Physiological effects of electrotherapy for iontophoresis

Question 1

Iontophoresis History

Answer 1

• 1747 Pivati, 1833 Fabre-Palaprat
• *Used electromotive force to move ions through skin
• Early 1900s LeDuc
• *Neg charge potassium cyanide solution (lethal dose) under cathode (-) and pos charge strychnine sulfate solution (convulsive drug) under anode (+) on side of rabbit head (touching each other)
• *Constant DC current – produced tetanic convulsions in one and death in other rabbit
• To test effect, Le Duc reversed electrodes and -physiologic effects did not happen.
• Current polarity directed effect.
• Ionized medication must be placed under electrode of same charge

Question 2

Mechanism of topical drug delivery without iontophoreis

Answer 2

Passive diffusion

• stratum corneum: outermost layer of skin
• limits drug diffusion rate
• medicinal molecules permeate the dermis and are absorbed into the blood stream via the capillaries

Question 3

Iontophoresis description

Answer 3

• the introduction of medicinal ions into the body tissues by means of a low voltage direct electromotive force (DC current)
• occurs due to direct electrostatic repulsion of an ion by a similarly charged electrode (electrophysical effect)
• occurs due to increasing the permeability of the stratum corneum
• • electroporation
• • electroosmosis

Question 4

Electroporation

Answer 4

temporary production of water soluble pores in the skin

Question 5

electroosmosis

Answer 5

as water is carried through the skin it can carry other objects dissolved in it along with it

Question 6

Direct current (DC)

Answer 6

Produces a build up of ions under the electrodes producing chemical reactions and altering skin pH

• negative electrode= alkaline reaction
• positive electrode= acidic reaction
• to minimize these rxns, decrease current density, and electrodes are buffered to keep pH in specific region

Question 7

Negative electrode (cathode)

Answer 7

Sodium hydroxide (+ions) - alkaline reaction

Question 8

Positive electrode (anode)

Answer 8

Hydrochloric acid (-ions)- acidic reaction

Question 9

Iontophoresis dosage

Answer 9

• measured in mA. minutes
• • amplitude x duration
• depends upons specific electrode being used
• effective drug delivery with range of 40-80 mA minutes
• currently most manufacturers recommended 40 mA.minutes

Question 10

current amp and tx duration for iontophoresis treatment

Answer 10

• Current amp: 1 mA; tx time: 40 mins; dose : 40mA
• current amp: 2 mA; tx time: 20 mins; dose: 40 mA
• current amp: 3 mA; tx time: 13.3 mins; dose 40 mA
• current amp:4 mA; tx time: 10 mins; dose 40 mA

Question 11

higher current amp, shorter duration may provide greater delivery of drug because…

Answer 11

• higher current amp= higher push of drug through the skin
• side effects: higher current amp= build up of electrochemical effect under electrodes which could lead to irritation of skin/discomfort

Question 12

Iontophoresis depth of penetration

Answer 12

• 1-3 mm during tx

- 12-24 hrs after tx session, drug penetration may reach depths of 1.5 cm

Question 13

iontophoresis advantages

Answer 13

• Painless, sterile, noninvasive
• may avoid systemic distribution (leads to next)
• avoids the first pass effect at the liver
• less chance of overdose
• easy drug termination

Question 14

iontophoresis general indications

Answer 14

• localized problems (tendonitis/bursitis)
• fairly superficial
• pt able to tolerate drug and effective current dosage
• localized chronic and sub acute inflammation (itises)
• pain
• hyperhidrosis
• muscle spasm
• calcium deposit
• gout

Question 15

iontophoresis contraindications

Answer 15

• anesthetic skin in the area to be treated
• recent scars in tx area
• metal imbedded close to the surface of the skin
• damaged or denuded skin
• cardiac pacemaker or presence of arrythmias
• placement of electrodes over carotid sinus or areas of venous or arterial thrombosis
• sensitivity to the tx drug

Question 16

iontophoresis drug requirements

Answer 16

• Must be in ionized state
• must be soluble in water and lipids
• • drug molecule dissociates into positive, negative molecules, need to identify which is active ion
• Must be able to permeate through the skin
• Most medications require a prescription from a physician

Question 17

iontophoresis: electrodes

Answer 17

• Any can be used
• iontophoresis electrodes
• • small chamber to house ionized solution
• • covered by semipermeable membrane
• • self adheres to skin
• once prepared, electrode becomes active electrode
• dispersive electrode is prepared with water, gel, or other conducting material

Question 18

iontophoresis: current density at drug electrode

Answer 18

• current density: current amp/ electrode size (area)
• large electrode- current more spread out
• smaller electrode- current more focused
• • may result in tissue burn but,
• • may increase ion velocity, drug transmission

Question 19

recommended maximum current density

Answer 19

• 0.5 mA/cm^2 if delivered from cathode

- 1.0 m/A/ cm^2 if delivered from anode

Question 20

iontophoresis negative polarity

Answer 20

ion-source-indication

• acetate-acetic acid-calcium deposits
• chloride- NaCl- sclerotic
• dexamethasone phosphase- DexNa2PO3- inflammation
• salicylate- NaSal- inflammation, plantar warts
• iodine-iodine-scar

Question 21

iontophoresis positive polarity

Answer 21

ion- source- indication

• copper- CuSo4- sclerotic
• hyaluronidase- wydase-edema reduction
• lidocaine- lidocaine 1:50,000 with epinephrine- local anesthetic
• magnesium-MgSO4- muscle relaxant, vasodilator