Physiological effects of electrotherapy for iontophoresis Flashcards
Iontophoresis History
- 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
Mechanism of topical drug delivery without iontophoreis
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
Iontophoresis description
- 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
Electroporation
temporary production of water soluble pores in the skin
electroosmosis
as water is carried through the skin it can carry other objects dissolved in it along with it
Direct current (DC)
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
Negative electrode (cathode)
Sodium hydroxide (+ions) - alkaline reaction
Positive electrode (anode)
Hydrochloric acid (-ions)- acidic reaction
Iontophoresis dosage
- 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
current amp and tx duration for iontophoresis treatment
- 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
higher current amp, shorter duration may provide greater delivery of drug because…
- 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
Iontophoresis depth of penetration
- 1-3 mm during tx
- 12-24 hrs after tx session, drug penetration may reach depths of 1.5 cm
iontophoresis advantages
- 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
iontophoresis general indications
- 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
iontophoresis contraindications
- 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
iontophoresis drug requirements
- 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
iontophoresis: electrodes
- 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
iontophoresis: current density at drug electrode
- 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
recommended maximum current density
- 0.5 mA/cm^2 if delivered from cathode
- 1.0 m/A/ cm^2 if delivered from anode
iontophoresis negative polarity
ion-source-indication
- acetate-acetic acid-calcium deposits
- chloride- NaCl- sclerotic
- dexamethasone phosphase- DexNa2PO3- inflammation
- salicylate- NaSal- inflammation, plantar warts
- iodine-iodine-scar
iontophoresis positive polarity
ion- source- indication
- copper- CuSo4- sclerotic
- hyaluronidase- wydase-edema reduction
- lidocaine- lidocaine 1:50,000 with epinephrine- local anesthetic
- magnesium-MgSO4- muscle relaxant, vasodilator
