Week 43 – Vancomycin vs. Metronidazole for C. Diff

“A Comparison of Vancomycin and Metronidazole for the Treatment of Clostridium difficile-Associated Diarrhea, Stratified by Disease Severity”

Clin Infect Dis. 2007 Aug 1;45(3):302-7. [free full text]

Clostridium difficile-associated diarrhea (CDAD) is a common nosocomial illness that is increasing in incidence, severity, and recurrence. This trial, initiated in 1994, sought to investigate whether metronidazole PO or vancomycin PO was the superior initial treatment strategy in both mild and more severe disease.

Population: patients with diarrhea (3+ non-formed stools within 24hrs) and either stool C. difficile toxin A positivity within 48hrs after study entry or pseudomembranous colitis per endoscopy

(Patients were dropped from the study if the toxin A assay resulted negative.)

Notable exclusion criteria: prior failure of CDAD to respond to either study drug or treatment with either study drug during the previous 14 days.

Stratification: Prior to treatment randomization, patients were stratified to groups of either mild (0-1 points) or severe (≥2 points) CDAD.

  • One point: age > 60, T > 38.3º C, albumin < 2.5 mg/dL, WBC >15k within 48hrs of enrollment
  • Two points: endoscopic evidence of pseudomembranous colitis or treatment in the ICU

Intervention: vancomycin liquid 125mg QID and placebo tablet QID x 10 days

Comparison: metronidazole 250mg PO QID and “an unpleasantly-flavored” placebo liquid QID x 10 days


  1. Cure = resolution of diarrhea by day 6 of tx and negative toxin A assay at 6 and 10 days
  2. Treatment failure = persistence of diarrhea and/or positive toxin A assay after 6 days, the need for colectomy, or death after 5 days of therapy
  3. Relapse = recurrence of CDAD by day 21 after initial cure


172 patients were randomized. 90 had mild disease, and 82 had severe disease. 22 patients withdrew from the study prior to completion of 10 days of therapy. This study analyzed only the 150 patients who completed the trial (81 with mild disease, 69 with severe disease). Within severity groups, there were no differences in baseline characteristics among the two treatment groups.

Among patients with mild disease, 37 of 41 (90%) metronidazole patients were cured and 39 of 40 (98%) vancomycin patients were cured (p = 0.36). Among patients with severe disease, 29 of 38 (76%) metronidazole patients were cured and 69 of 71 (97%) vancomycin patients were cured (p = 0.02).

Among patients with mild disease, 3 of 37 (8%) metronidazole patients relapsed and 2 of 39 (5%) of vancomycin patients relapsed (p = 0.67). Among patients with severe disease, 6 of 29 (21%) of metronidazole patients relapsed and 3 of 30 (10%) of vancomycin patients relapsed (p = 0.30).

Patients with mild CDAD had similar cure rates (> 90%) with oral metronidazole and oral vancomycin, however, patients with severe disease had higher cure rates with vancomycin than with oral metronidazole.

This randomized, placebo-controlled trial was the first trial comparing oral metronidazole and vancomycin in CDAD that was blinded and that stratified patients by disease severity.

The authors hypothesize that “a potential mechanism for our observation that metronidazole performs less well in patients with severe disease is that the drug is delivered from the bloodstream through the inflamed colonic mucosa, and stool concentrations decrease as disease resolves.”

Study limitations include single-center design, low N, high dropout rates, lack of intention-to-treat analysis, and slow recruitment (1994-2002). The slow recruitment and long duration of the trial is particularly notable, given that the organism itself, disease prevalence in community settings, host factors, and disease-inciting antibiotic regimens shifted significantly over this extended period.

At the time of publication of this study (2007), the CDC was not recommending vancomycin as first-line therapy for CDAD (for fear of spread of VRE).

Following this study, the 2010 update to the IDSA/SHEA guidelines for the treatment of CDAD recommended metronidazole PO for the initial treatment of mild-to-moderate CDAD, vancomycin 125mg PO QID for the initial treatment of severe CDAD, and vancomycin + metronidazole IV for severe, complicated CDAD.

