Category Archives: Pharmacy

Pharmacy

Best Of EAST #4: 4-Factor PCC vs Andexanet Alfa For Factor Xa Inhibitor Reversal

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Falls are by far the most common mechanism of injuries in US trauma centers these days. They typically occur in elderly patients, and a growing number are on some type of oral anticoagulant for their medical conditions. And the number of these patients who are taking a DOAC (direct thrombin inhibitor or factor Xa antagonist) is rising quickly.

Unfortunately, most of the DOACs do not have good reversal agents, and they are very, very expensive. Specifically, Andexanet Alfa, the antidote for rivaroxaban and apixaban used to cost in excess of $50,000 per dose. This has come down over time to “only” $22,000 per dose. Unfortunately, the half-life is much shorter than the agent it is neutralizing, frequently requiring two doses. And the kicker is that there are no studies definitively showing that Andexanet Alfa improves mortality when used for CNS hemorrhage.

Prothrombin complex concentrate (PCC) has been used for reversal of these agents as well. Its efficacy is also not well known. The group at George Washington University is presenting an abstract comparing it against Andexanet Alfa (AA) for reversal of either of the Factor Xa inhibitors (rivaroxaban, apixaban). They performed a multicenter study involving 10 trauma centers. The endpoints studied were number of transfusions, mortality, and ICU length of stay.

Here are the factoids:

  • From a total of 263 patients, 77 received AA and 186 received PCC
  • Only 4% of patients received a second dose of AA despite its short half-life
  • There was no significant difference in the number of PRBCs transfused
  • The authors stated that the mortality was significantly lower with PCC but the p value in the data table provided was = 0.05
  • They also stated that the ICU LOS was significantly lower with PCC (1.2 vs 1.5 days, p = 0.04)

The authors concluded that PCC is non-inferior to AA for reversal in bleeding trauma patients. They recommended a randomized study be done.

Bottom line: The first thing for you to know is that I have never been impressed with the data on Andexanet Alfa. Which means I have to be very careful and aware of my own cognitive bias. In practice, this means I can’t just look at the study title or abstract and be happy that it meets my confirmation bias. I have to make a conscious effort to critically read the paper or abstract and see if it really does mean what I want it to mean, or if I need to change my opinion.

This abstract doesn’t really satisfy my confirmation bias. The title states that PCC is not inferior to AA. I would certainly like to believe that. But in order to safely say that, it is vitally important that a power analysis is performed to ensure that enough patients are present in both treatment groups to confidently state that there was no difference. If the number of patients is too small, significance can’t be detected and non-inferiority cannot be confirmed.

The body of the abstract claims that mortality was significantly lower in the PCC group, although the table states that the p value was 0.05, which technically is not significant. The difference in mortality numbers is impressive (PCC mortality 20% vs 32% for AA) so why the significance issue?

And one note about significance. Be careful not to conflate statistical significance with real-life significance. ICU length of stay in this study was statistically significantly shorter in the PCC group (1.2 vs 1.5 days) but I doubt that a difference of 7 hours in the ICU is clinically relevant.

Here are my questions for the authors and presenter:

  • Did you have enough patients in the study to assure that the PCC treatment was actually non-inferior? Please show us your power analysis.
  • What were the inclusion criteria for the study? This will help us understand the patient group better. Were these primarily head bleeds, actual external or intra-cavity hemorrhage?
  • Please clarify the significance claim for mortality. The raw percentages are impressively different, but the P value is not significant.
  • Could the low rate of administering a second dose of AA have influenced the outcomes? As mentioned above, the half-life of the antidote is much shorter than that of the DOAC. Perhaps giving a second dose is actually needed and could have moved the results in favor of AA.

This is a thought-provoking abstract for me. Let’s see if you can either confirm or refute my opinion on AA!

