Monday, August 27, 2018

Fosfomycin: The Forgotten Treasure





We have all been there, a patient with so many complicating factors that it’s difficult to choose the least worst option to treat a urinary tract infection. For example: a patient with a CrCl ~22 ml/min, a prolonged QTc, sulfa allergy (described as immediate death), and amoxicillin allergy (also somehow described as immediate death) who absolutely refuses to try a cephalosporin. How is it this difficult to treat a simple urinary tract infection?!?!?!

There is one antibiotic that has your back, fosfomycin (Monurol®). (And to get this out of the way, I fully endorse challenging penicillin allergies with appropriate agents, as long as the provider, the care team, and the patient are on board with the plan.)

What is Fosfomycin1,2
Fosfomycin is a bactericidal phosphoric acid derivative antibiotic that disrupts cell wall synthesis by inhibiting pyruvyl transferase. Fosfomycin is only available as a 3g oral sachet in the United States, though it is available as an intravenous product elsewhere.

Spectrum of Activity
Fosfomycin has activity against a broad range of gram-positive and gram-negative aerobic microorganisms commonly associated urinary tract infections. These include E.coli, Klebsiella spp. Enterococcus spp. (including vancomycin resistant Enterococcus spp [VRE]), Enterobacter spp., Citrobacter spp. Pseudomonas spp., and Serratia spp. Additionally, and discussed in more detail below, fosfomycin commonly retains activity against extended spectrum beta-lactamase (ESBL) producing organisms and  carbapenem-resistant enterobacteriaceae (CRE).

Notable PK1,2
     Absorption- Fosfomycin’s oral bioavailability is approximately 30-37%. Due to the limited systemic absorption, use in pyelonephritis, peri-nephric abscess, or any systemic infection is contraindicated.
     Distribution- Due to limited systemic absorption, it is expected that oral fosfomycin has minimal tissue distribution.

Adverse Effects of Significance 2
Fosfomycin is generally very well tolerated. The most common adverse effects include diarrhea, nausea, and headache, which happen to be common adverse effects of most drugs.

Fosfomycin in Pregnancy 1
Adverse events have not been observed in animal reproduction studies. Several studies have used a single dose of fosfomycin for the treatment of asymptomatic bacteriuria in pregnant women with no adverse fetal effects reported. Fosfomycin is classified as a pregnancy category B drug.

Preparation and Administration 1,2
The contents of each 3g sachet should be poured into 3-4 ounces (½ cup) of cold water and stirred until completely dissolved. Hot water should not be used. The solution should be administered by mouth immediately after it is prepared.

Potential Roles of Fosfomycin
Fosfomycin is a first line option for uncomplicated cystitis per the current IDSA guidelines for the treatment of uncomplicated cystitis. However, we have no shortage of agents for uncomplicated cystitis, many of which are less expensive, narrower in spectrum, and more readily available at a typical community pharmacy than fosfomycin. Where fosfomycin really presents a unique option is in the following situations:


Potential Role
Fosfomycin In-vitro susceptibility
Clinical Cure Rate
ESBL cystitis3,4,5,10,16  
95.1-100%
93%
VRE cystitis* 6,7,8,9,10,16
86-98.7%
82%
CRE cysitis† 10,11,16
73.5-93%
-
Pseudomonal cystitis† 10,14
75-85%
-
Patients with multiple severe allergies or predisposing factors that limit other options13,14,15,17,18


E.coli: 94-100%
(non-ESBL/CRE)


91.1-96%
Patients at high risk for noncompliance 13,14,15,17,18
*One study showed 77% in-vitro susceptibility with an additional 21% intermediate          †Due to the lack of acknowledged fosfomycin breakpoints for bacteria other than E. coli and E. faecalis, results were interpreted according to criteria for E.coli and E. faecalis (i.e. susceptible at a MIC ≤64 g/ml)

Despite promising in-vitro data for the treatment of CRE and Pseudmonal cysitits there is limited clinical data for use against these pathogens. Patients should be carefully selected when using fosfomycin in these situations.

Drug-Drug Interactions
Medications used to increase gastrointestinal motility (e.g. metoclopramide) may decrease oral absorption of fosfomycin, thus reducing its efficacy.

