Discussion
In the present post-marketing surveillance study with a large
sample size (1,057 patients as a cohort), the efficacy of tolvaptan,
including decrease in body weight, increase in urine volume,
and improvement of congestive symptoms, was reconfirmed
in the real-world clinic setting to be similar to that observed in
previous clinical trials. Serum sodium levels were elevated by
tolvaptan in hyponatremic patients at BL, but tolvaptan did not
significantly increase the serum sodium levels among the normonatremic
patients.
In Japan, a clinical trial in HF patients with volume overload
was conducted using 15, 30, and 45 mg/day of tolvaptan during
7 days in a dose-finding study.20 Next, the efficacy of tolvaptan
at 15 mg/day was compared with placebo in the QUEST study.18
After its launch onto the market, tolvaptan has been prescribed
for various HF patients in the real-world clinical setting, but
there has been no report so far confirming the efficacy of tolvaptan
under such real-world circumstances. In the present postmarketing
surveillance study, 1,057 HF patients with insufficient
response to loop diuretics participated in real-world therapy,
and the clinical efficacy (decreases in body weight and increases
in urine volume) of tolvaptan was reconfirmed as observed
in the QUEST study. In this study, these effects of tolvaptan
were maintained beyond the 14-day study period (Figure 1).
Furthermore, such clinical efficacy was associated with an improvement
of congestive symptoms that had been diuretic-resistant.
In the QUEST study, tolvaptan significantly improved
hepatomegaly and jugular venous distention after 7 days’ treatment,
but the improvement of lower limb edema and pulmonary
congestion was marginal. However, in the present study,
significant efficacy for all congestive symptoms was observed
within 7 days. In the real-world clinical setting, accumulated
experience with this drug may facilitate faster resolution of
patients’ symptoms; especially notable was that the proportion
of patients with dyspnea decreased by 50% at day 4 compared
with BL. The improvement in dyspnea was not evaluated in the
QUEST study. The early improvement in dyspnea observed in
this study is a clinically important result for physicians and patients,
because dyspnea is not only the most common cause for
hospitalization21 but also the most intolerable symptom.