Simultaneous quantification of berberine and lysergol by HPLC-UV: evidence that lysergol enhances the oral bioavailability of berberine in rats.

A sensitive and simple HPLC method was developed for the simultaneous quantification of berberine and lysergol in rat plasma. The chromatographic separation was achieved on a C(18) column using isocratic elution with methanol-acetonitrile-0.1% ortho-phosphoric acid (25:20:55, v/v/v), pH adjusted to 6.5 with triethylamine and detected at a UV wavelength of 230 nm. The extraction of the berberine and lysergol from the rat plasma with methylene chloride resulted in their high recoveries (82.62 and 90.17%). HPLC calibration curves for both berberine and lysergol based on the extracts from the rat plasma were linear over a broad concentration range of 50-1000 ng/mL. The limit of quantification was 50 ng/mL. Intra- and inter-day precisions were <15% and accuracy was 87.12-92.55% for berberine and 87.01-92.26% for lysergol. Stability studies showed that berberine and lysergol were stable in rat plasma for short- and long-term period for sample preparation and analysis. The described method was successfully applied to study the pharmacokinetics of berberine as well as lysergol following oral administration in Sprague-Dawley rats. The results of the study inferred that lysergol improved the oral bioavailability of berberine.

Physiologic disposition of pergolide.

Pergolide, a synthetic ergoline, is a potent long-acting dopaminergic drug effective in Parkinson's disease and amenorrhea-galactorrhea. After 138 micrograms 14C-pergolide orally to healthy subjects, radioactivity was present in plasma and red blood cells. Salivary radioactivity was one third to one tenth that in plasma. Radioactivity in plasma appeared after 15 to 30 min, peaked at 1 to 2 hr, and was barely detectable after 96 hr. Plasma radioactivity was not attributable to pergolide, and the levels did not correlate well with the duration of the prolactin-lowering effect induced by pergolide. Pergolide became bound to several plasma proteins and could not be displaced by other drugs that are also bound or by possible metabolites of pergolide. Radioactivity was eliminated as pergolide metabolites in urine (55%), feces (40%), and breath (5%, as 14CO2).

Cabergoline in Parkinson's disease: long-term follow-up.

We treated 36 patients with motor fluctuations and dyskinesias on chronic levodopa therapy with cabergoline (CBG) once a day for a mean period of 14.2 +/- 5.8 months. There was a significant increase in the "on" hours and a reduction in "off-period" dystonia. Ten patients continued to show a marked improvement after 28.3 months of treatment (mean dose, 11.3 +/- 4.5 mg). In 23 patients, increased dyskinesias (daily CBG dose, 11 +/- 4.3 mg) had complicated the positive effect after 17.2 +/- 4.8 months. Three patients (daily CBG dose, 14.3 mg) were therapeutic failures, and administration of CBG was stopped. Side effects leading to CBG discontinuation were visual hallucinations (n = 5), heart failure (n = 5), and nausea and vomiting (n = 1). Plasma CBG levels, measured in seven patients taking 3, 5, or 7 mg daily (po), showed fairly stable concentrations throughout the 24 hours. We concluded that CBG is an efficient dopamine agonist that can provide continuous dopaminergic stimulation when taken orally once a day.

Clinical pharmacokinetics of cabergoline.

Cabergoline is a synthetic ergoline dopamine agonist with a high affinity for D(2) receptors indicated for use in both early and advanced Parkinson's disease and in hyperprolactinaemic disorders. Following oral administration, peak plasma concentrations of cabergoline are reached within 2-3 hours. Over the 0.5-7mg dose range, cabergoline shows linear pharmacokinetics in healthy adult volunteers and parkinsonian patients. Cabergoline is moderately bound (around 40%) to human plasma proteins in a concentration-independent manner; concomitant administration of highly protein-bound drugs is unlikely to affect its disposition. The absolute bioavailability of cabergoline is unknown. Cabergoline is extensively metabolised by the liver, predominantly via hydrolysis of the acylurea bond of the urea moiety. Cytochrome P450-mediated metabolism appears to be minimal. The major metabolites identified thus far do not contribute to the therapeutic effect of cabergoline. A significant fraction of the administered dose undergoes a first-pass effect. Less than 4% is excreted unchanged in the urine. The elimination half-life of cabergoline estimated from urinary data of healthy subjects ranges between 63 and 109 hours. Mild to moderate renal and hepatic impairment, administration of food and the use of concomitant antiparkinsonian medications, such as levodopa and selegiline, have no effect on the pharmacokinetics of cabergoline.The pharmacokinetic properties of cabergoline allow once daily administration in patients with Parkinson's disease and twice weekly administration in patients with hyperprolactinaemia, making this drug advantageous over other dopaminergic agents in term of both therapeutic compliance and better symptom control.