Help with Adding to Formulary

Susceptibility Testing
Most microbiology laboratories do not routinely perform susceptibility testing for fosfomycin. Send outs usually take some time, and in my experience I rarely receive the results before the patient has finished their course of fosfomycin. Meaning the results weren’t useful in that we already clinically knew if the treatment had worked or not. For this reason I generally don’t recommend send out fosfomycin susceptibilities, even when using fosfomycin for a pathogen for which it has variable activity.

Other Tips
     Team up with your inpatient colleagues- They have just as much incentive to want fosfomycin available. Fosfomycin can prevent admissions solely for IV antibiotic therapy to treat MDR-pathogens for which no other oral options are available, this is important to us from an ED perspective. From an inpatient perspective fosfomycin may help facilitate the discharge of a patient receiving IV antibiotics for MDR-pathogens. It’s a great way to build relationships and having multiple areas of the institution pushing for fosfomycin make it difficult to say no.
     Reach out to local pharmacies-  Ask them to stock fosfomycin so you have a go to place for patients to get it. Preferably something close to the ED.
     Work with case management- Many insurances require a prior authorization to cover fosfomycin. Pharmacies in my area charge about $90 per dose without insurance making it cost prohibitive for many patients. I’ve found case management to be extremely helpful in these instances.

Dosing Considerations1,2,10,12


Indication
Dose*
Uncomplicated UTI
3g PO x 1 dose
Complicated UTI
3g PO q48-72h x 3 doses
Prostatitis
3g q48-72h x 21 days

*There are no renal or hepatic doses adjustments for oral fosfomycin.





One Punch Knockout Too Good To Be True?
Huttner et al. recently published a study comparing clinical and microbiologic efficacy of nitrofurantoin 100mg po three times daily and fosfomycin 3g as a single dose in women with uncomplicated cystitis.19 They found clinical resolution through day 28 was achieved in 70% of patients receiving nitrofurantoin vs 58% receiving fosfomycin ([95% CI, 4%-21%]; P = 0.004). This calls into question if a single 3g dose of fosfomycin is adequate for the treatment of uncomplicated cystitis. Until there is a study to specifically answer this question, we will have to practice in a grey area. Here are some things to consider:

     MacroTID???- nitrofurantoin 100mg po twice daily is endorsed by the IDSA rather then the three times daily used in this study. Since the pharmacokinetic/pharmacodynamic index that best correlated to the antibacterial activity of nitrofurantoin against E.coli was T>MIC, increasing the frequency of nitrofurantoin dosing may make it an unfair comparison.20
     Most patients with MDR pathogens have complicated cystitis- in reserving fosfomycin primarily for MDR pathogens we will therefore primarily be using 3 dose regimens
     One dose of fosfomycin > zero doses of anything else- for non-compliant patients giving a single dose in the ED may be the only reasonable option


If you read nothing else:
     Fosfomycin is an often forgotten oral antibiotic available for the treatment of lower urinary tract infections.
     Fosfomycin retains activity against many MDR-pathogens such as ESBL, VRE, CRE, and Pseudomonas spp. making it an attractive oral option for cystitis caused by these pathogens.
     Despite being a first line recommendation for uncomplicated cystitis per IDSA guidelines, fosfomycin may not be ideal for the majority of these situations. It is more broad in spectrum of activity,  is more expensive, and is less commonly stocked in retail pharmacies then many other options for uncomplicated cystitis.
     Consider fosfomycin in patients with current or recent  history of MDR lower urinary tract infections, in patients with multiple drug allergies/predisposing factors that make other options not feasible, and/or in patients at high risk for noncompliance.
     Fosfomycin can prevent admissions solely for IV antibiotic therapy to treat MDR-pathogens for which no other oral options are available.
     Dosing of fosfomycin is unique in that uncomplicated UTIs may be treated with a single dose, though recent data has called this into question. Complicated UTIs should be treated with 3 doses.



Tony Mixon, PharmD, BCPS
Emergency Medicine/Infectious Disease Clinical Pharmacist




Peer reviewed by Craig Cocchio, PharmD, BCPS (@iEMPharmD), Nadia Awad, PharmD, BCPS (@Nadia_EMPharmD), and Scott Dietrich, PharmD (@PCC_PharmD)


