[Pharmacokinetic/pharmacodynamic analysis of anti-hyperprolactinemic effect of terguride based on dopamine D2 receptor occupancy].

Terguride has been widely used for the treatment of hyperprolactinemia via partial agonistic action on dopamine D2 receptors in the pituitary. The present study analyzed retrospectively the dopamine D2 receptor binding occupancy (phi) of terguride. The average phi value was estimated to be 14.1% after oral administration of the average/standard therapeutic dose of terguride. Taking the intrinsic activity (alpha) into consideration, the value of alpha. phi was 2.33%. These results suggest that the antihyperprolactinemic effect of terguride was elicited despite the low receptor occupancy. Furthermore, we developed a pharmacokinetic/pharmacodynamic model for ascertaining the serum prolactin-lowering effect of terguride, considering both the reversible binding to D2 receptors and the effect on the increase rate in the prolactin level. The developed model fit well with the actual data. Although this model could be improved, it could explain the long duration of the antihyperprolactinemic activity of terguride and might be useful for designing its rational dosage regimen.

The trigonometric responder approach: a new method for detecting responders to pharmacological or experimental challenges.

The paper presents a newly developed response measure that is particularly suitable for the evaluation of pharmacokinetic data. This method is based on trigonometric considerations, defining a hormone response as the difference between the angle of the slope of the curve before and after drug intake. In addition, the size of this difference is compared to the difference obtained in placebo conditions. In this way, the trigonometric response measure overcomes one of the most problematic shortcomings of the 'area under the curve' (AUC) approach, the problem of the initial value. We will present the mathematical background of the trigonometric method and demonstrate its usefulness by evaluating empirical data (a pharmacological challenge test using the dopamine agonist lisuride) and comparing it to classical AUC measures. This has been achieved by contrasting both approaches with responder definitions according to binary time series analysis and the peak value of the curve.

Quantitative analysis of striatal dopamine D2 receptors with 123 I-iodolisuride SPECT in degenerative extrapyramidal diseases.

123I-Iodolisuride has high specific affinity for binding on dopamine D2 receptors in the striatum and has been used in a few single photon emission computed tomography (SPECT) studies of extrapyramidal disorders. The diagnosis of Parkinson's disease (PD) is very difficult in the first 5 years of evolution, with 15-25% false positive diagnoses. The aim of this study was therefore to determine the value of iodolisuride SPECT in discriminating Parkinson's from the most frequent Parkinson-plus syndromes (PPS). Seventeen patients with an extrapyramidal syndrome had a SPECT examination 1 h after injection of 180-185 MBq of 123I-iodolisuride. They were followed under dopaminergic treatment for at least 2 years. After 2 years, they were separated in two groups according to specific clinical criteria and sensitivity to dopaminergic treatment: nine patients had PD (age = 59.8+/-8.8 years; Hoehn and Yahr = 1.8+/-0.7; evolution = 4.3+/-3 years) and eight had PPS (age = 71.6+/-7.3 years; Hoehn and Yahr = 2.9+/-2.0; evolution = 4.1+/-1.5 years). The binding potential of iodolisuride in the striatum was assessed by considering the striatum (S)/occipital lobe (O) ratio at the pseudo-equilibrium 1 h after injection. The S/O ratio was statistically different between PD and PPS (1.97+/-0.3 vs. 1.65+/-0.2 (P<0.02)). Iodolisuride SPECT could differentiate both groups with a sensitivity of 88.8% and a specificity of 75%. Iodolisuride is a good specific D2 receptor ligand for SPECT and complements specific clinical criteria for the diagnosis of Parkinson's disease and differentiation between different extrapyramidal disorders.

[Dermal application of lisuride on parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the common marmoset and on cases with Parkinson's disease].

Dermal administration is a nonoral drug delivery system that can keep the concentration of a drug in the body at a proper level for a long time. This is suitable especially in patients in the advanced stages of Parkinson's disease with a wearing-off phenomenon (short duration of effects on antiparkinsonian drugs), or in postoperative patients who cannot be treated with oral administration. We studied the effects of lisuride, a dopamine receptor agonist, in the dermal application on MPTP-treated common marmosets and on 5 patients with Parkinson's disease. Lisuride was applied to 4 x 5 cm of skin of the abdomen of monkeys. In patients with Parkinson's disease, lisuride was applied to the skin of the chest. The agent reversed akinesia of MPTP-treated animals within 30 min following the application and relieved the animal of parkinsonism for 5 days at a dose of 2 mg/kg. In patients, the dermal application of lisuride increased the duration of the ON period at doses of 1 to 2 mg/kg. These results suggest that the dermal application of lisuride is a useful treatment in parkinsonism.

2-[123I]-iodolisuride SPET visualizes dopaminergic loss in de-novo parkinsonian patients: is it a marker of striatal pre-synaptic degeneration?

