Superiority of Newly Developed Vaginal Suppositories Over Vaginal Use of Commercial Bromocriptine Tablets: A Randomized Controlled Clinical Trial

The objective of this study is to verify the safety and efficacy of new vaginal bioadhesive suppositories as compared with vaginal use of commercial bromocriptine tablets in hyperprolactinemic patients. This study is a randomized, double-blind, active comparator clinical trial in which a subset of patients had some pharmacokinetic measurements. The setting was an outpatient private infertility clinic in a developing country, and the subjects were 171 patients with hyperprolactinemia. A pilot phase comprised 32 patients who were divided into 2 groups. Group A comprised 16 patients who used vaginal suppositories containing 2.5 mg bromocriptine mesthylate with pluronics and bioadhesive agents once daily for 1 month, while group B included 16 patients who used commercial 2.5-mg bromocriptine mesthylate tablets inserted vaginally once daily for 1 month. The clinical phase comprised 139 patients who were again divided into 2 groups in the same way (group A, 68 patients; group B, 71 patients). Serum prolactin (SP) was measured before and after therapy in all cases. The main outcome measure was the decline of SP level after 1 month of therapy. In both groups, there was a significant decline of the SP. However, it was more significant in group A. Patient convenience was more evident, and local side effects were less in group A than group B in the clinical phase. The introduction of bioadhesive technology for bromocriptine mesylate/pluronic F-126 administration is valuable in achieving prominent serum prolactin reduction in hyperprolactinemic patients in a relatively short duration of therapy. The formulated vaginal suppositories expressed better convenience with minimal local side effects when compared with vaginally administered commercial bromocriptine tablets.

Bromocriptine: old drug, new formulation and new indication

Bromocriptine is an ergot alkaloid dopamine D(2) receptor agonist that has been used extensively in the past to treat hyperprolactinaemia, galactorrhoea and Parkinsonism. It is known that hypothalamic hypodopaminergic states and disturbed circadian rhythm are associated with the development of insulin resistance, obesity and diabetes in animals and humans. When administered in the early morning at the start of the light phase, a new quick release (QR) formulation of bromocriptine appears to act centrally to reset circadian rhythms of hypothalamic dopamine and serotonin and improve insulin resistance and other metabolic abnormalities. Phase II and III clinical studies show that QR-bromocriptine lowers glycated haemoglobin by 0.6-1.2% (7-13 mmol/mol) either as monotherapy or in combination with other antidiabetes medications. Apart from nausea, the drug is well tolerated. The doses used to treat diabetes (up to 4.8 mg daily) are much lower than those used to treat Parkinson's disease and have not been associated with retroperitoneal fibrosis or heart valve abnormalities. QR-bromocriptine (Cycloset™) has recently been approved in the USA for the treatment of type 2 diabetes mellitus (T2DM). Thus, a QR formulation of bromocriptine timed for peak delivery in the early morning may provide a novel neurally mediated approach to the control of hyperglycaemia in T2DM.

A review of the receptor-binding and pharmacokinetic properties of dopamine agonists

BACKGROUND

Dopamine agonists (DAs), which can be categorized as ergot derived and non-ergot derived, are used in the treatment of Parkinson's disease.

OBJECTIVES

This review describes the pharmacologic and pharmacokinetic properties of selected DAs and relates these characteristics to clinical outcomes, with an emphasis on adverse events.

METHODS

Relevant articles were identified through a search of MEDLINE (to May 2006) using the terms dopamine agonists (or each individual drug name) and pbarmacokinetics, metabolism, drug-drug interaction, interactions, CYP450, fibrosis, valvular heart disease, tremor, clinical trials, reviews, and meta-analyses. Abstracts from recent sessions of the International Congress of Parkinson's Disease and Movement Disorders were also examined. Clinical studies with <20 patients overall or <10 patients per treatment group in the final analysis were excluded. All DAs that were graded at least possibly useful with respect to at least 3 of 4 items connected to the treatment/prevention of motor symptoms/complications in the most recent evidence-based medical review update were included. This resulted in a focus on the ergot-derived DAs bromocriptine, cabergoline, and pergolide, and the non-ergot-derived DAs pramipexole and ropinirole.

RESULTS

Bromocriptine, cabergoline, pergolide, and ropinirole, but not pramipexole, have the potential for drug-drug interactions mediated by the cytochrome P450 (CYP) enzyme system. The occurrence of dyskinesia may be linked to stimulation of the dopamine D(1) receptor, for which cabergoline and pergolide have a similar and relatively high affinity; bromocriptine, pramipexole, and ropinirole have been associated with a lower risk of dyskinesias. The valvular heart disease (VHD) and pulmonary and retroperitoneal fibrosis seen with long-term use appear to represent a class effect of the ergot-derived DAs that may be related to stimulation of serotonin 5-HT(2B) (and possibly 5-HT(2A)) receptors. The incidence of valvular regurgitation was 31% to 47% with ergot-derived DAs, 10% with non-ergot-derived DAs, and 13% with controls.

CONCLUSIONS

As reflected in the results of the clinical trials included in this review, dyskinesia associated with DA therapy may be linked to stimulation of the D(1) receptor. Fibrosis (including VHD) seemed to be a class effect of the ergot-derived DAs. Each of the DAs except pramipexole has the potential to interact with other drugs via the CYP enzyme system.

