Metabolism and disposition of N,N-dimethyltryptamine and harmala alkaloids after oral administration of ayahuasca.

Ayahuasca is an Amazonian psychotropic plant tea obtained from Banisteriopsis caapi, which contains ß-carboline alkaloids, chiefly harmine, harmaline and tetrahydroharmine. The tea usually incorporates the leaves of Psychotria viridis or Diplopterys cabrerana, which are rich in N,N-dimethyltryptamine (DMT), a psychedelic 5-HT(2A/1A/2C) agonist. The ß-carbolines reversibly inhibit monoamine-oxidase (MAO), effectively preventing oxidative deamination of the orally labile DMT and allowing its absorption and access to the central nervous system. Despite increased use of the tea worldwide, the metabolism and excretion of DMT and the ß-carbolines has not been studied systematically in humans following ingestion of ayahuasca. In the present work, we used an analytical method involving high performance liquid chromatography (HPLC)/electrospray ionization (ESI)/selected reaction monitoring (SRM)/tandem mass spectrometry(MS/MS) to characterize the metabolism and disposition of ayahuasca alkaloids in humans. Twenty-four-hour urine samples were obtained from 10 healthy male volunteers following administration of an oral dose of encapsulated freeze-dried ayahuasca (1.0 mg DMT/kg body weight). Results showed that less than 1% of the administered DMT dose was excreted unchanged. Around 50% was recovered as indole-3-acetic acid but also as DMT-N-oxide (10%) and other MAO-independent compounds. Recovery of DMT plus metabolites reached 68%. Harmol, harmalol, and tetrahydroharmol conjugates were abundant in urine. However, recoveries of each harmala alkaloid plus its O-demethylated metabolite varied greatly between 9 and 65%. The present results show the existence in humans of alternative metabolic routes for DMT other than biotransformation by MAO. Also that O-demethylation plus conjugation is an important but probably not the only metabolic route for the harmala alkaloids in humans.

Rapid determination of piperazine-type stimulants in human urine by microextraction in packed sorbent after method optimization using a multivariate approach.

This paper describes the analysis of piperazine-type stimulants [1-benzylpiperazine (BZP), 1-(3-trifluoromethylphenyl)piperazine (TFMPP), 1-(3-chlorophenyl)piperazine (mCPP) and 1-(4-methoxyphenyl)piperazine (MeOPP)] in low volume urine samples (0.1 mL) by microextraction in packed sorbent and liquid chromatography-diode array detection. Analyte extraction has been comprehensively optimized, and the influencing factors were screened by means of the fractional factorial design approach. Several parameters susceptible of influencing the process were studied, and these included extraction sorbent type (C(8) and C(18)), sample dilution (1:2 and 1:4), number of aspirations through the device (2 and 8) and the amount of methanol on both the washing (0 and 10%) and eluting solvents (10 and 100%). The method was linear from 0.5 (lower limit of quantitation) to 5 µgmL(-1), with determination coefficients higher than 0.99 for all compounds. Intra- and interday precision ranged from 1 to 9%, trueness was within a ± 11% interval for all analytes, and analyte recoveries were of about 70% for mCPP and TFMPP, and of about 10% for MeOPP and BZP. The method has shown to be selective, as no interferences from endogenous substances were detected by analysis of blank samples, and the analytes were stable in the samples for short periods at room temperature, after three freeze/thaw cycles and in processed samples. Due to its simplicity and speed, this method can be successfully applied in the screening and quantitation of these compounds in urine samples, and is suitable for application in forensic toxicology routine analysis.

Disposition and metabolism of almotriptan in rats, dogs and monkeys.

Almotriptan is a new highly potent selective 5-HT1B/1D receptor agonist developed for the treatment of migraine, and the disposition of almotriptan in different animal species is now addressed in the current study. Almotriptan was well absorbed in rats (69.1%) and dogs (100%) following oral treatment. The absolute bioavailability was variable reflecting different degrees of absorption and first-pass metabolism (18.7-79.6%). The elimination half-life was short and ranged between 0.7 and 3 h. The main route of elimination of almotriptan was urine with 75.6% and 80.4% of the dose recovered over a 168-h period in rats and dogs, respectively. The gamma-aminobutyric acid metabolite formed by oxidation of the pyrrolidine ring was the main metabolite found in urine, faeces, bile, and plasma of rats and in monkey urine. By contrast, the unchanged drug, the indole acetic acid metabolite formed by oxidative deamination of the dimethylaminoethyl group, and the N-oxide metabolite were the main metabolites in dog.

