Crossover randomized comparison of intravenous versus intravenous/oral mesna in soft tissue sarcoma treated with high-dose ifosfamide.

PURPOSE: We conducted our study to determine the pharmacokinetics (PK) and clinical efficacy of oral mesna in patients receiving ifosfamide for soft tissue sarcoma. EXPERIMENTAL DESIGN: Seventeen patients were enrolled in a randomized prospective Phase I/II study. Seventeen patients were exposed to study medication. Ifosfamide was given at a dose of 2 g/m2/day for 5 days on a 21-day cycle. Before the first cycle, all patients were randomized onto a crossover design and received either the approved i.v. or i.v./oral mesna regimen, with crossover for the second cycle of chemotherapy. The i.v. mesna regimen consisted of dosings (20% ifosfamide dose) at 0, 4, and 8 h. The i.v./oral arm consisted of an i.v. mesna dosing (20% ifosfamide dose) at 0 h, followed by oral tablet dosing (40% ifosfamide dose) at 2 and 6 h. In-patient clinical monitoring and phlebotomy and urine sampling for mesna, dimesna, and ifosfamide PK were performed on all chemotherapy days. RESULTS: Thirteen patients were evaluable for PK and 17 for efficacy and toxicity. No significant differences were detected in the plasma PK of the concomitantly infused ifosfamide. Rates of hemorrhagic cystitis were similar across mesna schedules. Four of 10 evaluable patients demonstrated objective response. CONCLUSION: On the basis of our study, an i.v./oral mesna regimen is at least as uroprotective as the approved i.v. regimen. The i.v./oral regimen will improve patient tolerance and convenience, allow for a reduction in elective hospitalizations for ifosfamide chemotherapy, reduce the potential morbidity associated with inpatient administration of chemotherapy, and likely result in decreased costs of care.

Pharmacokinetic interaction between retigabine and lamotrigine in healthy subjects.

PURPOSE: The antiepileptic drugs (AEDs) retigabine (RGB) and lamotrigine (LTG) undergo predominantly N-glucuronidation and renal excretion. This study was performed to evaluate potential pharmacokinetic interactions between both AEDs. METHODS: Twenty-nine healthy male subjects participated in the study. Group A ( n=14) received single oral 200-mg RGB doses on day 1 and day 7, and 25 mg o.i.d. LTG on days 3-8. Group B ( n=15) received single oral 200-mg LTG doses on day 1 and day 17, and was up-titrated to 300 mg RGB b.i.d. on days 6-20. Blood samples were collected to compare the pharmacokinetics of both AEDs and the N-acetyl metabolite of RGB (AWD21-360) after single and concomitant treatments. RESULTS: RGB was rapidly absorbed and eliminated with a mean half-life (t(1/2)) of 6.3+/-1.1 h and an apparent clearance (CL/F) of 0.69+/-1.4 l/h/kg. Under co-administration of LTG, mean RGB t(1/2) and area under the plasma concentration-time curve (AUC) were increased by 7.5% ( P=0.045) and 15% ( P=0.006), respectively, while CL/F was decreased by 13% ( P=0.06). Consistent results were obtained for AWD21-360. LTG was moderately rapidly absorbed, eliminated with a mean t(1/2) of 37+/-10.4 h and a CL/F of 0.028+/-0.007 l/h/kg. Under co-administration of RGB, mean LTG t(1/2) and AUC decreased by 15% and 18%, respectively, while CL/F increased by 22% (all parameters, P=0.001). CONCLUSIONS: RGB and LTG exhibit a modest pharmacokinetic interaction on each other. The slight decline in RGB clearance due to LTG is believed to result from competition for renal elimination rather than competition for glucuronidation. The induction of LTG clearance due to retigabine was unexpected since RGB did not show enzyme induction in various other drug-drug interaction studies. Further studies in patients are needed to assess the clinical relevance of these findings for concomitant treatment with both drugs in the upper recommended dose range.