In clinical trials, mild elevations in serum aminotransferase levels were found in 1% to 2% of patients taking montelukast chronically, but similar rates are reported in matched placebo recipients. The ALT abnormalities were usually mild, asymptomatic and self limited. Clinically apparent liver injury from montelukast is extremely rare; with fewer than a dozen cases reported in the literature. In these cases, the latency to onset of injury was highly variable, ranging from a few days to several years. Patients presented with anorexia, nausea, right upper quadrant pain, dark urine, and jaundice. The pattern of enzyme elevation is usually mixed, but both hepatocellular or cholestatic patterns have been reported. Allergic features and autoantibody formation were rare. Eosinophilia was often reported, but this may have been due to the underlying allergic condition rather than the liver injury. The injury usually resolved within 1 to 4 months of stopping the drug.
In another randomized, placebo-controlled, parallel-group trial (n=642) in a similar population of adult patients previously maintained, but not adequately controlled, on inhaled corticosteroids (beclomethasone 336 mcg/day), the addition of SINGULAIR to beclomethasone resulted in statistically significant improvements in FEV 1 compared with those patients who were continued on beclomethasone alone or those patients who were withdrawn from beclomethasone and treated with montelukast or placebo alone over the last 10 weeks of the 16-week, blinded treatment period. Patients who were randomized to treatment arms containing beclomethasone had statistically significantly better asthma control than those patients randomized to SINGULAIR alone or placebo alone as indicated by FEV 1 , daytime asthma symptoms, PEFR, nocturnal awakenings due to asthma, and “as-needed” β-agonist requirements.
The incidence of common adverse events in Table 1 below is based upon pooled data from three 12-week, double-blind, placebo-controlled clinical studies in which 401 adult and adolescent patients (148 males and 253 females) age 12 years and older were treated with 2 inhalations of Symbicort 80/ or Symbicort 160/ twice daily. The Symbicort group was composed of mostly Caucasian (84%) patients with a mean age of 38 years, and a mean percent predicted FEV 1 at baseline of 76 and 68 for the 80/ mcg and 160/ mcg treatment groups, respectively. Control arms for comparison included 2 inhalations of budesonide HFA metered dose inhaler (MDI) 80 or 160 mcg, formoterol dry powder inhaler (DPI) mcg, or placebo (MDI and DPI) twice daily. Table 1 includes all adverse events that occurred at an incidence of > 3% in any one Symbicort group and more commonly than in the placebo group with twice-daily dosing. In considering these data, the increased average duration of patient exposure for Symbicort patients should be taken into account, as incidences are not adjusted for an imbalance of treatment duration.