Cytochrome P450 dependent metabolism of the new designer drug 1-(3-trifluoromethylphenyl)piperazine (TFMPP). In vivo studies in Wistar and Dark Agouti rats as well as in vitro studies in human liver microsomes.

1-(3-Trifluoromethylphenyl)piperazine (TFMPP) is a designer drug with serotonergic properties. Previous studies with male Wistar rats (WI) had shown, that TFMPP was metabolized mainly by aromatic hydroxylation. In the current study, it was examined whether this reaction may be catalyzed by cytochrome P450 (CYP)2D6 by comparing TFMPP vs. hydroxy TFMPP ratios in urine from female Dark Agouti rats, a model of the human CYP2D6 poor metabolizer phenotype (PM), male Dark Agouti rats, an intermediate model, and WI, a model of the human CYP2D6 extensive metabolizer phenotype. Furthermore, the human hepatic CYPs involved in TFMPP hydroxylation were identified using cDNA-expressed CYPs and human liver microsomes. Finally, TFMPP plasma levels in the above mentioned rats were compared. The urine studies suggested that TFMPP hydroxylation might be catalyzed by CYP2D6 in humans. Studies using human CYPs showed that CYP1A2, CYP2D6 and CYP3A4 catalyzed TFMPP hydroxylation, with CYP2D6 being the most important enzyme accounting for about 81% of the net intrinsic clearance, calculated using the relative activity factor approach. The hydroxylation was significantly inhibited by quinidine (77%) and metabolite formation in poor metabolizer genotype human liver microsomes was significantly lower (63%) compared to pooled human liver microsomes. Analysis of the plasma samples showed that female Dark Agouti rats exhibited significantly higher TFMPP plasma levels compared to those of male Dark Agouti rats and WI. Furthermore, pretreatment of WI with the CYP2D inhibitor quinine resulted in significantly higher TFMPP plasma levels. In conclusion, the presented data give hints for possible differences in pharmacokinetics in human PM and human CYP2D6 extensive metabolizer phenotype subjects relevant for risk assessment.

Absolute bioavailability, pharmacokinetics, and urinary excretion of the novel antimigraine agent almotriptan in healthy male volunteers.

Absolute bioavailability, pharmacokinetics, and urinary excretion of almotriptan, a novel 5-HT(1B/1D) receptor agonist, were studied in 18 healthy males following single intravenous (i.v.) (3 mg), subcutaneous (s.c.) (6 mg), and oral (25 mg) doses. Volunteers received each dose in a randomized sequence separated by a 7-day washout. Blood and urine samples for pharmacokinetic evaluations were taken for up to 24 hours after dosing. The disposition kinetics of almotriptan after i.v. and s.c. administration showed biphasic decline described by a two-compartment model. The fastest disposition phase was well observed, although estimates of the rate constant showed high variability. After s.c. administration of almotriptan, the bioavailability was 100% with a time to maximum plasma concentration (tmax) of 5 to 15 minutes, whereas after oral administration, the bioavailability was about 70% with a tmax of 1.5 to 3.0 hours. No significant differences were observed between administration routes in the elimination half-life (t(1/2), obtaining mean values ranging from 3.4 to 3.6 hours. The volume of distribution, total clearance, and t(1/2) indicated that almotriptan was extensively distributed and rapidly cleared from the body irrespective of dose or route of administration. The primary route of elimination was renal clearance (approximately 50%-60% of total body clearance). About 65% of the i.v. and s.c. dose and 45% of the oral dose were excreted unchanged in urine in 24 hours, with nearly 90% of this in the first 12 hours. Renal clearance was approximately 2- to 3-fold that of the glomerular filtration rate in man, suggesting that almotriptan is eliminated in part by renal tubular secretion.

The pharmacokinetics of the antimigraine compound zolmitriptan in Japanese and Caucasian subjects.

