption mechanism.
Oxazolidinones - Oxazolidinones are a new class of chemical agents which have the potential for
use in many cosmetic and personal care product formulations. This is due to their ability to
localize co-administered drug in skin layers, resulting in low systemic permeation.
Oxazolidinones such as 4-decyloxazolidin-2-one has been reported to localize the delivery of
many active ingredients such as retinoic acid and diclofenac sodium in skin layers.
Cyclodextrins - These compound can form inclusion complexes with lipophilic drugs with a
resultant increase in their solubility, particularly in aqueous solutions.

14. Essential oils, Terpenes, and Terpenoids - They have been used as medicines, flavoring, and
fragrance agents. The essential oils of eucalyptus, Chenopodium, Ylang have been found to be
effective enhancers for 5-fluorouracil. Modifying the solvent nature of stratum corneum improves
drug partitioning.
L-methanol has been used to facilitate in vitro permeation of HCL.
Surfactants – Usually surfactants are added to formulations in order to solubilize lipophilic
active ingredients. They have the potential to solubilize lipids within the stratum corneum.
Anionic Surfactants – include cetry trimethyl ammonium bromide
Non-ionic Surfactants and Zwitterionic surfactants include dodecyl betaine

15. PHYSICAL PENETRATION ENHANCERS
Physical Enhancers Definition Characteristics
Sonophoresis Sonophoresis is the application
of ultrasonic energy that
temporarily improves skin
permeability.
Sonophoresis functions at
frequencies of 20 kHz-16
MHz and intensities up to 14
W/cm2 (spatial average pulse
average intensity, ISAPA) to
enhance skin permeability.
Iontophoresis Iontophoresis is the use of
slight electric current in order
to improve the transport of
drugs, which consists of an
anode and a cathode deposited
on a surface (e.g. skin).
Iontophoresis uses an electric
current of ~ 0.5 A/cm). A drug
can pass through the surface
by electromigration,
electroosmosis or passive
diffusion.

16. Physical Enhancers Definition Characteristics
Electroporation The electroporation technique consists of the
application of a high electrical field pulses
with the purpose to create nanosized pores in
a cell membrane and thus, increase the
passage of ions and macromolecules through
the skin.
Electroporation can be
reversible and irreversible.
Microneedles Microneedles are used to open holes into the
skin to create a pathway for the following
delivery of drugs.
Generally, microneedles
have a length of 100-500
µm.
Radiofrequency Radiofrequency ablation (RF) is a simple,
safe, and effective therapy for chronic
radiation proctopathy.
The frequency is between
10 kHz and 900 MHz.