Inhaled glucocorticoids in children: A favourable therapeutic index

In children with persistent asthma, inhaled glucocorticoids decrease symptoms and exacerbations, decrease the need for rescue bronchodilator medications, improve airway patency and reduce airway hyperresponsiveness. When administered in the lowest doses that prevent symptoms and eliminate the need for supplemental courses of oral glucocorticoids, they are unlikely to cause clinically important systemic adverse events. Inhaled glucocorticoids have a favourable risk to benefit ratio in this population

In children with persistent asthma, inhaled glucocorticoids decrease symptoms and exacerbations, decrease the need for rescue bronchodilator medications, improve airway patency and reduce airway hyperresponsiveness.When administered in the lowest doses that prevent symptoms and eliminate the need for supplemental courses of oral glucocorticoids, they are unlikely to cause clinically important systemic adverse events.Inhaled glucocorticoids have a favourable risk to benefit ratio in this population.proved pulmonary function.The improvement in symptoms, rescue medication use, peak expiratory flow, and forced expiratory volume in 1 s is dose-related (4).In children with mild or moderate asthma, the beneficial effects occur with a total beclomethasone dipropionate dose of 400 mg/day or less, a budesonide dose of 400 mg/day or less, or a fluticasone propionate dose of 200 mg/day or less.The doses needed to normalize airway responsiveness to bronchoconstricting agents and to eliminate exercise-induced bronchospasm are generally higher than those needed to reduce symptoms at rest and to improve baseline pulmonary function (5).
An open study demonstrated that inhaled glucocorticoid treatment may be more effective if started early during the course of childhood asthma rather than after symptoms have been present for several years (6).Unfortunately, accurate diagnosis of asthma remains difficult during the first few years of life; many infants and toddlers with wheeze, cough and shortness of breath do not have asthma (16) and will be overtreated if inhaled glucocorticoids are recommended routinely for all 'little wheezers'.
The onset of action of inhaled glucocorticoids in asthma is not immediate.Significant improvement in symptoms may occur within weeks, but maximum improvement takes longer.Airway hyperresponsiveness continues to decrease even after many months of regular treatment (7-10) (Figure 1).Tachyphylaxis to long term inhaled glucocorticoid treatment does not occur.Permanent remission is uncommon.The effectiveness of inhaled glucocorticoid treatment begins to disappear within weeks of discontinuing the medication (10,17).
The comparative efficacy of inhaled glucocorticoids has not been adequately studied in children.Delivery systems differ markedly in their efficiency (18).A glucocorticoid administered using the new hydrofluoroalkane propellants has enhanced deposition in the peripheral airways compared with the same glucocorticoid administered using chlorofluorocarbon propellants, and its benefit to risk ratio needs to be redefined (19).
Persistent asthma in children generally responds extremely well to inhaled glucocorticoid treatment.If it does not, the following issues should be considered: poor compliance, psychosocial problems, or missed diagnosis of vocal cord dysfunction, hyperventilation syndrome, gastroesophageal reflux or sinusitis.Rarely, a lack of response is due to persistent inflammation, abnormal glucocorticoid pharmacokinetics or glucocorticoid resistance (20).