BACKGROUND: Zolmitriptan is a 5HT(1B/1D) receptor agonist effective in the acute treatment of migraine. Clinical trials in the USA and Europe have demonstrated the optimal oral therapeutic dose to be 2.5 mg. The 2.5-mg oral tablet has recently been licensed in Japan. OBJECTIVE: To compare the pharmacokinetics of zolmitriptan and its metabolites in Japanese and Caucasian subjects and evaluate the effect of gender on these pharmacokinetics in Japanese volunteers. METHODS: In this open, parallel-group study, 30 Japanese and 30 Caucasian volunteers (20-45 years) received a single 2.5-mg zolmitriptan tablet in the fasting state. Blood samples were taken up to 15 h post-dose to determine plasma concentrations of zolmitriptan and its active metabolite, 183C91. Urinary excretion of zolmitriptan, 183C91 and the inactive N-oxide and indole acetic acid metabolites were measured over 24 h. RESULTS: Japanese volunteers were, on average, smaller and lighter than Caucasian volunteers. Plasma-concentration profiles of zolmitriptan and 183C91 were similar in the two groups. Although geometric mean zolmitriptan and 183C91 area under the plasma concentration-time curve (AUC) and maximum plasma concentration (C(max)) were slightly higher in Japanese subjects (up to 20%), these differences were not considered to be of clinical relevance as the 90% confidence interval for the ratio of AUCs fell within pre-specified limits (0.67 to 1.5). Mean zolmitriptan and 183C91 half-lives were around 2.5 h for both populations. Urinary excretion of the four analytes was similar in Japanese and Caucasians. Plasma concentrations of zolmitriptan were higher in Japanese females than males (AUC 40% and C(max) 29% higher), consistent with the results previously obtained in Caucasians. CONCLUSION: Pharmacokinetic parameters of zolmitriptan were similar between Caucasian and Japanese volunteers.

Pharmacokinetics of rizatriptan in healthy elderly subjects.

OBJECTIVE: Rizatriptan is a serotonin 5-HT1B/1D receptor agonist for acute treatment of migraine. Its pharmacokinetics were assessed in healthy elderly males and females receiving a single 10 mg tablet oral dose. The pharmacokinetic data (AUC(0-infinity) and Cmax) for the elderly in this study were compared with historical data from previous studies for healthy young adults (n = 65). METHODS: In a double-blind, parallel, placebo-controlled study, healthy elderly female and male subjects aged 65 or older (n = 8 each) received a single oral dose of 10 mg rizatriptan. Plasma and urine concentrations of drug were determined by HPLC with tandem mass spectrometry detection at several collection time points or intervals starting at predose and postdose over 24 h. RESULTS: In elderly subjects, the geometric mean values for AUC(0-infinity) and Cmax were 77.7 ng/h/ml and 21.9 ng/ml; the average values for tmax, half-life (t 1/2), renal clearance (Clr), and percent urinary excretion of dose (Ue) were 1.2 h, 1.8 h, 197 ml/min and 9.3%, respectively. The AUC(0-infinity) and Cmax of rizatriptan were similar in elderly and young subjects. The geometric mean AUC ratio of elderly to young was 0.96 with 90% confidence interval (0.83, 1.11), p > 0.25. The geometric mean Cmax ratio was 0.89 with 90% confidence interval (0.72, 109), p > 0.25. No significant pharmacokinetic differences were observed between elderly males and females. CONCLUSIONS: The plasma pharmacokinetics of rizatriptan appear to be similar in the elderly and young. In the elderly, the pharmacokinetics of rizatriptan do not appear to differ between male and female to a clinically significant extent.

Evaluation of the potential pharmacokinetic interaction between almotriptan and fluoxetine in healthy volunteers.

This study was designed to assess the pharmacokinetics of almotriptan, a 5HT1B/1D agonist used to treat migraine attacks, when administered in the presence and absence of fluoxetine. Healthy male (n = 3) and female (n = 11) volunteers received (1) 60 mg fluoxetine daily for 8 days and 12.5 mg almotriptan on Day 8 and (2) 12.5 mg almotriptan on Day 8, according to a two-way crossover design. Plasma and urinary almotriptan concentrations were measured by HPLC methods. Treatment effects on pharmacokinetic parameters were assessed by analysis of variance. Mean almotriptan Cmax was significantly higher following combination treatment with fluoxetine (52.5 +/- 11.9 ng/ml vs. 44.3 +/- 10.9 ng/ml, p = 0.023). Mean AUC0-infinity was not significantly affected by fluoxetine coadministration (353 +/- 55.7 ng.h/ml vs. 333 +/- 33.6 ng.h/ml, p = 0.059). Confidence interval analysis (90%) of log-transformed pharmacokinetic parameters showed that the confidence interval for AUC0-infinity was within the 80% to 125% limit for equivalence, but Cmax was not (90% CI 106%-134% of the reference mean). Adverse events were mild to moderate in intensity, and no clinically significant treatment effects on vital signs or ECGs were observed. The results show that fluoxetine has only a modest effect on almotriptan Cmax. Concomitant administration of the two drugs is well tolerated, and no adjustment of the almotriptan dose is warranted.