However, both the disease and the evidence base for its treatment have evolved over the past 8 years. In March 2018, an update to the IDSA/SHEA guidelines was published. As a departure from prior recommendations, vancomycin 125mg PO QID (or fidaxomicin 200mg PO BID) x10 days is now the first-line treatment for non-severe C. diff. See Table 1 of these updated guidelines for a summary of pertinent definitions and treatment regimens.

Further Reading/References
1. Wiki Journal Club
2. 2 Minute Medicine
3. “Clinical practice guidelines for Clostridium difficile infection in adults: 2010 update by the society for healthcare epidemiology of America (SHEA) and the infectious diseases society of America (IDSA).”
4. “Clinical Practice Guidelines for Clostridium difficile Infection in Adults and Children: 2017 Update by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA).” Clin Infect Dis. 2018 Mar 19;66(7).

Summary by Duncan F. Moore, MD

Week 42 – IDNT

“Renoprotective Effect of the Angiotensin-Receptor Antagonist Irbesartan in Patients with Nephropathy Due to Type 2 Diabetes”

aka the Irbesartan Diabetic Nephropathy Trial (IDNT)

N Engl J Med. 2001 Sep 20;345(12):851-60. [free full text]

Diabetes mellitus is the most common cause of ESRD in the US. In 1993, a landmark study in NEJM demonstrated that captopril (vs. placebo) slowed the deterioration in renal function in patients with T1DM. However, prior to this 2002 study, no study had definitively addressed whether a similar improvement in renal outcomes could be achieved with RAAS blockade in patients with T2DM. Irbesartan (Avapro) is an angiotensin II receptor blocker that was first approved in 1997 for the treatment of hypertension. Its marketer, Bristol-Meyers Squibb, sponsored this trial in hopes of broadening the market for its relatively new drug.

Population: patients age 30-70 with T2DM, HTN, proteinuria (≥ 900mg/24hrs), and Cr 1.0-3.0 in women and 1.2-3.0 in men

Intervention: irbesartan, titrated from 75mg to 300mg per day

Comparison #1: amlodipine, titrated from 2.5mg to 10mg per day
Comparison #2: placebo

(All patients had a target SBP goal ≤ 135, and all patients were allowed non-ACEi/non-ARB/non-CCB drugs as needed.)

Primary – time to doubling of serum Cr, onset of ESRD, or all-cause mortality


  • individual components of the primary outcome
  • composite cardiovascular outcome – death from CV causes, nonfatal MI, hospitalization for CHF, CVA with permanent neurologic deficit, or lower limb amputation above ankle

1715 patients were randomized. Baseline characteristics were similar among the groups, except for a slightly lower proportion of women in the placebo group. The mean blood pressure after the baseline visit was 144/77 in the irbesartan group, 141/77 in the amlodipine group, and 144/80 in the placebo group (p = 0.001 for pairwise comparisons between irbesartan or amlodipine and placebo).

Regarding the primary composite renal endpoint, the unadjusted relative risk was 0.80 (95% CI 0.66-0.97, p = 0.02) for irbesartan vs. placebo, 1.04 (95% CI 0.86-1.25, p = 0.69) for amlodipine vs. placebo, and 0.77 (0.63-0.93, p = 0.006) for irbesartan vs. amlodipine.

The groups also differed with respect to individual components of the primary outcome. The unadjusted relative risk of creatinine doubling was 33% lower among irbesartan patients than among placebo patients (p = 0.003) and was 37% lower than among amlodipine patients (p < 0.001). The relative risks of ESRD and all-cause mortality did not differ significantly among the groups.

There were no significant group differences with respect to the secondary, cardiovascular outcome (see Table 3).

Sensitivity analyses were performed. Inclusion of baseline covariates in a Cox regression of the primary outcome did not alter the conclusions. Similarly, the conclusions of the primary analysis were not impacted significantly by adjustment for mean arterial pressure achieved during follow-up.

Hyperkalemia occurred in 1.9% of the irbesartan patients, but only 0.5% of the amlodipine patients and 0.4% of the placebo patients (p = 0.01 for both pairwise comparisons with irbesartan).

Irbesartan treatment in T2DM resulted in superior renal outcomes when compared to both placebo and amlodipine. This beneficial effect was independent of blood pressure lowering.

This was a well-designed, double-blind, randomized, controlled trial. However, it was industry-sponsored, and in retrospect, its choice of study drug seems quaint.

