Ejaz Hassan Khan, Farooq Ahmad Khan, Asma Shaukat, Samina Ghayur.
Laboratory-based audit of lithium, digoxin and gentamicin therapeutic monitoring.
Pak J Pathol Jan ;8(2):11-8.

Therapeutic gains can be accomplished with minimal dosing strategies, targeted drug therapy for patients refusing medication, psychological interventions, and new drugs. Clinicians can use therapeutic drug monitoring (TDM) to optimise dosage decisions, in order to maximise efficacy and prevent toxicity, especially when individuals are non-responsive to treatment or vulnerable to adverse reactions with standard doses because age, disease state or drug interactions complicate therapy. A study was planned to evaluate the usefulness of drug analysis in our clinical setup. Lithium, gentamicin and digoxin were selected out of therapeutic drugs. The analytical performance of the method, establishment of quality control, validity of the therapeutic ranges, assessment of percentage of patients achieving therapeutic, toxic or sub-therapeutic levels and clinical presentation were main aspects of study. Our results showed that the fluorescent polarisation immunoassay was an accurate and precise method and met all requirements of good quality control. The study on lithium revealed that monitoring serum levels was essential to avoid toxic effects. About 35% of patients had either toxic levels or sub-therapeutic level with the routinely prescribed dosage regimens of lithium. It was also observed that therapeutic level could not be achieved in any of the patients who were prescribed the dosage of 400mg/day. 30% of patients receiving routinely prescribed doses of digoxin. had sub-therapeutic levels while 15% had toxic levels. GIT symptoms and atrial fibrillations were common toxic manifestations. Non compliance of patients was a major factor in those with sub-therapeutic level. Individualisation of dosage regimen for gentamicin was also found to be essential. Nephrotoxicity was a major toxic effect with high serum gentamicin concentrations. TOM of gentamicin was especially important in obstetric patients.

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