Pharmacokinetic interaction between verapamil and almotriptan in healthy volunteers.

OBJECTIVE: To assess the interaction between almotriptan, a 5-HT1B/1D-receptor agonist used to treat migraine, and verapamil, an agent for migraine prophylaxis. METHODS: Twelve healthy volunteers received the following treatments in a crossover design: (1) 120-mg sustained-release verapamil tablet twice daily for 7 days and one 12.5-mg almotriptan tablet on day 7 and (2) one 12.5-mg almotriptan tablet alone on day 7. Serial plasma and urine samples were obtained on day 7. Almotriptan plasma concentrations were determined by liquid chromatography-tandem mass spectrometry; urine samples were analyzed by ultraviolet HPLC. Safety measures included blood pressure and pulse measurements, electrocardiography, and adverse event monitoring. Statistical comparisons of pharmacokinetic parameters and vital sign data were made by ANOVA. RESULTS: Mean almotriptan peak concentration and area under the plasma concentration-time curve were significantly higher and volume of distribution and oral clearance were significantly lower after coadministration of almotriptan and verapamil compared with administration of almotriptan alone. The magnitudes of these differences were approximately 20%. Renal clearance was unaffected by verapamil coadministration. No significant effects of treatment on blood pressure or pulse were detected, with the exception of sitting systolic blood pressure at 2 hours after administration. However, the difference in mean change from baseline at this time point was only 8 mm Hg. CONCLUSIONS: Verapamil modestly inhibited almotriptan clearance to a degree consistent with the modest contribution of CYP3A4 to almotriptan metabolism. This observation and the lack of effect of verapamil on the tolerability to almotriptan administration suggest that no reduction of the almotriptan dose is warranted.

Disposition and pharmacokinetics of the antimigraine drug, rizatriptan, in humans.

The absorption and disposition of rizatriptan (MK-0462, Maxalt(TM)), a selective 5-HT(1B/1D) receptor agonist used in the treatment of migraine headaches, was investigated in humans. In a two-period, single i.v. (3 mg, 30-min infusion), and single oral (10 mg) dose study with [(14)C]rizatriptan in six healthy human males, total recovery of radioactivity was approximately 94%, with unchanged rizatriptan and its metabolites being excreted mainly in the urine (89% i.v. dose, 82% p.o. dose). Approximately 26 and 14% of i.v. and oral rizatriptan doses, respectively, were excreted in urine as intact parent drug. In a second, high-dose study (60 mg p.o.), five metabolites excreted into urine were identified using liquid chromatography-tandem mass spectrometry and NMR methods. They were triazolomethyl-indole-3-acetic acid, rizatriptan-N(10)-oxide, 6-hydroxy-rizatriptan, 6-hydroxy-rizatriptan sulfate, and N(10)-monodesmethyl-rizatriptan. Urinary excretion of triazolomethyl-indole-3-acetic acid after i.v. and oral administrations of rizatriptan accounted for 35 and 51% of the dose, respectively, whereas the corresponding values for rizatriptan-N(10)-oxide were 4 and 2% of the dose. Plasma clearance (CL) and renal clearance (CL(r)) were 1325 and 349 ml/min, respectively, after i.v. administration. A similar CL(r) value was obtained after oral administration (396 ml/min). The primary route of rizatriptan elimination occurred via nonrenal route(s) (i.e., metabolism) because the CL(r) of rizatriptan accounted for 25% of total CL. Furthermore, the CL(r) was higher than normal glomerular filtration rate ( approximately 130 ml/min), indicating that this compound was actively secreted by renal tubules. The absorption of rizatriptan was approximately 90%, but it experienced a moderate first-pass effect, resulting in a bioavailability estimate of 47%.

Pharmacokinetics and tolerability of a novel 5-HT1D agonist, PNU-142633F.