Disease Progression and Pharmacodynamics in Parkinson Disease – Evidence for Functional Protection with Levodopa and Other Treatments

We have modelled the Unified Parkinson's Disease Rating Scale (UPDRS) scores collected in 800 subjects followed for 8 years. Newly diagnosed and previously untreated subjects were initially randomized to treatment with placebo, deprenyl, tocopherol or both and, when clinical disability required, received one or more dopaminergic agents (levodopa (carbidopa/levodopa), bromocriptine, or pergolide). Using models for disease progression and pharmacodynamic models for drug effects we have characterized the changes in UPDRS over time to determine the influence of the various drug treatments. We have confirmed and quantitated the relative symptomatic benefits of the dopaminergic agents and provide model-based evidence for slowing of disease progression.

Kinetics and Thermodynamics of Ligand Binding by Cytochrome P450 3A4

Cytochrome P450 (P450) 3A4, the major catalyst involved in human drug oxidation, displays substrate- and reaction-dependent homotropic and heterotropic cooperative behavior. Although several models have been proposed, these mainly rely on steady-state kinetics and do not provide information on the contribution of the individual steps of P450 catalytic cycle to the observed cooperativity. In this work, we focused on the kinetics of substrate binding, and the fluorescent properties of bromocriptine and alpha-naphthoflavone allowed analysis of an initial ligand-P450 3A4 interaction that does not cause a perturbation of the heme spectrum. The binding stoichiometry for bromocriptine was determined to be unity using isothermal titration calorimetry and equilibrium dialysis methods, suggesting that the ligand bound to the peripheral site during the initial encounter dissociates subsequently. A three-step substrate binding model is proposed, based on absorbance and fluorescence stopped-flow kinetic data and equilibrium binding data obtained with bromocriptine, and evaluated using kinetic modeling. The results are consistent with the substrate molecule binding at a site peripheral to the active site and subsequently moving toward the active site to bind to the heme and resulting in a low to high spin iron shift. The last step is attributed to a conformational change in the enzyme active site. The later steps of binding were shown to have rate constants comparable with the subsequent steps of the catalytic cycle. The P450 3A4 binding process is more complex than a two-state system, and the overlap of rates of some of the events with subsequent steps is proposed to underlie the observed cooperativity.

Interactions between the dopamine agonist, bromocriptine and the efflux protein, P-glycoprotein at the blood–brain barrier in the mouse

Bromocriptin (BCT) is a dopaminergic receptor agonist, poorly transported through the blood-brain barrier (BBB) and responsible for central side effects. Interactions between BCT and the efflux protein, P-glycoprotein (Pgp), have been described in vitro but nothing is known in vivo nor at the BBB level. At the BBB, in vivo, we investigated BCT as (i) a Pgp substrate by comparing the brain uptake in CF1 mdr1a(-/-) and mdr1a(+/+) mice with or without inhibitors of Pgp (valspodar, elacridar); (ii) a Pgp inducer by looking at the effect of repeated doses of BCT on cerebral uptake of digoxin and comparing it to the effect of dexamethasone and rifampicin; (iii) a Pgp inhibitor by determining the effect of a single dose of BCT on cerebral uptake of digoxin and comparing it to the effect of valspodar. CF1 mdr1a(-/-) mice showed much higher brain uptake of BCT than CF1 mdr1a(+/+) mice and brain uptake of BCT was higher in CF1 mdr1a(+/+) mice pre-treated with valspodar or elacridar indicating that BCT is a Pgp substrate at the BBB level. Brain uptake of digoxin was not modified in CF1 mdr1a(+/+) mice pre-treated with a single dose or repeated doses of BCT, indicating that BCT is neither a Pgp inductor nor a Pgp inhibitor at the BBB in the chosen experimental setting. In vivo, at the mouse BBB level and in our experimental conditions, bromocriptin is a Pgp substrate but is not a Pgp modulator.

Differential dopaminergic modulation of executive control in healthy subjects

RATIONALE

Executive control (EC) has different subcomponents, e.g., response inhibition (measured, for example, by the Stroop task) and working memory (WM-measured, for example, by delayed response tasks, DRT). EC has been associated with networks involving the prefrontal cortex (PFC). Moreover, there is evidence that dopamine agonists, especially those with a D1 profile, may modulate EC, since in the PFC D1 subtype receptors are more abundant.

OBJECTIVE

This study aimed to selectively distinguish whether D1 versus D2 dopamine agonism differentially influences EC related to the inhibition of irrelevant information and WM. Because of its D1 component, we predicted that the administration of pergolide (mixed D1/D2 agonist), in comparison with bromocriptine (D2 selective agonist) and placebo, would enhance performance in both EC tasks. Using a lateralized Stroop task, we predicted a decrease in the interference effect, as well as error rates, while no increase in facilitation effects. For the DRT task, we predicted fewer error scores in the delay condition.

METHODS

Forty male healthy subjects participated in this randomized, double-blind, placebo-controlled, crossover study.

RESULTS

For the Stroop task no superiority of pergolide was found; however, with bromocriptine, decreased interference was found. No modulation of lateralization effects was shown in interference measures. Moreover, subjects on pergolide showed an absence of facilitation effects. No effects of either agonist were found for the DRT.

CONCLUSION

Our findings suggest that dopamine agonists modulate two EC tasks differently. Furthermore, there seems to be a selective modulation of different aspects of the Stroop task.

