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1. Introduction

2. Sonophoresis: a historical perspective

3. Generation of ultrasound

4. Biological effect of ultrasound

5. Mechanism of sonophoresis

6. Synergetic effect with other enhancers

7. Safety

8. Future trends

9. Applications of sonophoresis

10. Advantages

11. Limitations

12. Drugs used by sonophoretic drug delivery

13. Conclusion

14. References



2. Sonophoresis: a historical
 Sonophoresis was shown to enhance transdermal

drug transport about 40 years ago by Fellinger and
Schmidt who showed that application of ultrasound
increases transport of hydrocortisone across the skin.

 ultrasound was also reported for local anesthetics.

 Hofman and Moll who studied the percutaneous
absorption of benzyl nicotinate.

 Bommannan et al. hypothesized that since the
absorption coefficient of the skin varies directly with
the ultrasound frequency



1. Introduction

 Definition: sonophoresis is the enhancement of
migration of drug molecules through the skin by
ultrasonic energy

 Sonophoresis occurs because ultrasound waves
stimulate micro-vibrations within the skin epidermis
and increase the overall kinetic energy of molecules

 When sound is emitted at a particular frequency, the
sound waves disrupt the lipid bilayers

 The higher the frequency, the more dispersed the



The skin

 Protective layer with large no. of dead cells, hence
acts as barrier to penetration.

 Penetration varies with humidity, pigmentation, age,
chemical status

 Of all layers Stratum Corneum (SC) offers
maximum resistance. SC consists of keratinocytes
and lipid bilayer

 Permeability can be increased by Chemicals,
Electrical Fields or Ultrasound which disrupt lipid
bilayer of SC and increase permeability.




Figure 1: Ultrasonic generation system

Pulse generator Amplifier

Gate H. F. Generator
(20 KHz – 20MHz)


Ultrasound gel
+ Drug Skin + Transducer interface

Stratum cornium





3. Generation of ultrasound

 Ultrasound is a sound wave possessing frequencies above 20 kHz .

 The waves used for sonophoresis which reduce the resistance
offered by SC lie in the frequency range of 20 KHz to 20 MHz

 Voltage generator produces a voltage which is applied to the
crystal of the transducer generating energy between 1 to10watts.

 Ultrasound is generated with the help of a device called sonicator
which is a AC electric signal generator. It produces a AC electric
signal which is applied across a piezoelectric crystal i.e.
transducer. (The active element the transducer – it converts the electrical
energy to acoustic energy, and vice versa.)

 Transducer made up of quartz, rochelle salt, lithium sulphate,
ammonium dihydrogen phosphate




 Ultrasound is applied by bringing the transducer in
contact with the skin.

 For sonophoretic delivery, the desired drug is
dissolved in a solvent and applied to the skin.

 The coupling medium can be the same as the
solvent used to dissolve the drug or it can be a
commercial ultrasound coupling e.g. gel.

 It Helps to match impedence of tissue with the
impedence of the transducer, so that the Ultrasound
gets properly into the tissue.




Selection of ultrasound parameters

(1) Ultrasound frequency
a) Therapeutic Frequency Ultrasound (1-3 MHz)

b) Low Frequency Ultrasound (Below 1MHz)

c) High Frequency Ultrasound (Above 3MHz)

(2) Ultrasound intensity

Various ultrasound intensities in the range of 0.1 to 2 W/cm2

(3) Pulse length
 Ultrasound can be applied in a continuous or pulse mode.

The pulse mode is frequently used because it reduces
severity of side effects such as thermal effects.

 It was also found that permeability of membrane increased
from 6 to 56% as pulse length increased from 100 to 400 ms.



4. Biological effect of ultrasound

 Significant attention has thus been given to
investigating the effects of ultrasound on biological

 Ultrasound affects biological tissues via three main

(1) Thermal effect may important when,

 The tissue has a high protein content

 A high intensity of continuous wave ultrasound is used

 Vascularization is poor





(2) Cavitation effect

Bubble formation takes place. These bubbles grow and collapse and
results in cavitation.

may important when,
 Low-frequency ultrasound is used

 Small gas filled space are exposed

 The tissue temperature is higher than normal

(3) Acoustic streaming – unidirectional fluid movement at velocity
gradient in US field. It increases heat transfer and acceleration of
fluid transport.

may important when,
 The medium has an acoustic impedance different from its surrounding

 The fluids in the biological medium is free to move

 Continuous wave application is uwsewdw.


