***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Summary Background Leukotriene B4 ( LTB4 ) recruits and activates neutrophils . Accordingly , this leukotriene is involved in innate defense actions . Objective To examine if nasal LTB4 can produce neutrophil activity and to explore whether or not LTB4 can condition neutrophils to exert virucidal effects in vitro and in vivo . Methods 1 . Twenty-three healthy subjects received nasal LTB4  in a r and omized and sham-controlled design . Symptoms were scored and nasal lavages carried out . Myeloperoxidase ( MPO ) and α-defensins were monitored as indices of neutrophil activity . IL-8 , eosinophil cationic protein ( ECP ) and α2-macroglobulin were measured as indices of pro-inflammatory cytokine production , eosinophil activity , and plasma exudation . 2 . Supernatants from neutrophils activated by LTB4 in vitro were assayed for virucidal activity against respiratory viruses . 3 . In 38 healthy individuals , nasal inoculation with human rhinovirus-16 ( HRV-16 ) was performed . In a preliminary study , intervention with LTB4 was given in a r and omized and controlled design . Symptoms , virus replication , and antibody-titres were monitored . Results 1 . LTB4 produced statistically significant increases in MPO and α-defensins , whereas IL-8 , ECP , and α2-macroglobulin were unaffected . 2 . The supernatants efficiently killed human coronavirus , respiratory syncytial virus , and influenza B virus . 3 . HRV-16 replication was lower in subjects receiving LTB4 , but this difference failed to reach statistical significance . Common cold symptoms and incidence of seroconversion were unaffected . Conclusion Nasal LTB4 induces a selective recruitment/activation of neutrophils . LTB4 can condition neutrophils to exert virucidal effects in vitro and may reduce virus replication in vivo . We suggest that the condition induced by LTB4 reflects an enhanced state of innate defense BACKGROUND . Cysteinyl leukotrienes are implicated in the inflammation of bronchiolitis . Recently , a specific cysteinyl leukotriene receptor antagonist , montelukast ( Singulair [ MSD , Haarlem , Netherl and s ] ) , has been approved for infants in granule sachets . OBJECTIVE . Our goal was to evaluate the effect of montelukast on clinical progress and on cytokines in acute bronchiolitis . METHODS . This was a r and omized , placebo-controlled , double-blind , parallel-group study in 2 medical centers . Fifty-three infants ( mean age : 3.8 ± 3.5 months ) with a first episode of acute bronchiolitis were r and omly assigned to receive either 4-mg montelukast sachets or placebo , every day , from hospital admission until discharge . The primary outcome was length of stay , and secondary outcomes included clinical severity score ( maximum of 12 ) and changes in type 1 and 2 cytokine levels ( including interleukin4/IFN-γ ratio as a surrogate for the T-helper 2/T-helper 1 ratio ) in nasal lavage . RESULTS . Both groups were comparable at baseline , and cytokine levels correlated positively with disease severity . There were neither differences in length of stay ( 4.63 ± 1.88 [ placebo group ] vs 4.65 ± 1.97 days [ montelukast group ] ) nor in clinical severity score and cytokine levels between the 2 groups . No differences in interleukin 4/IFN-γ ratio between the 2 groups were seen . There was a slight tendency for infants in the montelukast group to recover more slowly than those in the placebo group ( clinical severity score at discharge : 6.1 ± 2.4 vs 4.8 ± 2.2 , respectively ) . CONCLUSIONS . Montelukast did not improve the clinical course in acute bronchiolitis . No significant effect of montelukast on the T-helper 2/T-helper 1 cytokine ratio when given in the early acute phase could be demonstrated Background : Controlled clinical trials on the effects of leukotriene antagonists on asthma‐like symptoms , bronchial hyperresponsiveness and airway inflammation have not been performed in elite athletes Effective treatment of respiratory symptoms , airway inflammation and impairment of lung function is the goal of any asthma therapy . Although montelukast has been shown to be a possible add-on