Pharmacokinetic and pharmacodynamic analyses, based on dopamine D2-receptor occupancy of bromocriptine, of bromocriptine-induced contralateral rotations in unilaterally 6-OHDA-lesioned rats

Bromocriptine is a selective agonist for dopamine D2-receptors and is used in the treatment of Parkinson's disease. In this study, we performed pharmacokinetic and pharmacodynamic (PK/PD) analyses of the antiparkinsonian effect of bromocriptine and evaluated drug-induced contralateral rotations in rats in which unilateral striatal lesions had been generated by microinjection of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle. The plasma concentration (Cp) and D2 receptor occupancy (Phi(D2)) were quantitated by HPLC and with an in vivo back-titration method using [(3)H]-raclopride, respectively. Bromocriptine induced contralateral rotations (E(rot)) in a dose-dependent manner following intraperitoneal administration in an animal model of Parkinson's disease. The Cp of bromocriptine peaked at 15-30 min after the administration and decreased time-dependently, whereas the Phi(D2) of bromocriptine increased gradually for 180 min after administration. The relationship between Cp and E(rot) exhibited an anticlockwise hysteresis, whereas the relationship between Phi(D2) and E(rot) showed a linear correlation. These results suggest that in vivo Phi(D2) is a good pharmacological indicator of the effect of a D2 agonist.

Biodegradable bromocryptine mesylate microspheres prepared by a solvent evaporation technique. I: Evaluation of formulation variables on microspheres characteristics for brain delivery

The aim of this study was to formulate biodegradable microspheres containing an anti-parkinsonian agent, bromocryptine mesylate, for brain delivery. The effect of formulation parameters (e.g. polymer, emulsifying agent type and concentration) on the characteristics of the microspheres produced, the efficiency of drug encapsulation, the particle size distribution and in vitro drug release rates from the bromocryptine mesylate microspheres were investigated using a 3(2) factorial design. Bromocryptine mesylate was encapsulated into biodegradable polymers using the following three different polymers; poly(L-lactide), poly(D,L-lactide) and poly(D,L-lactide-co-glycolide). The SEM photomicrographs showed that the morphology of the microspheres greatly depended on the polymer and emulsifying agent. The results indicate that, regardless of the polymer type, increase in emulsifying agent concentration from 0.25-0.75% w/v markedly decreases the particle size of the microspheres. Determination of particle size revealed that the use of 0.75% w/v of emulsifying agent concentration and a polymer solution concentration of 10% w/v resulted in optimum particle size. In order to prepare biodegradable microspheres with high drug content and small particle size, selection of polymer concentration as well as emulsifying agent concentration is critical. Polymer type has a less pronounced effect on the percentage encapsulation efficiency and particle size of microspheres than on the t(50%). The microspheres prepared by all three polymers, at a polymer concentration of 10% w/v and an emulsifying agent concentration of 0.75% w/v with NaCMC:SO (4:1, w/v) mixture was as the optimum formulation.

In-vitro and in-vivo evaluation of a matrix-controlled bromocriptine mesilate-releasing vaginal ring

The aim of this study was to evaluate the in-vitro release rates and in-vivo effectiveness of a controlled release, intravaginal dosage form of bromocriptine mesilate. The dimeticone (poly(dimethylsiloxane)) elastomer vaginal ring contained 3 mg bromocriptine mesilate and low molecular weight gelatin in a ratio of 1:3, and 10% propylene glycol. The daily release rate of the drug was designed to be 10% of the total administered dose and was confirmed with release experiments under sink conditions. The effect of the vaginal ring preparation on plasma prolactin level in the rabbit was investigated over a 10-day period. The results showed that the vaginal ring of bromocriptine mesilate significantly decreased the plasma prolactin level of the test group (P < 0.001-0.05) compared with the control and placebo groups. It was concluded that bromocriptine mesilate was effectively absorbed from rabbit vagina and that this controlled release intravaginal ring preparation of bromocriptine mesilate was effective in decreasing the plasma prolactin level in rabbits for ten days.

An overnight switch to ropinirole therapy in patients with Parkinson's disease. Short communication

Patients with Parkinson's disease (n = 68) switched from pergolide or bromocriptine to ropinirole overnight (dose equivalence ratios 1:6 and 10:6, respectively). The activities of daily living score for the Unified Parkinson's Disease Rating Scale (UPDRS) was significantly improved 4 weeks after the bromocriptine-ropinirole switch. All other UPDRS scores, including that for the side-effect component, were not significantly different after either switch. Overnight switching may be a safe therapeutic approach that may reduce hospitalisation and related socio-economic costs.

Receptor imaging with 111In-pentreotide and 123I-methoxybenzamide, and inhibition tests with octreotide and bromocriptine of mixed growth hormone/prolactin-secreting pituitary tumors

We have performed pituitary scintigraphy with 111In-pentreotide (OCT), a somatostatin analogue, and with metoxybenzamide (IBZM) by 123I-IBZM in two patients affected by mixed growth hormone/prolactin-secreting pituitary tumors. Short-term growth hormone (GH) inhibition by a single injection of OCT (100 micrograms s.c.), and short-term prolactin (PRL) inhibition by oral administration of 2.5 mg of bromocriptine (BCR), were also performed in both patients. The first patient, a 26 year old man, showed intense tumor uptake of 123I-IBZM scintigraphy, whereas 111In-OCT scintigraphy showed moderate tumor uptake. Five hours after the BCR inhibition test, a fall of 83% in PRL plasma levels (from 8,336 micrograms/L to 1,417 micrograms/L), and of 91.6% in GH plasma levels (from 39.5 micrograms/L to 3.3 micrograms/L) were observed. OCT inhibition test suppressed GH plasma levels from 36 micrograms/L to 3.5 micrograms/L. The patient was submitted to treatment with BCR and OCT. A dramatic shrinkage of the tumor was seen after six months of therapy. The lesion disappeared one year after the start of therapy. The second patient, a 64 year old man, showed intense uptake at 111In-OCT scintigraphy, while 123I-IBZM uptake was not observed. A test dose of BCR resulted in an acute fall of PRL (from 145 micrograms/L to 118 micrograms/L), but not of GH. A test dose of OCT decreased the GH plasma level from 61 micrograms/L to 4.5 micrograms/L. The patient was submitted to treatment with BCR and OCT that resulted in a computed tomography and magnetic resonance imaging decrease of 45% of tumor volume one year after the start of therapy. Our results suggest that both suppression tests with OCT and BCR, and scintigraphic studies in vivo with 123I-IBZM and 111In-OCT can be predictive for the effectiveness of therapies with dopamine agonists and/or SS-analogs in patients with mixed PRL/GH-secreting pituitary tumors. Further studies are required to evaluate the role of suppressive tests in selecting patients for appropriate clinical treatments.

