What is the calculated dosing of tinzaparin (a low molecular weight heparin) for Deep Vein Thrombosis (DVT) prophylaxis in a 150 kilogram adult?

From the Guidelines

For DVT prophylaxis in a 150 kg adult, I recommend tinzaparin 175 U/kg subcutaneously once daily, which translates to 26,250 U daily. This is based on the most recent and highest quality study available, which suggests weight-based dosing for therapeutic purposes, but also provides a clear dose for tinzaparin in the context of VTE treatment 1. Although the standard prophylactic dose for most adults is often considered to be fixed, the provided evidence suggests that for therapeutic purposes, a weight-based approach is used, and it is reasonable to consider this in the context of prophylaxis for extremely obese patients. When administering tinzaparin, it is crucial to use the prefilled syringes, inject the full needle length at a 90-degree angle into a skin fold of the anterolateral or posterolateral abdominal wall, and rotate injection sites daily. Monitoring for signs of bleeding and thrombocytopenia is also essential. The rationale for using a weight-based dose in very obese patients is that standard fixed doses may provide inadequate anticoagulation due to altered drug distribution in adipose tissue and increased blood volume, though pharmacokinetic studies specifically in extreme obesity are limited.

Some key points to consider:

• The dose recommended is based on the treatment dose, as the prophylactic dose may not provide adequate anticoagulation in extremely obese patients.
• The administration technique is crucial to ensure the effectiveness of the treatment and minimize the risk of complications.
• Monitoring for potential side effects is essential to promptly identify and manage any issues that may arise.
• The decision to use a weight-based dose should be made on a case-by-case basis, considering the individual patient's risk factors and medical history.

It's worth noting that while the provided evidence does not directly address the prophylactic use of tinzaparin in extremely obese patients, the weight-based dosing approach for therapeutic purposes can be considered as a guideline for prophylaxis in this specific population 1. However, the most recent and highest quality study available should always be the primary reference for clinical decision-making 1.

From the Research

Dosing of Tinzaparin for DVT Prophylaxis

• The calculated dosing of tinzaparin for Deep Vein Thrombosis (DVT) prophylaxis in a 150 kilogram adult can be determined based on the available evidence.
• According to the study 2, for thromboprophylaxis with LMWH in non-bariatric surgery and in medical inpatients, tinzaparin 75 IU/kg once daily may be considered in obese patients.
• Since the patient weighs 150 kg, the dose would be calculated as 75 IU/kg * 150 kg = 11,250 IU once daily.
• It is worth noting that the study 3 mentions that the dose of tinzaparin does not need to be altered in patients with a body mass index of > 25, and the study 4 states that no dose "cap" is required for obese patients.
• However, the study 2 provides a specific dose recommendation for tinzaparin in obese patients, which is 75 IU/kg once daily.
• Therefore, based on the available evidence, the calculated dosing of tinzaparin for DVT prophylaxis in a 150 kilogram adult would be 11,250 IU once daily 2.

Considerations for Renal Function

• The study 5 evaluated the safety and effectiveness of LMWH VTE prophylaxis in critically ill patients with renal dysfunction, but it did not provide specific dosing recommendations for tinzaparin in patients with renal impairment.
• However, the study 3 mentions that tinzaparin can safely be given to patients with significant renal impairment (creatinine clearance of > or = 20 ml/min).
• The study 4 also states that no initial dosing adjustments are necessary in elderly and/or renally impaired patients, although some monitoring is recommended.
• Therefore, based on the available evidence, it appears that tinzaparin can be used in patients with renal impairment, but monitoring may be necessary 4, 3.

Comparison with Other LMWHs

• The study 6 compared LMW heparins, including tinzaparin, with unfractionated heparin for the initial treatment of DVT, and found that LMW heparins were effective and had similar frequencies of recurrent thromboembolism and bleeding complications.
• The study 2 also compared different LMWHs, including tinzaparin, and found that they had similar efficacy and safety profiles.
• Therefore, based on the available evidence, it appears that tinzaparin is a suitable option for DVT prophylaxis, with a similar efficacy and safety profile to other LMWHs 2, 6.