Pharmacokinetics and pharmacodynamics of the ergot derivative, transdihydrolisuride, in man

Plasma levels and urinary excretion of the dopamine agonist, transdihydrolisuride (TDHL), were measured by radioimmunoassay in healthy male volunteers given TDHL 50 micrograms i.v. and oral doses of 200, 400 and 800 micrograms. Plasma prolactin was also measured by radioimmunoassay. Following i.v. injection, the concentration of TDHL declined with a half-life of 37 +/- 19 min. The total clearance was 38 +/- 27 ml/min/kg and the apparent volume of distribution was 1.3 +/- 0.41/kg. The bioavailability of oral TDHL was proportional to the dose; after 200, 400 and 800 micrograms the bioavailability was 20 +/- 25%, 31 +/- 24% and 48 +/- 26%. TDHL was almost totally metabolized and less than 0.5% of the dose was excreted unchanged in urine in 24 h. Plasma prolactin levels were depressed by 66 +/- 15%, 75 +/- 11% and 80 +/- 7% after TDHL 200 micrograms, 400 micrograms and 800 micrograms. The effect lasted for more than 12 h after the lowest dose and for more than 24 h after 400 and 800 micrograms. Side effects, mainly nausea and headache, only occurred at the two highest dose levels.

Guanine nucleotides reveal differential actions of ergot derivatives at D-2 receptors labelled by [3H]spiperone in striatal homogenates

The specific binding of [3H]spiperone (35 pM), as defined by the D-2 antagonist sulpiride, was potently displaced by ergot derivatives of both the ergoline and ergopeptine type, and by dopamine agonists and antagonists. The potency of the ergot derivatives ranged widely from an IC50 value of 3 nM for bromocriptine to a value of 1000 nM for the partial ergoline, LY-141865. GTP and its stable analogue, guanyl-5'-yl-imidodiphosphate (Gpp(NH)p), did not affect the affinity (100 pM) or density (30 pmol/g wet wt) of [3H]spiperone binding sites, but did decrease the potency of a number of ergoline compounds including pergolide, lergotrile and LY-141865, as well as dopamine agonists to displace [3H]spiperone binding. The affinities of the ergopeptines, bromocriptine and dihydroergocryptine, and of the isolysergic acid ergoline, lisuride, and dopamine antagonists were unaltered by the presence of guanine nucleotides. The effect was specific for guanine nucleotides, with near maximal effects on agonist affinity observed in the presence of a 100 microM concentration of nucleotide. The relative decrease in affinity found in the presence of GTP or Gpp(NH)p varied widely for individual ergot derivatives and dopamine agonists. The largest decrease was seen with dopamine itself, and agonists such as the tetralins and with LY-141865. Many ergolines had shifts in potency between those seen for agonists and antagonists, suggesting a partial agonist action at D-2 receptors. Guanine nucleotide sensitivity may represent a valuable in vitro method for studying the agonist/antagonist properties of dopaminergic drugs, such as the semi-synthetic ergoline compounds.

Mesulergine and its 1,20-N,N-bidemethylated metabolite interact directly with D1- and D2-receptors

Mesulergine (CU 32-085), an 8 alpha-aminoergoline, has been reported to influence striatal dopamine turnover in a time-dependent biphasic manner, suggesting initial dopamine antagonistic and late dopamine agonistic effects. To clarify whether these opposing in vivo effects are due to a metabolic conversion in vivo or reflect mixed antagonist/agonist effects expressed at different dose levels, mesulergine and a 1,20-N,N-bidemethylated metabolite, identified in rat urine, were investigated in functional dopamine receptor models. Dopamine-sensitive adenylate cyclase in homogenates of rat striatum and modulation of electrically evoked tritium overflow from rat striatal slices previously labelled with [3H]choline were used as tests for D1- and D2-receptors, respectively. Mesulergine was found to antagonise D1-receptor responses at micromolar, and D2-receptor responses at nanomolar concentrations. In contrast, the bidemethylated metabolite of mesulergine stimulated both D1- and D2-receptors at micromolar and nanomolar concentrations, respectively. These in vitro results suggest that at dopamine receptors, mesulergine has antagonistic effects and that the late agonistic effects seen in vivo are mostly due to metabolic conversion into a potent dopaminomimetic drug.