Bromocriptine modulates P-glycoprotein function

The multidrug resistance (MDR)-associated P-glycoprotein (P-gp) is a membrane transporter which carries, at the expense of MgATP hydrolysis, many amphiphilic molecules, such as the MDR-related cytotoxic drugs vincristine and vinblastine, and the MDR-reversing agents verapamil and progesterone. We have tested the effects on P-gp function of bromocriptine (BCT), an ergot alkaloid known as a D2 dopaminergic receptor agonist. BCT (at 4 microM) partially reverses the P-gp-mediated vincristine resistance of the Chinese hamster lung fibroblasts DC-3F/ADX, a MDR cell line. P-gp containing membrane vesicles prepared from the DC-3F/ADX cells exhibit, in the absence of any added drug, a basal MgATPase activity due to P-gp. BCT inhibits this basal ATPase activity, with a half-inhibiting concentration of 0.30 +/- 0.15 microM. BCT also inhibits the verapamil-induced P-gp ATPase stimulation competitively (Ki approximately 0.2 microM), and the progesterone-induced P-gp ATPase stimulation non-competitively (Ki approximately 0.07-0.10 microM). BCT also non-competitively inhibits the vinblastine-dependent P-gp ATPase activity within the same concentration range. Hydroxylated metabolites of BCT have different effects on P-gp ATPase, only the monohydroxylated being able to modulate both the basal and the drug-stimulated ATPase activities. In conclusion, these effects of BCT on P-gp function can be linked to a specific interaction with P-gp, probably involving inhibition of P-gp-mediated drug transport.

Contribution of cytochrome P450 3A pathway to bromocriptine metabolism and effects of ferrous iron and hypoxia-re-oxygenation on its elimination in the perfused rat liver

The contribution of the cytochrome P450 3A pathway to bromocriptine metabolism, and the effects of ferrous iron and hypoxia-re-oxygenation on its elimination, were evaluated with the perfused rat liver. Outflow profiles of bromocriptine after bolus administration were estimated by moment analysis and dispersion model analysis. Kinetic parameters were not significantly changed by troleandomycin, a P450 3A inhibitor. The inhibition of bromocriptine metabolism by troleandomycin was 5.7 +/- 2.4%. These findings indicate that cytochrome P450 3A does not play an important role in bromocriptine elimination with the perfused rat liver. Elimination rate constant (ka) values were significantly increased by ferrous iron perfusion or hypoxia-re-oxygenation. Free-radical generation can, therefore, affect bromocriptine elimination. Our observations suggest that bromocriptine might be eliminated by scavenging of free radicals in the liver.

Nasal spray administration of bromocriptine: pharmacology and effect on serum prolactin level in puerperal women

This study was aimed at investigating the absorption of nasally administered bromocriptine and its effect on serum prolactin level. Fifteen physiologically hyperprolactinemia women who had asked to discontinue breast feeding received a single nasal spray administration of 0.8 mg bromocriptine. Serum prolactin levels were measured by radioimmunoassay at 30 and 15 min before drug administration, at the time of administration and at 15, 30, 60, 120, 240, 480 and 720 min after administration; bromocriptine was radioimmunoassayed in only five of the patients from time 0 to 720 min after administration. Serum bromocriptine levels increased rapidly after administration, reached a maximum at 120 min and thereafter declined slowly over the subsequent 10 h. As the bromocriptine level increased there was a decline in the serum prolactin level. The first significant decline in serum prolactin level compared with the baseline level occurred at 30 min after administration and the level continued to decrease significantly until time 120 min. Four hours after administration the mean serum prolactin level was within the normal assay range. The maximum decline in serum prolactin level was reached at 720 min after administration. Correlation analysis between serum bromocriptine and prolactin concentrations yielded a significant negative value between times 0 and 120 min after administration. There was no significant change in mean orthostatic systolic or diastolic blood pressure or in mean heart rate. Only one patient complained of headache and dizziness; another experienced mild transient nausea, and none had vomiting. Ten patients (66.67%) reported light endonasal burning and an unpleasant taste which subsided after a few minutes; no patient showed nasal irritation at nasal examination. In conclusion, nasal administration of 0.8 mg bromocriptine was effective in reducing the serum prolactin level for more than 12 h after administration without inducing significant side-effects.

