In this episode I’ll:

1. Review an article on monitoring enoxaparin with antifactor Xa levels in morbidly obese patients

2. Answer a drug information question about using morphine in a patient on dialysis

3. Share a great resource I use for researching which medications exacerbate porphyria

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Article

Monitoring Enoxaparin with Antifactor Xa Levels in Obese Patients

Lead author: Young R. Lee

Published in Pharmacotherapy November 2015

Background

The bleeding risk potential and best dosing strategy for enoxaparin in morbidly obese patients is unknown.

Methods

This study was a retrospective cohort of 99 morbidly obese patients in a community hospital. All patients either weighed more than 150 kg or had a BMI >40, and had steady-state antifactor Xa peak levels between April 2009 and January 2014.

Purpose

To characterize antifactor Xa peak levels (as therapeutic, subtherapeutic, and supratherapeutic) in morbidly obese patients receiving treatment doses of enoxaparin, using a therapeutic range of 0.5–1.1 units/ml, and to assess the occurrence of bleeding complications in these patients.

Results

Enoxaparin therapy was monitored by using antifactor Xa levels; steady-state enoxaparin antifactor Xa levels were measured 4 hours after administration of the third dose for peak level monitoring. The primary outcome was the proportion of patients whose steady-state antifactor Xa peak values were in the therapeutic, subtherapeutic, and supratherapeutic ranges. The secondary outcome was occurrence of major bleeding. Univariate regression analysis was performed to identify the correlation between baseline patient characteristics and antifactor Xa levels. Most of the patients (50.5%) had supratherapeutic levels, 35.4% had levels within the therapeutic peak range (0.5–1.1 units/ml), and 14.1% had subtherapeutic levels. No bleeding was observed in any of the patients. Univariate analysis revealed a negative association between antifactor Xa levels and serum creatinine concentration (r = −0.262, p=0.009).

The authors concluded that monitoring antifactor Xa levels is warranted to ensure the safety and efficacy of enoxaparin in the obese patient population. Enoxaparin dose individualization and antifactor Xa level monitoring need further validation with clinical outcomes.

I really appreciate this article being published, as there is a dearth of evidence with how to treat morbidly obese patients with enoxaparin. Most often when I have a morbidly obese patient who needs full dose parenteral anticoagulation I favor the use of a heparin infusion since it can be monitored quantitatively.

Drug information question

Q: My patient has new onset end-stage renal disease requiring dialysis – do I need to stop their extended release morphine?

A: Yes.

I do not use morphine for patients with chronic kidney disease (CKD). In normal renal function it is the drug of choice for acute pain, but in CKD the active metabolites accumulate. Toxicity can be expected with chronic use of morphine in CKD. One of the metabolites that accumulates, morphine-6-glucoronidine, may result in neurotoxicity. Even though other opioids will accumulate in CKD, I choose one that does not have active metabolites such as hydromorphone, or fentanyl. A minority (<15%) of oxycodone is metabolized to oxymorphone.

Resource

The resource I’d like to share today is the Porphyria Foundation’s drug database. Porphyria is a rare disorder of heme synthesis. The Porphyria Foundation’s database contains expert assessments of the potential of drugs to provoke attacks of acute porphyria. The database provides guidance based on a very careful evaluation of international clinical experience, published case reports, previously published drug lists, and theoretical considerations. Whenever I take care of a patient with porphyria, I always evaluate their current medication regimen by checking the Porphyria Foundation’s database.

Have you thought about starting a podcast? If you can Skype with your Mom and upload a photo to Facebook, you have all the skills necessary to start a podcast. I’ve created a step-by-step course that will take you from beginning to publishing your medical podcast, and I’ll be there to support you along the way. For a free pdf download of all the resources I use to make this podcast, go to howtostartamedicalpodcast.com.

If you like this post, check out my book – A Pharmacist’s Guide to Inpatient Medical Emergencies: How to respond to code blue, rapid response calls, and other medical emergencies.

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