Microbial transformations of pergolide to pergolide sulfoxide and pergolide sulfone

Fifty-eight microorganisms were investigated for their ability to effect the biotransformation of the ergoline alkaloid pergolide. A majority of these organisms formed pergolide sulfoxide, and a Helminthosporium species was investigated in greater detail since it yielded significant amounts of pergolide sulfoxide. A preparative-scale transformation afforded material which was identified as the sulfoxide based on melting point, spectral, and chromatographic comparison with authentic material as well as its conversion to pergolide by reduction with triphenylphosphine. An analytical high-performance liquid chromatographic determination of the enzymatic versus spontaneous air-oxidation of pergolide in growing cultures and controls showed negligible air-oxidation and an approximately 40% enzymatic conversion of pergolide to the sulfoxide. Several organisms, including Aspergillus alliaceus formed a second metabolite, pergolide sulfone, which was identified on the basis of co-chromatographic data.

The affinity of metergoline for 3H-serotonin (5HT) binding sites is regulated by guanine nucleotide

100 microM guanine nucleotide Gpp (NH)p reduces the affinity of the serotonergic antagonist metergoline for 3H-5HT binding sites in rat cerebral cortex. This effect is present both in inhibition binding and in saturation experiments. The hypothesis that the interaction of some serotonergic antagonists with 3H-5HT binding sites is regulated by guanine nucleotides is discussed.

[3H]Mesulergine, a selective ligand for serotonin-2 receptors

[3H]Mesulergine binds with high affinity to rat cerebral cortex membranes. (KD = 1.9 nM, Bmax = 11.3 pM/g tissue). The binding of this ligand is selective for serotonin-2 receptors: Its next highest affinity, which is for dopamine receptors labelled by neuroleptics, is about 50 times weaker than its affinity for serotonin-2 receptors. No significant affinity for serotonin-1, alpha 1-adrenergic or histamine H1 receptors was observed. Specific [3H]mesulergine binding was diminished in the presence of low concentrations of lithium ions.

Clinical pharmacokinetics of ergotamine, dihydroergotamine, ergotoxine, bromocriptine, methysergide, and lergotrile

The clinical pharmacokinetics of ergotamine, dihydroergotamine, ergotoxine, bromocriptine, methysergide, and lergotrile are reviewed. Generally the new radioimmunoassay methods have partially resolved the problems involved in determining some of these ergot derivatives in biologic fluids after the low doses used clinically. However, our present knowledge of their pharmacokinetics is limited and much work remains to be done in this area. Many cases show a great difference between results produced with a radioactive drug and with radioimmunoassay. The longer half-lives measured by using a radioactive derivative are apparently due to the many metabolites of ergot alkaloids. However, we still do not know the clinical importance of these metabolites. For instance, the amount of dihydroergotamine reaching the systemic circulation remains below 1% (radioimmunoassay), but according to studies performed with a radioactive derivative the absorption quotient is about 30%. Further studies are needed to resolve the problem of an apparently high "first-pas" metabolism of this and other ergot alkaloids in the liver or gastrointestinal mucosa.

Microbial models of mammalian metabolism

A solid basis for the M4-approach has been developed over the past 10 years. Recent examples of the production of difficult-to-synthesize mammalian metabolites through microbial transformations attest to the utility of the methodology. There is, however, much more to be done. Model studies should be conducted to test parallels between microbial and mammalian S- and N-oxidations, O-glucuronidations, and ester and amide hydrolyses. Subsequently, even greater applications of M4- work can be envisioned. We have been pleased to see our colleagues in industry and academia adopt the M4- approach to solve difficult pharmacological and toxicological problems. In large measure, this has been our greatest reward for efforts initially presented before the membership of the American Society of Pharmacognosy in 1973.

Metabolism of metergoline in the rat

[19,10-3H] Metergoline was administered orally to female rats and radioactive metabolites were recovered form urine and bile. Besides unchanged drug, the presence of 1-demethylmetergoline (II) was confirmed both in urine and bile. Two other urinary metabolites were identified, namely 8 beta-aminomethyl-6-methylergoline (IX) and 8 beta-acetylaminomethyl-6-methylergoline (VI). A third metabolite, 1,6-dimethyl-8 beta-aminomethylergoline (VIII), was identified only in bile. Beside these metabolites, further polar and so far unidentified biotransformation products are present both in bile and urine, accounting for about half of the radioactivity present in these excreta.

