There is concern that P-glycoprotein mediated efflux contributes to steroid resistance. Therefore, this study examined bidirectional corticosteroid transport and induction capabilities for P-glycoprotein (P-gp) to understand which of the systemic and inhaled corticosteroids interacted with P-gp to the greatest extent. Hydrocortisone, prednisolone, prednisone, methylprednisolone, and dexamethasone represented systemically active drugs, while fluticasone propionate, beclomethasone dipropionate, ciclesonide and budesonide represented inhaled corticosteroids. Aldosterone and fludrocortisone represented mineralocorticoids. All drugs were detected using individually optimised HPLC protocols. Transport studies were conducted through Caco-2 monolayers. Hydrocortisone and aldosterone had efflux ratios below , while prednisone showed a P-gp mediated efflux ratio of only compared to its active drug, prednisolone, with an efflux ratio of . Dexamethasone and beclomethasone had efflux ratios of and respectively, while this increased to for methylprednisolone. Fluticasone showed an efflux ratio of . Protein expression studies suggested that all of the inhaled corticosteroids were able to induce P-gp expression, from to 2 times control levels. Most of the systemic corticosteroids had higher passive permeability (>20×10(-6) cm/s) compared to the inhaled corticosteroids (>5×10(-6) cm/s), except for budesonide, with permeability similar to the systemic corticosteroids. Inhaled corticosteroids are not transported by P-gp to the same extent as systemic corticosteroids. However, they are able to induce P-gp production. Thus, inhaled corticosteroids may have greater interactions with other P-gp substrates, but P-gp itself is less likely to influence resistance to the drugs.
Inhaled corticosteroids are medications used to treat asthma. They are taken by using an inhaler. This medication should be taken consistently so that it decreases inflammation in the airways of your lungs and prevents asthma flare-ups. Inhaled corticosteroids are considered the most effective long term usage medication for control and management of asthma. Depending upon the severity of your asthma, your physician may combine an inhaled corticosteroid with a long-acting beta-2 agonist to treat your condition. Oral and intravenous corticosteroids may be required for acute asthma flare-ups or for severe symptoms.