The direct conclusion of this trial is that irbesartan is renoprotective in T2DM. In the discussion of IDNT, the authors hypothesize that “the mechanism of renoprotection by agents that block the action of angiotensin II may be complex, involving hemodynamic factors that lower the intraglomerular pressure, the beneficial effects of diminished proteinuria, and decreased collagen formation that may be related to decreased stimulation of transforming growth factor beta by angiotensin II.”

In September 2002, on the basis of this trial, the FDA broadened the official indication of irbesartan to include the treatment of type 2 diabetic nephropathy.

This trial was published concurrently in NEJM with the RENAAL trial. RENAAL was a similar trial of losartan vs. placebo in T2DM, and demonstrated a similar reduction in the doubling of serum creatinine, as well as a 28% reduction in progression to ESRD.

In conjunction with the original 1993 ACEi in T1DM study, these two 2002 ARB in T2DM studies led to the overall notion of a renoprotective class effect of ACEis/ARBs in diabetes.

Enalapril and lisinopril’s patents expired in 2000 and 2002, respectively. Shortly afterward, generic, once-daily ACE inhibitors entered the US market. Ultimately, such drugs ended up commandeering much of the diabetic-nephropathy-in-T2DM market share for which irbesartan’s owners had hoped.

Further Reading/References
1. “The effect of angiotensin-converting-enzyme inhibition on diabetic nephropathy. The Collaborative Study Group.” NEJM 1993.
2. CSG Captopril Trial @ Wiki Journal Club
3. IDNT @ Wiki Journal Club
4. IDNT @ 2 Minute Medicine
5. US Food and Drug Administration, New Drug Application #020757
6. RENAAL @ Wiki Journal Club
7. RENAAL @ 2 Minute Medicine

Summary by Duncan F. Moore, MD

Week 41 – PROVE IT-TIMI 22

“Intensive versus Moderate Lipid Lowering with Statins after Acute Coronary Syndromes”

by the Pravastatin or Atorvastatin Evaluation and Infection Therapy–Thrombolysis in Myocardial Infarction 22 Investigators

N Engl J Med. 2004 Apr 8;350(15):1495-504. [free full text]

Statins are a cornerstone of therapy for the primary and secondary prevention of atherosclerotic cardiovascular disease. In the early 2000s, atorvastatin (Lipitor) was an immensely popular and profitable drug for its maker Pfizer. Notably, the 2001 MIRACL trial demonstrated that early use of high-intensity atorvastatin after UA/NSTEMI significantly reduced the risk of adverse cardiovascular outcomes at 16 weeks. In this context, Bristol-Meyers Squibb designed a non-inferiority trial to compare a relatively low dose of its new drug pravastatin (Pravachol) to high-intensity atorvastatin 80mg for the prevention of adverse cardiovascular outcomes following ACS.

Population: adults with ACS in the preceding 10 days, post-PCI (if planned/applicable), with total cholesterol < 240 (< 200 if already on lipid-lowering therapy)

Intervention: pravastatin 40mg PO daily

Note – the dose of pravastatin could be increased to 80mg daily in a blinded fashion if LDL remained > 125 mg/dL on two consecutive follow-up visits.

Comparison: atorvastatin 80mg PO daily (“intensive therapy”)

Primary – composite of all-cause mortality, MI, UA requiring rehospitalization, revascularization > 30 days after randomization, and stroke

The authors pre-specified an upper limit of non-inferiority as a 17% increase in the hazard ratio for the primary outcome within the pravastatin group at 2 years.


  • composite of death from CAD, non-fatal MI, or revascularization
  • composite of death from CAD or non-fatal MI
  • the individual components of the composite primary outcome

Subgroup analyses of primary outcome: sex, baseline LDL > 125, UA, MI, DM

4162 patients were randomized. Baseline characteristics were similar among the two groups, aside from a higher rate of peripheral arterial disease among the pravastatin group. Regarding the type of ACS, approximately 1/3 of cases were UA, 1/3 were NSTEMIs, and 1/3 were STEMIs. 69% of patients received PCI prior to randomization. Approximately 25% of patients were taking statins at the time of inclusion. At inclusion, the median LDL level was 106 mg/dL.