High-sensitivity quantitation of cabergoline and pergolide using a triple-quadrupole mass spectrometer with enhanced mass-resolution capabilities.

Quantitative analysis of pharmaceuticals with low systemic plasma levels requires the utmost in sensitivity and selectivity from the analytical method used. A recently introduced triple-quadrupole mass spectrometer with unique enhanced mass-resolution capability was evaluated in the analysis of two such drugs, cabergoline and pergolide, in plasma. Liquid chromatographic/electrospray ionization selected reaction monitoring determination of cabergoline in plasma at unit mass-resolution demonstrated improved sensitivity (50 fg on-column), coupled with suitable accuracy and precision over a broad linear dynamic range covering five orders of magnitude (50 fg to 5 ng on-column). Liquid chromatographic/atmospheric pressure chemical ionization selective reaction monitoring determination of pergolide in plasma also attained a high level of sensitivity (500 fg on-column) at unit mass-resolution, with accuracy and precision values well within pharmaceutical industry standards. Again, a linear dynamic range covering five orders of magnitude (500 fg to 50 ng on-column) was achieved for the assay. Utility of the enhanced mass-resolution feature of the triple-quadrupole mass spectrometer in the determination of pergolide resulted in an improvement in analyte sensitivity (250 fg on-column) and linear dynamic range (250 fg to 50 ng on-column).

Lack of pharmacokinetic interaction between the selective dopamine agonist cabergoline and the MAO-B inhibitor selegiline.

The addition of a dopamine agonist and of a monoamine oxidase type B inhibitor to I-dopa has been suggested in the therapy of Parkinson's disease. The plasma pharmacokinetics of both cabergoline and I-dopa have previously been shown to remain unaffected when the two drugs are given concomitantly. This study aimed at examining whether the plasma pharmacokinetic parameters of cabergoline and selegiline are modified when given in combination. Selegiline is hardly detectable in plasma. Therefore, the plasma levels of its metabolites amphetamine, methamphetamine and desmetylselegiline were used to assess the effect of cabergoline co-administration. Plasma levels of the selegiline metabolites were determined first after selegiline administration (10 mg/day) for 8 days, and then after administration of both drugs for 22 additional days (day 30). Cabergoline plasma levels were measured on day 30, and then after administration of cabergoline (1 mg/day) alone for further 22 days. No statistical difference was found between the Cmax.ss, tmax.ss, AUC0-24h.ss, C0h.ss, C24h.ss values of cabergoline and of the selegiline metabolites when the two drugs were given alone or in combination, indicating the absence of pharmacokinetic interaction between cabergoline and selegiline.

Determination of cabergoline and L-dopa in human plasma using liquid chromatography-tandem mass spectrometry.

We determined cabergoline and L-dopa in human plasma using liquid chromatography-mass spectrometry with tandem mass spectrometry (LC-MS-MS). The deproteinized plasma samples with organic solvent or acid were analyzed directly by reversed-phase liquid chromatography. Using multiple reaction monitoring (MRM, product ions m/z 381 of m/z 452 for cabergoline and m/z 152 of m/z 198 for L-dopa) on LC-MS-MS with electrospray ionization (ESI), cabergoline and L-dopa in human plasma were determined. Calibration curves of the method showed a good linearity in the range 5-250 pg/ml for cabergoline and 1-200 ng/ml for L-dopa, respectively. The limit of determination was estimated to be approximately 2 pg/ml for cabergoline and approximately 0.1 ng/ml for L-dopa, respectively. The method was applied to the analysis of cabergoline and L-dopa in plasma samples from patients treated with these drugs. The precision of analysis showed coefficients of variation ranging from 3.8% to 10.5% at cabergoline concentration of 13.8-26.2 pg/ml and from 2.9% to 8.9% at an L-dopa concentration of 302.5-522.1 ng/ml in patient plasma. As a result, the procedure proved to be very suitable for routine analysis.

