Studies on the metabolic clearance of ciclotropium to alpha-phenylciclopentylacetic acid using a new enantiospecific metabolite assay.
Ester hydrolysis represents an important biotransformation pathway for various parasympatholytic agents. Cleavage of the ciclotropium ester bond results in the formation of alpha-phenylciclopentylacetic acid (PCA). The relevance of this metabolic route for ciclotropium bromide (HIT-PCE, CAS 85166-20-7) including its stereochemical aspects was studied in a preliminary pharmacokinetic study. An enantiospecific assay for biological material was developed that is based on chiral derivatization of PCA with N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide (EDAC) and the primary amine S-FLOPA, a chiral coupling component for carboxylic acids derived from S-flunoxaprofen, followed by HPLC resolution. R-(--)-Ibuprofen was used as internal standard. From plasma or urine PCA can be extracted into n-hexane/ethanol (9:1) at pH 4 under addition of sodium chloride. Derivatization with EDAC/FLOPA was performed under addition of 1-hydroxybenzotriazole in anhydrous dichloromethane that contained trace amounts of pyridine (ambient temperature; 2 h reaction time). The chromatographic separation was performed on a silica gel stationary phase (Zorbax Sil) using n-hexane-chloroform-ethanol (100:10:1, by vol.) as mobile phase (flow rate, 2 ml/min; fluorescence-detection, 305/355 nm; elution order of the derivatives, (-) before (+)). Limit of quantification was 1.0 ng/ml for plasma and 10 ng/ml for urine. In the pharmacokinetic study in two healthy volunteers who received a single i.v. dose of 10 mg ciclotropium race-mate the PCA concentrations in plasma were below the detection limit, but approx. 1.5% of the administered dose were excreted into urine as the respective glucuronides.(ABSTRACT TRUNCATED AT 250 WORDS)
Liebmann
B
B
Department of Pharmacology, Johann Wolfgang Goethe-University, Frankfurt/Main, Fed. Rep. of Germany.
Mayer
S
S
Mutschler
E
E
Spahn-Langguth
H
H
D019086:Bridged Bicyclo Compounds, Heterocyclic; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007202:Indicators and Reagents; D010084:Oxidation-Reduction; D010276:Parasympatholytics / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D010648:Phenylacetates / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D013237:Stereoisomerism; D014326:Tropanes
D019086:Bridged Bicyclo Compounds, Heterocyclic; D007202:Indicators and Reagents; D010276:Parasympatholytics; D010648:Phenylacetates; D014326:Tropanes; C079302:alpha-phenylcyclopentylacetic acid; C040095:cyclotropium