References
1.)   Product Information: MONUROL(R) sachet oral solution, fosfomycin tromethamine oral solution. Zambon Switzerland Ltd, Cadempino, Switzerland, 2007
2.)   Lexicomp Online®, Lexi-Drugs®, Hudson, Ohio: Lexi-Comp, Inc.; February 1, 2018.
3.)   Pullukcu H, Tasbakan M, Sipahi OR, et al. Fosfomycin in the treatment of extended spectrum beta-lactamase-producing Escherichia coli-related lower urinary tract infections. Int J Antimicrob Agents 2007; 29: 62-5.
4.)   Rodriguez-Bano J, Alcala JC, Cisneros JM, et al. Community infections caused by extended-spectrum beta-lactamase-producing Escherichia coli. Arch Intern Med 2008; 168: 1897-902.
5.)   Auer S, Wojna A, Hell M. Oral treatment options for ambulatory patients with urinary tract infections caused by extended-spectrum-beta-lactamase-producing Escherichia coli. Antimicrob Agents Chemother 2010; 54: 4006-8
6.)   Varughese C, Tichy E, Topal J. Oral fosfomycin in the treatment of vancomycin-resistant enterococcal urinary tract infections. Abstract #215. IDSA Annual Meeting; October 21, 2011 Boston, MA.
7.)   Shrestha NK, Chua JD, Tuohy MJ, et al. Antimicrobial susceptibility of vancomycin-resistant Enterococcus faecium: potential utility of fosfomycin. Scand J Infect Dis. 2003; 35: 12-4.
8.)   Allerberger F, Klare I. In-vitro activity of fosfomycin against vancomycin-resistant enterococci. J Antimicrob Chemother 1999; 43: 211-7.
9.)   Perri MB, Hershberger E, Ionescu M, et al. In vitro susceptibility of vancomycin-resistant enterococci (VRE) to fosfomycin. Diagn Microbiol Infect Dis 2002; 42: 269-71.
10.) Neuner EA, Sekeres J, Hall GS, van Duin D. Experience with fosfomycin for treatment of urinary tract infections due to multidrug-resistant organisms. Antimicrob Agents Chemother 2012 ;56:5744-8.
11.) Endimiani A, Patel G, Hujer KM, et al. In vitro activity of fosfomycin against blaKPC-containing Klebsiella pneumoniae isolates, including those nonsusceptible to tigecycline and/or colistin. Antimicrob Agents Chemother 2010; 54: 526–9.
12.) Los-Arcos I,  Pigrau C, RodrĂ­guez-Pardo D, et al.  Long-term fosfomycin-tromethamine oral therapy for difficult-to-treat chronic bacterial prostatitis. Antimicrob Agents Chemother 2016 ; 60: 1854–58.
13.) Swiatlo E, Sells N, Chasta D et al. In Vitro Susceptibility of Common Urinary Tract Pathogens to Fosfomycin. Open Forum Infectious Diseases, Volume 1, Issue suppl_1, 1 December 2014, Pages S36
14.) Maraki S, Samonis G, Rafailidis P et al. Susceptibility of urinary tract bacteria to fosfomycin. Antimicrob Agents Chemother. 2009 Oct;53(10):4508-10
15.) Karlowsky JA, Denisuik AJ, Lagacé-Wiens PR et al. In Vitro activity of fosfomycin against Escherichia coli isolated from patients with urinary tract infections in Canada as part of the CANWARD surveillance study. Antimicrob Agents Chemother. 2014;58(2):1252-6
16.) Vardakas KZ, Legakis NJ, Triarides N, Falagas ME. Susceptibility of contemporary isolates to fosfomycin: a systematic review of the literature. Int J Antimicrob Agents. 2016 Apr;47(4):269-85.
17.) Stein GE. Comparison of single-dose fosfomycin and a 7-day course of nitrofurantoin in female patients with uncomplicated urinary tract
infection. Clin Ther. 1999; 21: 1864-72
18.) Bozkurt O, Kara C, Akarsu S et al. Comparison efficacy of single dose fosfomycin with ciprofloxacin in the treatment of urinary tract infection in symptomatic women. Turk Uroloji Dergisi 2008; 34: 360–2.
19.) Huttner A, Kowalczyk A, Turjeman A et al. Effect of 5-Day Nitrofurantoin vs Single-Dose Fosfomycin on Clinical Resolution of Uncomplicated Lower Urinary Tract Infection in Women: A Randomized Clinical Trial. JAMA. 2018 May 1;319(17):1781-1789
20.) Komp Lindgren P, Klockars O, Malmberg C et al. Pharmacodynamic studies of nitrofurantoin against common uropathogens.J Antimicrob Chemother. 2015 Apr;70(4):1076-82


Wednesday, July 25, 2018

BCPS Recertification: Follow Up

In two previous post, I outlined my impressions of High-Yield Med Reviews based on my experience going through the modules and webinar. While I still stand behind my evaluation of HYMR, my assessment was somewhat limited because it was all before the exam. Now that I have my scores, I feel I can give a more complete assessment of HYMR. In a nutshell: I passed, and highly recommend HYMR. 