5. Mechanism of sonophoresis

(1) Cavitation
 Cavitation occurs due to the nucleation of small gaseous

cavities during the negative pressure cycles of ultrasound

 This cavitation leads to the disordering of the lipid
bilayers and formation of aqueous channels in the skin
through which drugs can permeate



 The minimum ultrasound intensity required for the onset

of cavitation, referred to as cavitation threshold

a) Cavitation inside skin
 cavitation bubbles near the keratinocytes–lipid bilayers

interfaces may, in turn cause oscillations in the lipid
bilayers, thereby causing structural disorder of the SC

b) Cavitation out side skin
 cavitation bubbles can potentially play a role in the

observed transdermal transport enhancement. these
bubbles cause skin erosion, due to generation of shock
waves, thereby enhancing transdermal transport




(2) Convective transport
 Fluid velocities generated in this way may affect

transdermal transport by inducing convective
transport of the permeant across the skin.

 especially through hair follicles and sweat ducts




(3) Mechanical stress
 Ultrasound is a longitudinal pressure wave inducing

pressure variations in the skin, which, in turn, induce
density variation

 Due to density variations, such as generation of
cyclic stresses because of density changes that
ultimately lead to fatigue of the medium

 Lipid bilayers, being self-assembled structures, can
easily be disordered by these stresses, which result
in an increase in the bilayers permeability




6. Synergistic effect with other enhancer

(1) Chemical enhancer
 Enhanced Partitioning

 Lipid Bilayer Disordering

 Keratin Denaturation
e.g. Application of SLS alone for 90 min induced about 3-

fold increase in mannitol permeability, while application
of ultrasound alone for 90 min induced about 8-fold
enhancement. However, when combined, application of
ultrasound from 1% SLS solution induced about 200-fold
increase in skin permeability to mannitol





(2) Iontophoresis
 Electrophoresis

 Lipid Bilayer Disordering

 Electroosmosis
e.g. The enhancement of heparin flux due to ultrasound +

iontophoresis treatment was about 56-fold. This
enhancement was higher than the sum of those obtained
during ultrasound alone (3-fold) and iontophoresis alone

Thus, the effect of ultrasound and iontophoresis on
transdermal heparin transport was truly synergistic.



7. Applications

1) Sonophoresis is used in the treatment of damaged

2) Hormone Delivery.

3) In surgery it helps in dissection and treatment of
biological tissue.

4) Low-Frequency Ultrasonic Gene Delivery.

5) Sonophoresis is also very useful in drug
enhancement in tumors. Most cancer therapy drugs
act intracellularly.

6) Ultrasound is used for Calcific Tendinitis of the

8) Ultrasound Helps in Treating Tennis Elbow.


8. Advantages
1) Avoids problems associated with gastrointestinal absorption due

to pH, enzymatic activity, drug-food interactions etc.

2) Substitute oral administration when the route is unsuitable as in
case of vomiting, diarrhea.

3) Avoids hepatic “first pass” effect.

4) Avoids the risks and inconveniences of parenteral therapy.

5) Reduces daily dosing, thus, improving patient compliance.

6) Extends the activity of drugs having short plasma half-life
through the reservoir of drug present in the therapeutic delivery
system and its controlled release characteristics.

7) Rapid termination of drug effect by removal of drug application
from the surface of the skin.




8) Elimination of the hazards and difficulties of I.V. infusions or

I.M. injections.

9) Enhance therapeutic efficacy, reduced side effects due to
optimization of the blood concentration-time profile and
elimination of pulse entry of drugs into the systemic

10) Provide predictable activity over extended duration of time and
ability to approximate zero-order kinetics.

11) Improved control of the concentrations of drug with small
therapeutic indices.

12) Minimize inter and intrapatient variation.

13) Suitability for self-administration.




9. Limitations
1) Only limited number of drugs can be absorbed in therapeutic


2) Many systemically effective therapeutic drugs produce skin

3) The drug must have some desirable physicochemical properties
for penetration through stratum corneum.

4) If the drug dosage required for therapeutic value is more than
10mg/day, the transdermal delivery will be very difficult.

5) The barrier function of the skin changes from one site to another
on the same person, from person to person and with age



10. Drug used by sonophoresis

(1) Sonophoresis with Corticosteroid
 Majority of studies on sonophoresis, ultrasound was used

to enhanced the delivery of steroidal anti-inflammatory
drugs (e.g. hydrocortisone).