Dopamine receptor affinities in vitro and stereotypic activities in vivo of cabergoline in rats

An ergot alkaloid derivative, cabergoline, and its metabolites were investigated for their affinities for dopamine D1 and D2 receptors in rat striatum in vitro in comparison with those of bromocriptine and pergolide. The affinity for D1 receptors was in the following order: pergolide > des-dimethylaminopropyl cabergoline (FCE21904) > cabergoline > or = bromocriptine > or = des-methyl cabergoline (FCE27395) > or = des-ethylcarbamoyl cabergoline (FCE21590). From the effects of GTP on these affinities for the D1 receptor, cabergoline, some of its metabolites, and pergolide were characterized as agonists in contrast to bromocriptine which was classified as an antagonist. The affinity for D2 receptors was ranked as follows: pergolide > or = cabergoline > or = FCE27395 > or = FCE21904 > bromocriptine > FCE21590 > carboxylic acid-type derivative of cabergoline (FCE21589). The affinity of each compound for the D2 receptor was much higher than that for the D1 receptor. The selectivity of cabergoline for D2 receptor was higher than those of bromocriptine and pergolide. Furthermore, these ergot alkaloids were investigated for eliciting stereotypy after subcutaneous administration to normal rats. Pergolide potently induced stereotypy at doses of 0.5 and 1.0 mg/kg, cabergoline slightly induced it only at a high dose of 2.0 mg/kg, whereas bromocriptine did not induce it at any of the doses tested, 10-40 mg/kg. These results suggest that pharmacological properties of cabergoline for the D1 and D2 receptors differ from those of bromocriptine and pergolide.

Nasal spray vs oral administration of bromocriptine: pharmacology and effect on serum prolactin in puerperal women

The oral administration of bromocriptine induces a variety of side-effects in about 50-70% of patients, the most common being nausea and vomiting, probably related to the local gastrointestinal effect of the drug. Nasal administration makes it possible to avoid intestinal and liver metabolism. This study compared the serum concentrations of bromocriptine and prolactin (PRL) in twenty puerperal women who had asked to discontinue breast feeding and were randomized to receive a single oral (2.5 mg) or nasal spray dose (0.8 mg) of bromocriptine. Serum bromocriptine and PRL concentrations were measured at various times before and after drug administration. At 15 min, the circulating concentrations of bromocriptine were about eight times higher after nasal than after oral administration; peak serum concentration (CMax) was reached respectively 45 min and 60 min after administration, and was about three times higher after nasal administration (314 +/- 102 pg/ml vs 112.30 +/- 34.47 pg/ml). The reduction in serum PRL concentrations was also more rapid in the nasally-treated group reaching the normal assay range of < 20 micrograms/l within two as against five hours post-administration. Four orally-treated patients complained of nausea; in the nasally-treated group, six patients reported only a mild endonasal burning that disappeared within a few minutes of administration. Our results suggest that the nasal administration of bromocriptine may lead to a reduction in the required overall dose and fewer gastrointestinal side-effects, and may therefore improve therapy compliance.

Differential regional and kinetics effects of piribedil and bromocriptine on dopamine metabolites: a brain microdialysis study in freely moving rats

Brain microdialysis coupled to HPLC was applied to freely moving rats to investigate the regional kinetics of piribedil and bromocriptine on the extracellular levels of 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in striatum, nucleus accumbens, and frontal cortex. Both D2 agonists (20 mg/kg i.p.) decreased DOPAC and HVA in the three brain regions. The responsiveness of frontal cortex to both compounds was greater than those previously reported with other dopaminergic drugs. Regional and temporal differences were observed under piribedil: DOPAC and HVA levels decreased more in the nucleus accumbens than in striatum or frontal cortex but increased over basal values from the 5th hour in the frontal cortex suggesting a late stimulatory effect of piribedil on dopamine synthesis in this area. Such regional effects differentiate piribedil from most other D2 agonists and could explain some behavioural and therapeutic actions possibly related to involvement of nucleus accumbens or/and frontal cortex.

Tolerance to peripheral, but not central, effects of ropinirole, a selective dopamine D2-like receptor agonist

Studies were conducted to determine possible development, and underlying mechanisms, of tolerance to the hypotensive effects of ropinirole (4-[2-(dipropylamino)ethyl]-1-3-dihydro-2H-indol-2-one HCl), a selective dopamine receptor agonist, following twice daily oral administration to cynomolgus monkeys and spontaneously hypertensive rats (SHR). Tolerance to the hypotensive effects of the compound developed in both species within one week of repeated dosing. Tolerance which developed in rats was dose-related and could not be attributed to altered plasma/drug concentrations or be overcome by increasing the i.v. challenge dose of ropinirole. Cross-tolerance was shown to the dopamine receptor agonist bromocriptine. Similar hypotensive responses to bethanidine were seen in rats treated with ropinirole or vehicle. Tolerance to hypolocomotor effects of the compound were not apparent in the same time frame. The dopamine D2 receptor antagonist, domperidone, caused hypertension in ropinirole-but not vehicle-treated rats. Results reported in this paper are not consistent with a down-regulation of peripheral dopamine D2-like receptors but suggest a compensatory increase in basal sympathetic tone.

Kinetics of bromocriptine release from microspheres: comparative analysis between different in vitro models

This paper describes how the use of different in vitro experimental systems can influence the determination of (a) the drug release profile from microparticles and (b) the interpretation of the release mechanism(s). We employed, as model dosage form, the Parlodel LA, a recently marketed microsphere system especially designed for bromocriptine-controlled delivery. The release kinetics of bromocriptine from microspheres were determined by using two different experimental approaches: a dialysis method and a flow-through cell method. From the comparison of the obtained data it clearly appears that different in vitro experimental models lead to distinct results in terms of drug availability. On the contrary both series of data can be convincingly fitted with the same mathematical equation, giving almost identical results in terms of postulated release mechanism. Taken together these results indicate that different experimental approaches should always be employed to determine drug release kinetics from microparticles in order to obtain more reliable information on the therapeutic dose (bioavailable drug, for in vivo experiments) and on the uniformity of different batches of microspheres.