In the final days before the exam, I was actually contemplating sitting for the full 200 question exam rather than the abridged recertification. My rationale was simply that I’d rather have more questions to attempt given the VAST amount of material that encompasses the pharmacotherapy exam. While I am glad I still went with the shorter version based on my result, my exam preparation had to consider that I couldn’t possibly cover all subjects of pharmacotherapy. Rather I took a more measured, calculated approach. With that in mind, I have a few tips to get the most out of studying with HYMR.

1) Get started early (3 months before) and do a little every day. It could be as little as 20 minutes, but getting in a regular habit of studying can have that initial 20 minutes stretch to an hour or two after a few weeks. With the format of the lecture modules from Dr. Busti, it’s easy to fit in at least one lecture during my morning run. For subjects like hypertension or asthma that I knew pretty well, I played them at 1.5x or 2x speed to review and slow down or rewind for elements I needed to hear again (ie, newish drugs, guideline updates, etc.)

2) Do as many practice questions as you can. Practice questions are the easiest way to identify weak areas, and brush up on your test taking skills. Similarly to the lectures, when you only have 5-10 minutes when your 10 month old is napping, you can bang out 5 questions and review the rationale, core concept and fast facts. Closer to the exam date, I set up ‘practice’ exams by selecting 200 randomized questions.

3) Don’t ignore practice management and regulatory issues. These are always the questions test takers talk about among each other after the exam. They aren’t difficult questions and there isn’t that much material. The succinct practice management modules are certainly a high-yield study tool.

4) It’s no secret that if you know stats inside out, you have a good chance of passing the exam. Spend time studying stats, participate in the webinars conducted with Dr. Busti, and read primary literature on a regular basis. These steps will ensure you’re able to answer any question.

5) Don’t forget, the reason you’re putting in all this effort is to become a better pharmacist! So constantly think of ways to implement your new knowledge (or reinforced knowledge) in practice through either direct patient care, clinical activities, or research.

Incorporating these five simple tips into your studying efforts with HYMR will ensure that you’re a) getting the most out of your investment, b) practicing efficient studying habits, and c) becoming a better clinician.

Disclosure:

I have a continuing partnerships with HYMR. I believe in Dr. Busti, and I am actively contributing to HYMR.

Friday, June 29, 2018

Choosing NOACs in the ED

Patient Case:
A 62-year-old female presents to the ED with left lower extremity pain and swelling and is diagnosed with a LLE deep vein thrombosis (DVT) on ultrasound. The patient’s past medical history is significant for hypertension and she takes amlodipine at home. Laboratory values, pulse oximetry, and vital signs are within normal limits. The ED physician approaches you about discharge anticoagulation options and asks for a recommendation. Which agent would you recommend for outpatient management of this patient’s DVT?

Background:
EM pharmacists are frequently involved in the drug selection, ordering, dose verification, and patient education regarding anticoagulants in the ED for admitted and discharge patients. We are in a unique situation in which we work closely with providers everyday to make our recommendation on the the best option for individual patients based on patient-specific factors, cost, potential drug interactions, and balancing safety with efficacy.

Since FDA approval of dabigatran in 2010, the NOAC class of anticoagulants has rapidly gained popularity. Zhu et al.1 recently published data concerning NOAC use among atrial fibrillation (AF) patients between 2010 and 2017. In 2017, they identified more than 7500 new patients started on an oral anticoagulant and 79% received a NOAC compared to 21% with warfarin. Of those NOACs, apixaban was the most common agent at 50.1%, followed by rivaroxaban at 25%, and dabigatran at 3.8%. With so many options available, how do you choose which agent to send your patient home on?

Efficacy and Safety Data
Based on the results of the industry sponsored trials, we know apixaban and rivaroxaban are non-inferior to warfarin,2-5 but what about compared to each other?