Effects of GTP and sodium on rat striatal dopamine receptors labeled with lisuride

[3H]Lisuride binding to rat striatal membranes appeared to be stereospecifically displaced by the dopamine antagonist butaclamol. Sodium increased the number of [3H]lisuride binding sites (Bmax) without changing the dissociation constant (Kd). GTP did not affect [3H]lisuride binding characteristics, either with or without sodium. These results suggest that dopamine receptor sites labeled by lisuride are at least in part sodium-dependent, possibly the D2-receptors not involved in adenylate cyclase stimulation.

Potent dopamine agonist activity of a novel ergoline, 6-ethyl-9-oxaergoline (EOE)

6-Ethyl-9-oxaergoline (EOE) and its enantiomers were compared with apomorphine in a number of tests designed to measure dopamine (DA) agonist activity within the central nervous system. In rats, the tests were: interaction with DA receptors labeled with 3H-apomorphine or 3H-spiroperidol; the effects on DA synthesis as assessed by the gamma-butyrolactone procedure; turning in 6-OHDA lesioned animals; stereotypy; and, slowing of DA cell firing rates. In the mouse, locomotor activity, hypothermia and postural asymmetry in caudectomized animals were studied. Emesis in the beagle was also examined. The (-)-enantiomer of EOE was more potent than either the (+)-enantiomer or the racemate in all tests. With the exception of inducing stereotypy and the displacement of 3H-apomorphine from rat striatal membranes, (-)-EOE was equi- or more potent than apomorphine in all test procedures. (-)-EOE was effective following oral administration and exhibited a longer duration of action than apomorphine. The results indicate EOE is a potent DA agonist.

Pergolide mesylate: its effects on circulating anterior pituitary hormones in man

Pergolide mesylate is a synthetic ergoline with dopamine agonist properties. The endocrine profile was studied in a double blind crossover design in six normal males. Circulating PRL, TSH, GH, LH, FSH, and cortisol were measured in the basal state and after TRH (500 micrograms iv) administration at 4.5, 11.5, and 23.5 h after placebo or pergolide (100 micrograms orally). Pergolide caused suppression of basal PRL from 2-8 ng/ml to less than 2 ng/ml commencing 60 min after administration and persisting throughout the 23.5-h study period. For the three TRH tests, a suppression of peak PRL (mean +/- SEM) response to TRH of 54.6 +/- 5.1 vs. 1.9 +/- 0.5, 45.2 +/- 4.1 vs. 4.5 +2- 0.6, and 34.4 +/- 2.9 vs. 6.9 +/- 1.4 ng/ml, respectively, for placebo and pergolide was noted. Basal TSH levels were unaffected by pergolide, but after pergolide the peak TSH response to the first two TRH challenges was blunted (placebo vs. pergolide: 12.3 +/- 1.2 vs. 6.8 +/- 1.0 and 14.8 +/- 2.0 vs. 9.6 +/- 1.0, respectively); however, the third TSH response (9.8 +/- 1.1 vs. 9.3 +/- 1.2) was not blunted after pergolide. GH secretion was stimulated by pergolide with a consistent pulse observed within 60 min of pergolide administration and an enhancement in the number and amplitude of subsequent GH pulses throughout the 24-h period. Cortisol levels rose after pergolide and returned to levels seen on the control day at 16.5 h. FSH levels were unaffected but LH levels were lowered pergolide. Side effects including nausea, vomiting, and hypotension were observed in all subjects. Pergolide is a potent dopamine agonist with the anticipated endocrine profile and clinical effects; its long duration of actions offers promise of single daily dose therapy for hyperprolactinemia.

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).

The pharmacokinetics of lisuride hydrogen maleate in rat, rabbit and rhesus monkey