During follow-up, the median LDL level among pravastatin patients was 95 mg/dL and 62 mg/dL in the intensive therapy (atorvastatin) patients. Ultimately, 8% of pravastatin patients had their dose uptitrated to 80mg daily due to LDL levels remaining above 125 mg/dL.

At two-year follow-up, the primary composite outcome was noted in 26.3% of patients in the standard-dose pravastatin group but only 22.4% of the intensive-therapy atorvastatin group (ARR = 3.9%, p = 0.005, NNT = 25.6). Pravastatin therapy failed to meet its prespecified non-inferiority criteria; in fact, atorvastatin was decidedly superior.

The composite of death due to CAD, non-fatal MI, or revascularization was reduced by 25% in the atorvastatin group (p < 0.001). The composite of death due to CAD or non-fatal MI was not different among the two groups. Regarding individual components of the primary outcome: there was a 14% reduction in the need for revascularization and a 29% reduction in recurrent UA in the atorvastatin group (p = 0.04 and 0.02, respectively). There were no group differences in all-cause mortality, MI, or stroke. Discontinuation rates were 21.4% in the pravastatin group and 22.8% in the atorvastatin group (p = 0.11).

Among patients with recent ACS, high-intensity atorvastatin was superior to standard-dose pravastatin in preventing a composite of cardiovascular outcomes.

Bristol-Meyers Squibb had counted on this trial to show the non-inferiority of its new drug pravastatin to high-intensity atorvastatin in the secondary prevention of ASCVD. Instead, this trial established the dominance of high-intensity statin therapy for secondary prevention.

The treatment groups in this trial differed both by drug and by relative dosage intensity of the assigned drug. Whether the improvements in outcomes were from one or both of these factors is unknown. The marked group difference in LDL reduction correlates with these interventions and outcomes, but this paper does not establish a causal relationship between LDL reduction and improved cardiovascular outcomes.

The current standard of care is to initiate high-intensity statin therapy as early as possible after the diagnosis of ACS. Per UpToDate, atorvastatin 80mg is the best-studied high-intensity statin regimen and an excellent default. However, rosuvastatin 20mg or 40mg is an acceptable alternative. Their expert opinion also recommends adding ezetimibe 10mg daily in patients with LDL > 70 mg/dL despite high-intensity statin therapy.

Further Reading/References:
1. Wiki Journal Club
2. 2 Minute Medicine
3. UpToDate “Low density lipoprotein-cholesterol (LDL-C) lowering after an acute coronary syndrome”

Summary by Duncan F. Moore, MD

Week 40 – TORCH

“Salmeterol and Fluticasone Propionate and Survival in Chronic Obstructive Pulmonary Disease”

by the Towards a Revolution in COPD Health (TORCH) investigators

N Engl J Med. 2007 Feb 22;356(8):775-89. [free full text]

When the TORCH study was published in 2007, no prospective study to date had demonstrated a mortality benefit of inhaled corticosteroids (ICS) in COPD. Pulmonary inflammation occurs in COPD, and it had been hypothesized that ICS would improve COPD in multiple measures. Previously, ICS had been shown to reduce the frequency of COPD exacerbations, and retrospective data suggested that ICS reduced mortality, particularly when used in combination with a long-acting beta-agonist (LABA). TORCH was designed to evaluate prospectively the potential mortality benefit of combined ICS/LABA vs. ICS vs. LABA vs. placebo.

Population: COPD patients age 40-80, current or former smokers with ≥ 10-pack-year smoking hx, FEV1 < 60% predicted value and increase in FEV1 < 10% with albuterol administration, and prebronchodilator FEV1/FVC ratio of ≤ 70%

Intervention: combination salmeterol 50 µg and fluticasone propionate 500 µg BID


  1. placebo BID
  2. salmeterol 50 µg BID
  3. fluticasone 500 µg BID

Note: all patients underwent a two-week run-in period during which the use of all corticosteroids and long-acting bronchodilators was stopped. Other classes COPD medications were allowed throughout the study.

Primary – time to all-cause mortality by 3 years, per log-rank test


  • time to all-cause mortality, per Cox proportional hazards model
  • time to all-cause mortality, per log-rank test stratified by smoking status and country of residency
  • frequency of COPD exacerbations
  • quality of life per the St. George’s Respiratory Questionnaire
  • lung function, per postbronchodilator spirometry
  • incidence of pneumonia


6184 patients were randomized, but only 6112 were included in the final analyses (several sites excluded for not adhering to quality standards). The four groups were similar in all baseline characteristics (see Table 1).

