Radioimmunoassay for psychotropic drugs. III: Synthesis and properties of haptens for trifluoperazine and fluphenazine

Anodic voltammetry of fluphenazine at different solid electrodes

The electrochemical behaviour of fluphenazine based on its oxidation at platinum and glassy carbon electrodes was investigated by linear sweep and cyclic voltammetry. The influence of pH, concentration, nature of the buffer and scan rate was carefully examined. At both electrodes, three anodic steps (representing an irreversible oxidation) were obtained. The method was applied to the determination of fluphenazine in sugar-coated tablets.

Evaluation of peroxyoxalate chemiluminescence postcolumn detection of fluphenazine in urine and blood plasma using high performance liquid chromatography

Peroxyoxalate chemiluminescence may be used for sensitive postcolumn detection of phenothiazine analytes separated by high performance liquid chromatography with appropriate optimization of measurement conditions such as solvent, pH and oxalate ester. Detectability of fluorescent analytes by chemical excitation varies greatly, but analytes with low oxidation potentials are generally more readily detected at low levels, as demonstrated for phenothiazines, an important class of fluorescent drugs. Some improvement in detection limits is observed for fluphenazine when chemiluminescence detection is compared to conventional fluorescence detection. Because of the specificity of chemical excitation, fewer interferences from fluorescent impurities in a urine matrix are observed.

Radioimmunoassay for fluphenazine sulfoxide in human plasma

Antisera to fluphenazine sulfoxide were raised in New Zealand white rabbits to an immunogen synthesized by covalent linkage of bovine serum albumin to 10-[[3-[4-(4-carboxybutyl)-1-piperazinyl] propyl]]-2-trifluoromethyl-10H-phenothiazine 5-sulfoxide. With use of an antiserum, a radioimmunoassay for fluphenazine sulfoxide was developed that is able to quantitate 0.156 ng ml-1 using only a 200 microliter plasma sample with a coefficient of variation less than 5%. The antiserum had negligible cross-reactivities to fluphenazine (less than 1%) and its important metabolites, such as fluphenazine N4'-oxide (1%), 7-hydroxyfluphenazine (less than 1%), and N4'-deshydroxy-ethylfluphenazine (1%). The cross-reactivities with structurally similar phenothiazine 5-sulfoxides, such as those of trifluoperazine, prochlorperazine, perphenazine, and N4'-deshydroxyethylfluphenazine, were considerable, such that the antiserum can be used to develop a quantitative radioimmunoassay for any of these compounds. The reported radioimmunoassay was found to be suitable and adequate to quantitate fluphenazine sulfoxide in the plasma of patients treated with oral or intramuscular fluphenazine.

A highly sensitive and specific radioimmunoassay for quantitation of plasma fluphenazine

Antisera of high sensitivity and selectivity were obtained from rabbits immunized with conjugates of hemisuccinylated fluphenazine and porcine thyroglobulin. The antiserum selected (titer 1:6000) for the development of the RIA was obtained after a priming dose and a single iv booster injection three months later. This antiserum had negligible crossreactivity with known available metabolites of fluphenazine (FPZ) and an affinity constant of 2 X 10(10) L/mol. Tritiated FPZ was further purified by HPLC and used as a ligand. The method detects as little as 20 pg/mL of plasma (4 pg/RIA tube) after 1 mL of plasma is extracted. The extraction was performed at a basic pH with heptane: isoamyl alcohol (99:1); the solvent was then back extracted using an acetic phosphate buffer. Recoveries were uniformly high (88.6 +/- 2.1%), and this aqueous buffer extract was used directly in the RIA procedure. The assay has intra- and interassay coefficients of variation of 5.8 and 8.2%, respectively, in a plasma concentration of 95 pg/mL. Results using this procedure have been cross validated against an HPLC procedure (r = 0.952, slope = 1.032, intercept = 0.009, n = 18). In a single-dose FPZ study (10 mg, po), plasma FPZ levels in 25 normal volunteers could be monitored greater than 48 h post dose. Single plasma level profiles, after an initial injection of 12.5 mg of FPZ decanoate, could be measured greater than 36 d, and, in some cases, up to 100 d post dose.