The pharmacokinetics of lisuride hydrogen maleate (LHM) were investigated in rat, rabbit and rhesus monkey. Experiments were designed to meet not only the requirements of drug registration but also to serve other preclinical disciplines (toxicology, pharmacology). LHM is absorbed almost completely at a dose level of 100-250 micrograms/kg. During absorption and first liver passage (FPE) LHM is metabolized. The FPE was highest in the rhesus monkey and lowest in the rat. Calculated on bioavailability during chronic tolerance studies, in the highest dose group rats were burdened with 180-fold and rhesus monkeys with 70-fold the highest human dose (parkinsonism). Total clearance values indicated the presence of extrahepatic metabolism in all animal species. Terminal half-lives of unchanged drug in plasma were in the range of a few hours. Therefore, no accumulation of unchanged drug was expected to occur following daily repeated administration in the animal species investigated. Elimination of 14C-radioactivity proceeded mainly via the liver in rat and rabbit. The rhesus monkey excreted most of the dose administered in the urine. Enterohepatic circulation of 14C-material was demonstrated in the rat. In the rat but not in the other two species a small part of the dose (about 2%) accumulated in blood cells in the form of metabolites. Unchanged lisuride is able to cross membranes very rapidly, this was shown in distribution studies (whole-body autoradiography of rat, direct measurements in rat and rabbit). Transfer of lisuride into fetuses and brain is governed by its concentration in plasma. Drug level decrease in fetuses and brain was shown to somewhat slower than in plasma. Detailed evaluation of the distribution pattern in the brain of rat and rabbit showed a high affinity of lisuride for its preferential target tissue, the pituitary.

Biotransformation of lisuride in the hemoglobin-free perfused rat liver and in the whole animal

Isolated rat livers were perfused with an oxygenated saline medium containing 14C-lisuride. Metabolites obtained in the bile and the perfusate were characterized as the glucuronide of hydroxylisuride and hydroxy, 2-oxo, monode-ethyl, dide-ethyl, N6-demethyl and monode-ethyl-N6-demethyl derivatives of lisuride. In addition, the metabolite patterns were examined in various tissue homogenates in vitro and also in the rat in vivo. Whereas dealkylation reactions occurred predominantly under in vitro conditions, the metabolite profile observed in vivo was similar to that found in the perfused liver system. The principal routes for biotransformation of lisuride in the intact rats as well as in the perfused rat liver are those through aromatic hydroxylation and subsequent conjugation with glucuronic acid.

[3H]Metergoline: a new ligand of serotonin receptors in the rat brain

A specific binding site for [3H]metergoline characterized by a KD of 0.5-1.0 nM was detected in microsomal and synaptic plasma membranes from various areas of the adult rat brain. Experiments with 5,7-dihydroxytryptamine- and kainic acid-induced lesions indicated that this specific binding site was localized post-synaptically with respect to serotoninergic neurons. The pharmacological characteristics of [3H]metergoline binding to microsomal membranes from the whole forebrain strongly suggest that this ligand labels a class of serotonin receptors. This was particularly obvious in the hippocampus in which serotonin was about 400 times more potent than dopamine and noradrenaline for displacing bound [3H]metergoline. In the striatum, serotonin was only 10 times as potent as dopamine in inhibiting [3H]metergoline binding, suggesting that this ligand may also bind to dopamine receptors. Striking similarities between the binding sites for [3H]metergoline and [3H]serotonin were observed in the hippocampus. Thus, not only the total numbers of binding sites for these two ligands in control rats but also their respective increases following intracerebral 5,7-dihydroxytryptamine treatment were very similar. Therefore, at least in the hippocampus, [3H]metergoline might well be the appropriate ligand for studying the characteristics of the 'antagonist form' of serotonin receptors postulated by Bennett and Snyder.

Binding of antiparkinsonian ergot derivatives to the dopamine receptor

The effects of bromocriptine, lisuride and apomorphine on specific binding of 3H-spiroperidol to homogenates of rat caudate nucleus were studied. (+)-Butaclamol was used to define specific binding. Bromocriptine and lisuride inhibited binding markedly, in vitro and also 30 min after in vivo injection. Bromocriptine continued to inhibit binding 24h after a single injection and also after 4 days of drug administration. Lisuride did not affect net specific binding at these periods. Apomorphine produced a mild reduction in binding after 30 min but none after 4 days. It appears that the ergot alkaloids inhibit binding of 3H-spiroperidol by binding strongly to the dopamine receptor.

Binding of [3H]pergolide mesylate to dopamine receptors of mammalian brains

The ergoline dopamine agonist, [3H]pergolide, binds with pharmacological specificity to particulate fractions of rat and calf brains. Dopamine agonists (apomorphine, 5,6-dihydroxy-2-dimethylaminotetralin, 6.7-dihydroxy-2-methylaminotetralin, lergotrileand bromocriptine) and dopamine antagonists (haloperidol and (+)butaclamol but not its pharmacologically inactive isomer, (-)butaclamol) were potent inhibitors, while monoamines (dopamine, norepinephrine, epinephrine and serotonin) were weaker inhibitors of [3H]pergolide binding. Olfactory tubercle was the only brain region other than striatum which exhibited significant [3H]pergolide binding displaceable by 1 microM (+)butaclamol. Saturable of calf and rat striatum with dissociation constants, kd values, of 1.2 to 3.1 nM. The number of binding sites was enriched in crude synaptosomal fractions. The relationship of [3H]pergolide binding to the binding of other dopaminergic ligands is discussed.

