Pharmacokinetic analysis of enoxaparin in a term neonate and review of literature

The Trilogy of SARS-CoV-2 in Pediatrics (Part 3): Thrombosis, Anticoagulant, and Antiplatelet Considerations

The hypercoagulable state induced by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) affects all patients regardless of age. The incidence of venous thromboembolism in pediatric patients with SARS-CoV-2-related illnesses is not well established. Although deep vein thrombosis is rare in children in the absence of risk factors, coagulopathy and the development of thromboses have been described in pediatric patients with acute COVID-19 and multisystem inflammatory syndrome. This comprehensive review provides a detailed overview of SARS-CoV-2-associated coagulopathy as well as strategies for optimizing the evaluation, management, and prevention of thrombosis in pediatric patients.

A Critical Evaluation of Enoxaparin Dose Adjustment Guidelines in Children

OBJECTIVES

The purposes of this study are to perform a large-scale evaluation of the standardized dosage adjustment nomogram recommended by the American College of Chest Physicians (CHEST) for the management of enoxaparin in hospitalized pediatric patients and to determine the necessity of routine and repeated anti-factor Xa (anti-Xa) levels.

METHODS

A retrospective cohort study was designed, and charts were reviewed in a single tertiary care institution for all patients who received enoxaparin between October 1, 2010, through September 30, 2016. Patients were included if they were receiving treatment doses of enoxaparin according to the pediatric CHEST guidelines, had a subtherapeutic or supratherapeutic anti-Xa level drawn at 3.5 to 6 hours after a dose, had a dose changed in an attempt to attain a therapeutic anti-Xa level, and had a second anti-Xa level drawn 3.5 to 6 hours after the dose change. Descriptive statistical methods were used to characterize the ability of dose adjustment via a nomogram to attain an anti-Xa of 0.5 to 1 unit/mL.

RESULTS

A total of 467 patients were identified who received the appropriate initial dose and dosage adjustment and whose levels were drawn according to the CHEST guidelines. In patients who had an initial anti-Xa level of <0.35 units/mL and received the nomogram recommended dose increase of 25% ± 5%, 28 out of 96 patients (29.2%) reached therapeutic levels. Of 197 patients who had an initial anti-Xa level between 0.35 and 0.49 units/mL and who received the nomogram recommended dose increase of 10% ± 5%, 116 (58.9%) reached therapeutic levels. Of 50 patients with an initial anti-Xa level between 1.1 and 1.5 units/mL and who received the nomogram dose decrease of 20% ± 5%, 31 (62%) reached therapeutic levels.

CONCLUSIONS

The current dosage adjustment nomogram recommended by the CHEST guidelines does not reliably lead to therapeutic anti-Xa levels when used to adjust enoxaparin doses in pediatric patients.

Enoxaparin Population Pharmacokinetics in the First Year of Life

AIMS

Enoxaparin dosing requirements in the first year of life can be highly variable. Characterization of pharmacokinetics in this patient population can assist in dosing.

METHODS

Patients less than 1 year postnatal age who received enoxaparin and had an anti-factor Xa activity level drawn as inpatients were identified through the pharmacy database over a 5-year period. Patients on renal replacement therapy or with hyperbilirubinemia were excluded. Data collection included demographic variables, indication for enoxaparin, enoxaparin doses, anti-factor Xa activity levels, serum creatinine, hemoglobin, hematocrit, platelet count, and urine output over the previous 24 hours. Population pharmacokinetic analysis was performed with NONMEM.

RESULTS

A total of 182 patients [male 50%, median 100 days postnatal age (range: 4-353 days)] met the study criteria. Patients received median 22 doses (range: 1-526) at a mean starting dose of 1.38 ± 0.43 mg/kg with median 5 (range: 1-56) anti-factor Xa activity levels measured. A 1-compartment proportional and additive error model best fits the data. Allometrically scaled weight significantly decreased the objective function value, as did serum creatinine on clearance, and postmenstrual age (PMA) on volume of distribution. When evaluated graphically, dosing based on PMA appeared to have less variability as compared to postnatal age-based dosing.