A comparison of octreotide, bromocriptine, or a combination of both drugs in acromegaly

We investigated the pharmacokinetics of bromocriptine and octreotide, both individually and in combination, in 12 patients with active acromegaly. The pharmacodynamics of the drugs were assessed by 12-h profiles of GH secretion and insulin-like growth factor-I (IGF-I) measurements. During the 42-day study period, bromocriptine was administered for 28 days (from day 8; 5 mg, orally, twice daily) and octreotide (200 micrograms, sc, twice daily) from days 15-42. IGF-I levels, 12-h GH, and plasma bromocriptine and octreotide profiles were obtained on days 0, 14, 28, and 42. During bromocriptine treatment, both the area under the GH day curves (AUC) and mean IGF-I decreased to 64% (95% confidence limits, 43-72% and 48-82%, respectively) of initial values. During octreotide treatment, the respective values were 23% (18-30%) and 32% (21-36%), which were greater decreases than those during bromocriptine treatment [36% (95% confidence limits, 32-54%) for AUC for GH and 50% (95% confidence limits, 34-58%) for IGF-I]. With combined treatment, the AUC for GH was reduced to 16% (12-21%) and that of IGF-I to 25% (16-27%) of initial values. This combination was more effective than bromocriptine [25% (95% confidence limits, 22-37%) for AUC for GH and 39% (95% confidence limits, 25-43%) for IGF-I] and octreotide alone [78% (95% confidence limits, 53-89%) for AUC for GH and 78% (95% confidence limits, 57-98%) for IGF-I]. The pharmacokinetic parameters of octreotide were unchanged by the coadministration of bromocriptine. The bioavailability of bromocriptine increased by approximately 40% when bromocriptine was administered together with octreotide compared with administration alone (P < 0.01). Bromocriptine disposition parameters were unaltered. In conclusion, treatment of acromegalics with a combination of octreotide and bromocriptine increases the bioavailability of bromocriptine and reduces both GH and IGF-I levels more effectively than treatment with either drug alone. This presents the possibility of less frequent drug administrations, lower doses of octreotide, and, consequently, lower treatment costs.

In vitro-in vivo correlation for modified-release formulations

A correlation of in vitro dissolution rate measurements with in vivo pharmacokinetic results in a human study was obtained for a sustained-release formulation of bromocriptine. Different methods were applied to reach this correlation, and the various outcomes were compared.

The effect of food and metoclopramide on the pharmacokinetics and side effects of bromocriptine

The effect of food and metoclopramide on the pharmacokinetics of bromocriptine was investigated in 7 healthy subjects. Plasma concentrations of bromocriptine were measured by radioimmunoassay after a single oral dose of 7.5 mg bromocriptine. Maximal plasma concentrations of bromocriptine were slightly lower when the drug was given after breakfast. Bioavailability of the drug was not significantly reduced by food nor by metoclopramide pre-treatment. Side effects of bromocriptine were considerably reduced by metoclopramide pre-treatment (0.5 mg/kg); the decrease was about 83% as estimated from Table II.

Effects of withdrawal of antiparkinson medication on gait and clinical score in the Parkinson patient

Objective testing of medication is needed in Parkinson's disease. Gait analysis and clinical evaluation were done before and after a 24-h withdrawal of Parkinson medication. Twelve patients with stable, mild to moderate idiopathic parkinsonism (Hoehn and Yahr 1-3; seven men and five women mean age 59.9 years, mean duration of disease 6 years) were tested with gait analysis walking in five different paces. Velocity of gait, stride length and stride frequency, as well as stride length at constant velocity were calculated. Regression coefficients for the relation between stride length and stride frequency were also calculated. Clinical scoring according to the Webster rating scale and Hoehn and Yahr were performed for each test. Clinical functional assessment with a specially designed rise and gait test, an arm cycle test and the wooden rods test were done. Evaluated clinical score increased significantly (p less than 0.05) using both clinical tests. Maximum gait velocity (p less than 0.01), stride length at max. velocity (p less than 0.01), and stride length at constant velocity (p less than 0.03) were significantly decreased without medication. Stride frequency did not change. In the functional assessment tests only performance on the arm cycle test (p less than 0.03) was less well performed without medication. There was correlation between clinical score, gait and clinical functional assessment. The methods used detected significant changes in variables of gait as well as clinical scoring and some of the clinical functional assessments when medication was withdrawn for a 24-h period. The methods were useful in evaluation of pharmacological treatment.

Increased circulating levels of bromocriptine after vaginal compared with oral administration

OBJECTIVE

To compare the circulating levels of bromocriptine after oral and vaginal administration of the drug.

DESIGN

Experimental

PARTICIPANTS

Seven ovulatory female volunteers and one hyperprolactinemic patient.

INTERVENTIONS

Ovulatory volunteers were randomized to receive either oral or vaginal bromocriptine (2.5 mg). In a second session, the subjects were crossed-over to bromocriptine by the alternate route. An additional hyperprolactinemic patient received vaginal bromocriptine only.

MAIN OUTCOME MEASURE

Serum bromocriptine and prolactin (PRL) levels were measured hourly for 12 hours in the normal volunteers and for 10 hours in the hyperprolactinemic patient.

RESULTS

Circulating bromocriptine levels were significantly higher after vaginal bromocriptine after the 7th hour (P less than 0.05). The reduction in serum PRL was significantly greater after oral administration between 2 and 6 hours.

CONCLUSIONS

Vaginally administered bromocriptine may result in a reduction in the overall dose required, thereby improving compliance without compromising therapeutic efficacy.

