Lack of a Fluoxetine Effect on Prednisolone Disposition and Cortisol Suppression

Budesonide-Related Iatrogenic Cushing's Syndrome in Microscopic Colitis

Budesonide is the treatment of choice for microscopic colitis because of its excellent risk to benefit ratio. It is a potent, well-absorbed corticosteroid, but because of a high rate of first-pass metabolism in the liver, its systemic bioavailability is low. It has fewer corticosteroid-related adverse effects than prednisone, and adrenal suppression is considered to be rare. We present a middle-aged woman with lymphocytic colitis whose symptoms responded to budesonide but developed budesonide-related iatrogenic Cushing’s syndrome. Withdrawal of budesonide led to restoration of normal pituitary-adrenal responsiveness but at the price of recurrent diarrhea due to re-emergence of lymphocytic colitis.

Biotransformation and in vitro assessment of metabolism-associated drug-drug interaction for CRx-102, a novel combination drug candidate

CRx-102 is an oral synergistic combination drug which contains the cardiovascular agent, dipyridamole (DP) and a very low dose of the glucocorticoid, prednisolone (PRED). CRx-102 works through a novel mechanism of action in which DP selectively amplifies the anti-inflammatory activity of PRED without replicating its side effects. CRx-102 is in clinical trials for the treatment of osteoarthritis. Here we delineate the in vitro metabolism and explore the potential for a drug-drug interaction between the active agents in CRx-102. Our study using human hepatocyte suspensions showed that both DP and PRED were metabolized by CYP3A4 isozymes, resulting in the formation of diverse arrays of both oxidative and oxidative-reduced metabolites. Within phase 1 biotransformation, CYP3A4 was one of the pathways responsible for the metabolism of PRED, while phase 2 biotransformation played a significant role in the metabolism of DP. Glucuronidation of DP was substantial and was catalyzed by many UGT members, specifically those in the UGT1A subfamily. Based on the tandem mass (MS/MS) product ion spectra (PIS) acquired, the major metabolites of both agents, namely, monooxygenated, mono-N-deethanolaminated, dehydrogenated and O-glucuronidated metabolites of DP and the monooxygenated (e.g., 6-hydroxyl), dehydrogenated (prednisone) and reduced (20-hydroxyl) metabolites of PRED, were identified and elucidated. The affinities for DP biotransformation, including CYP3A4-mediated oxidative pathways and UGT-mediated O-glucuronidation, appeared high (K(m)<10 microM), as compared with the modest affinities of PRED biotransformation catalyzed by CYP3A4 (K(m) approximately 40-170 microM). DP, but not PRED, exerted a minimal inhibitory effect on the drug-metabolizing CYP isoforms, including CYP3A4, which was determined using a panel of CYP isoform-preferred substrate activities in pooled human liver microsomal (HLM) preparations and microsomal preparations containing the recombinant enzymes (K(i) approximately 2-12 microM). Using the DP maximal plasma concentration (C(max)) observed in the clinic and a predictive mathematical model for metabolism-associated drug-drug interaction (DDI), we have demonstrated that there is little likelihood of a pharmacokinetic interaction between the two active agents in CRx-102.

Assessment of the impact of dosing time on the pharmacokinetics/pharmacodynamics of prednisolone

Prednisolone is widely used for the treatment of inflammation and auto-immune diseases. It exhibits nonlinear pharmacokinetics (PK); and its induced systemic effects (pharmacodynamics (PD)) are commonly evaluated with two biomarkers, cortisol and blood lymphocytes in plasma. Circadian patterns are observed in both biomarkers. Furthermore, the disease itself may show a circadian pattern. For example, in rheumatoid arthritis patients, better therapeutic outcomes have been reported when prednisolone was administered in the very early morning. The aim of this study is to evaluate the impact of dosing time on the PK/PD of prednisolone with a simulation approach using an interactive algorithm. A series of simulations were performed with either intravenous or oral administration of prednisolone or prednisone. The results showed that the initial or maximum concentration and trough concentration of total prednisolone were lower when the drug was administered in the early morning around 6 AM: . Oscillation patterns were observed in cumulative cortisol suppression (CCS) and alteration of total lymphocyte trafficking in blood. When the drug was given in the morning within the therapeutic dose range, or around 6 PM: for a small dose amount (<1 mg), the minimum CCS and maximum effect on lymphocytes were observed. These results indicated that the PK/PD of prednisolone are time- and dose-dependent, and suggested that it is necessary to consider the application of chronotherapy to achieve better clinical outcomes with fewer side effects of prednisolone, and a PK/PD simulation approach could provide a valuable tool to evaluate and predict time-dependency in the system.