OBJECTIVES: The objectives of this study were to characterize the safety, tolerability and pharmacokinetics of a single, oral dose of PNU-142633F escalating over the range of 1.0 mg to 100 mg (free base equivalents). METHODS: This was a randomized, double-blind, single-dose, placebo-controlled, dose-escalation trial, with each dose group (1.0, 3.0, 10, 30, 50, 75 and 100 mg) having eight volunteers (six PNU-142633F and two placebo). Clinical laboratory tests, electrocardiogram, Holter monitoring, and assessment of adverse events were used to gauge the tolerability of PNU-142633. Serial blood samples and urine collections were obtained and plasma and urine PNU-142633 concentrations were determined by a validated HPLC fluorescence method. RESULTS: PNU-142633 was well tolerated after oral administration. There were no reports of serious or unexpected adverse events. The most common adverse event that was possibly medication-related was transient dizziness. There were no clinically significant or dose-related effects of PNU-142633 on any vital sign parameters (aural temperature, systolic and diastolic blood pressure, pulse rate or respiratory rate), at any study time or dose. There were no clinically significant ECG changes. Only sporadic abnormalities in clinical chemistry values and hematology were noted. After the 1.0 mg and 3.0 mg doses, plasma concentrations of PNU-142633 were either below or only slightly above the lower limit of quantitation (2 ng/ml). At higher doses (30-100 mg) the terminal half-life was relatively constant at approximately 11 hours. Neither Cmax nor AUC(0-infinity) increased proportionally with the administered dose. The mean percentage of the dose excreted in the urine as intact PNU-142633 increased from 14.3% after the 1 mg dose to 49.3% after the 100 mg dose. CONCLUSIONS: The clinical safety and pharmacokinetic data support the study of this agent as a potential treatment for migraine attacks.

Disposition of [14C]avitriptan in rats and humans.

Avitriptan is a new 5-HT1-like agonist with abortive antimigraine properties. The study was conducted to characterize the pharmacokinetics, absolute bioavailability, and disposition of avitriptan after intravenous (iv) and oral administrations of [14C]avitriptan in rats and oral administration of [14C]avitriptan in humans. The doses used were 20 mg/kg iv and oral in the rat, 10 mg iv in humans, and 50 mg oral in humans. The drug was rapidly absorbed after oral administration, with peak plasma concentrations occurring at 0.5 hr postdose. Absolute bioavailability was 19.3% in rats and 17.2% in humans. Renal excretion was a minor route of elimination in both species, with the majority of the dose being excreted in the feces. After a single oral dose, urinary excretion accounted for 10% of the administered dose in rats and 18% of the administered dose in humans, with the remainder excreted in the feces. Extensive biliary excretion was observed in rats. Avitriptan was extensively metabolized after oral administration, with the unchanged drug accounting for 32% and 22% of the total radioactivity in plasma in rats and humans, respectively. Plasma terminal elimination half-life was approximately 1 hr in rats and approximately 5 hr in humans. The drug was extensively distributed in rat tissues, with a tendency to accumulate in the pigmented tissues of the eye.

The absolute bioavailability and metabolic disposition of the novel antimigraine compound zolmitriptan (311C90).

AIMS: Two open studies in healthy volunteers were conducted to determine the absolute bioavailability and metabolic disposition of zolmitriptan (311C90), a novel 5HT1D agonist for the acute treatment of migraine. METHODS: After an initial test i.v. infusion, bioavailability was assessed by comparison of AUC after an i.v. infusion (3.5 mg) and an oral tablet (10 mg), in six men and six women using a randomised, crossover design. Disposition was studied by administration of a 25 mg capsule, labelled with 100 microCi [14C]-zolmitriptan, to five men and one woman on a single occasion. RESULTS: Zolmitriptan was well tolerated by both i.v. and oral routes. Adverse events were mostly mild, consistent with earlier studies and characteristic of this class of drug. Reports were similar in nature and number after both oral and i.v. dosing. Mean +/- s.d. oral bioavailability was 0.49 +/- 0.24 (0.38 +/- 0.16 in men and 0.60 +/- 0.28 in women). After oral dosing, Cmax and AUC values in women were approximately double those in men. Relative to zolmitriptan concentrations, metabolite concentrations were higher after oral dosing than after i.v., and higher in men compared with women. Half-life was significantly longer after oral dosing (mean 22%, 95% CI 6-35%). Mean +/- s.d. values for CL, V2 and t1/2,z after i.v. dosing (all subjects) were 8.7 +/- 1.7 ml min-1 kg-1, 122 +/- 321 and 2.30 +/- 0.59 h respectively. Following administration of 25 mg [14C]-zolmitriptan, 91.5% of the dose was recovered in 7 days, 64.4 +/- 6.5% in urine and 27.1 +/- 6.0% in faeces. Less than 10% was recovered unchanged in urine, with 31.1 +/- 6.4% recovered as the inactive indole acetic acid metabolite. Most of the faecal material was unchanged zolmitriptan, representing unabsorbed drug. Plasma concentrations of [14C] were slightly higher than those of the summed concentrations of known analytes zolmitriptan, the active N-desmethyl metabolite (183C91), the inactive N-oxide (1652W92) and indole acetic acid (2161W92) metabolites, which accounted for 86% of total plasma radioactivity. No other significant metabolites were detected in plasma. Some minor additional metabolites were detected in urine, none of which contributed more than 5% of the dose. CONCLUSIONS: The data suggest that zolmitriptan undergoes first-pass metabolism and this is more extensive in men than in women. Zolmitriptan has suitable bioavailability for an acute oral migraine treatment and there are no significant unidentified metabolites in man.

