Torsemide seems to top furosemide for heart failure

I had done a blog many years ago of a review article arguing that torsemide was a more useful loop diuretic overall, and specifically in heart failure, than our much more commonly used furosemide (see Wargo KA. Ann Pharmacother 2009;43:1836-47).  A recent review article on "Diuretic Treatment in Heart Failure (see Ellison D. N Engl J Med 2017;377:1964​) commented that "when administered orally, furosemide has a limited and highly variable bioavailability (mean, approximately 50%, range 10 to 90)" and as a result the IV dose is half the po dose, food delays its absorption, the half-life for its excretion is shorter than its GI absorption rate, and in those with acute decompensated heart failure, a higher peak level may be required (and necessitating an IV dose, though gut edema may contribute some to this). In contrast, torsemide has a higher and more consistent oral bioavailability of >90% (so its po and IV doses, for example, are the same), and a longer half-life in patients with heart failure (6 hours vs 2.7 house with furosemide)

The actual clinical difference between the 2 drugs is a bit less clear (available data are limited), but:
--a systematic analysis found that torsemide, vs furosemide, reduced hospital admissions for heart failure (see DiNicolantonio JJ. Future Cardiol. 2012;8(5): 707). In 417 patients with systolic heart failure randomized to torsemide vs furosemide: total heart failure readmissions with torsemide were decreased by 59%, RR 0.41 (0.28-0.61, p<0.0001), and heart failure readmissions as well as cardiovascular readmissions in patients with "at least one readmission" were decreased by 47% (p=0.008) and 23% (p=0.03), respectively. One of the studies also found a significant decrease in hospital days for heart failure (total of 296 for furosemide group vs 106 for torsemide), with patients receiving 136 mg furosemide vs 72mg of torsemide, the usual 2:1 ratio (p=0.02, see Murray MD. AmJMed. 2011; 111:513. ) And there was a 14% trend to decreased all-cause mortality. Studies have also found significantly less fatigue with torsemide.

-- the TORIC study (Torsemide in Congestive Heart Failure), an open-label study of 1,337 patients with NYHA class 2-3 heart failure, found that torsemide vs furosemide led to a greater improvement of functional class (45.8% vs 37.2%, p<0.00017) and lower all-cause mortality (2.2% s 4.5%, p<0.05). see Bikdeli B. JACC 2013; 61: 1549.

--a few studies have documented that torsemide, as opposed to furosemide, inhibits the renin-angiotensin-aldosterone system (eg Uchida T. Cardiology 1994; 84 (Suppl 2):14). The heart failure studies showing benefit of torsemide over furosemide were despite high levels of concomitant ACE-I usage (?synergistic effect with ACE-I’s). One study reported much less hypokalemia with torsemide vs furosemide, with 3% vs 30% requiring potassium supplementation, despite the improved clinical efficacy of torsemide.  ???related to its RAS inhibition effects

--studies done in patients with cirrhosis also showed significant increase in diuresis vs furosemide, and another study of patients with pulmonary hypertension found a greater decrease  in RV stroke volume with torsemide

--One issue this brings up is the strong effect of local culture in medicine.  In our training and afterwards, we clinicians tend to accept the local approach to care, partly because that's what we learn and partly because it is reinforced by the local medical role models. One of the more interesting findings if we train in different areas of the US is that there can be pretty different approaches to care. It  is humbling to know that there is not always one "correct" answer. Or perhaps that what we do in Boston may in fact be a bit less good than what the comparative data suggest.

-- these articles on torsemide do challenge one of these local "wisdoms".  From my assessment of the literature, it does seem that torsemide may well be a better choice as a loop diuretic. It is more reliably absorbed, has a longer half-life, has the additional putative mechanism of RAS inhibition, and seems to have better clinical outcomes than furosemide (perhaps directly related to these features).  I had switched to using torsemide after I saw the 2009 review noted above, and it has been a seemless transition away from furosemide (ie, it works well and is well-tolerated).

so, seems reasonable to me to switch from furosemide to torsemide. Likely benefit, with no evident downside from what I can see…. [and, they are both generics, with very similar prices to consumers, at least for someone on Medicaid in Massachusetts, not sure how that translates to other insurers or other areas]

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