N-demethylation of lergotrile by Streptomyces platensis

Thirty-eight microorganisms were screened for their ability to produce metabolites of the semisynthetic alkaloid, lergotrile. A total of five microorganisms were found to biotransform lergotrile, and N-desmethyl lergotrile was detected as the principal metabolite with most organisms. Streptomyces platensis (NRRL 2364) appeared to form the metabolite in highest yield, and a preparative-scale conversion was accomplished with a recovered yield of 50%. Structure proof was accomplished with comparative thin-layer chromatography, mixed melting point, mass spectrometry, and remethylation to lergotrile.

Physiologic disposition of lergotrile

Lergotrile, an ergot alkaloid, has been shown to be effective in treating disorders associated with elevated serum prolactin levels (e.g., galactorrhea-amenorrhea). Lergotrile has also been found to be a potent dopaminergic agonist and thus to be effective in Parkinson's disease. This study describes the physiologic disposition of lergotrile after administration to human volunteers. N-14CH3-lergotrile was rapidly absorbed from the gastrointestinal tract. Lergotrile was detected at low concentrations in plasma when subjects received large doses over extended periods of time. The major portion of radioactivity in plasma was attributed to the presence of circulating metabolites of lergotrile. Lergotrile metabolities were eliminated in the feces (ca. 60%), urine (ca. 20%), and breath (ca. 7% as 14CO2). A metabolite in feces was identified as 13-OH-lergotrile (up to 30% of the dose). A metabolite in urine was formed by conversion of the C8-acetonitrile group of lergotrile to a carboxyl group (about 10% of the dose). The presence of 14CO2 in the expired air after administering N-14C-methyl-lergotrile indicated that the drug was N-demethylated to form norlergotrile.

Variation of blood glucose and serum growth hormone, prolactin and insulin in subjects with insulin-dependent diabetes, after OGTT and pretreatment with 2-Br-alpha-ergocryptine

In insulin-dependent diabetics high GH values are usually observed. The OGTT does not modify these levels. It was observed that CB 154 (2-Br-alpha ergocryptine) seems capable of lowering GH in acromegalics. We thought it pertinent to check whether or not CB 154 could reduce GH also in diabetics. OGTT was performed in insulin-dependent diabetic patients; 5 days later the same test was repeated after pretreatment with 2.5 mg of CB 154. Serum IRI, GH, hPRL levels and blood glucose values were checked during the test. Significant GH and hPRL variations were not observed after OGTT in the diabetic subjects examined; IRI was always absent, and glycemia followed the model of the diabetic curve. On the contrary, after pretreatment with CB 154, we observed: 1) hPRL reduction; 2) GH increase, sometimes as early as 30 min after OGTT; 3) IRI was never present and blood glucose levels were lower than the values observed with glucose alone. Contrary to what is observed in acromegalics, CB 154 is unable to lower the increased GH levels normally present in insulin-dependent diabetics. After pretreatment with CB 154, OGTT seems to release GH, which is not observed after glucose alone. This can be accounted for only by postulating an antagonism at the hypothalamic level between the adrenergic and serotoninergic pathways of GH stimulation.

The uptake of DH-ergotoxine by different parts of the cat brain

The distribution pattern of 3H-DH-ergotoxine, labelled by a direct hydration with tritium, was investigated in the cat brain. Apart from the pituitary gland, the brain shows an average DH-ergotoxine concentration of 10(-7) M. A 15% greater incorporation of DH-ergotoxine occurs in the cerebellum than in the cerebrum. In gradient centrifugation studies it is seen that 60% of the incorporated DH-ergotoxine is localized in the synaptosomal fraction. This finding seems to verify the microhistautoradiographic results of this investigation. The observation of a DH-ergotoxine binding in selected structures of the CNS , predominantly the synapses, could explain central nervous activities of DH-ergotoxine.