Optimization of the Fluvoxamine dose for a poor metabolizer child using TDM: case study

Abstract

Therapeutic drug monitoring is a good tool for dose optimization and therapy improvement. TDM is needed when problems arise as uncertain drug adherence, intolerability, non-response at therapeutic doses, or drug-drug interactions. It is mainly helpful for children, elderly patients, forensic patients, patients with known or suspected genetically determined pharmacokinetic abnormalities. Our work represents the case of a twelve year old girl that has been treated at the in-patient clinic due to severe obsessive-compulsive disorder. She was treated with fluvoxamine in combination with behavioral therapy und has had a suspected problem with her metabolism state. Method: Fluvoxamine concentration was measured using HPLC method. The obtained values were then evaluated by using the program CONBEST. Results: The dose of fluvoxamine was increased slowly within a month to 200 mg/d. The measured concentration was between 1400 and 1600 ng/ml, which exceeding the therapeutic range (60 – 230 ng/ml). After dose reduction we found that elimination of the drug took place very slowly. Following three-day pausing, the reduction of the dose to 50 mg every second day gave an insignificant decrease in drug concentration. Conclusion: The steady state concentration reached slowly because of the poor metabolism, so the assessment of the current dosage is possible after about two weeks. TDM was helpful for dose optimization and therapy improvement in combination with a behavioral therapy.