Background: For the narrow therapeutic index anti-epileptic drugs, monitoring of plasma
concentration is a necessity for avoiding complications related to fluctuation of plasma level.
Objective: The work was aimed at extracting gabapentin by transdermal reverse iontophoresis to investigate
its feasibility for noninvasive therapeutic drug monitoring.
Methods: Gabapentin was delivered in phosphate buffer (pH 7.4) at a therapeutic concentration range
of 2-10 µg/ml. The same media was also used in receiver compartment. Extractions were carried out
under an electric field of 5 V (current intensity range 0.3 -0.5 mA/cm2), provided by a custom-made
power source for a period of 4 h. Samples were withdrawn at hourly intervals and drug content was
analyzed by HPLC.
Results: Results indicated that gabapentin extraction occurred at both anode and cathode with cathodal
extractions showing higher value at all concentrations. Extraction rates at both the chambers were affected
by time, the first hour extraction was notably higher than the later hours. Highest extraction rate
was noted at pH 5. Surprisingly, anodal extraction was found to show greater positive correlation with
current intensity compared to cathodal extraction.
Conclusions: As gabapentin carried no net charge at pH 7.4, orientation mediated electromigration was
suggested to be the cause.