(a) Fellinger & Schmid (1954) showed that ultrasound could
carry hydrocortisone across a vascular membrane for the
effective treatment of polyarthritis

(b) Newman et al. (1992) suggested that hydrocortisone
sonophoresis is useful in the treatment of numerous
musculo-skeletal injuries.





(2) Sonophoresis with Salicylates
 In combination with ultrasound it is thought that

Salicylate could be moved into deeper, subdermal tissues
to help to reduce pain.

(a) Ciccone et al. (1991) reported on a study to evaluate
ultrasound as an enhancer of topically applied Salicylates






(3) Sonophoresis with Anesthetics
 The effectiveness of sonophoresis has been explored

extensively for delivery of local anesthetics.

(a) McElnay (1985) and associates described a sonophoresis
study using lignocain

(b) Moll (1979) studied the enhanced effects of topically
applied Lidocaine (140.7 mg) and Decadron (3.75 mg).
She obtained that 88% of the patients receiving
sonophoresis with Decadron and Lidocaine obtained
relief from their trigger point pain.





(4) Sonophoresis with other Drugs
(a) Benson and colleagues (1987, 1989) studied ultrasound

as an enhancer of benzydamine hydrochloride (3%) a
nonsteroidal anti-inflammatory drug.

(b) Levy et al. (1989) studied the sonophoresis of D-
mannitol, a diuretic.

(c) Romanenko (1992) used ultrasound with topically
applied Amphotericin B.




Sonophoresis vs. iontophoresis

 Both techniques deliver chemical to
biological tissues.



Sr Sonophoresis Iontophoresis


1 Sonophoresis is the enhancement Iontophoresis is movement of ions

of migration of drug molecules of soluble salts across a membrane

through the skin by ultrasonic under an externally applied

energy potential difference

2 Sonophoresis uses acoustic energy Iontophoresis uses electiral current to

(ultrasound) to drive molecules transport ions into tissues

into tissues

3 Proper choice of ultrasound Proper choice of electricity

parameters including ultrasound parameters including Current density,

energy dose, frequency, intensity, Current profile, Duration of

pulse length, and distance of treatment, Electrode material,

transducer from the skin is critical Polarity of electrodes, is critical for

for efficient sonophoresis. efficient Iontophoresis

4 Sonophoresis usually employs a Iontophoresis usually employs a

ultrasound between 20 KHz to 20 direct current between 0.5 mA to 5.0

MHz mA



5 In sonophoresis drugs mixing In Iontophoresis drug is mix with

with a coupling agent like gel, solvent

cream, ointment

6 The main mechanism for The main mechanism for transport of

transport of drug is “Cavitation” drug is “Electroporation”

7 Drug should be in aqueous or Drug must be in aqueous and must be

non aqueous and ionized or non in ionized form

ionized form

8 Enhanced partitioning, Lipid Electrophoresis, Lipid bilayer

bilayer disordering, Keratin disordering, Electroosmosis etc. gives

denaturation etc. gives the the synergetic effect of Iontophoresis

synergetic effect of sonophoresis

9 Ultrasound can be applied in a Electrical current can be applied only in

continuous or pulse mode continuous mode

10 Sonophoresis mostly used for Iontophoresis mostly used for

delivery of corticosteroids, local hyperhydrosis diagnosis of cystic

anesthetics and salicylates fibrosis, metallic and non-metallic ions



13. Conclusion
 Proper choice of ultrasound parameters including

ultrasound energy dose, frequency, intensity, pulse
length, and distance of transducer from the skin is
critical for efficient sonophoresis.

 Various studies have indicated that application of
ultrasound under conditions used for sonophoresis
does not cause any permanent damage to the skin

 Ultrasound also works synergistically with several
other enhancers including chemicals and




14. References

 N.K.Jain, Sonophoresis: Biophysical of Transdermal
Drug Delivery, Controlled and Novel Drug Delivery,
1st edition, 1997, page. 208-235

 James Swarbrick, Transdermal Delivery:
Sonophoresis, Encyclopedia of pharmaceutical
technology, 3rd edition, Volume-6, 2007, page no.

 Mr. Ashish Pahade, Dr. Mrs. V.M.Jadhav, Dr. Mr.
V.J.Kadam, Sonophoresis: an overview,
International Journal of Pharmaceutical Science,
2010, Volume 3, Issue 2, page. 24-32