The aim of this study was to assess the correlation between the functional integrity and density of striatal dopaminergic receptors and clinical data in 15 de-novo patients with idiopathic Parkinson's disease by single photon emission tomography (SPET) using 2-[123I]-iodolisuride (ILIS), a tracer based on the D2-dopamine receptor agonist lisuride. Deficient striatal uptake of ILIS correlated with the severity of the disorder, scored by the Unified Parkinson's Disease Rating Scale (UPDRS) (n = 15; ratio of ILIS uptake: basal ganglia/cerebellum [B/C] & UPDRS I-III, Spearman R = -0.562, P = 0.013), Beck's Depression Inventory (BDI) (n = 12; B/C & BDI, Spearman R = -0.825, P = 0.0009) and the ZUNG Depression Scale (ZDS) (n = 11; B/C & ZDS, Spearman R = -0.7425, P = 0.008). Experimental data indicate that lisuride shows a higher affinity for pre-synaptic dopaminergic autoreceptors than for post-synaptic D2-dopamine receptors under conditions of low applied ILIS concentrations as in this study. From the results of this study and these experimental data, we speculate that ILIS-SPET can visualize pre-synaptic striatal dopaminergic degeneration in Parkinson's disease.

Clinical implications of sustained dopaminergic stimulation.

Fluctuations in motor performance are the major problems in chronic management of Parkinson's disease. Most of these fluctuations reflect the decline of levodopa availability. As a consequence, levodopa dosage might be increased and the interdose interval progressively shortened. The postsynaptic dopamine receptors at this point are exposed to a nonphysiologic shift in dopamine level, which may induce changes at the receptor site and contribute to the appearance of "on-off" phenomena and dyskinesias. We compared a group of 18 patients treated for 60 consecutive months with continuous subcutaneous lisuride infusion with a group of 20 patients treated with conventional oral levodopa treatment. The clinical evaluations performed during the study showed in the lisuride group only a worsening of dyskinesias, whereas the other symptoms remained unchanged. In the other group the evaluation scores showed a significant worsening of all long-term treatment complications. The slow-release preparations of levodopa may ensure a more continuous dopaminergic stimulation than standard formulations. However, the use of these compounds is difficult in severely fluctuating patients because the lack of a plasma peak level usually leads to a very long delay before patients turn "on." We studied the pharmacokinetic and clinical effects of the two slow-release preparations of levodopa [Madopar HBS and Sinemet controlled-release (CR)] and a combination of Sinemet CR plus standard Sinemet in 13 fluctuating parkinsonian patients. The results of this study show that the combination of standard Sinemet and Sinemet CR ensures a more prolonged clinical effect with a very short latency to the "on" phase.

[A preclinical study of the organ distribution and radiation dosage of radioiodinated iodolisuride]. / Vorklinische Untersuchung zur Organverteilung und Strahlenbelastung von Radiojod-Jodlisurid.

The distribution in rats of 125I-iodo-lisuride was studied. Three rats each were sacrificed at fixed intervals between 5 min and 24 h p.i., and the radioactivity was measured in isolated organs and parts of the body. The organ distribution and biexponential blood disappearance were similar to values for unlabeled lisuride. The radiation dose was estimated for man assuming a 123I label. The resulting doses were comparable to those from other radiopharmaceuticals in clinical use.

Pharmacokinetics of 3H-terguride in elderly volunteers.

Blood and plasma levels and excretion of labeled compounds and of the unchanged drug were measured after i.v. injection of 54 micrograms and p.o. administration of 540 micrograms of the ergoline derivative, terguride (CAS 37686-84-3), labeled with tritium, in 6 elderly male volunteers. Following i.v. injection plasma levels of terguride declined with a half-life of 0.5 h and those of radiolabeled compounds with half-lives of 0.5 h, 7 h and 19 h. The total clearance was 17 ml/min/kg and the volume of distribution was 0.7 l/kg. After p.o. administration terguride was rapidly and completely absorbed. The bioavailability was around 20%. Elimination of labeled compounds was complete within 7 days and proceeded mainly via the urine. Computer simulation of plasma levels after 4-times-a-day multiple administrations indicated slight accumulation of metabolites (factor 3) and no accumulation of terguride (factor 1).

The estimated density of D2 striatal receptors in schizophrenia. A study with positron emission tomography and 76Br-bromolisuride.

The striatal D2 receptors of 19 untreated schizophrenics and 14 normal control subjects were investigated with PET and 76Br-bromolisuride. The ratio of radioactivity in the striatum to that in the cerebellum was taken as an index of the striatal D2 receptor density. There was no significant difference between the control and the schizophrenic groups, nor any difference between subgroups of patients defined by clinical type or course of illness, and no relationship between the striatum:cerebellum activity ratio and SANS or SAPS ratings of symptoms. Unlike in the controls, this ratio was not correlated with age in schizophrenics. This study suggests that there is no quantitative abnormality of striatal D2 dopamine receptors in schizophrenia.

The pharmacokinetics and pharmacodynamics of lisuride in healthy volunteers after intravenous, intramuscular, and subcutaneous injection.