CONCLUSIONS

Dosing of enoxaparin in infants younger than 1 year should incorporate PMA.

Treatment and follow-up of venous thrombosis in the neonatal intensive care unit: a retrospective study

OBJECTIVE

The critically ill, premature patients of neonatal intensive care units are susceptible to venous thrombosis, an adverse event associated with short- and long-term morbidity. Venous thrombosis is frequently treated with low-molecular-weight heparins (LMWHs) such as enoxaparin, but optimal dosing of LMWH must balance the morbidity of venous thrombosis with the potential adverse affects of anticoagulation. The optimal dosing of enoxaparin for premature infants is unclear. The objective of this study was to describe enoxaparin therapy and follow-up in critically ill neonates diagnosed with venous thrombosis.

STUDY DESIGN

Retrospective medical record review in the neonatal intensive care unit (NICU) in a single tertiary care institution. Infants with venous thrombosis diagnosed in the NICU were identified using preexisting quality improvement lists and medical records.

RESULTS

Twenty-six infants with 30 venous thromboses were identified with a median gestational age of 31 weeks at birth. Eighteen (69%) infants received enoxaparin for venous thrombosis during their hospitalization, beginning with a median dose of 1.5 mg kg^-1 every 12 h. This dose was increased to a median of 2.1 mg kg^-1 every 12 h to achieve target anti-factor Xa levels. The target dose was significantly higher in patients with a postmenstrual age of <37 weeks. Enoxaparin treatment was documented after discharge in 12 patients, continuing for a median of 99 days. Four patients died during hospitalization and their deaths were not attributable to venous thrombosis or anticoagulation complication. Follow-up documentation between 6 and 24 months after venous thrombosis diagnosis revealed no major morbidity of venous thrombosis or enoxaparin therapy.

CONCLUSION

Our data reinforce the relative safety and necessity of enoxaparin doses above 1.5 mg kg^-1 per 12 h in most neonates. This was particularly true for infants at lower postmenstrual age.

Stability and Sterility of Enoxaparin 8 mg/mL Subcutaneous Injectable Solution

BACKGROUND: Enoxaparin is often diluted to accurately deliver doses to neonatal and infant patients. Current recommendations for dilutions may not be adequate for the smallest patients. METHODS: Review of dosing at our institution occurred, and an 8 mg/mL concentration of enoxaparin was chosen. A concentration of 8 mg/mL was compounded by diluting 0.4 mL of enoxaparin (100 mg/mL) into 4.6 mL of sterile water for injection into an empty sterile vial. Four syringes of the 8 mg/mL concentration were prepared by 5 technicians (20 total syringes). Stability and sterility testing occurred a 0, 7, 14, and 30 days. One-way repeated-measures analysis of variance was used to detect significant differences in Anti-Factor Xa concentrations at the testing time points. RESULTS: The dilution of enoxaparin was sterile at 30 days but exhibited significant degradation at the 30-day point (p < 0.05). CONCLUSION: A dilution of enoxaparin 8 mg/mL is stable and sterile for 14 days refrigerated but is not stable at 30 days.

Lovenox Induced Tissue Necrosis, a Case Report and Literature Review

Lovenox is a trade name for Enoxaparin. It is a low molecular weight heparin (LMWH) and has other trade names like Clexane and Xaparin. It is an anticoagulant used to prevent and treat venous thromboembolism events (VTE) like deep vein thrombosis or pulmonary embolism, and is given as a subcutaneous injection. General speaking, the most common skin reactions as a result of enoxaparin use are: urticarial, ecchymosis, and even skin necrosis due to vasculitis. These side effects are usually located at the injection site. New studies have pointed out the side effect that could occur a distance from the site of Lovenox injection. In our case extensive skin and subcutaneous tissue necrosis developed at the abdominal wall injection site.