Lopez-Lopez et al. completed a systematic review and meta-analysis of all available Phase II and Phase III superiority and non-inferiority trials of NOACs and VKAs for stroke prevention in patients with AF.6 The best part about this study (aside from being open-access) was they actually compared each agent against each other. In terms of efficacy, rivaroxaban 20 mg daily was shown to be no different than apixaban 5 mg twice-daily in terms of stroke and systemic embolism, ischemic stroke, myocardial infarction, or all-cause mortality (see Table 1). When looking at safety outcomes, rivaroxaban was shown to increase the risk for major bleeding, GI hemorrhage, and clinically relevant bleeding compared to apixaban with no difference in intracranial hemorrhage (see Table 2).

Table 1: Indirect efficacy comparison of rivaroxaban and apixaban

Stroke or systemic embolism
Ischemic stroke
Myocardial infarction
All-cause mortality
Rivaroxaban 20 mg daily vs apixaban 5 mg BID,
OR (95% CI)
 1.11
(0.87-1.41)
1.01
(0.74-1.38)
0.92
(0.63-1.34)
0.94
(0.76-1.17)

Table 2: Indirect safety comparison of rivaroxaban and apixaban

Major Bleeding
Intracranial hemorrhage
Gastrointestinal hemorrhage
Clinically relevant bleeding
Rivaroxaban 20 mg daily vs
apixaban 5 mg BID,
OR (95% CI)
1.45 
(1.19-1.78)
1.55
(0.97-2.49)
1.66
(1.19-2.33)
1.53
(1.33-1.75)

What about real-world data? We know that Phase II and Phase III clinical trial results don't always translate equally to the general public, so how might these numbers change? Larsen et al. completed a large, retrospective, Danish study which extracted prescription data from three nationwide databases.7 Patients with AF were identified by first time purchases of NOACs or warfarin between 2011 and 2015. More than 122,000 patients were identified, and after exclusions approximately 62,000 patients were analyzed. Patients were mostly males aged 68 to 72 years with a CHADS2-VASC Score of 2.2-2.8. When compared to warfarin, there was no difference in hazard ratios (HR) for ischemic stroke or ischemic stroke + systemic embolism for apixaban compared to warfarin. Rivaroxaban showed a reduced HR compared to warfarin with the composite endpoint of ischemic stroke + systemic embolism (with the 95% CI upper limit at 0.99); but no difference in ischemic stroke alone. The composite endpoint of ischemic stroke + systemic embolism + death favored apixaban and rivaroxaban compared to warfarin (see Table 3).

In terms of safety outcomes including death, any bleeding event, and major bleeding events, HRs were lower with apixaban compared to warfarin, but not with rivaroxaban compared to warfarin (see Table 3). These trends favoring apixaban also continued when patients were stratified based on age of <65 or >65 years. Interestingly, intracranial hemorrhages with apixaban were no different compared to warfarin, but actually lower with rivaroxaban compared to warfarin in this cohort (see Table 3).

However, the original AMPLIFY2 and ARISTOLE4 trials both showed lower intracranial hemorrhage risk with apixaban compared to warfarin. Additionally, this systematic review and meta-analysis showed a lower ICH risk with apixaban vs warfarin and no difference between rivaroxaban vs warfarin.8 Taken together, I give the slight advantage to the RCT data over the Danish registry data given multiple trials with the same results and trust that apixaban is safer than warfarin.

Table 3: Real-world comparison of NOACs to warfarin
Apixaban vs Warfarin
HR (95% CI)
Rivaroxaban vs Warfarin
HR (95% CI)
Ischemic stroke + systemic embolism
1.08 (0.91-1.27)
0.83 (0.69-0.99)
Ischemic stroke
1.11 (0.904-1.3)
0.86 (0.72-1.04)
Ischemic stroke +
systemic embolism + death
0.79 (0.7-0.88)
0.87 (0.79-0.96)
Death
0.62 (0.56-0.75)
0.9 (0.82-1.03)
Any bleeding event
 0.63 (0.53-0.76)
0.99 (0.86-1.14)
Major bleeding
0.61 (0.49-0.75)
1.06 (0.91-1.23)
Intracranial hemorrhage
0.72 (0.42-1.24)
 0.56 (0.34-0.9)

Granted these data do not represent a direct, head-to head comparison between apixaban and rivaroxaban (and neither did the previous study as that data was generated via an indirect method). However, when the real world data closely mirrors clinical trial data with such large study populations, I feel fairly confident generalizing these overall trends when comparing apixaban and rivaroxaban against each other in terms of efficacy and safety.