Determination of FCE 23884, a new ergolene derivative, and its possible metabolite, the 6-nor-derivative in plasma by high-performance liquid chromatography with fluorescence detection.

A sensitive and selective high-performance liquid chromatographic method for the determination of FCE 23884 and its 6-nor-derivative (FCE 26506) in plasma has been developed. After buffering the plasma samples, the compounds and the internal standard were extracted with ethyl ether-n-octanol (9:1, v/v), back-extracted into 0.01 M phosphoric acid and then analysed by reversed-phase liquid chromatography. Quantification was achieved by fluorescence detection of the eluate. The linearity, precision and accuracy of the method were evaluated. No interference from the biological matrix was observed. The assay was adequate for the quantification of plasma levels of the two compounds after a single oral dose of 1 mg of FCE 23884 in humans.

A fatal overdose of the ergot derivative cabergoline.

A 79-year-old woman, with Parkinson's disease treated with cabergoline, was admitted to a hospital due to jaundice and weakness. She was found confused, absent minded, and died after 2 weeks. Autopsy showed an extrahepatic bile duct adenocarcinoma with spread to the gall bladder, the liver, and regional lymphnodes. While cleaning the hospital bed after her death, the nurses found several tablets hidden in the bed. Biological samples obtained at the autopsy were screened for common drugs and narcotics. Several drugs such as buprenorphine, codeine, paracetamol, and propranolol were detected in the blood at therapeutic levels. A method to determine cabergoline in whole blood and other forensic matrices was developed, and further investigations determined cabergoline concentrations in whole blood and liver tissue of 94 and 3100 microg/kg, respectively. The blood concentration was 100 times above the therapeutic level reported on cabergoline in plasma and in combination with her symptoms, suggest she took a fatal overdose of cabergoline.

Shortening of interestrous intervals with cabergoline in bitches: a clinical trial.

Two consecutive interestrous intervals (n=46) were recorded in 23 bitches of different breeds. At varying times after day 100 from the onset of the second proestrus, cabergoline (5 microg/kg per os q 24 hours) was administered from early (n=11), mid- (n=10), and late (n=2) anestrus until 2 days after the beginning of the following proestrus. Interestrous intervals (IEI) were significantly shorter in the cabergoline-treated time periods when compared to the nontreated IEI (184+/-4.5 days versus 239+/-4.5 days; P<0.01). The mean number of days of cabergoline treatment until the onset of proestrus was 21.4+/-2.9 (least square means and standard error of the mean [LSM+/-SEM]). Mean cabergoline treatment durations beginning in early, mid-, and late anestrus were 27.4+/-3.7, 17.6+/-3.8, and 5+/-3 days (LSM+/-SEM), respectively. A significant correlation was found between the stage of anestrus in which the treatments began and the duration of the treatments required to induce estrus (0.51, P=0.01).

Effect of clarithromycin on the pharmacokinetics of cabergoline in healthy controls and in patients with Parkinson's disease.

Cabergoline is used in the treatment of Parkinson's disease (PD). Clarithromycin is a potent inhibitor of CYP3A4 and P-glycoprotein and is often co-administered with cabergoline in usual clinical practice. We studied the effect of clarithromycin co-administration on the blood concentration of cabergoline in healthy male volunteers and in PD patients. Study 1: Ten healthy male volunteers were enrolled and were randomized to take a single oral dose of cabergoline (1 mg/day) for 6 days or a single oral dose of cabergoline plus clarithromycin (400 mg/day) for 6 days. Study 2: Seven PD patients receiving stable cabergoline doses were enrolled. They were evaluated for the plasma cabergoline concentration before and after the addition of clarithromycin 400 mg/day for 6 days, and again 1 month after discontinuation of clarithromycin. The dose and duration of clarithromycin were decided according to usual clinical practice. In healthy male volunteers, mean Cmax and AUC(0-10 h) of cabergoline increased to a similar degree during co-administration of clarithromycin. Mean plasma cabergoline concentration over 10 h post-dosing increased 2.6-fold with clarithromycin co-administration. In PD patients, plasma cabergoline concentration increased 1.7-fold during clarithromycin co-administration. Co-administration with clarithromycin may increase the blood concentration of cabergoline in healthy volunteers and in PD patients.

