The introduction of substances into the body by the ultrasound energy is called phonophoresis. This non-invasive procedure has been improperly compared with iontophoresis. Iontophoresis involves the transfer of ions into tissues, whereas phonophoresis transmit molecules- a different process, although a similar concept.


Molecules introduced into the tissues must be broken into components elements and radicals by natural chemical processes and recombined with existing blood stream radicals. There seems to be no clinical evidence of molecule transfer to depths greater than 1 to 2 mm. However, many experienced authorities suggest the penetration of molecules to depth of 5 cm or 4 to 6 cm and even many authorities (James Cyriax) suggest a penetration of 6 to 8 cm.

Controversies exist in literature about the effective depth of penetration of molecules by the phonophoresis.


Phonophoresis is the deriving of selected medications into biological tissues by the use of ultrasound. These medications usually in the form of topical creams or gels are liberally applied to skin over the target tissue. A coupling agent is used in addition o the medications. Continuous ultrasound over a period of 10 min effectively drives physiological useful amount of medications to a depth of 5 cm. Often the two modalities i.e. phonophoresis and iontophoresis are improperly equated. Iontophoresis is the introduction of ions into the body whereas phonophoresis is the molecular transmission across the skin. The question of availability for recombination to useful compounds becomes evident when the two levels of physical state are involved. Ultrasound is often more rapid in effect, whereas iontophoresis requires more time to produce results. These more rapid effects are attributable to the enhanced absorption across the membranes that the ultrasound causes; however, it causes that absorption at the molecular level, necessitating break down and recombination for lasting effects.


The technique for phonophoresis is same as that for standard ultrasound administration. The ointment is massaged into the target area prior to ultrasound. Solutions are not used for phonophoresis, nor are this procedure suited to sub aqueous ultrasound. The dissipation of substances into solution minimizes molecular transfer, as does the reduction of the sound energy when it enters the water. Transmission gel is used in addition to other ointments, since many of the ointments are too viscous for smooth sound head movements.


The selection of molecular substances depends upon the requirements of the condition- not the disease by name, but the physiological need of the patient.

The different chemical substances available for phonophoresis are as under depending upon the availability in different countries:


Hydrocortisone is available over the counter as 1 percent ointment. As an excellent anti inflammatory agent, hydrocortisone also provides analgesia in many instances.


Mecholyl can be obtained as an ointment with 0.025 percent methacholine and 10 percent salicylate in a suitable base for either iontophoresis or phonophoresis. Mecholyl is an effective vasodilator and is recommended in vascular conditions, neurovascular deficits, and as a mild analgesic.


Lidocaine is available as a 5 percent ointment (Xylocaine). Lidocaine is used primary as an analgesic/anesthetic in acute conditions or when decreased sensitivity is required.


Available as an ointment form, iodine is combined with methyl salicylate (iodex). Iodex contain 4.8 percent methyl salicylate, with 4.7 percent iodine in petroleum base. Iodine is used as a vasodilator agent, an anti inflammatory agent, and as a sclerolytic agent in cases involving scar tissue, adhesions, calcific deposits and adhesive joints.


Salicylate is available as a 10 percent ointment (Myoflex), over the counter. It is a basic anti inflammatory agent, used as a decongestant.


Zinc is available over the counter as a 20 percent zinc oxide ointment. Zinc is a trace element noted for contributing to the healing process. Zinc is indicated in treatment of open wounds and lesions.


It contains histamine phosphate 0.1 percent, methyl nicotinate 1 percent, glycol salicylate 5 percent; in vanishing cream base contained capsaicin.

It is analgesic/counter irritant/rubefacient. It is indicated in fibrositis, lumbago, sprains, strains, stiffness, bronchitis, bruises, sciatica, neuralgia, neuritis.


It is a non steroidal anti inflammatory drug available in emulgel or gel form. Per 100gm: Diclofenac diethyl ammonium salt 1.16 gm (equiv. diclofenac sodium 1 gm).

It is used in rheumatic and muscular pain, post traumatic pain, post operative inflammation and swelling, acute musculoskeletal disorders including bursitis, myositis, tendonitis, ligament injuries, sports injuries, sprains, strains, low back pain.


It is an NSAID available in gel form as imidazole salicylate. It is used in rheumatoid arthritis, ankylosing spondylitis, osteoarthritis, rheumatic disorders, pain and inflammation.


It is an NSAID of propionic acid category. Cream or gel contain per 100 gm: Ibuprofen 10 gm.

It is used in rheumatic and muscular pain, sprains and strains.


It is an NSAID with the name Benzydamine HCL. The gel contains 5 percent Benzydamine HCL.

It is used in treatment of musculoskeletal pain.


It is an analgesic and counter irritant.


It is an NSAID of propionic acid category. The gel contains 2.5 percent ketoprofen.

It is used in rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, and acute articular and periarticular disorders.


The cream or gel being related to NSAID category contains adrenal cortical extract 1 percent, mucopolysaccharide polysulphate 0.2 percent, salicylic acid 2 percent.

It is indicated in musculoskeletal pain and inflammation, sprains, strains, frozen shoulder.


It is an NSAID of oxicam category. The gel contains piroxicam 0.5 percent.

It is indicated in osteoarthritis of superficial joints, acute musculoskeletal injuries, periarthritis and tendonitis.


Diethyl amine salicylate is rubefacient. The gel contains diethyl amine salicylate 10 percent w/w.

It is indicated in pain associated with lumbago, neuralgia, cervical spondylosis, fibrositis.


Naproxen is a NSAID of propionic acid category. The gel contains Naproxen betaine sodium 10 percent.

It is indicated in rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, musculoskeletal disorders, including sprains, strains, and lumbosacral pain.


Flurbiprofen is a NSAID of propionic acid category. It is available in gel form and is used in rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, musculoskeletal pain syndromes, sprains, strains, sports injuries, etc.


It is available in gel preparation and is most effective in painful musculoskeletal disorders and arthritis especially in osteoarthritis.


Skin and systemic reactions with phonophoresis are rare. These are as under:

1. Those patients who cannot eat sea food should not be treated with iodine. Should skin irritation and itching be reported, the usual antidote is antihistamine.
2. Those patients sensitive to metals should not be treated with zinc. These patients usually cannot wear metallic watch bands, jewelry, etc., without having skin and, at times, systemic reactions. Dermatological consultation should be sought for specific antidotes for the offending metals. Non metallic substances should be substituted.
3. If the patient has a reaction to mecholyl with vasomotor shifting, administer a simple stimulant. Vertigo from orthostatic adjustment is usually momentary.
4. Reactions to hydrocortisone are not as common as you think that the patient has.
5. There has been no untoward reaction to lidocaine.
6. Do not treat the patients who are sensitive to aspirin with salicylates.