Renal dosing concerns:
Both apixaban and rivaroxaban require renal dose adjustments. It is very important to note the dose cutoffs for each agent vary depending on the indication (AF vs VTE). Rivaroxaban can be utilized for AF patients with a CrCl > 15 ml/min but for VTE patients the cutoff is increased to a CrCl > 30 ml/min. Apixaban’s adjustments are based on serum creatinine and not necessarily a specific CrCl cutoff. Additionally, there is some data with reduced-dose apixaban showing similar AUCs in patients on hemodialysis as standard doses in patients with normal renal function.9 As only 4% of the drug was removed during a 4-hour HD session, it is unclear if the same dosing scheme of 2.5 mg BID could be applied to non-dialysis patients with significant chronic renal impairment.

Overall, check your drug references to ensure proper dosing given the varying cutoffs in CrCl, Scr, age, and indication used. If you have a patient in your ED with renal disease and for some reason they cannot (or refuse to) be treated with warfarin, choosing an alternative oral agent may be difficult. Among AF patients, rivaroxban’s lower CrCl cutoff of 15 ml/min should encompass a large number of potential patients. Alternatively, given the PK data of apixaban in HD patients, you could consider having a conversation with the provider and patient to decide if apixaban would be worth a try.

Drug interaction considerations:
Compared to warfarin, both apixaban and rivaroxaban have less concerns for drug-drug interactions. However, significant interactions do remain and the ED pharmacist should be vigilant to identify and correct such interactions. Both agents are substrates of CYP3A4 and P-glycoprotein (see Table 4 and Table 5). The most concerning interaction for either agent is with diltiazem and apixaban as is not uncommon for patients with atrial fibrillation to be maintained on diltiazem for rate control and therefore need long term anticoagulation. It’s unknown if the approximate 40% increase in apixaban AUC has any clinical significance, but for elderly patients, or those with a high bleeding risk, this combination should likely be avoided.

Table 4: Drug interactions with apixaban10,11
Drug
Dose
Change in apixaban AUC
Diltiazem
360 mg x10 days
↑ 40%
Ketoconazole
400 mg x6 days
↑ 100%
Naproxen
500 mg, single dose
↑ 50%
Rifampin
600 mg x11 days
↓ 54%


Table 5: Drug interactions with rivaroxaban12
Drug
Dose
Change in rivaroxaban AUC
Clarithromycin
500 mg BID x5 days
↑ 54%
Erythromycin
500 mg TID x5 days
↑ 34%
Ketoconazole
200 mg x3 days
↑ 53%
Ketoconazole
400 mg x5 days
↑ 2.6-fold
Rifampin
150 mg, 300 mg, 450 mg, then 600 mg x4 days
↓ 49%
Ritonavir
600 mg BID x6 days
↑ 2.5-fold


Cost considerations:
Given the relative “newness” of the NOACs, generic equivalents are not yet available. Therefore, as can be expected, these medications can be expensive. However, as they are no longer brand new, a larger percentage of private insurance and some state’s Medicaid Formularies will cover at least one NOAC. Additionally, cost-effectiveness analyses have shown favorable results with NOACs compared to warfarin, with apixaban conferring the greatest cost savings.13,14

In my home state of Colorado, the Medicaid Preferred Drug List still has warfarin as its first line option. However, rivaroxaban is a “preferred” agent, albeit second-line. Patients must meet some eligibility criteria to receive coverage, but we have not encountered any problems so far when properly selecting patients for discharge on rivaroxaban.

Most private insurance companies will cover at least one NOAC, likely more. According to Eliquis’s website, almost 95% of patients nationwide “have access to Eliquis.” They even have a tool for people to enter their state or ZIP code to find common prescription insurance plans in those areas to see if coverage is an option.

Luckily, our outpatient pharmacies associated with the hospitals have the ability to offer the first 30-days of therapy for either apixaban or rivaroxaban at no cost to the patient through manufacturer-sponsored programs. Although this is classic “drug dealing behavior,” we take advantage as frequently as possible. This one month of free therapy likely increases compliance which in turn would hopefully decrease the risk for return visits related to thromboembolic events. Additionally, the free month allows the patient to work with their insurance company to verify long term prescription coverage. If a different agent is required, it allows the patient time to meet with their PCP and set up the plan for change. Overall, these free “starter packs” are a great resource. Patients love being able to leave the ED with a 30-day supply of free medication and I’ll take any opportunity for the drug companies to give out free medication. It is unclear if this is available everywhere, but it may not hurt to contact a drug rep in your area to inquire about it if it is not something already available.