Efficacy and safety of high-dose cabergoline in Parkinson's disease.

OBJECTIVES: To assess the efficacy and safety of high-dose (up to 20 mg/day) cabergoline in Parkinson's disease (PD) patients with motor fluctuations and/or dyskinesias. MATERIALS AND METHODS: Thirty-four PD patients had cabergoline up-titrated and their levodopa (L-dopa) reduced over a maximum of 20 weeks, followed by at least 6 weeks steady cabergoline dosing. Primary endpoint was change in mean hyperkinesia intensity at the final visit (week 26). RESULTS: Mean (+/- SD) cabergoline was increased from 6.43 +/- 2.66 to 12.78 +/- 5.67 mg/day and mean L-dopa reduced from 606.6 +/- 263.9 to 370.6 +/- 192.5 mg/day. A significant reduction (P < 0.001) in mean hyperkinesia intensity occurred from baseline (day 0) to week 26. Improvements in 'on with dyskinesias', mean dystonia intensity (P < 0.05), time spent in 'severe off' condition, severity of 'off' periods as well as clinical/patient global impression, and health-related quality of life were observed. Twenty-four drug-related adverse events were recorded of which four were regarded as serious. CONCLUSION: High-dose cabergoline was well tolerated and provided significant improvements in the Parkinson symptomatology and a reduced requirement for L-dopa.

Determination of cabergoline by electrospray ionization tandem mass spectrometry: picogram detection via column focusing sample introduction.

An electrospray ionization tandem mass spectrometric method was developed for low-picogram detection of an ergot alkaloid, cabergoline, in coyote plasma extracts. Cabergoline is under investigation as an abortifacient in canid species. Central to the successful development of this method was the ability to introduce relatively large sample volumes into the mass spectrometer. This was achieved by focusing the analyte on a conventional high-performance liquid chromatography guard column prior to elution into the spectrometer. Volumes up to at least 900 microL could be injected onto the guard column using a 100% aqueous mobile phase. Cabergoline retained on the column was eluted as a discreet band into the mass spectrometer by the rapid addition of methanol (30%) to the mobile phase. As compared to flow injection sample introduction, the ability to inject larger sample volumes led to a greatly lowered detection limit. Using this technique and a modification of a previously reported extraction procedure, cabergoline could be determined in coyote plasma at concentrations as low as 9 pg of cabergoline/mL of plasma.

Quantitative determination of cabergoline in human plasma using liquid chromatography combined with tandem mass spectrometry.

A liquid chromatography/mass spectrometry (LC/MS) method using electrospray ionization (ESI) is described for the quantitative determination of cabergoline (N-[3-(dimethylamino)propyl]-N-(ethylamino)-carbonyl-6-(2-propenyl)- ergoline-8 beta-carboxamide) in human plasma. The method consists of liquid-liquid extraction after addition of deuterated internal standard, and reverse-phase liquid chromatography with electrospray ionization combined with tandem mass spectrometry (MS/MS). Using selected reaction monitoring, the method provides a quantitation limit of 1.86 pg/mL. Calibration curves acquired on five different days showed good linearity (r > 0.99) in the range 1.86-124 pg/mL and reproducibility of the slope (% relative standard deviation, RSD = 10.0). The intra-day precision, determined by assaying plasma containing four different concentrations of cabergoline processed in replicate, was found to range from 2.4 to 17.0% (RSD). The inter-day precision, evaluated for the same concentrations, ranged from 7.9 to 10.7% (RSD). The accuracy of the method, expressed as the percent ratio between found to added amount, was 99.1 +/- 10.2% (RSD = 10.3%, n = 78).

Radioimmunoassay of plasma lisuride in man following intravenous and oral administration of lisuride hydrogen maleate: effect on plasma prolactin level.