The plasma concentration of lisuride and prolactin have been measured in twelve healthy male volunteers after IV, IM or SC injection of 25 micrograms lisuride hydrogen maleate as an aqueous solution. After IV administration the plasma lisuride fell in two phases with half-lives of 14 min and 1.5 h. Total clearance was 13 ml.min-1.kg-1. After IM and SC injection the plasma concentrations peaked at 12 to 15 min and the profiles were similar to that found after IV administration. The systemic availabilities were 90% and 94%, respectively. Prolactin concentrations were reduced by a maximum of 60% relative to the normal circadian rhythm after all three routes of administration. The treatments were well tolerated, the only adverse reactions reported by some of the volunteers being mild, transient dizziness, tiredness, and nausea.

Pharmacokinetics and endocrine effects of terguride in healthy subjects.

Plasma levels of the partial dopamine agonist, terguride, were measured by RIA in healthy volunteers after a single i.v. dose of 50 micrograms and on the first and seventh day of an oral treatment with 250 micrograms, 500 micrograms and 750 micrograms b.d. Basal and releasing hormone (TRH, GHRH, CRF, LHRH)-stimulated pituitary hormone secretion (PRL, TSH, GH, FSH, LH) and cortisol were also determined by RIA. Following the i.v. injection, plasma terguride levels declined biphasically, with half-lives of 0.2 and 1.5 h; total clearance was 17 ml.min-1.kg-1. The oral bioavailability of terguride over all doses was about 20%. Basal and TRH-stimulated prolactin levels were dose-dependently depressed, but the secretion of other hormones remained unaffected. Tolerance of terguride was excellent and there was no negative effect on performance or mood, nor on mixed-function oxygenase activity, assessed as urinary 6 beta-OH cortisol.

Studies on the biotransformation of lonazolac, bromerguride, lisuride and terguride in laboratory animals and their hepatocytes.

1. Metabolic patterns and the extents of metabolism of four drugs, namely [14C]lonazolac (LON), [14C]bromerguride)BRO), [14C]lisuride (LIS) and [3H]terguride (TER) have been studied in three experimental models, namely hepatocyte suspensions of rat, guinea pig, beagle dog and cynomolgus monkey, isolated perfused liver of rat and guinea pig and intact animals (rat, guinea pig, dog and monkey). 2. Selection of compounds was based on differences in phase I metabolic pathways. LON is exclusively hydroxylated in the N-substituting aromatic ring, BRO is mainly N-deethylated in the urea moiety, and LIS and TER are both degraded into numerous metabolites. 3. The decrease in unchanged drug levels in hepatocyte suspensions was characterized by half-lives, with LON as the most stable and LIS as the least stable compound. Marked interspecies differences were found. De-ethylation and aromatic hydroxylation were much slower in rat hepatocytes than in the liver cells of other species; BRO was slowly biodegraded in dog hepatocytes while LIS was broken down extremely quickly. 4. Liver perfusion experiments and studies in vivo were evaluated for the extents of metabolism of each drug. 5. Metabolism studies in hepatocytes did not show any quantitative correlation to those of metabolism in vivo. The suitability of evaluating parameters for in vitro studies is discussed.

Pharmacokinetics and pharmacodynamics of terguride following intramuscular administration in cows and goats.

The pharmacokinetics of intramuscular terguride (transdihydrolisuride) was evaluated in a single-dose study in cows (doses 100, 62 and 31 micrograms/kg b.w.) and goats (dose 100 micrograms/kg b.w.). A radioreceptor assay was used to quantitative plasma terguride concentrations. The peak plasma concentrations of terguride were attained within 0.6 h of the drug administration and then decreased monoexponentially with half-life of 1.3 h (cows) and 2 h (goats). The pharmacokinetics of terguride in cows is nearly linear. Pharmacodynamics of terguride was expressed as reduction in plasma prolactin levels. Maximal decline in prolactin was observed 3-4 h following terguride administration and the effect lasted for about 24 h.

Pharmacokinetics of the dopamine partial agonist, terguride, in the rat and rhesus monkey.

3H-labelled terguride was rapidly and completely absorbed in the rat after oral administration of up to 50 mg/kg. In the rhesus monkey, absorption was prolonged. The bioavailability of terguride was 79% in the rat and 15% in the monkey. Plasma levels of the unchanged drug declined with a half-life of 50 min (rat) or 20 min (monkey). Tissue distribution as studied by autoradiography in pregnant rats showed highest concentrations of labelled compounds in the liver, the cervical gland and the kidney. Lower levels were found in the thymus, the spinal cord, the placenta and the heart muscle followed by the fetal tissue, the muscles and the brain. Radioactivity was excreted mainly in the faeces when administered to the rat and to a higher extent in the urine after treatment of rhesus monkeys.

Pharmacokinetics of lisuride after subcutaneous infusion.

Six parkinsonian patients received a constant subcutaneous infusion of 60 micrograms lisuride per hour in the abdominal region for 2 hours. Plasma levels of the unchanged drug were measured by radio-immunoassay. During infusion, a steady state plasma level of 0.78 +/- 0.19 ng/ml was achieved. After discontinuation of the infusion, concentrations declined with a half-life of 1.4 +/- 0.4 hour. The total clearance of lisuride was 20 +/- 6 ml/min/kg. Due to the low interpatient variability of plasma levels, a good control of clinical effects is to be expected.