Microbore liquid chromatography of tertiary amine anticholinergic pharmaceuticals with tris(2,2'-bipyridine)ruthenium(III) chemiluminescence detection.

The post-column chemiluminescent reaction of six anticholinergic alkaloid compounds with tris(2,2'-bipyridine)ruthenium(III) (Ru(bpy)3(3+)) is applied to microbore high-performance liquid chromatography (HPLC). At flow rates less than 200 microL/min, the capillary mixing cell in which Ru(bpy)3(3+) and the analyte are mixed directly allows for good light detection. In contrast, a diminished signal occurs at these low flow rates with conventional post-column mixing in a tee. Optimal chemiluminescent pH conditions for atropine, scopolamine, dicyclomine, cyclopentolate, Cyclobenzaprine ( Flexeril ), and procyclidine are determined at moderately basic conditions (pH 7 to 9). 2-Butanone is found to be compatible with the chemiluminescent reaction, whereas tetrahydrofuran and propionitrile cause an increase in background noise and a chemiluminescent signal loss. As 2-butanone is more nonpolar than acetonitrile, it assists in the elution of these hydrophobic anticholinergic compounds. Five anticholinergic compounds are resolved successfully with a PRP-1 polymeric column and a slightly basic mobile phase, but a C8 silica column is better suited for the more hydrophobic compounds (Cyclobenzaprine ( Flexeril ), procyclidine, and dicyclomine).

Plasma levels and bioavailability of Cyclobenzaprine ( Flexeril ) in human subjects.

Cyclobenzaprine ( Flexeril ) was extensively metabolized in man, less than 1% of the dose being excreted unchanged in the urine. Comparison of areas under plasma level curves (AUC) after oral and intravenous doses suggests that the drug may be partly metabolized in the lumen or during its first passage through the gut wall and/or liver. Average plasma levels of the drug increased with increasing dosage, but the AUC increased less rapidly with increasing dose, possibly because of dose-dependent absorption.

Identification of human liver cytochrome P450 isoforms involved in the in vitro metabolism of Cyclobenzaprine ( Flexeril ).

Cyclobenzaprine ( Flexeril ) is a muscle relaxant, possessing a tricyclic structure. Numerous therapeutic agents containing this structure are known to be metabolized by polymorphic cytochrome P4502D6. The aim of this study was to determine if cytochrome P4502D6 and other isoforms are involved in the metabolism of Cyclobenzaprine ( Flexeril ) in human liver microsomes. Selective cytochrome P450 inhibitors for CYP1A1/2 (furafylline and 7,8-benzoflavone) and CYP3A4 (troleandomycin, gestodene, and ketoconazole) inhibited the formation of desmethylCyclobenzaprine ( Flexeril ), a major metabolite of Cyclobenzaprine ( Flexeril ), in human liver microsomes. Antibodies directed against CYP1A1/2 and CYP3A4 inhibited the demethylation reaction whereas anti-human CYP2C9/10, CYP2C19, and CYP2E1 antibodies did not show any inhibitory effects. When a panel of microsomes prepared from human B-lymphoblastoid cells that expressed specific human cytochrome P450 isoforms were used, only microsomes containing cytochromes P4501A2, 2D6, and 3A4 catalyzed N-demethylation. In addition, demethylation catalyzed by these recombinant cytochromes P450 can be completely inhibited with selective inhibitors at concentrations as low as 1 to 20 microM. Interestingly, Cyclobenzaprine ( Flexeril ) N-demethylation was significantly correlated with caffeine 3-demethylation (1A2) and testosterone 6 beta-hydroxylation (3A4) but not with dextromethorphan O-demethylation (2D6) in human liver microsomes. To further determine the involvement of cytochrome P4502D6 in Cyclobenzaprine ( Flexeril ) metabolism, liver microsomes from a human that lacked CYP2D6 enzyme activities was included in this study. The data showed that Cyclobenzaprine ( Flexeril ) N-demethylation still occurred in the incubation with this microsome. These results suggested that cytochrome P4502D6 plays only a minor role in Cyclobenzaprine ( Flexeril ) N-demethylation whereas 3A4 and 1A2 are primarily responsible for Cyclobenzaprine ( Flexeril ) metabolism in human liver microsomes. Due to the minimum involvement of CYP2D6 in the vitro metabolism of Cyclobenzaprine ( Flexeril ), the polymorphism of cytochrome P4502D6 in man should not be of muci concern in the clinical use of Cyclobenzaprine ( Flexeril ).

Cyclobenzaprine ( Flexeril ) effects on locus coeruleus cells in tissue slice.

Tissue slices 400 mu thick were taken from the brain stem, at the level of the locus coeruleus, of 150-250 g Sprague-Dawley rats. Microelectrodes were placed in the locus coeruleus under visual control, and a cell whose discharge rate would decrease with microiontophoretic application of norepinephrine or clonidine was sought. Cyclobenzaprine ( Flexeril ) (CBZ) was then introduced into the perfusion medium at a concentration equivalent to 1 mg/kg body weight of the whole animal. Discharge rates before and during CBZ administration were compared. The six cells with initial discharge rates between 2 and 10 Hz decreased firing with CBZ, whereas the four cells with initial rates between 0.5 and 1.5 Hz increased their rates with CBZ.