Curative Effect and Safety of Tolvaptan Combined with Traditional Diuretics in Treatment of Patients with Cirrhotic Ascites and Relevant Research on its Dose: A Systematic Review with Meta-Analysis of Randomized Controlled Trials

Background: Tolvaptan is a receptor antagonist of highly selective vasopressin V2, and it can promote excretion of water without electrolyte. Aims: To evaluated curative effect and safety of Tolvaptan in treatment of cirrhotic ascites, and its relationship with drug dose. Methods : Computer retrieval of PubMed, EMbase and The Cochrane Library was carried out to search the clinical trials of cirrhotic ascites treatment by Tolvaptan. The time limit of retrieval is from the database setup to May 31, 2019. 2 researchers independently screened studies, extracted the data and crosschecked. RevMan 5.3 software was used for Meta-analysis. Results : Finally, 6 articles and 848 patients were included in the study. Meta-analysis indicates that after the intervention for 7 days, serum sodium ion concentration of the combined diuretic group obviously increased, compared with the traditional diuretic group (WMD=2.92mmol/L, 95%CI [2.15, 3.70], P<0.001). In addition, Tolvaptan also can decrease patients’ ascites amount through increasing liquid discharge. However, the drug dose has no obvious correlation with the reduction degree of ascites amount. The rise of blood uric acid is the major adverse event in the treatment of cirrhotic ascites patients by Tolvaptan (OR=6.01, 95%CI [1.11, 32.56], P=0.04). When the dose of Tolvaptan rose to 15mg or 30mg, the total incidence of adverse events was obviously higher than it of traditional diuretic group. Conclusion : Tolvaptan combined with traditional diuretics has good curative effect for the patients with cirrhotic ascites. As its adverse reactions, the recommended dose of Tolvaptan is 7.5mg in the combined therapy. in treatment its drug dose, this study reviews the randomized treatment of cirrhotic ascites. encephalopathy, insomnia, increase of blood uric acid, and hypokalemia); dose-related

Computer retrieval of PubMed, EMbase and The Cochrane Library was carried out to search the clinical trials of cirrhotic ascites treatment by Tolvaptan. Retrieval time limit from database Settings to August 31, 2019 Meanwhile, supplementary retrieval of research data was conducted, including WHO clinical trial registry platform (http://apps.who.int/trialsearch), Chinese clinical trial registry platform (http://www.chictr.org.cn) and American clinical trial registry library (https://clinicaltrials.gov). Retrieval time limit from database Settings to August 31, 2019.
Furthermore, the references included in the papers were traced to supplement and gain relevant studies. The subject terms and free words were combined for the retrieval. The search terms contains Tolvaptan, Samsca, Jinarc, Jynarque, OPC41061, OPC 41061, OPC-41061, and Ascites. The search algorithm is ((Tolvaptan or Samsca or Jinarc or Jynarque or OPC41061 or OPC 41061 or OPC-41061) and Ascites). Literature retrieval is not restricted by language.

Study screening and data extraction
2 researchers independently screened studies, extracted the data and cross-analyzed them.
Differences should be resolved through discussion and consultation. During the screening period, the title was read for the first time. After excluding apparently unrelated studies, the abstract and full text are further read to determine whether the article was included. If necessary, the original authors could be contacted by email and telephone for information that is uncertain but important in this study. The extracted data include (1) research features, including the first author, publication year, country, random method, blind method and duration of mediation (research period); (2) general features of patients, including the number, age and gender in each research group; (3) therapeutic evaluation indexes, including the changes of serum sodium ion, bodyweight abdominal girth, and ascites amount as well as the change in urine volume on the first day of medication; (4) safety evaluation indexes, including total incidence of adverse events, total incidence of severe adverse events, and the incidence of various common adverse events (diarrhea, frequency of urination, fever, hepatic encephalopathy, insomnia, increase of blood uric acid, and hypokalemia); (6) dose-related safety evaluation indexes and therapeutic evaluation indexes: the occurrence rates of safety evaluation indexes and therapeutic evaluation indexes under different dose were collected.

Methodological quality evaluation
The two researchers assessed the risk of bias within the study. According to the Cochrane Handbook for Systematic Reviews of Interventions, 2011) [15], the evaluation indexes include: ① selection bias, random sequence generation and allocation concealment; ② implementation, the blind method was implemented for the researchers and subjects; ③ measurement, evaluation of research results with the blind method; ④ follow-up visit, integrity of result data; ⑤ reporting, selective reporting of research results; ⑥ others. If the above indexes are of low risks, the study is evaluated as low bias risk, and other results are considered to have high bias risk.