The development of a sensitive radioimmunoassay for the determination of lisuride in plasma is described. The antiserum against lisuride-4-hemisuccinate-BSA was raised in rabbits. Using this method the plasma levels of lisuride were monitored following one intravenous (25 microgram) and two oral (100 microgram and 300 microgram) doses of lisuride hydrogen maleate in three female and three male volunteers (intra-individual comparison). The plasma prolactin was also determined by radioimmunoassay. Following i. v. injection, the concentration of lisuride declined in three phases, with half-lives of 5 min, 25 min and 2 h. The total plasma clearance of 800 +/- 250 ml X min-1 was in the range of "plasma flow" through the liver. In agreement with the high rate of biotransformation, the bioavailability of lisuride administered orally was 10% +/- 7% of the 100-microgram dose, and 22% +/- 7% of the 300-microgram dose. The plasma prolactin was lowered to 3%-18% of its pretreatment value depending on the route of administration and the dose. The reduction appeared to be short-lived and to be directly dependent on the plasma concentration of lisuride. Following intravenous injection, the prolactin level declined after a so far unexplained lag-time of 0.5 h.

Determination of ergot alkaloids in plasma by high-performance liquid chromatography and fluorescence detection.

Liquid chromatographic methods for the determination of ergotamine and methylergometrine in plasma have been developed. The samples are extracted with an organic solvent at pH 9.0 cleaned by extractions and finally injected on an ODS-Hypersil reversed-phase column with acetonitrile-ammonium carbonate buffer as the mobile phase. THe polarity of solvents used for extraction and the mobile phase are varied with the compounds of interest. Ergocristine is used as internal standard for ergotamine, and methysergide for the determination of methylergometrine. The stability of samples and standard solutions for calibration are discussed. Conditions for high selectivity and sensitivity of detection are given. Concentrations down to 100 pg/ml of plasma can be detected with a 3-ml sample.

Description of the time course of the prolactin suppressant effect of the dopamine agonist CQP201-403 by an integrated pharmacokinetic-pharmacodynamic model.

Six male volunteers (mean age 24 years) received a single oral dose of 0.025 mg CQP201-403 and placebo in a randomised double-blind crossover design. Fifteen plasma samples were collected over 48 h and were assayed by radioimmunoassay for drug substance and prolactin (PRL). Three of the samples were drawn during sleep on the first study day. The pharmacological effect (E%) of CQP201-403 was expressed as reduction in plasma PRL levels. The pharmacokinetic (PK)-pharmacodynamic (PD) model consisted of two kinetic compartments and an effect compartment linked to the central compartment. A sigmoid Emax model (Hill equation) described the relationship between the drug concentration in the effect compartment and E%. Curve-fitting of PK and PD data provided individual parameter estimates which served to generate computer-simulated PK and PD profiles after single and multiple doses in order to: investigate the in vivo concentration-effect relationship; evaluate the consequence of dosage reduction on the steady-state PD profile; and study the robustness of the response to changes in drug potency and bioavailability.

Disposition and biotransformation of quinpirole, a new D-2 dopamine agonist antihypertensive agent, in mice, rats, dogs, and monkeys.

The disposition and metabolism of quinpirole were studied in rats, mice, dogs, and monkeys. A single 2 mg/kg dose of 14C-quinpirole was administered orally to rats, mice, and monkeys. Dogs were given a single 0.2 mg/kg iv dose of 14C-quinpirole. Of the dose administered, 75-96% was recovered in the urine within 72 hr, with the majority being excreted during the first 24 hr. Peak plasma concentrations of radioactivity and quinpirole were coincident and were observed within 0.25 hr in rodents and at 2 hr in monkeys. Unchanged quinpirole accounted for 0.9%, 36%, and 69% respectively. Biotransformation of quinpirole was compared by quantitating the urinary metabolites by HPLC. The percentage of the radioactivity in urine representing unchanged drug was determined for each species: monkey (3%), dog (13%), mouse (40%), and rat (57%). The majority of 14C-quinpirole was shown to be biotransformed in rats, mice, and monkeys through common metabolic pathways but to various extents. Most metabolites resulted from structural alterations (N-dealkylation, lactam formation, omega and omega-1 hydroxylation) that centered around the piperidine ring portion of the molecule. These metabolites were less important in dogs. The major metabolic pathway in dogs involved hydroxylation of a methylene carbon adjacent to the pyrazole nucleus of quinpirole followed by O-glucuronidation. Evidence of metabolism of the pyrazole moiety was found in the isolation of an N-glucuronide conjugate of quinpirole from monkey urine.