Relevance of pH dependency on in vitro release of bromocriptine from a modified-release formulation

Since pH profiles of the dissolution rate are thought to be predictive for the in vivo performance of oral modified-release formulations with respect to bioavailability and dose dumping with food, these pH profiles were established for a new modified-release (MR) formulation for bromocriptine (Parlodel SRO). The results show a marked decrease of bromocriptine dissolution with increasing pH of the dissolution medium. However, when measured in native human duodenal juice (pH 8.1), dissolution was significantly higher than when measured in buffer of comparable pH. In a human pharmacokinetic study, this MR formulation showed good bioavailability and no food effect on the pharmacokinetic profile. Therefore, pH profiles alone seem to have only a limited predictive power for the in vivo performance of this MR formulation for bromocriptine.

Pharmacokinetic evaluation of erythromycin and caffeine administered with bromocriptine

A study was performed to determine if the pharmacokinetics of bromocriptine is altered by factors that have been shown to interact with other ergot compounds. The effects on bromocriptine plasma concentrations by bromocriptine coadministration with caffeine and erythromycin were evaluated in five male volunteers. Serial blood samples were obtained during a 12-hour period after a single 5 mg oral dose of bromocriptine (alone and after 4-day treatments of either erythromycin estolate, 250 mg four times/day, or caffeine, 200 mg four times/day). There were no significant alterations of bromocriptine pharmacokinetic parameters after caffeine, although statistical power was very low. With the use of erythromycin, the bromocriptine area under the concentration-time curve standardized to body weight increased significantly by 268%, whereas peak bromocriptine plasma concentration (Cmax) increased to 4.6 times the Cmax from bromocriptine alone. Time to achieve Cmax was not altered by erythromycin. We conclude that erythromycin can markedly increase the systemic bioavailability of bromocriptine, which can lead to increased therapeutic or adverse effects, whereas the effects of caffeine require further study.

Lactation inhibition by a single injection of a new depot-bromocriptine

Recently, long-acting injectable forms of bromocriptine have become available for the prevention of lactation. The first developed depot-form was very effective, but had the disadvantage of a slowly metabolized carrier. we investigated the pharmacokinetics, efficacy, tolerance and safety of 40 and 50 mg of a new rapidly eliminated depot-form in 61 postpartum women. Bromocriptine rapidly increased after injection and prolactin was effectively suppressed during the study-period of 60 days. Overall efficacy was very good or good in 98% and no rebound lactation occurred. Sixteen women experienced side effects. Tolerance at the injection site was good and safety tests did not show abnormalities. There were no differences between the two dosages. We conclude that this new depot-bromocriptine is a safe, well tolerated and effective drug in the suppression of prolactin and the prevention of post-partum lactation.

Bromocriptine blood levels after the concomitant administration of levodopa, amantadine and biperiden in Parkinson's disease

We recently demonstrated that when different drugs (mainly used for the treatment of Parkinson's disease) are administered in combination they interfere with the availability of bromocriptine in the brain of rats (striatum and hypothalamus). In the present study performed with parkinsonian patients, we measured plasma levels of bromocriptine (RIA) over 4 h after giving orally 5 mg bromocriptine alone; together with levodopa 250 mg plus 25 mg DCI (10 patients); with 100 mg amantadine HCl (5 patients) and with biperiden 5 mg (5 patients). Amantadine and biperiden did not interfere with the pharmacokinetics of bromocriptine. However, levodopa significantly diminished plasma levels (a mean increment of 1.78 mg +/- 0.30 vs 0.92 +/- 0.18 mg/ml). We postulate that levodopa may interfere with the metabolism of bromocriptine in the liver. Although we did not observe substantial clinical differences among the patients (Webster scale), this study supports our previous findings and suggests that one of the advantages of combined treatment may result from a modification of the plasma levels of bromocriptine by levodopa. A "smoothing" of the plasma bromocriptine curve possibly avoids sudden oscillations of the drug availability and enables a more "stable" penetrability of the medication into the central nervous system.

The influence of levodopa in the pharmacokinetics of bromocriptine in Parkinson's disease

The administration of bromocriptine in addition to levodopa in Parkinson's disease produces beneficial results. Several hypotheses have explained the advantage of the combined treatment by a pharmacodynamic interaction in the striatum. However, no study has considered the possibility that levodopa modifies the kinetics of bromocriptine. In the present study performed with parkinsonian patients, we measured blood levels of bromocriptine (by radioimmunoassay) at 0, 30, 60, 90, 120, 180, and 240 min after the oral administration of bromocriptine alone and together with 250 mg levodopa plus 25 mg DCI. After loading of bromocriptine alone, we found mean peak levels at 60 min (1.42 ng/ml) and at 90 min (1.82 ng/ml). These values were reduced by levodopa (0.97 ng/ml at 60 min and 0.93 ng/ml at 90 min). Although we did not observe substantial clinical differences among the groups after the drug challenge (Webster scale), this study supports our previous findings and suggests that one of the advantages of a combined treatment may result from a modification of the plasma levels of bromocriptine by levodopa. A "smoothing" of the plasma bromocriptine curve possibly avoids sudden oscillations of the drug and enables a more "stable" penetrability of the medication into the central nervous system. Therefore long-term combined treatment is advised in preference to bromocriptine alone.