Radioimmunoassay for the 7-hydroxy metabolite of trifluoperazine and its application to a kinetic study in human volunteers

A hapten derivative of the 7-hydroxy metabolite of trifluoperazine, 7-hydroxy-10-[[3-[4-(2-carboxyethyl)-1-piperazinyl]propyl]]-2 -tri-fluromethyl-10H-phenothiazine, was synthesized and coupled to bovine serum albumin. Immunization of New Zealand white rabbits with this drug-protein conjugate resulted in the production of antisera, one of which was subsequently utilized in the development of an RIA procedure. The described RIA for the first time enables the quantitation of the 7-hydroxy metabolite of trifluoperazine in human plasma after oral administration of single and therapeutic doses of trifluoperazine, in which 20 pg of the nonconjugated 7-hydroxy metabolite in 200 microL of plasma can be measured with a CV of less than 3% in B/Bo readings. Similar results were obtained by this assay procedure with or without the selective extraction of the 7-hydroxy metabolite and in the presence or absence of a large excess of trifluoperazine and other suspected major metabolites, such as the sulfoxide and N4'-oxide metabolites. This RIA procedure, together with a previously developed RIA for trifluoperazine, was used to directly determine plasma concentrations of trifluoperazine and its 7-hydroxy metabolite after administration of a single 5-mg oral dose of trifluoperazine to six healthy male volunteers. The mean +/- SD for the peak concentration (Cmax), the time to Cmax, the area under the curve from 0 to 24 h and, the apparent terminal elimination half-life for the 7-hydroxy metabolite were found to be 0.86 +/- 0.2 ng/mL, 6.2 +/- 1.6 h, 11.1 +/- 4.9 ng . h/mL, and 10.6 +/- 5.7 h, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Radioimmunoassay for trimeprazine in human plasma

Antisera to trimeprazine were raised in New Zealand white rabbits to an immunogen synthesized by covalent linkage of bovine serum albumin to N-(2-carboxyethyl)desmethyltrimeprazine. By use of an antiserum, a radioimmunoassay for trimeprazine was developed that is able to quantitate 0.38 ng/ml-1 in a 200 microliter plasma sample with a coefficient of variation of approximately 12%. The antiserum did not cross-react with the supposedly pharmacologically inactive metabolite trimeprazine sulfoxide; however, the cross-reactivity with the supposedly active metabolite N-desmethyltrimeprazine is significant (49%). The radioimmunoassay was able to measure the drug and/or N-desalkyl metabolites in plasma samples obtained as late as 24 hr following administration of a single oral dose (10mg) of trimeprazine tartrate. Analysis of the same plasma samples by a published high-performance liquid chromatographic procedure gave values much lower than those obtained by the radioimmunoassay, indicating the N-desalkyl metabolites are produced significantly after trimeprazine oral administration.

Radioimmunoassay for the sulfoxide metabolite of trifluoperazine and its application to a kinetic study in humans

Antibodies were produced in rabbits immunized with 10-[[3-[4-(2-carboxyethyl)-1-piperazinyl]-propyl]]-2 -trifluoromethyl-10H-phenothiazine sulfoxide-bovine serum albumin conjugate. The subsequently developed radioimmunoassay (RIA) procedure enables, for the first time, the quantitation of the sulfoxide metabolite of trifluoperazine in the plasma of humans after administration of therapeutic doses of trifluoperazine, in which 60 pg of the sulfoxide metabolite in 200 microL of plasma can be measured with a CV of less than 3%. Similar results were obtained by this assay with or without a benzene extraction step and also in the presence or absence of a large excess of trifluoperazine and suspected major metabolites of trifluoperazine. This RIA procedure, together with a previously developed RIA for trifluoperazine was used to directly determine plasma concentrations of trifluoperazine and its sulfoxide metabolite after administration of a single, low, oral dose of trifluoperazine to five healthy volunteers. The rapidly appearing, relatively high concentrations of the sulfoxide metabolite are indicative of presystemic sulfoxidation. The mean plasma elimination half-life for the sulfoxide metabolic of trifluoperazine was 5.8 +/- 1.3 h.

Development of radioimmunoassays for trifluoperazine and their application to metabolic studies of the drug

Antisera to trifluoperazine have been raised in New Zealand white rabbits to several different types of immunogens, where there was variation in the length and nature of the side chain attached to the phenothiazine nucleus, as well as in the number of hapten residues coupled to bovine serum albumin. A radioimmunoassay for trifluoperazine has been developed which is capable of quantitating 0.3125 ng ml-1 in a 200 microliter plasma sample, with cross-reactivities to the sulfoxide, 7-hydroxy, and N-desmethyl metabolites of trifluoperazine of the order of less than 1, 11, and 12%, respectively. Some of the investigated antisera were applied to metabolic studies involving trifluoperazine, where it was demonstrated that N-desmethyltrifluoperazine, rather than 7-hydroxytrifluoperazine, was a major metabolite of trifluoperazine in plasma of a volunteer following administration of a single 5 mg oral dose.