Metabolism and excretion of a new antianxiety drug candidate, CP-93,393, in cynomolgus monkeys: identification of the novel pyrimidine ring cleaved metabolites.

The metabolism and excretion of a new anxiolytic/antidepressant drug candidate, CP-93,393, ((7S, 9aS)-1-(2-pyrimidin-2-yl-octahydro-pyrido[1, 2-a]-pyrazin-7-yl-methyl)-pyrrolidine-2,5-dione) were investigated in cynomolgus monkeys after oral administration of a single 5 mg/kg dose of 14C-CP-93,393. Urine, bile, feces, and blood samples were collected and assayed for total radioactivity, parent drug, and metabolites. Total recovery of the administered dose after 6 days was 80% with the majority recovered during the first 48 hr. An average of 69% of the total radioactivity was recovered in urine, 4% in bile, and 7% in feces. Mean Cmax and AUC(0-infinity) values for the unchanged CP-93,393 were 143.2 ng/ml and 497.7 ng.hr/ml, respectively, in the male monkeys and 17.2 ng/ml and 13.7 ng.hr/ml, respectively, in the female monkeys. HPLC analysis of urine, bile, feces, and plasma from both male and female monkeys indicated extensive metabolism of CP-93,393 to several metabolites. The identification of metabolites was achieved by chemical derivatization, beta-glucuronidase/sulfatase treatment, and by LC/MS/MS, and the quantity of each metabolite was determined by radioactivity detector. CP-93,393 undergoes metabolism by three primary pathways, aromatic hydroxylation, oxidative degradation of the pyrimidine ring, and hydrolysis of the succinimide ring followed by a variety of secondary pathways, such as oxidation, methylation, and conjugation with glucuronic acid and sulfuric acid. The major metabolites, oxidation on the pyrimidine ring to form 5-OH-CP-93,393 (M15) followed by glucuronide and sulfate conjugation (M7 and M13), accounted for 35-45% of the dose in excreta. Two metabolites (M25 and M26) were formed by further oxidation of M15 followed by methylation of the resulting catechol intermediate presumably by catechol-O-methyl transferase. A novel metabolic pathway, resulting in the cleavage of the pyrimidine ring, was also identified. The metabolites (M18, M20, and M21) observed from this pathway accounted for 8-15% of the dose. Aliphatic hydroxylation of the succinimide ring was a very minor pathway in monkey. 5-Hydroxy-CP-93,393 (M15, 37-49%), its sulfate and glucuronide conjugates (M7 and M13, approximately 34%), and the pyrimidine ring cleaved product (M18, approximately 8%) were the major metabolites in monkey plasma. The identified metabolites accounted for approximately 90, 93, 97, and 92% of the total radioactivity present in urine, bile, plasma, and feces, respectively. The major in vivo oxidative metabolites were also observed after in vitro incubations with monkey liver microsomes.

Determination of sumatriptan succinate in plasma and urine by high-performance liquid chromatography with electrochemical detection.

Methods are described for the determination of sumatriptan succinate (1) in plasma and urine. Prior to chromatography, plasma is subjected to liquid/liquid extraction and urine is diluted in pH 7 buffer without further pretreatment. Both procedures use reversed-phase high-performance liquid chromatography with electrochemical detection. The analytical range for the plasma assay is 1-30 ng/mL and that for the urine assay is 0.2-12 micrograms/mL. The assays are linear over the analytical ranges and specific with respect to endogenous interference and the major metabolite (2) of sumatriptan. For the plasma assay, intra-assay data (n = 6) indicate a maximum coefficient of variation (CV) and bias across the calibration range of 6.0 and 3.0%, respectively. The interassay CV (n = 4) is approximately 15% at the bottom of the calibration range, falling to 4% or less at 8 ng/mL and above. Bias is approximately 12% at the bottom, reducing to < 2% at 8 ng/mL and above. The urine intra-assay data indicate a maximum CV and bias of 8.9 and 8.3%, respectively. The interassay is CV 15% for the lowest calibrant, reducing steadily across the calibration range to < 2% for the top calibration value, and bias is < 7% across the range.