Creatininuria in asthmatic children treated with a combination of glucocorticoid and beta-agonist

We examined whether a combination of glucocorticoids and beta-agonists inhaled by asthmatics had an influence on the metabolism of L-arginine, an amino acid involved in the production of urea, creatinine, and NO that is known to play a significant role in asthma. After lung function tests, we assayed nitrates, urea, and creatinine and determined urinary osmolality in urine samples taken from groups of 129 children (10+/-3 years old) with mild-to-moderate asthma treated with different regimens of drugs. No significant differences in urinary urea levels were noted between the groups. On the other hand, the children treated by the combination of glucocorticoid and beta-agonist (n = 52) had a higher level of urinary creatinine (+40%, P < .001, and a higher creatinine/urea ratio (C/U) expressed as % mass= 5.98 +/- 2.44, P < .001) than did the untreated children (n = 43, C/U = 4.03 +/- 1.24), those treated with glucocorticoid (n = 23, C/U = 4.01 +/- 1.32) or beta-agonist alone (n = 11, C/U = 4.09 +/- 1.01) or control children of the same age (n = 20, C/U = 4.81 +/- .90). Children treated with beta-agonist alone had the lowest mean levels of urinary nitrates (P < .05). The children in group 1 whose C/U ratio was above 6 (n = 24) had a higher FVC (P < .02) and FEV1 (not significant (NS)). However, an overly high C/U may also be indicative of a deleterious influence on the biosynthesis of NO from arginine. Further investigations will be required to determine whether there is a relationship between C/U ratios and lung function parameters, and whether the urinary C/U ratio could be employed as a simple and noninvasive parameter for assessment of treatment in asthmatics.