Pharmakokinetic Study of Systemic Bioavailability |

Pharmakokinetic Study of Systemic Bioavailability

Generally it is not felt to be appropriate to subject children to repeated venopuncture and therefore pharmacokinetic studies and the repeated measurement of plasma cortisol have not been used as first line methods to assess the systemic burden of ICSs in this young age group. However in the light of the very real need to ensure the systemic safety of these drugs in children and the acceptance that other methods to assess the systemic load are far from robust or even satisfactory, the use of an indwelling cannula to enable the collection of blood samples to measure both blood levels of the drug and any active metabolites and plasma cortisol at intervals over time should be considered. This approach may represent the best way of collecting reliable information on comparative systemic safety in children with asthma treated with ICSs.

A pharmacokinetic study designed to investigate systemic safety has to measure total systemic exposure and therefore must not exclude that amount of the active moiety absorbed through the gastrointestinal tract. In accordance with the standard accepted methods of assessment of bioequivalence Cmax, the time to Cmax (Tmax) and the area under the curve (AUC) should be compared.

Equivalent pulmonary deposition of two inhaled products may be concluded if the 95 % confidence interval for each parameter lies within the acceptance range of 0.8 to 1.25.
Professor Hans Bisgaard • Copenhagen • Denmark •