Rapid metabolic inactivation of tipredane, a structurally novel topical steroid

Soft steroids: a new approach to the treatment of inflammatory airways diseases

Inhaled synthetic glucocorticosteroids are widely used in the treatment of bronchial asthma where they provide very effective first line treatment. However, a range of unwanted side effects and the often complex dosing schedules associated with these drugs frequently result in poor patient compliance. The soft drug approach has been utilised as a means of delivering these potent anti-inflammatory agents close to their site of action while reducing the degree of systemic exposure and thus limiting or eliminating the associated systemic and local side effects. A further target for pharmaceutical companies is to deliver these new treatments in a once daily formulation thus further enhancing patient compliance. While many soft steroids have failed to progress into the clinic two are meeting with some degree of success. Loteprednol etabonate, an inactive metabolite soft steroid, has been accepted for the treatment of ophthalmic disorders and is being examined in clinical trials for its effects on airway inflammation. Ciclesonide, a pro-drug soft steroid, has demonstrated efficacy without side effects in a once daily formulation in asthma patients and is being developed for the treatment of both asthma and chronic obstructive pulmonary disease with launches of a once daily inhaler formulation expected in 2003. These drugs may represent a significant step forward in the treatment of inflammatory diseases of the airways.

Determination of the two major human metabolites of tipredane in human urine by high-performance liquid chromatography with column switching

An automated method based on column-switching reversed-phase in high-performance liquid chromatography the heart-cutting mode has been developed for the simultaneous determination of the two major human metabolites of tipredane, FPL 66365XX and FPL 66366XX, in human urine. The limit of quantification of the method was 25 ng/ml for both analytes from a urine injection volume of 100 microl. The intra- and inter-assay precision and accuracy were acceptable between 25 and 5000 ng/ml. No significant interferences were observed from either tipredane or a selection of its putative metabolites, or urine constituents in samples from male and female volunteers. Both analytes were found to be stable in human urine when stored at room temperature for two days, at 4 degrees C for six days, in a freezer at or below -20 degrees C for three weeks, and when the urine samples were subjected to three freeze-thaw cycles The method was unusual in that the initial separation was performed on a non-polar, octadecylsilane, column and the final separation on a more polar, trimethylsilane column. These columns were selected only after the investigation of a wide range of reversed-phase columns. The method's success was based on the greatly differing selectivities shown towards the two analytes by the organic modifiers, methanol and acetonitrile, present in the mobile phases used for the extraction and analytical stages

Determination of a major metabolite of tipredane in rat urine by high-performance liquid chromatography with column switching

An automated method, based on column-switching reversed-phase high-performance liquid chromatography, has been developed for the determination of a major metabolite of tipredane in rat urine. Samples are injected directly onto a cyanopropyl extraction column. The portion of eluate containing the metabolite is switched, via an injection loop, onto an octadecylsilane analytical column. The limit of quantification of the method was 25 ng/ml for a 20 microl injection volume of urine. The intra-assay precision (0.7-4.8%) and accuracy (94-105%), and the inter-assay precision (2.7-12.6%) and accuracy (94-105%), were acceptable. The analyte was found to be stable in rat urine when stored at room temperature for six days, in a freezer at or below -20 degrees C for twelve weeks, and when the samples were subjected to two freeze-thaw cycles. No significant interference was observed from tipredane and its major human metabolites, or urine constituents in male and female rats. The method was successfully used to analyse samples from a long-term toxicology study.

A radioimmunoassay for the determination of tipredane in human plasma

A sensitive method for the determination of tipredane in human plasma has been developed. Prior to radioimmunoassay, proteins are removed from plasma by precipitation with acetonitrile. A [125I]iodohistamide derivative of tipredane is used as a heterogeneous radioligand. The primary antiserum is raised in sheep against a tipredane (O-carboxymethyl) oxime-bovine serum albumin conjugate. Donkey anti-sheep IgG antiserum is used as the secondary antiserum in a double antibody separation procedure. The limit of quantification of the method is 1 ng ml-1 for 500 microliters of plasma. There is no significant interference from either established or putative metabolites of tipredane, endogenous steroids or a wide range of other drugs. The assay was used to determine the concentrations of tipredane in plasma samples collected in pilot clinical studies.