Reference: 4-FACTOR PROTHROMBIN COMPLEX CONCENTRATE IS NOT INFERIOR TO ANDEXANET ALFA FOR THE REVERSAL OF FACTOR XA INHIBITORS: AN EAST MULTICENTER STUDY. EAST 25th ASA, oral abstract #15.

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Complications, Pharmacy

Salmon Calcitonin After Spine Fractures?

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In my last post, I reviewed some data on the effectiveness of starting Vitamin D supplements after a patient sustains a fracture. The idea was that they might start building better bone and heal their fractures more readily if they boost their D levels. Unfortunately, this was not shown to be true.

Vitamin D improves bone health by facilitating absorption of calcium from the gut. This is a bit indirect and relies on sufficient intake of calcium and good hormonal regulation that directs osteoblasts to incorporate the mineral into bone. Why not work with those hormones directly to try to increase the amount of calcium that is deposited?

Calcitonin is a peptide hormone that has two major effects on calcium levels: it inhibits osteoclast activity that is breaking down bone and releasing calcium from it, and it inhibits calcium reabsorption in the kidneys which causes more to be excreted in the urine.

Perhaps giving calcitonin after sustaining a fracture might improve healing. Many orthopedic surgeons and neurosurgeons swear by this drug. Unfortunately, there are very few randomized, controlled studies of its use for this indication. A meta-analysis was performed that examined both utility and cost-effectiveness that I found interesting.

Here are the factoids:

  • There was some mild evidence that nasal calcitonin was effective in preventing vertebral fractures
    • One paper showed a benefit when giving 200 IU of intranasal salmon calcitonin daily over a 5 year period
    • But a benefit was not shown if 100 or 400 IU were given (this is weird)
    • A marker of bone turnover showed equal reduction in 200 and 400 IU groups (why isn’t this less in the 200 IU group?)
  • Financial analysis showed that it was only marginally cost effective
  • Current retail pricing is about $125 for a month supply
  • Mild side effects like runny nose and nausea are common
  • Intranasal calcitonin has been shown to reduce pain during healing of vertebral fractures

Bottom line: What does all of this mean? First, salmon calcitonin might decrease the number of future vertebral fractures. I say might because only the 200 IU dose in the study showed this effect. I can see where higher doses might be more effective to a point, but having only the middle dose show up as effective is just odd and makes me worry about the study.

The data does seem compelling that taking this product decreases pain during fracture healing. A meta-analysis of this showed that the effect probably only lasts up to a month. 

And finally, from a cost-effectiveness standpoint for avoiding future fractures, this medication is marginal. Luckily, it is relatively cheap at $125 retail and about $25 with insurance in the US. 

Wrapping it all up, intranasal salmon calcitonin might reduce fracture pain for a month and might decrease the likelihood of future vertebral fractures. However, the data are weak enough that cost-effectiveness is borderline. And there are more effective (and cheaper) analgesics available.

The absolute best way to strengthen bones is to exercise, especially engaging in weight-bearing activities. Not only does this strengthen bones, it also increases overall fitness and health. In general, medications are not the way to go to strengthen bones. It took decades for your patient to become osteoporotic. And while these drugs might improve their bone density slowly, a graduated and supervised exercise regimen is probably the best thing you can do for them.

References:

  • Efficacy of calcitonin for treating acute pain associated with osteoporotic vertebral compression fracture: an updated systematic review. CJEM 2020 May;22(3):359-367.
  • A Randomized Trial of Nasal Spray Salmon Calcitonin in Postmenopausal Women with Established Osteoporosis: the Prevent Recurrence of Osteoporotic Fractures Study. PharmacoEconomics, 2001, Vol.19 (5), p.565-575.
  • A randomized, double-blind, multicenter, placebo-controlled study to evaluate the efficacy and safety of oral salmon calcitonin in the treatment of osteoporosis in postmenopausal women taking calcium and vitamin D. Bone 2016 Oct;91:122-9.
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Pharmacy

Is Daily Enoxaparin Dosing As Good As Twice Daily?

