title: Dose-finding and pharmacokinetics of therapeutic doses of tinzaparin in pediatric patients with thromboembolic events.
abstract: In children, there is an increasing off-label use of low molecular weight heparin (LMWH). However, there is an absence of information on dosing and pharmacokinetics of LMWH over all age groups. The objectives of the current study were to determine i) the once daily dose required to achieve anti-Xa levels of 0.5-1.0 IU/mL, ii) the pharmacokinetics and iii) preliminary safety data using tinzaparin. The study took the form of a single centre open-label Phase II study performed in 35 children requiring anticoagulation for treatment of thromboembolism. Age groups studied were: 0- < 2 months; 2 months- < 1 year; 1- < 5 years; 5- < 10 years; 10-16 years. Both population pharmacokinetic analysis using nonlinear mixed-effect modeling techniques and model-independent pharmacokinetic methods were employed. Results showed a relationship of age and dose requirements, clearance, time to peak anti-Xa level and volume of distribution. Younger children required an increased dose, cleared tinzaparin more rapidly, had anti-Xa levels peak earlier and had an increased volume of distribution. Younger children were more likely to be below target range than older children,with up to 75% of children < 1 year being below the target anti-Xa level. Four recurrences and one major bleed occurred. In conclusion, there is an inverse relationship of age on dose requirements related to volume of distribution, clearance and time to peak anti-Xa. Children < 5 years likely require dose adjustment samples to be drawn 2-3 hours post injection. Infants require anti-Xa levels to be monitored at least twice monthly.
authors.affiliation: Stollery Children's Hospital, Edmonton, Alberta, Canada.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kuhle
authors.forename: Patti
authors.initials: P
authors.lastname: Massicotte
authors.forename: Maria
authors.initials: M
authors.lastname: Dinyari
authors.forename: Patsy
authors.initials: P
authors.lastname: Vegh
authors.forename: Debra
authors.initials: D
authors.lastname: Mitchell
authors.forename: Velma
authors.initials: V
authors.lastname: Marzinotto
authors.forename: Antony
authors.initials: A
authors.lastname: Chan
authors.forename: Hank
authors.initials: H
authors.lastname: Pieniaszek
authors.forename: Lesley G
authors.initials: LG
authors.lastname: Mitchell
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D004348:Drug Labeling; D016903:Drug Monitoring; D065427:Factor Xa Inhibitors; D005260:Female; D005343:Fibrinolytic Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D006207:Half-Life; D006495:Heparin, Low-Molecular-Weight / Q000008:administration & dosage* / Q000493:pharmacokinetics; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008657:Metabolic Clearance Rate; D013923:Thromboembolism / Q000188:drug therapy*; D000078222:Tinzaparin
chemical_list: D065427:Factor Xa Inhibitors; D005343:Fibrinolytic Agents; D006495:Heparin, Low-Molecular-Weight; D000078222:Tinzaparin