Acute and subchronic effects of low-dose bromocriptine in haloperidol-treated schizophrenics

The effects of the acute (within 24 hr) and subchronic (21 days) addition of low-dose bromocriptine (2.5 mg/day) were compared to placebo in schizophrenic patients treated concomitantly with haloperidol. After 24 hr patients on bromocriptine (n = 15) showed a mean improvement of 29% in the total score of the Brief Psychiatric Rating Scale (BPRS) as compared to 14% in the placebo group (n = 15) (p less than 0.10). The acute improvement correlated negatively with bromocriptine plasma levels; patients with the highest reduction in BPRS score had the lowest plasma levels (between 50 and 150 pg/ml) at 60, 90, and 120 min after intake. The improvement in the bromocriptine group continued until the 10th day of the trial, when a nonsignificant increase in the total BPRS score took place. Analysis of Variance of the overall BPRS improvement during the 21 days revealed no significant difference between both patient groups. Our results give modest support to the idea of an acute antipsychotic response to low-dose dopamine agonists in neuroleptic-treated patients, but fail to support their clinical usefulness in the subchronic treatment of schizophrenia.

Vaginal bromocriptine: pharmacology and effect on serum prolactin in normal women

Oral bromocriptine treatment of hyperprolactinemia is frequently associated with gastrointestinal side effects. To assess the efficacy and safety of an alternate route of treatment, we randomly administered 2.5, 5.0, and 7.5 mg of bromocriptine vaginally to five normal women at 1-week intervals. Plasma bromocriptine and prolactin (PRL) levels were measured hourly for 12 hours, then every 2 hours for 12 hours after each dose. At the end of each study, the vagina was flushed with saline for measurement of residual drug. For comparison of serum PRL levels, six additional women were given 2.5 mg bromocriptine orally. After administration of 2.5, 5.0, and 7.5 mg vaginally, plasma bromocriptine was initially detectable at 5.4 +/- 0.4, 4.4 +/- 0.7, and 3.5 +/- 0.6 hours, respectively. For the same vaginal doses, the mean (+/- SEM) peak plasma levels were 555 +/- 164 pg/mL at 12 +/- 0.6 hours, 702 +/- 252 pg/mL at 11.2 +/- 0.9 hours, and 1055 +/- 220 pg/mL at 10.7 +/- 1.7 hours, respectively. After each dose, there was a slow decline in plasma bromocriptine levels, remaining above 50% of peak values at 24 hours. Less than 1% of the administered drug was recovered from the vagina at 24 hours. The pattern of PRL inhibition with all three doses was similar. The mean plasma PRL level decreased by 7 hours, the maximum PRL decrease (64 +/- 3, 75 +/- 1, and 66 +/- 4% after 2.5, 5.0, and 7.5 mg, respectively) occurring at 11 hours, and the plasma PRL levels changed little during the remaining 13 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Triple stage quadrupole mass spectrometric determination of bromocriptine in human plasma with negative ion chemical ionization

A new MS/MS assay for the quantitative determination of bromocriptine in body fluids is presented. The selective reagent gas in combination with the registration of selected, characteristic negative ions (SIM) after collision activated decomposition (CAD) in a Triple-Stage-Quaddrupole-mass spectrometer, provides an exceptional selective and sensitive assay in the low pg/ml range. The lower limit of detection was about 1 pg/ml (at optimal measuring conditions) and the calibration curve was linear in the range of 10-200 pg/ml. The coefficient of variation for the imprecision and inaccuracy data was typically below 10%; the recovery from plasma always exceeded 75%. The sample introduction to the mass spectrometer was done by a direct exposure probe (DEP). Thus, the method is well suited for the reliable, rapid processing of large sample numbers generated e.g. from clinical studies evaluating the pharmacokinetics and/or bioavailability/bioequivalence of different formulations or from drug monitoring/clinical response programs. The assay has been successfully approved in several clinical studies evaluating different bromocriptine preparations.

Differential effect of food on kinetics of bromocriptine in a modified release capsule and a conventional formulation

The influence of food on release of drug from a modified release capsule of bromocriptine 5 mg (Parlodel SRO) and a conventional formulation of bromocriptine 5 mg has been studied in 8 healthy male volunteers. Both formulations produced objective and subjective effects, such as orthostatic reactions, nausea, dizziness, vomiting and nasal congestion. The modified release capsule caused fewer side-effects than the normal capsule. Both formulations had less cardiovascular effect in the fed than in the fasting state. There was no significant difference between the normal and the modified release capsules taken fasting or after a meal in terms of the AUC extrapolated to infinity. The relative bioavailability of the 5 mg modified release capsule was 84.6% of the normal capsule under fasting conditions and 107.5% after food. In contrast to the virtually unchanged extent of absorption, the rate of absorption was markedly affected by food, especially from the conventional capsule. The mean time of 50% absorption increased from 1.06 h (fasting) to 3.2 h (fed), whereas for the modified release capsule food mainly resulted in an increased lag time of absorption. The almost instantaneous dissolution of bromocriptine from the normal capsule in vitro (both in HCl and fasting human gastric juice) and the delay of absorption after a meal in vivo suggest that the rate limiting step in absorption of the normal capsules is delivery of released drug from the stomach to the small intestine, which is delayed by food. Both the modified release 5-mg capsule and the normal 5-mg capsule showed extended suppression of prolactin over 36 h, in all subjects, both fasted and after a meal.

Growth hormone responses to hp GRF 1-44 amide, bromocriptine and stress in acromegaly are correlated

The results of testing growth hormone (GH) reserve using human pancreatic growth hormone-releasing factor 1-44 amide (hp GRF 1-44 amide) have been compared with the GH responses in a variety of other dynamic tests in seven acromegalic patients. The GH release following hp GRF 1-44 amide correlated with the GH suppression following bromocriptine, but showed an inverse correlation with the GH release following stress tests (insulin-induced hypoglycaemia/glucagon). There was no correlation between the GH responses in these three tests and any of the other tests: TRH, GnRH and glucose. A hypothesis is proposed to explain these findings on the basis of varying degrees of GH secretion from adenomatous and normal pituitary somatotrophs in acromegaly.