Statistical method
RevMan 5.3 software (The Nordic Cochrane Centre, Copenhagen, Denmark) was used for Metaanalysis.The weighted mean difference (WMD) was used as the effect quantity in the continuous outcome data. For the result data of dichotomy, the odds ratio (OR) was used as the effect size. The point estimate and 95% credibility interval (95% CI) were given for each effect size. The heterogeneity of research results was analyzed by χ 2 test, and the heterogeneity degree was quantitatively determined by combining I 2 . P<0.10 or I 2 >50% were considered as significant heterogeneity. The publication bias of all end points was first judged by the funnel plot. Then, Egger test was adopted for quantitative assessment. P<0.05 means the difference is statistically significant.

Study screening and bias analysis
Based on the above search method, a total of 220 qualified literatures were found.. A total of 46 articles were retrieved by reading and removing abstracts of the studies that did not meet the inclusion criteria. They were downloaded, read and further assessed. Among them, 32 references are non-RCT researches; There were no objective indexes in 6 literatures; two references are of abstract form, without objective outcome indexes. The detailed screening process is shown in Fig 1. Finally, 6 articles [16][17][18][19][20][21] were eventually included, with a total of 848 patients (table 1). Among them, 530 patients received Tolvaptan treatment, and there were 318 persons in the control group.
3 studies do not explain the detailed and specific randomization methods, and the other 3 studies interpret the randomization methods, including random number generated by the computer and center randomization. 4 articles describe the specific allocation scheme hiding method. 5 studies were double-blind and 1 was triple-blind. 5 articles report the changes in serum sodium ions, and 5 articles report the overall incidence of adverse events. All articles describe specific follow-ups, including the number and reasons of patients without follow-up visit. All studies are registered in the clinical database. The risk of bias in the study is shown in Supplement Fig 1.

Curative effect
To evaluate the curative effect, the changes in serum sodium concentration, average body weight, average waistline and average ascites amount and changes in urine volume 7 days after intervention were compared between the two groups on the first day of intervention and the last day.
Meta analysis indicates that after 7 days of intervention, the serum sodium concentration of the combined diuretic group was significantly higher than that of the conventional diuretic group (WMD=2.92mmol/L, 95%CI [2.15, 3.70], P<0.001, Fig 2D). There was a significant heterogeneity (I 2 =61%, Fig 2D), sensitivity analysis showed that I 2 was 4% when Isao 2014 was removed (Supplement Fig 2A).
In terms of the minor indexes, the changes in the average weight, average waistline and average ascites amount are reported in 4 studies (499 patients) [17][18][19][20], 3 studies (440 patients) [17][18]20], and 2 studies (216 patients) [17,19], respectively. Four studies (498 patients) reported changes in urine volume on the first day of intervention and on the last day of intervention [16][17][19][20][21]. After In the subgroup analysis, with the increase of Tolvaptan rose (7.5mg-15mg-30mg), the serum sodium concentration in the combination diuretic group also increased significantly ( Fig 3A). However, the increase in Tolvaptan dose did not cause significant changes in body weight ( Fig 3B) and abdominal circumference ( Fig 3C). In general, the rise of Tolvaptan dose resulted in limited improvement of curative effect for patients.

