A missed opportunity - consequences of unknown levetiracepam pharmacokinetics in a peritoneal dialysis patient.

BACKGROUND: Levetiracetam is a frequently used drug in the therapy of partial onset, myoclonic and generalized tonic-clonic seizures. The main route of elimination is via the kidneys, which eliminate 66% of the unchanged drug as well as 24% as inactive metabolite that stems from enzymatic hydrolysis. Therefore dose adjustments are needed in patients with chronic kidney disease stage 5 D, i.e. patients undergoing dialysis treatment. In this patient population a dose reduction by 50% is recommended, so that patients receive 250-750 mg every 12 hours. However "dialysis" can be performed in using different modalities and treatment intensities. For most of the drugs pharmacokinetic data and dosing recommendations for patients undergoing peritoneal dialysis are not available. This is the first report on levetiracetam pharmacokinetics in a peritoneal dialysis patient. CASE PRESENTATION: A 73-y-old Caucasian male (height: 160 cm, weight 93 kg, BMI 36.3 kg/m2) was admitted with a Glasgow Coma Scale of 10. Due to diabetic and hypertensive nephropathy he was undergoing peritoneal dialysis for two years. Eight weeks prior he was put on levetiracetam 500 mg twice daily for suspected partial seizures with secondary generalization. According to the patient's wife, levetiracetam lead to fatigue and somnolence leading to trauma with fracture of the metatarsal bone. Indeed, even 24 hours after discontinuation of levetiracetam blood level was still 29.8 mg/l (therapeutic range: 12 - 46 mg/l). Fatigue and stupor had disappeared five days after discontinuation of the levetiracepam. A single dose pharamockinetic after re-exposure showed an increased half life of 18.4 hours (normal half life 7 hours) and levetiracetam content in the peritoneal dialysate. Both half-life and dialysate content might help to guide dosing in this patient population. CONCLUSION: If levetiracetam is used in peritoneal dialysis patients it should be regularly monitored to avoid supratherapeutic levels that could lead to severe sequelae.

Phosphorylation of paxillin at threonine 538 by PKCdelta regulates LFA1-mediated adhesion of lymphoid cells.

We investigated the PKCdelta-mediated phosphorylation of paxillin within its LIM4 domain and the involvement of this phosphorylation in activation of LFA-1 integrins of the Baf3 pro-B lymphocytic cell line. Using phosphorylated-threonine-specific antibodies, phosphorylated amino acid analysis and paxillin phosphorylation mutants, we demonstrated that TPA, the pharmacological analog of the endogenous second messenger diacyl glycerol, stimulates paxillin phosphorylation at threonine 538 (T538). The TPA-responsive PKC isoform PKCdelta directly binds paxillin in a yeast two-hybrid assay and phosphorylates paxillin at T538 in vitro and also co-immunoprecipitates with paxillin and mediates phosphorylation of this residue in vivo. Recombinant wild-type paxillin, its phospho-inhibitory T538A or phospho-mimetic T538E mutants were expressed in the cells simultaneously with siRNA silencing of the endogenous paxillin. These experiments suggest that phosphorylation of paxillin T538 contributes to dissolution of the actin cytoskeleton, redistribution of LFA-1 integrins and an increase in their affinity. We also show that phosphorylation of T538 is involved in the activation of LFA-1 integrins by TPA.