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Venous thromboembolism (VTE) remains a big problem for trauma professionals and the patients they take care of.  Every trauma center has some sort of VTE prophylaxis protocol for stratifying risk, prescribing mechanical or pharmacologic prophylaxis, and monitoring effectiveness.

This is all well and good for patients in the hospital. But what happens once they go home?  Who needs to continue chemoprophylaxis? For how long? And what product? These are all tough questions, and are not usually part of the protocol. It is an important issue, and I’d like to address the last question in this post.

Typically, patients who need ongoing chemical prophylaxis after trauma are sent home on a low molecular weight heparin product. This is usually enoxaparin. As you know, this drug has two possible dosing regimens for prophylaxis: 30 mg subq twice a day or 40 mg subq once a day.

Now, nobody likes to give themselves a shot, ever. But if one has the choice between once a day vs twice, I think it’s safe to say everyone would pick the single dose. But it just doesn’t seem right that 60 mg spread out over two doses is just as effective as 40 mg once a day. Unless, of course, we are radically overdosing on the twice a day regimen.

So is the one-a-day regimen as good as twice a day? There is older support in the orthopedic surgery literature that it is. However, general trauma patients are probably at higher risk than those old studies would suggest. The trauma group in Gainesville FL looked at this question. They had been using the once a day dose for years, then changed to twice daily administration. They performed a retrospective study of their experience.

Here are the factoids:

  • The authors excluded the extremes of injury: patients admitted for < 2 days, or death within 2 days
  • There were 409 patients in the once daily group and 278 patients with twice daily dosing
  • About 3% of patients with once daily dosing developed VTE vs only 1% in the twice daily group
  • Bleeding complications occurred in 1.8% of the once daily group vs 2.7% in the twice daily group
  • Neither of these results was statistically significantly different

Bottom line: Although the authors try to imply that twice daily dosing “may be more effective” than once daily, they do admit that the statistics don’t show that. Unfortunately, the study design makes it nearly impossible to derive any firm results. It is a retrospective study designed long after the actual patient care, and does not take into account anything other than rudimentary risk stratification. 

My take on the topic is that it is unlikely that once daily dosing is as good as twice daily. Unfortunately, we just don’t have any literature to support that yet. Until we do, I recommend that you take a close look at your individual patient’s risk for VTE, and err on the side of giving enoxaparin twice daily until we know better.

Reference: Once- Versus Twice-Daily Enoxaparin for Venous Thromboembolism Prophylaxis in High-Risk Trauma Patients. J Intensive Care Med 26(2):111-115, 2011.

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Pharmacy

Reversing Direct Oral Anticoagulants With Andexxa

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I just finished a summary of the Australian consensus paper regarding anticoagulants (and anti-platelet agents) in patients with hemorrhagic TBI. One of the issues addressed was reversal of these agents. Today I’m going to provide more specific information on one of the new reversal agents, Andexxa (recombinant Factor Xa, inactivated-zhzo).

First, maybe someone can help me here. What does zhzo mean? I’ve done a deep dive including a review of the FDA filings, and still can’t figure out what this is. I have a hard enough time with the thousands of something-umab monoclonal antibody products out there. Now we’re adding on a bunch of z’s to the end of drug names?

There are currently two classes of direct oral anticoagulant drugs (DOACs) available, direct thrombin inhibitors and Factor Xa inhibitors. Andexxa was designed to reverse the latter by providing a lookalike of Factor Xa to selectively bind to apixaban (Eliquis) and rivaroxaban (Xarelto).

The Austrian consensus paper I previously discussed recommended giving Andexxa in patients taking apixaban or rivaroxaban if it was not possible to show that the drugs were non-therapeutic. This means that if your lab could not measure anti-Factor Xa levels in a timely manner and the patient was known to be taking one of these agents, reversal should be considered.