therapy for anti-inflammatory treatment in older children , its efficacy in infants and young children is not well known . The aim of this study was to investigate its effect in infants and young children with early childhood asthma . In a prospect i ve r and omised double-blind placebo-controlled study , 24 young children ( 10–26 months ) with wheeze , allergy and a positive family history of asthma consistent with the diagnosis of early childhood asthma were r and omised to receive montelukast 4 mg or placebo . The forced expiratory volume in 0.5 seconds ( FEV0.5 ) was measured using the raised volume rapid thoracic compression technique , and fractional exhaled nitric oxide ( FeNO ) and symptom scores were determined . No change was noted in FEV0.5 , FeNO or symptom score in the placebo group following the treatment period . In contrast , significant improvements in mean±sd FEV0.5 ( 189.0±37.8 and 214.4±44.9 mL before and after treatment , respectively ) , FeNO ( 29.8±10.0 and 19.0±8.5 ppb ) and median symptom score ( 5.5 and 1.5 ) were noted following treatment with montelukast . In conclusion , montelukast has a positive effect on lung function , airway inflammation and symptom scores in very young children with early childhood asthma RATIONALE A pilot study ( Bisgaard H ; Study Group on Montelukast and Respiratory Syncytial Virus . A r and omized trial of montelukast in respiratory syncytial virus postbronchiolitis . Am J Respir Crit Care Med 2003;167:379 - 383 ) reported the efficacy of montelukast in post-respiratory syncytial virus ( RSV ) bronchiolitic respiratory symptoms . OBJECTIVES To evaluate the efficacy and safety of montelukast , 4 and 8 mg , in treating recurrent respiratory symptoms of post-RSV bronchiolitis in children in a large , multicenter study . METHODS This was a double-blind study of 3- to 24-month-old children who had been hospitalized for a first or second episode of physician-diagnosed RSV bronchiolitis and who tested positive for RSV . Patients ( n = 979 ) were r and omized to placebo or to montelukast at 4 or 8 mg/day for 4 weeks ( period I ) and 20 weeks ( period II ) . The primary end point was percentage symptom-free days ( % SFD ; day with no daytime cough , wheeze , and shortness of breath , and no nighttime cough ) . MEASUREMENTS AND MAIN RESULTS No significant differences were seen between montelukast and placebo in % SFD over period I : mean + /- SD for placebo and for montelukast at 4 and 8 mg were 37.0 + /- 30.7 , 38.6 + /- 30.4 , and 38.5 + /- 29.9 , respectively . Least-squares mean differences ( 95 % confidence interval ) between montelukast ( 4 mg ) and placebo and between montelukast ( 8 mg ) and placebo were 1.9 % ( -2.9 , 6.7 ) and 1.6 % ( -3.2 , 6.5 ) , respectively . Secondary end points were similar across treatments . Both doses were generally well tolerated . During the first two treatment weeks , average % SFD was approximately 29 % . In post hoc analyses of patients ( n = 523 ) with persistent symptoms ( % SFD < or = 30 % over Weeks 1 - 2 ) , differences in % SFD were seen between montelukast and placebo over Weeks 3 - 24 : difference were 5.7 ( 0.0 , 11.3 ) for montelukast ( 4 mg ) minus placebo and 5.9 ( 0.1 , 11.7 ) for montelukast ( 8 mg ) minus placebo . CONCLUSIONS In this study , montelukast did not improve respiratory symptoms of post-RSV bronchiolitis in children Our aim was to investigate the effectiveness of montelukast in recurrently wheezy infants . We r and omised 113 , 6–24-month-old children with recurrent wheezing to receive either placebo or montelukast daily for an 8-week period . The primary end-point was symptom-free days . The secondary aims were to evaluate the effect of montelukast on rescue medication , on lung function , airway responsiveness and exhaled nitric oxide fraction ( FeNO ) . Clinical response and FeNO were determined , the functional residual capacity ( FRC ) and specific airway conductance ( sGaw ) were measured using an infant whole-body plethysmograph , the maximal flow at functional residual capacity ( V′max , FRC ) was recorded using the squeeze technique and airway responsiveness was evaluated by performing