Safety
In safety evaluation, total incidence of adverse events, total incidence of severe adverse events, and the incidence of various common adverse events (diarrhea, frequency of urination, fever, hepatic encephalopathy, insomnia, increase of blood uric acid, and hypokalemia) in the both groups were mainly compared during the intervention. And, the occurrence rates of total adverse events, diarrhea and frequency of urination in different dose groups were evaluated. 5 studies report the total incidence of adverse events (including 620 patients) during the intervention [16][17][18][19][20]. Mate analysis result shows that the total incidence of adverse events was obviously higher than that of traditional diuretic group (OR=1.98, 95%CI [1.11, 3.52], P=0.02, Fig 5A). There was a significant heterogeneity (I 2 =50%, Fig 4A), sensitivity analysis showed that I 2 was 0% when Haruki 2017 was removed (Supplement Fig. 1B).
In the subgroup analysis of adverse events, we found no statistical difference in the total incidence of adverse events between the combined diuretic group and the conventional diuretic group when the daily dose of the combined diuretic group was maintained at 7.5mg (OR=1.  Fig 4C), the total incidence of adverse events in the combined diuretic group was significantly higher than that of traditional diuretic group. In terms of the incidence of severe adverse events, there was no statistical difference between the two groups (OR=1.05, 95%CI [0.60, 1.84], P=0.88, Fig 4B).  [18,20] report the occurrence rate of blood uric acid rise in the intervention process. The combined diuretic group was significantly higher than that of traditional diuretic group (OR=6.01, 95%CI [1.11, 32.56], P=0.04, Fig 5A).Although the frequency of urination and the incidence of thirst were not statistically different between the two groups (Supplement Table 1), the subgroup analysis shows that when the daily dose of Tolvaptan reached 15mg or 30mg, the occurrence rates of frequency of thirst ( Fig 5B) and urination (Fig 5C) in the combined diuretic group were obviously higher than those of traditional diuretic group.

Discussions
In this study, compared with the traditional diuretic group, the combination of Tolvaptan and traditional diuretics can effectively increase the serum sodium level of patients with cirrhotic ascites.
As the dose increased, the increase degree of serum sodium level also rises. In addition, Tolvaptan also can decrease patients' ascites amount (weight, abdominal girth and ascites amount decrease, while the urine volume on the first day increases) through increasing liquid discharge. However, there was no significant correlation between drug dosage and the degree of reduction of abdominal water volume. Meanwhile, the rise of blood uric acid is the major adverse event in the treatment of cirrhotic ascites patients by Tolvaptan combined with traditional diuretics. The rise of Tolvaptan dose did not increase the occurrence rates of severe adverse events and various common adverse events. When the dose of Tolvaptan was controlled at 7.5mg, the total incidences of adverse events in both groups was not abnormal. However, when the dose of Tolvaptan rose to 15mg or 30mg, the total incidence of adverse events, and the occurrence rates of frequency of urination and thirst were obviously higher than those of traditional diuretic group.
Although the meta analysis of changes of overall serum sodium in our study showed high heterogeneity, the sensitivity analysis found that it was mainly caused by Isao 2014, which focused only on 7.5mg Tolvaptan, while changes of overall serum sodium combined the results of 7.5-30mg Tolvaptan in the other four studies. The results of subgroup analysis can also explain this high heterogeneity, that is, Isao 2014 did not cause heterogeneity at 7.5mg tolvaptan. Due to its low therapeutic dose, the incidence of total adverse events was reduced, resulting in high heterogeneity in meta analysis of total adverse events.
The common complications of liver cirrhosis include refractory ascites, hyponatremia and hepatic encephalopathy, etc. Especially when the above complications happen to the patients with liver cirrhosis, the death rate will also increase greatly [22]. Tolvaptan is a drug approved by FDA for the treatment of hyponatremia. But multiple countries including China still have not approved it to treat cirrhotic ascites. At present, there are only 6 RCT studies on the patients with cirrhotic ascites who are treated by Tolvaptan [16][17][18][19][20][21]. The curative effect and safety of Tolvaptan in treatment of cirrhotic ascites are still unclear, and there is conclusive evidence that it is not recommended. Moreover, hyponatremia caused by traditional diuretics are also denounced all the time. Some studies also verify that the patients with cirrhotic ascites combined with hyponatremia are closely associated with high mortality [23][24]. Thus, serum sodium level is an important index which cannot be ignored in treatment of cirrhotic ascites by diuretics. The data from this study showed that the application of Tolvaptan significantly improved hyponatremia in patients. Besides, with the increase of Tolvaptan dose (7.5-30mg), the increase degree of patients' serum sodium level also rises.