RISKS
Local adverse effects of inhaled glucocorticoid treatment include oropharyngeal candidiasis, hoarseness, throat irritation and coughing.These problems are not usually troublesome and seldom necessitate discontinuation of treatment (20).
Inhaled glucocorticoids have the potential to reduce linear growth in children (9)(10)(11)(12)(21)(22)(23)(24)(25).Height measurements must be interpreted carefully because persistent asthma itself may  result in delayed onset of puberty and preadolescent deceleration of height increase.Studies in which a delay in short term growth is assessed over weeks using knemometry to measure lower leg length must be interpreted with particular caution because their predictive value for long term growth is unknown (21).
There is evidence from prospective, randomized, doubleblind studies, several of which are placebo-controlled (10,12) (Figure 2), that intermediate term growth, defined as growth monitored for at least six months, is delayed by beclomethasone dipropionate 400 mg/day or greater and possibly by equivalent doses of other inhaled glucocorticoids in children with mild to moderate asthma (9)(10)(11)(12)(21)(22)(23)(24).The delay appears soon after starting treatment, is not progressive and is not necessarily associated with adrenal insufficiency (25).A five-year, placebo controlled, double-blind study of budesonide is in progress (26).Studies of fluticasone propionate 100 mg/day or 200 mg/day suggest that at these low doses it does not affect growth in most children (27,28).
There is no information from prospective randomized, double-blind studies about the effect of inhaled glucocorticoids on long term growth from infancy to adulthood, al-though a recent retrospective study suggests that despite glucocorticoid use, normal adult height is reached (29) (Figure 3).
In addition to measuring linear growth, bone metabolism may be assessed using biochemical markers of osteoblast and osteoclast activity or by using imaging techniques such as dual-energy x-ray absorptiometry to measure cortical and trabecular bone mineral density (30).
Abnormalities in tests of hypothalamic-pituitary-adrenal (HPA) axis function vary with the inhaled glucocorticoid administered, dose, delivery system and duration of treatment.At a total daily beclomethasone dipropionate dose of 400 mg/day or greater, tests of HPA axis function, such as single morning serum cortisol measurement or HPA response to metyrapone stimulation, are normal.Other more sensitive tests, such as serial early morning cortisol measurements or the area under the curve of 24 h serum or 24 h urine free cortisol measurements, may show evidence of HPA axis suppression (20,31,32).The clinical significance of these biochemical abnormalities is not fully understood.Adrenal insufficiency during or after discontinuing, inhaled glucocorticoid treatment is extremely rare.
Compared with oral glucocorticoids, inhaled glucocorticoids are much less likely to cause any systemic adverse effects in children, not only linear growth suppression or HPA axis suppression as described above, but also posterior subcapsular cataracts, skin thinning or bruising, disseminated or opportunistic infection, or adverse central nervous system effects (20,33,34).The risks of inhaled glucocorticoid treatment, which are already low, can be minimized further (Table 1).

SUMMARY
Although inhaled glucocorticoids do not cure asthma, they are the most efficacious medications available for reducing morbidity in this increasingly prevalent disorder.In-

Figure 2 )
Figure 2) In the study described in Figure 1, during months 1 through 12, height increased by 5.40 cm in the salmeterol-treated children (P=0.004versus beclomethasone), 5.04 cm in the placebo treated children (P=0.018versus beclomethasone) and 3.96 cm in the beclomethasone-treated children

TABLE 1 Inhaled glucocorticoids: Enhancing the margin of safety
25haled glucocorticoids in asthmaFigure3) This study was designed to compare the attained adult height of children with asthma with the attained adult height of non asthmatic children, and to compare the attained adult height of asthmatic children treated with glucocorticoids with that of asthmatic children who did not receive glucocorticoids.Glucocorticoid exposure was assessed from medical records retrospectively.The mean of five stadiometer measurements of adult height, adjusted for sex and parental height, was analyzed.One hundred and fifty-three patients with asthma (mean age at onset 6.1±4.8 years), and 153 age-and sex-matched nonasthmatic subjects were studied.The adult height of patients with asthma (mean age at measurement25.7±5.2 years) did not differ significantly from the adult height of nonasthmatic subjects.The adult height of asthmatic children treated with glucocorticoids did not differ significantly from the adult height of patients not treated with glucocorticoids.The figure shows the difference between the measured adult height of patients with asthma and midparental height versus logarithm of cumulative potency-adjusted glucocorticoids from onset of asthma to age of adult height (17 years of age for girls, and 19 years of age for boys) (Adapted with permission from reference 29)

•
Recommend the lowest dose that prevents symptoms • Monitor height velocity and pulmonary function regularly • Reduce systemic absorption by teaching children to rinse and expectorate after inhalation* • If a pressurized metered-dose inhaler is used, add a spacer device to reduce oral deposition* *Especially important for beclomethasone dipropionate ,which has little inactivation by first-pass metabolism