All-cause mortality at 3 years was 12.6% in the combination-therapy group, 15.2% in the placebo group, 13.5% in the salmeterol group, and 16.0% in the fluticasone group. The hazard ratio for the comparison between combination-therapy and placebo was 0.825 (95% CI 0.681–1.002, p = 0.052, per log-rank test). See Figure 2B. This comparison was repeated in a pre-specified secondary analysis, using the Cox proportional hazards model, which yielded a HR of 0.811 (95% CI 0.670-0.982, p = 0.03), and in another pre-specified secondary analysis, using the log-rank test stratified according to smoking status and country of residency, which yielded a HR of 0.815 (95% CI 0.673-0.987, p = 0.04). In the primary analysis, the mortality risk did not differ among the salmeterol or fluticasone groups relative to the placebo group (see Table 2). Mortality risk in the combination-therapy group was less than that of the fluticasone group (HR 0.774, 95% CI 0.641-0.934, p = 0.007).

COPD exacerbations occurred at an annual rate of 0.85 in the combination therapy group and 1.13 in the placebo group, thus the rate ratio for exacerbations was 0.75 (95% CI 0.69-0.81, p < 0.001, NNT = 4). Exacerbation rates were also lower in the salmeterol and fluticasone groups (see Table 2).

The adjusted mean quality of life score per the St. George’s Respiratory Questionnaire improved in the combination-therapy, salmeterol, and fluticasone groups, and worsened slightly in the placebo group (see Table 3). All groups initially demonstrated an improvement in quality of life. In pairwise comparisons, combination therapy was superior to placebo, salmeterol, and fluticasone (p ranging from < 0.001 to 0.02).

Mean postbronchodilator FEV1 averaged over 3 years improved in the combination therapy group and decreased in the other groups. In all groups, the overall trend was a decrease in FEV1 following an initial improvement (see Figure 2E). In pairwise comparisons, combination therapy was superior to the other groups with respect to change in FEV1 (see Table 3).

The incidence of pneumonia was increased in groups receiving an ICS. The probability of developing pneumonia within the 3 year period was 19.6% in the combination-therapy group, 12.3% in the placebo group, 13.3% in the salmeterol group, and 18.3% in the fluticasone group (p < 0.001 for comparison between both combination-therapy versus placebo and fluticasone versus placebo).

44% of patients in the placebo group withdrew from the study. Only 34% of the combination-therapy group withdrew.

In this large, international, double-blind, placebo-controlled, randomized, parallel-group trial of patients with COPD, combination therapy with ICS/LABA did not improve mortality when compared to a placebo. However, combination therapy improved the frequency of COPD exacerbations, improved quality of life, and slowed the decline in FEV1 relative to placebo.

It is notable that, according to this study’s pre-specified secondary analyses of mortality per Cox proportional hazards and log-rank test stratified by smoking status and location, there was a mortality benefit of combination therapy.

The authors suspect that there is indeed a mortality benefit, but that the trial was underpowered to detect it. Furthermore, the higher rate of treatment-group withdrawal among placebo patients may have biased the study toward a null result, given the intention-to-treat analysis.

In the years since TORCH, meta-analyses that included TORCH have concluded that ICS therapy in COPD slows the rate of decline in FEV1 and decreases the rate of COPD exacerbations when compared with placebo, but it does not reduce mortality.

Today, inhaled corticosteroids remain an integral component of our management of moderate to very severe COPD. See the Global Initiative for Chronic Obstructive Lung Disease (GOLD) Pocket Guide to COPD Diagnosis, Management, and Prevention (2017) pages 14-16.

Further Reading/References
1. Wiki Journal Club
2. 2 Minute Medicine
3. UpToDate “Role of inhaled glucocorticoid therapy in stable COPD”
4. “Inhaled corticosteroids for stable chronic obstructive pulmonary disease.” Cochrane Database Syst Rev (2012).
5. Global Initiative for Chronic Obstructive Lung Disease (GOLD) Pocket Guide to COPD Diagnosis, Management, and Prevention (2017)

Summary by Duncan F. Moore, MD