Sounds cut and dried, right? Your patient is taking a Factor Xa inhibitor and they are bleeding, so give the reversal agent. Unfortunately, it’s much more complicated than that.

  • The half-life of Andexxa is much shorter than that of the drugs it reverses. The reversal effect of Andexxa begins to wear off two hours after administration, and is gone by four hours. On the other hand, the half life of rivaroxaban is 10+ hours in the elderly. The half-life of apixaban is even longer, 12 hours. This means that it is likely that multiple doses of Andexxa would be necessary to maintain reversal.
  • There are no studies comparing use of Andexxa with the current standard of care (prothrombin complex concentrate, PCC). The ANNEXA-4 study tried to do this. It was a single-arm observational study with 352 subjects. These patients were given Andexxa if major bleeding occurred within 18 hours of their DOAC dose. Two thirds of the patients had intracranial bleeding. All were given a bolus followed by a two hour drip. All showed dramatic drops in anti-Factor Xa levels, and 82% of patients had good or excellent control of hemorrhage. However, 15% died and 10% developed thrombotic complications.
  • The FDA clinical reviewers recommended against approval due to the lack of evidence for clinical efficacy. The director for the Office of Tissues and Advanced Therapies overruled the reviewers and allowed approval until such time a definitive study was completed. So far there have been no justifiable claims that Andexxa is superior to PCC.
  • To be fair, PCC has not been compared to placebo either. So we don’t really know how useful it is when treating bleeding after DOAC administration.
  • Andexxa is very expensive. Old literature showed a single dose price of $49,500 but this has been revised downward. Effective in October 2019, Medicare agreed to reimburse a hospital about $18,000 for Andexxa over and above the DRG for the patient’s care. Remember, due to the half life of the Factor Xa inhibitors, two doses may be needed. This comes to about $36,000, which is much higher than the cost for PCC (about $4,000).

Bottom line: Any hospital considering adding Andexxa to their formulary should pay attention to all of the factors listed above and do the math for themselves. Given the growing number of patients being placed on DOACs, the financial and clinical impact will continue to grow. Is the cost and risk of this therapy justified by the meager clinical efficacy data available?

References:

  1. Full Study Report of Andexanet Alfa for Bleeding Associated with Factor Xa Inhibitors. NEJM 380(14):1326-1335, 2019.
  2. Key Points to Consider When Evaluating Andexxa for Formulary Addition. Neurocrit Care epub ahead of print, 22 Oct 2019.
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Pharmacy

How Many Salt Tabs In A Liter Of Saline?

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Seems like a simple, silly question, right? I dare you to figure it out without reading this post!

horse-salt-block-lick2

On occasion, our brain injured trauma patients have sodium issues. You know, cerebral salt wasting. Trying to maintain or regain the normal range, without making any sudden moves can be challenging. There are a lot of tools available to the trauma professional, including:

  • Saline
  • Hypertonic saline
  • Salt tablets
  • Fluid restriction
  • Some combination thereof

Fun times are had trying to figure out how much extra sodium we are giving with any of the first three items. This is important as you begin to transition from the big guns (hypertonic), to regular saline, and then to oral salt tabs.

Below is a quick and dirty conversion list. I won’t make your heads explode by trying to explain the math involved changing between meq, mg, moles, sodium and sodium chloride.

  • The “normal saline” bags we use are actually 0.9% saline (9 gm NaCl per liter)
  • Hypertonic saline can be 3% or 5% (30 gm or 50 gm per liter)
  • Salt tabs are usually 1 gm each (and oh so yummy)

Therefore, a liter of 0.9% normal saline is the same as 9 salt tabs.

A liter of 3% hypertonic saline is the same as 30 salt tabs. The usual 500cc bag contains 15.

A liter of  5% hypertonic saline is the same as 50 salt tabs. The usual 500cc bag contains 30.

To figure out how many tablets you need to give to match their IV input, calculate the number of liters infused, then do the math! And have fun!

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