a dosimetric methacholine challenge test . There was no significant difference in changes in weekly symptom-free days between the montelukast and the placebo group ( 3.1–3.7 days versus 2.7–3.1 days , p = 0.965 ) . No significant differences were detected in the secondary end-points , i.e. use of rescue medication , FRC , sGaw , V′max , FRC , FeNO or airway responsiveness between groups . Montelukast therapy did not influence the number of symptom-free days , use of rescue medication , lung function , airway responsiveness or airway inflammation in recurrently wheezy , very young children BACKGROUND Acute wheezing illnesses in preschoolers require better management strategies to reduce morbidity . OBJECTIVES We sought to examine the effectiveness of episodic use of an inhaled corticosteroid and a leukotriene receptor antagonist in preschoolers with intermittent wheezing . METHODS In a r and omized , double-blind , placebo-controlled 12-month trial , 238 children aged 12 to 59 months with moderate-to-severe intermittent wheezing received 7 days of either budesonide inhalation suspension ( 1 mg twice daily ) , montelukast ( 4 mg daily ) , or placebo in addition to albuterol with each identified respiratory tract illness ( RTI ) . Proportion of episode-free days ( EFDs ) during the 12-month trial was the primary outcome . RESULTS The 3 treatment groups did not differ in proportions of EFDs , with adjusted mean EFDs of 76 % ( 95 % CI , 70 % to 81 % ) for budesonide , 73 % ( 95 % CI , 66 % to 79 % ) for montelukast , and 74 % ( 95 % CI , 65 % to 81 % ) for conventional therapy ( P = .66 ) . The 3 groups did not differ in oral corticosteroid use , health care use , quality of life , or linear growth . However , during RTIs , budesonide and montelukast therapy led to modest reductions in trouble breathing ( 38 % [ P = .003 ] and 37 % [ P = .003 ] , respectively ) and interference with activity scores ( 32 % [ P = .01 ] and 40 % [ P = .001 ] , respectively ) that were most evident in those with positive asthma predictive indices . CONCLUSIONS In preschool children with moderate-to-severe intermittent wheezing , episodic use of either budesonide or montelukast early in RTIs , when added to albuterol , did not increase the proportion of EFDs or decrease oral corticosteroid use over a 12-month period . However , indicators of severity of acute illnesses were reduced , particularly in children with positive asthma predictive indices BACKGROUND : Infections with viruses causing upper respiratory tract infection ( URI ) are associated with increased leukotriene levels in the upper airways . Montelukast , a selective leukotriene-receptor antagonist , is an effective treatment of asthma and allergic rhinitis . OBJECTIVE : To determine whether prophylactic treatment with montelukast reduces the incidence and severity of URI  in children . METHODS : A r and omized , double-blind , placebo-controlled study was performed in 3 primary care pediatric ambulatory clinics in Israel . Healthy children aged 1 to 5 years were r and omly assigned in a 1:1 ratio to receive 12-week treatment with 4 mg oral montelukast or look-alike placebo .  Patients were excluded if they had a previous history of reactive airway disease . A study coordinator contacted the parents by phone once a week to obtain information regarding the occurrence of acute respiratory episodes . The parents received a diary card to record any acute symptoms of URI . The primary outcome measure was the number of URI episodes . RESULTS : Three hundred children were recruited and r and omly assigned into montelukast ( n = 153 ) or placebo ( n = 147 ) groups . One hundred thirty-one ( 85.6 % ) of the children treated with montelukast and 129 ( 
    Output:
    
Individual analyses of these studies did not show significant differences between the leukotriene inhibitors group and the control group in symptom-free days and incidence of recurrent wheezing .
The current evidence does not allow definitive conclusions to be made about the effects of leukotriene inhibitors on length of hospital stay and clinical severity score in infants and young children with bronchiolitis .