This study aims to determine the efficacy of montelukast in reducing the incidence of dengue warning signs in adult dengue patients.

Dengue has been the growing public health problem in many tropical countries. Almost 4 billion people were estimated to be at risk, with estimated 400 million infections occurring annually. In Asia, around 10% of febrile patients were virologically confirmed with dengue. The most common cause of death is from dengue shock as a result of vascular leak syndrome. This condition can occur in various clinical manifestations ranging from mild cases to life-threatening condition of dengue shock syndrome. The common sites of plasma leakage are pleural effusion and ascites. The contributing factors for endothelial dysfunction in dengue are cytokines such as soluble tumor necrosis factor receptor (sTNFR/75), interferon gamma, and vascular endothelial growth factor, NS1 antigenemia, complement activation, and activation of dendritic cells, macrophages, and mast cells.

Mast cells have recently been acknowledged as an important regulator for promoting innate immune responses. Important composition of granules in mast cells are proteases, chymase and tryptase, histamine, heparin and leukotriene. The activated mast cells can undergo degranulation, releasing these cytokines. These increase capillary permeability, leading to vascular leakage.

Leukotriene has an important role in promoting plasma leakage and leukocyte adhesion in postcapillary venules. In dengue patients, leukotriene levels usually elevate during febrile and defervescence stage for 35 and 38 times of the baseline values, and return to baseline in convalescence stage. Blocking leukotriene in dengue infected mice can significantly reduce plasma leakage.

The management of dengue consists of only symptomatic treatment, and intravenous fluid replacement. No specific treatment has yet been demonstrated of a benefit in preventing complications. In the recent decades, mast cells have been demonstrated as a major contributor of severe forms of dengue, leading to research in reduction of vascular permeability with mast cell stabilizers or anti-histamine drugs. An animal model studies found that a tryptase inhibitor, nafamostat, or leukotriene inhibitor, montelukast, could reduce the plasma leakage.

In 2018, an open-label study found that patients with montelukast had a 22% absolute risk reduction in dengue shock syndrome, compared to standard treatment. However, there has never been any randomized controlled trial evaluating the efficacy of montelukast in dengue patients.

This study aims to determine the efficacy of montelukast in reducing the incidence of dengue warning signs in adult dengue patients.

Inclusion Criteria:

• at least 18 years old
• diagnosis of dengue
• positive NS1 antigen or polymerase chain reaction (PCR) test

Exclusion Criteria:

• any warning sign of dengue
• concurrent diagnosis of other causes of fever, such as malaria or heat stroke
• pregnancy
• being unable to take medication by mouth
• critical illness needing intubation or admission to an intensive care unit
• being unable to communicate
• other indication of montelukast

Data requests can be made anytime from 6 months after the publication of this trial. De-identified participant data can be requested by researchers for use in independent scientific research and will be provided following review and approval of the research proposal (including statistical analysis plan).

starting 6 months after publication

De-identified participant data can be requested by researchers for use in independent scientific research and will be provided following review and approval of the research proposal (including statistical analysis plan). Requests should be sent to the corresponding author after publication.