Non-therapeutic anti-Xa levels in medical patients receiving anticoagulant therapy with enoxaparin.
BACKGROUND
Anticoagulant activity of enoxaparin is not routinely monitored even when previous studies have shown a high pharmacological variability. The aim of this study is to determine the prevalence of non-therapeutic anti-Xa levels among medical patients using enoxaparin as anticoagulant therapy and to point out potential risk factors related to the risk of having a sub-therapeutic level.


METHODS
Anti-Xa levels were measured in a cohort of sixty patients with medical indication for enoxaparin. Patients were categorized according to anti-Xa levels as follows: suboptimal anticoagulation (<0.5 IU/ml), optimal anticoagulation (between 0.5 and 1.2 IU/ml) or overanticoagulated (>1.2 IU/ml). Demographic and clinical variables and the use of concomitant medications were described for each group. Univariate and multivariate analysis were performed to assess the relationship between sub-optimal anticoagulation and potential predictive variables. A linear regression analysis was done to assess the relationship between anti-Xa activity, age, weight, body mass index, administered dose/weight and creatinine clearance.


RESULTS
The mean anti-Xa activity was 0.71±0.32 UI/ml. Thirty one percent of patients had anti-Xa levels out of the therapeutic range, most of them (twenty-eight percent of total population) with a sub-therapeutic level. None of the variables were associated with the risk of a sub-therapeutic anti-Xa level.


CONCLUSIONS
Almost one third of patients receiving enoxaparin had anti-Xa levels out of the therapeutic range. We need more studies to determine the clinical relevance of these findings.
Centro de Investigación en Hematología y Trastornos Afines, (CIHATA) Universidad de Costa Rica, Hospital San Juan de Dios, San José, Costa Rica. Electronic address: allan.ramos@ucr.ac.cr.
Allan
A
Ramos-Esquivel
Lizbeth
L
Salazar-Sánchez
D000368:Aged; D000789:Angina, Unstable / Q000097:blood* / Q000188:drug therapy* / Q000378:metabolism; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics / Q000494:pharmacology; D015331:Cohort Studies; D016903:Drug Monitoring / Q000379:methods; D017984:Enoxaparin / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics; D015951:Factor Xa / Q000378:metabolism; D065427:Factor Xa Inhibitors; D005260:Female; D006495:Heparin, Low-Molecular-Weight / Q000008:administration & dosage; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000097:blood / Q000188:drug therapy* / Q000378:metabolism; D011446:Prospective Studies
D000925:Anticoagulants; D017984:Enoxaparin; D065427:Factor Xa Inhibitors; D006495:Heparin, Low-Molecular-Weight; D015951:Factor Xa
Drug monitoring; Enoxaparin; Factor Xa; LMWH; Low-molecular-weight heparin; Low-molecular-weight-heparin