Paul Andersson

In vitro biotransformation of glucocorticoids in liver and skin homogenate fraction from man, rat and hairless mouse

The pharmacological effects of glucocorticoids are greatly influenced by their pharmacokinetic properties. In the present report, the in vitro biotransformation of the topical glucocorticoids [3H]-budesonide ([3H]-BUD). [3H]-triamcinolone acetonide ([3H]-TAAc) and [3H]-hydrocortisone ([3H]-HC) was studied in the 9000 g liver and skin supernatant from man, rat and hairless mouse. The rate of disappearance of the compounds was estimated during the initial 30 min of incubation by high performance liquid chromatography. In human liver the half life (t1/2) rank order was [3H]-BUD (7--23 min) less than [3H]-TAAc (13--68 min) less than [3H]-HC (40--67 min), in rat liver [3H]-HC (14--21 min) less than [3H]-BUD (28--38 min) less than [3H]-TAAc (161--196 min) and in hairless mouse liver [3H]-BUD (17--22 min) less than [3H]-TAAc (21--34 min) less than [3H]-HC (82--165 min). Negligible biotransformation of these glucocorticoids occurred in skin. BUD is a one to one mixture of the [22R]- and [22S]-epimers. It was found that the [22R]-epimer was more susceptible to liver biotransformation than the [22S]-epimer of [3H]-BUD. The results are discussed with particular reference to the extent of systemic side effects of these compounds.

Short Inhalation Exposures of the Isolated and Perfused Rat Lung to Respirable Dry Particle Aerosols; the Detailed Pharmacokinetics of Budesonide, Formoterol, and Terbutaline

There is an increasing interest in using the lung as a route of entry for both local and systemic administration of drugs. However, because adequate technologies have been missing in the preclinical setting, few investigators have addressed the detailed disposition of drugs in the lung following short inhalation exposures to highly concentrated dry powder aerosols. New methods are needed to explore the disposition of drugs after short inhalation exposures, thus mimicking a future clinical use. Our aim was to study the pulmonary disposition of budesonide, formoterol, and terbutaline, which are clinically used for the treatment of bronchial asthma. Using the recently developed DustGun aerosol technology, we exposed by inhalation for approximately 1 min the isolated and perfused rat lung (IPL) to respirable dry particle aerosols of the three drugs at high concentrations. The typical aerosol concentration was 1 mug/mL, and the particle size distribution of the tested substances varied with a MMAD ranging from 2.3 to 5.3 mum. The IPL was perfused in single pass mode and repeated samples of the perfusate were taken for up to 80 min postexposure. The concentration of drug in perfusate and in lung extracts was measured using LC-MS/MS. The deposited dose was determined by adding the amounts of drug collected in perfusate to the amount extracted from the tissues at 80 min. Deposited amounts of budesonide, formoterol fumarate, and terbutaline sulphate were 23 +/- 17, 36 +/- 8, and 60 +/- 3.2 mug (mean +/- SD, n = 3), respectively. Retention in lung tissues at the end of the perfusion period expressed as fraction of deposited dose was 0.19 +/- 0.05, 0.19 +/- 0.06, and 0.04 +/- 0.01 (mean +/- SD, n = 3) for budesonide, formoterol, and terbutaline, respectively. Each short inhalation exposure to the highly concentrated aerosols consumed 1-3 mg powder. Hence, this system can be particularly useful for obtaining a detailed pharmacokinetic characterization of inhaled compounds in drug discovery/development.

6α-Fluoro- and 6α,9α-difluoro-11β,21- dihydroxy-16α,17α-propylmethylenedioxypregn-4-ene-3,20-dione: Synthesis and evaluation of activity and kinetics of their C-22 epimers

Abstract It is generally accepted that the anti-inflammatory effect of glucocorticosteroids cannot be separated from their adverse effects at the receptor level. However, modification of the pharmacokinetics through structural alterations could provide steroids with a better therapeutic index than those currently used. Thus, new 16α,17α-acetals between butyraldehyde and 6α-fluoro- or 6α,9α-difluoro-16α-hydroxycortisol were synthesized and studied. Acetalization of the corresponding 16α,17α-diols or transacetalization of their 16α,17α-acetonides in dioxane produced mixtures of C-22 epimers, which were resolved by preparative chromatography. Alternatively, an efficient method was used to produce the 22R-epimer stereoselectively through performing the acetalization and transacetalization in a hydrocarbon with an inert material present. The C-22 configuration of (22R)-6α,9α-difluoro-11β,21-dihydroxy-16α,17α-propylmethylenedioxypregn-4-ene-3,20-dione was unambiguously established by single crystal X-ray diffraction. The present compounds, especially the 22R-epimer just mentioned, bind to the rat thymus glucocorticoid receptor with high potency. The C-22 epimers of the 6α,9α-difluoro derivatives showed a 10-fold higher biotransformation rate than the budesonide 22R-epimer when incubated with human liver S9 subcellular fraction. The high receptor affinity in combination with the high biotransformation rate indicates that (22R)-6α,9α-difluoro-11β,21-dihydroxy-16α,17α-propylmethylenedioxypregn-4-ene-3,20-dione may be an improved 16α,17α-acetal glucocorticosteroid for therapy of inflammatory diseases, in which the mucous membranes are involved, such as those in the intestinal tract as well in the respiratory tract.

Effect of structural alterations on the biotransformation rate of glucocorticosteroids in rat and human liver

The effect of structural alterations on the biotransformation rate of glucocorticosteroids (GCS) by rat- and human-liver 9000 g supernatant fraction was studied. Insertion of a 16 alpha-hydroxy group in the prednisolone molecule (16 alpha-hydroxyprednisolone) was found to decrease the rate of biotransformation. Substitution of the 16 alpha,17 alpha-hydroxy groups with a symmetric acetal (in, for example, desonide) or especially a non-symmetric acetal (in, for example, budesonide), enhanced the biotransformation rate several-fold, particularly in human liver. Differences in the rates of metabolism in rat and human liver were observed. Hydrogenation of the 1,2-double bond in prednisolone and budesonide (hydrocortisone and 1,2-dihydrobudesonide) enhanced the biotransformation rate nine-fold in rat liver but only two-fold in human liver. Fluorination of the steroid nucleus in 6 alpha- and 9 alpha-positions enhanced the biotransformation rate several-fold in human liver, but in rat liver fluorination marginally decreased the rate of biotransformation. These in vitro results correlate well with available data on the first-pass liver metabolism of the studied GCS. This indicates that in vitro data can be useful in predicting oral bioavailability of GCS.

Biotransformation rate (in vitro) and systemic potency (in vivo) of the topical glucocorticoid budesonide in male and female rats.

Budesonide is a glucocorticoid of clinical interest for the topical treatment of skin and respiratory diseases. The in vitro liver biotransformation rate and in vivo systemic potency (thymus involution) of budesonide were studied in male and female rats. The biotransformation rate of [3H]-budesonide was about 4 times slower in the female than in the male rat liver 9000 g supernatant (t 1/2; 230 and 57 min, respectively). The systemic potency of budesonide after peroral or subcutaneous administration was higher (by factors of 6 and 2, respectively) in the female than in the male rat. These results suggest that the liver biotransformation rate of budesonide is of great importance in reducing its systemic action in the male rat.