One hundred sixteen records were identified from all databases. After completion of the study selection process, five studies (n = 3960) met the inclusion criteria (Table 1) [2, 4, 13, 15, 18]. All studies were conducted in high-income countries except one study  with centres from Africa, South America and the Middle East. Montelukast was given intermittently in four studies [2, 13, 15, 18]. Intermittent montelukast therapy was started by parents/caregivers, as a chewable tablet or oral granules (4 or 5 mg) over 12 months. In one study, in addition to episode-driven montelukast, daily montelukast therapy was also investigated .Table 1Characteristics of included studiesAuthorNOutcomesSide effectsNotes/biasNwokoro et al. Mk, 669PBO, 677P: USMAS: Number and duration of WE, duration of hospital stay, number of OCS courses, time to first USMA, symptomatic daysNone● Intermittent use ● ALOX5 (5/5 and 5/x + x/x) strata● 71.5% EVW● 21 primary and 41 secondary care sites in the UKBacharier et al. MK (4 mg), 95 BIS (1 mg), 96PBO, 47P: Proportion of EFDsS: Symptom score, caregiver QOL, numbers and time to first OCS course, number of WEs, number of USMA, linear growth, days missed from day care and parental workN/A●Intermittent use● 2:1 randomisation● More dropouts in Mk group● 5 clinical centres in the USABisgaard et al. Mk, 278PBO, 271P: Number of AEES: Number of oral and ICS courses, duration of episodes, percentage of days without asthma, severity of AEE, blood eosinophil count, proportion of patients with an AEE, time to first AEE, asthma-related resource utilisation1 case of vomiting due to Mk overdose● Continuous use● Subgroup analysis based on atopic profile and blood eosinophil count● 68 sites in 23 countriesRobertson et al. Mk, 107 PBO, 113P: USMAS: Individual components of USMA, duration of episode, symptom score, O CS and β-agonist use, days missed from parental work and school or childcare, number of nights with disturbed sleepNone● Intermittent use● More children with history of atopy in Mk group● Country: AustraliaValovirta et al. Daily Mk, 58912-day Mk, 591PBO, 591P: Number of asthma episodes culminating in asthma attacksS: Symptom score, number of asthma attacks and episodes, percentage of EFDs, difference in efficacy between 2 regimens1 case of somnolence due to Mk overdose● Intermittent and continuous use● Double dummy● 111 multinational sitesAll double-blind randomised placebo-controlled trial Mk montelukast, PBO placebo, P primary, S secondary, USMA unscheduled medical attendance, WE wheezing episode, CS corticosteroid, EVS episodic viral wheeze, MTW multiple-trigger wheeze, ALOX5 arachidonate 5-lipoxygenase, BID budesonide inhalation suspension, EFD episode-free day, QOL quality of life, AEE asthma exacerbation episodes, ICS inhaled corticosteroid