At the same time, after the use of traditional diuretics, the diuresis effect is not obvious (refractory ascites), which is another problem in the treatment of cirrhotic [25][26]. In particular, inappetence, abdominal distension, dyspnea and other symptoms resulting from lots of ascites seriously affect patients' daily life [2]. So, for the patients with cirrhotic ascites, Tolvaptan combined with traditional diuretics is considered to be a new target for cirrhotic ascites treatment, and its liquid discharge curative effect receives much attention. The results of this study show that compared with pure use of traditional diuretics, Tolvaptan combined with traditional diuretics can significantly increase patients' urine volume (liquid discharge) to reduce ascites amount, indicating that the combined therapy has a better effect on reduction of ascites. In particular, we should encourage the use of it to treat the patients with refractory ascites. However, in terms of reducing the amount, the increase in daily dose of Tolvaptan fails to improve curative effect.
In addition to the good curative effect, complications caused by torvatan are also of great concern.
Existing RCT researches report the daily application of low-dose Tolvaptan (7.5mg or 15mg) promotes 6-month survival rate of patients with cirrhotic ascites [21], and a latest meta analysis also reported that Tolvaptan could significantly improve overall survival rate [13]. However, the concrete complications in the use have not been confirmed by a large number of data. This study demonstrates that it is safe when the daily dose of Tolvaptan is maintained at 7.5mg. The total incidence of adverse events, the incidence of severe adverse events and the incidence of various complications excluding the rise of blood uric acid have no significant differences with those of traditional diuretic group. When the daily dose of Tolvaptan exceeds 15mg, the total incidence of adverse events is obviously higher than that of traditional diuretic group. Especially, the occurrence rates of frequency of urination and thirst rise obviously. Although a previous meta analysis reported that Tolvaptan did not affect mortality and complications in patients with cirrhosis [11] and our study showed that the incidence of severe adverse events has no obvious difference with that of traditional diuretic group, it should be more prudent to apply high-dose Tolvaptan combined with traditional diuretics in treatment of patients with cirrhotic ascites. Furthermore, regardless of Tolvaptan dose, the rise of blood uric acid is the major complication of Tolvaptan combined with traditional diuretics.
The specific mechanism still remains to be further demonstrated.
Early meta studies for Vaptan drugs (including Tolvaptan, Satavaptan and Lixivaptan) reported that Vaptan drugs was not associated with prolonged survival in patients with cirrhosis [11][12]. In contrast, a recent meta analysis based on retrospective studies showed that Tolvaptan significantly improves overall survival in patients with cirrhosis and refractory ascites, but this paper has not a high level of evidence [13]. Given the good efficacy and safety of 7.5mg Tolvaptan demonstrated in this study, more RCT studies to study Tolvaptan and survival rates in patients with cirrhotic ascites should be performed to support the prognostic role of tolvaptan.
The limitations of this study are mainly as follows: 1. Currently, there are still few RCT studies on the treatment of cirrhotic ascites with Tolvaptan, and indexes of each study are not completely consistent; 2. Some studies did not research the relationship between dose and efficacy or safety, so the sample size of dose-related studies was small. In the future, we expect to conduct a larger sample of RCT study on the treatment of cirrhotic ascites with Tolvaptan.
Tolvaptan combined with traditional diuretics is effective in the treatment of cirrhotic ascites. When the dose of Tolvaptan is low (7.5mg), it is safe. However, from the safety results of high dose use (≥15mg) and the results of dose-related studies, it can be seen that high dose of Tolvaptan does not bring better efficacy, but causes the higher incidence of adverse events. In combination therapy, the recommended dose of Tolvaptan is 7.5mg. In patients who did not respond to 7.5mg of Tolvaptan, the data do not support application of higher dose Tolvaptan. Besides, it is required to pay close attention to the changes of patients' blood uric acid in the drug use.

Conclusions
Tolvaptan combined with traditional diuretics is effective in the treatment of cirrhotic ascites. Due to its adverse effects, the recommended dose of Tolvaptan is 7.5mg in the combined therapy. Changes in serum uric acid should be monitored throughout the course of treatment whether the Tolvaptan dose is elevated. methodology guidance. FL was responsible for the management of original document screening. LM was responsible for the review and revision of draft. HX and ZZ were responsible for the screening of original document. WZ was responsible for research design and management. All authors read and approved the final manuscript.    A: The comparison between the combination diuretic treatment groups and the conventional diuretic treatment groups about the mean change of serum sodium concentration (mmol/L) after 7-days intervention for the different daily dose of Tolvaptan (7.5mg-15mg-30mg). B: The comparison between the combination diuretic treatment groups and the conventional diuretic treatment groups about the mean change of weight (Kg) after 7-days intervention for the different daily dose of Tolvaptan (7.5mg-15mg-30mg). C: The comparison between the combination diuretic treatment groups and the conventional diuretic treatment groups about the mean change of abdominal girth (cm) after 7-days intervention for the different daily dose of Tolvaptan (7.5mg-15mg-30mg).