Iontophoretic delivery of lignocaine and epinephrine

Reena Rai¹ , Shanmuga V Sundaram¹ , S Karthick Prabhu¹ , CR Srinivas¹ , Anil Mathew²

¹ Departments of Dermatology, PSG Institute of Medical Sciences & Research, Coimbatore, India
² Departments of Community Medicine, PSG Institute of Medical Sciences & Research, Coimbatore, India

Correspondence Address:
C R Srinivas
Departments of Dermatology, PSG Institute of Medical Sciences & Research, Coimbatore - 641 004
India

Sir,

Lignocaine, like most local anesthetics, is a vasodilator and causes increased bleeding during surgical procedures. To counter this effect, it is often premixed with epinephrine, which is a powerful vasoconstrictor, at a concentration of 1:100,000 to reverse the vasodilatory response of the tissue to the anesthetic.[1] The pain associated with local anesthetic injections is more when epinephrine is included. This is due to the low pH of solutions necessary to stabilize the epinephrine for a long shelf-life.[2] Iontophoresis is a relatively painless means of delivering medication, whereby a drug having the same charge as the electrode is repelled and driven into the skin.[3] Iontophoretic delivery of lignocaine 2% was effective in reducing the pain of venipuncture and venous cannulation within 10 minutes.[4]

To assess the effectiveness of local anesthesia and for decreasing bleeding during surgery, we conducted a pilot study on ourselves. Iontophoresis was performed with 2 mA of direct current for 15 minutes with lignocaine 2% and epinephrine (1:200,000).

Four 1 inch squares were marked on both forearms with a template. A gauze piece soaked in 2% lignocaine with epinephrine was placed over the right forearm. An aluminium foil 12 cm x 3 cm in size was placed over the gauze piece and secured in place with micropore tape. The anode (positive) plate was placed over the gauze since lignocaine with adrenaline has a net positive charge. The feet were placed over the cathode (negative) plate. Iontophoresis was carried out for 15 minutes following which both test and control sites were tested for touch, pain and bleeding time at 15-minute intervals for 1 hour.

The bleeding time was recorded by a standard method:

The blood pressure was maintained at 40 mm Hg on both upper limbs. A lancet was pricked 3 mm deep and the bleeding time recorded with the help of Whatman filter paper No.1 and a stop-watch.[5]

The sensation of touch was unaffected, while pain was decreased after 15 minutes and up to 1 hour. The bleeding time was reduced after 15 minutes and showed a rebound increase at 30 minutes. The anesthetic effects of lignocaine lasted for a longer time (more than 1 hour), while the vasoconstrictive effects of epinephrine were short-lived (15 minutes), with a rebound increase in the bleeding time at 30 minutes.[6],[7]

The study was limited to two volunteers (both authors) since the bleeding time estimation involved multiple pricks over the control site and was painful. Hence a double-blind placebo-controlled study was not undertaken. A larger well-controlled study involved cannulation over the saline control and the site was treated with lignocaine iontophoresis.[8] This study was conducted on children and adults. Since we found a prick test on the untreated site to be very painful, we were not able to justify conducting the study on volunteers.

A randomized, controlled trial compared EMLA (eutectic mixture of local anesthetic) cream and lignocaine iontophoresis for cannulation analgesia.[9] Although EMLA was found to be superior, lignocaine iontophoresis was faster, cheaper and could be used over large areas with ease.[9]

We suggest that since the duration of effectiveness of epinephrine is limited, pre-treatment iontophoresis can be attempted with plain lignocaine 2% to reduce the pain due to multiple needle-stick injury.

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