Which Agent to Choose?
Several points must be considered when choosing between rivaroxaban and apixaban. Both agents appear to be equally efficacious, but from a safety standpoint, apixaban is the winner in my book. Renal disease may preclude NOAC use, but for some patients rivaroxaban has a lower CrCl cutoff when used for AF than apixaban, so potentially slight advantage there. Cost considerations are very patient- and location-specific. Not mentioned thus far, but worth considering is the BID dosing of apixaban vs daily dosing with rivaroxaban. If patient compliance is a major concern, rivaroxaban will likely be preferred.

Consideration
Winning Medication
Efficacy
Apixaban = Rivaroxaban
Safety
Apixaban
Renal Dosing
Maybe rivaroxaban, varies by indication
Drug Interactions
Patient specific, unless on diltiazem then maybe favor rivaroxaban
Cost
Variable
Compliance
Rivaroxaban

Taken all together, there is a preferred agent in my book. Given similar efficacy, interaction potential, and medication costs, the major deciding factor is safety. Given the fact we don’t have a reliable reversal agent for Xa inhibitors at this point, and knowing the morbidity and mortality associated with major bleeding events, minimizing bleeding risk is of the utmost importance. Apixaban is a clear winner in this regard and is the reason I routinely recommend apixaban over rivaroxaban when both agents are options. In my experience so far, after having a discussion with the patient regarding the improved safety profile weighed against taking the medication twice daily, the vast majority of patients want the safer medication (and I would too). Even if the patient is only on once daily medications at home, you shouldn't rule out apixaban as they may want the safer option and just because a patient isn’t on a BID therapy doesn’t mean they can’t start now. Have a conversation, discuss the pros and cons, and give your patient all of the information to allow them to make the best decision.

Apixaban is likely the safest oral anticoagulant available, it is equally effective as other NOACs, and with more and more patients eligible for prescription coverage, it is my preferred oral anticoagulant.

Scott Dietrich, PharmD, BCCCP
Emergency Medicine Pharmacist
University of Colorado Health – North Region


*** Dabigatran Disclaimer ***
This post only mentions two oral anticoagulants. There are several more Xa inhibitors now available, but they are cost-prohibitive at this point. The other alternative NOAC is dabigatran. As mentioned above, in 2017, < 4% of new NOAC prescriptions were for dabigatran.1 Why? According to a series of 2014 BMJ articles,15,16 the manufacturer of dabigatran, Boehringer  Ingelheim, withheld information regarding the potential utility of serum drug monitoring. The confidential internal documents were only made available during the litigation process in the US. Though not published within the initial RE-LY trial, there was a large sub-study within RE-LY that measured serum drug levels.17 While only analyzing patients receiving the 150 mg BID dose of dabigatran, researchers found a extraordinarily wide variability in measured plasma concentrations. After 30 days of therapy, plasma levels ranged from 2.3 ng/ml to a max of 1000 ng/ml. After some adjustments, the researchers determined there was a 5.5-fold variability amongst the population. While there was a negligible decrease in event rates with higher plasma levels, there was a clear linear relationship with increasing bleeding event rates (see figure below).14 Despite this, the drug company did not recommend routine drug level monitoring to ensure safety even though the company determined that measuring and appropriately dosing dabigatran could reduce major bleeding by 30-40%.16 Overall, this medication is not as safe as apixaban6 and given the unethical behavior of the manufacturer and likely requirement for drug level monitoring to ensure safety, I am not recommending dabigatran in anyone at this time.





































References:
  1. Zhu J, Alexander GC, Nazarian S, Segal JB, Wu AW. Trends and variations in oral anticoagulant choice in patients with atrial fibrillation, 2010-2017. Pharmacotherapy. 2018, June [epub ahead of print]
  2. Agnelli G, Buller HR, Cohen et al. Oral apixaban for the treatment of acute venous thromboembolism (AMPLIFY). NEJM. 2013;29;369(9):789-808
  3. Prins MH, Lensing AW, Brighton TA, et al. Oral rivaroxaban versus enoxaparin with vitamin K antagonist for the treatment of symptomatic venous thromboembolism in patients with cancer (EINSTEIN-DVT and EINSTEIN-PE): a pooled subgroup analysis of two randomised controlled trials. Lancet Haematology. 2014;1(1):e37-46
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