If side effects are important, why are we so ignorant of the dose inhaled?

Inhaled steroids play an extremely important part in the treatment of asthma. They are now regarded as the first line prophylactic drug for adults1 and are used by many as a first line prophylactic agent for children. Important side effects are rarely seen in users of low dose inhaled steroids, but there is concern over the potential effects of high dose inhaled steroids. The Committee on Safety of Medicines has recently concluded that clinically important systemic adverse effects can occur at licensed doses of inhaled corticosteroids,2 the risks being increased after prolonged high dose therapy. Effects mentioned included adrenal suppression, osteoporosis or changes in bone mineral density, growth retardation in children, cataracts, and glaucoma. A major problem in trying to identify possible side effects—and, indeed, in assessing clinical trials of inhaled steroids—is determining the amount of drug patients have actually inhaled. Compliance and inhaler technique vary considerably, but even when these are optimal the dose of drug inhaled may vary by up to fourfold without the …