Permeability of ergot alkaloids across the blood-brain barrier in vitro and influence on the barrier integrity.

SCOPE: Ergot alkaloids are secondary metabolites of Claviceps spp. and they have been in the focus of research for many years. Experiments focusing on ergotamine as a former migraine drug referring to the ability to reach the brain revealed controversial results. The question to which extent ergot alkaloids are able to cross the blood-brain barrier is still not answered. METHODS AND RESULTS: In order to answer this question we have studied the ability of ergot alkaloids to penetrate the blood-brain barrier in a well established in vitro model system using primary porcine brain endothelial cells. It could clearly be demonstrated that ergot alkaloids are able to cross the blood-brain barrier in high quantities in only a few hours. We could further identify an active transport for ergometrine as a substrate for the BCRP/ABCG2 transporter. Investigations concerning barrier integrity properties have identified ergocristinine as a potent substance to accumulate in these cells ultimately leading to a weakened barrier function. CONCLUSION: For the first time we could show that the so far as biologically inactive described 8-(S) isomers of ergot alkaloids seem to have an influence on barrier integrity underlining the necessity for a risk assessment of ergot alkaloids in food and feed.

Determination and pharmacokinetics of ergometrine maleate in rabbit blood with on line microdialysis sampling and fluorescence detection.

The study describes a flow injection on-line microdialysis system for in vivo monitoring of ergometrine maleate in rabbit blood with fluorescence detection. A flow-through microdialysis probe was used for intravenous sampling by pumping of the blood from the tested rabbit through the flow-through microdialysis probe located outside the living system at a flow rate of 15 microl min-1. The perfusion rate is 5 microl min-1. The ergometrine maleate in the dialysate was detected on-line with a flow injection fluorescence system after the ergometrine maleate administration (0.2 mg kg-1, i.v.). The dialysate sample volume was about 15 microl. The system was linearly related to the concentration of ergometrine maleate in the range 1-140 ng ml-1 (r=0.9989) with a detection limit 0.3 ng ml-1 (3sigma). The pharmacokinetic parameters of ergometrine maleate were calculated utilizing the pharmacokinetic software 'NDST-21' by a one-compartmental open model.

Ergot alkaloid transport across ruminant gastric tissues.

Ergot alkaloids cause fescue toxicosis when livestock graze endophyte-infected tall fescue. It is generally accepted that ergovaline is the toxic component of endophyte-infected tall fescue, but there is no direct evidence to support this hypothesis. The objective of this study was to examine relative and potential transport of ergoline and ergopeptine alkaloids across isolated gastric tissues in vitro. Sheep ruminal and omasal tissues were surgically removed and placed in parabiotic chambers. Equimolar concentrations of lysergic acid, lysergol, ergonovine, ergotamine, and ergocryptine were added to a Kreb's Ringer phosphate (KRP) solution on the mucosal side of the tissue. Tissue was incubated in near-physiological conditions for 240 min. Samples were taken from KRP on the serosal side of the chambers at times 0, 30, 60, 120, 180, and 240 min and analyzed for ergot alkaloids by competitive ELISA. The serosal KRP remaining after incubation was freeze-dried and the alkaloid species quantified by HPLC. The area of ruminal and omasal tissues was measured and the potential transportable alkaloids calculated by multiplying the moles of transported alkaloids per square centimeter of each tissue type by the surface area of the tissue. Studies were conducted to compare alkaloid transport in reticular, ruminal, and omasal tissues and to determine whether transport was active or passive. Ruminal tissue had greater ergot alkaloid transport potential than omasal tissue (85 vs 60 mmol) because of a larger surface area. The ruminal posterior dorsal sac had the greatest potential for alkaloid transport, but the other ruminal tissues were not different from one another. Alkaloid transport was less among reticular tissues than among ruminal tissues. Transport of alkaloids seemed to be an active process. The alkaloids with greatest transport potential were lysergic acid and lysergol. Ergopeptine alkaloids tended to pass across omasal tissues in greater quantities than across ruminal tissues, but their transport was minimal compared to lysergic acid and lysergol.

Ergot alkaloids. Current status and review of clinical pharmacology and therapeutic use compared with other oxytocics in obstetrics and gynaecology.

Ergot alkaloids are well known preparations. Ergot alkaloids used in obstetrics and gynaecology are ergometrine (ergonovine; EM), methylergometrine (methergine; ME) and bromocriptine. The pharmaceutical properties of ME EM) are critical. To guarantee stability, ME and EM ampoules should be stored in a cool, dark place. ME and EM tablets are unstable in all conditions and they show an unpredictable bioavailability, which prevents oral use of the drugs for any purpose. ME and EM are known for their strong uterotonic effect and, compared with other ergot alkaloids, for their relatively slight vasoconstrictive abilities. ME and EM do have a place in the management of the third stage of labour as they are strong uterotonics. They act differently from oxytocin and prostaglandins, and have different adverse effects. Oxytocin should be used as prophylaxis or a the drug of first choice; next, ME or EM should be used, and if none of these drugs produce the desired effects, prostaglandins should be used to control bleeding. Ergot alkaloid use in gynaecology has been limited and today is discouraged even in essential menorrhagia. It is suggested that EM and ME be used (parenterally) only in first trimester abortion curettage, to reduce blood loss. Bromocriptine has been used for lactation suppression. However, alternatives such as cabergoline, which possess fewer adverse effects, are now available and therefore preferred for this indication. In sum, there is no place for the prophylactic use of ME and EM in obstetrics or gynaecology. They can be used for therapeutic purposes in the third stage of labour. During use, the practitioner must be alert for adverse effects.

Ergometrine and methylergometrine tablets are not stable under simulated tropical conditions.

OBJECTIVES: This study is part of a programme on reduction of postpartum haemorrhage (PPH). Ergometrine and methylergometrine have a favourable effect on both blood loss and maternal morbidity and mortality and oral preparations were regarded as a possible treatment for use in tropical countries. The stability of oral preparations of the two ergometrine compounds under tropical conditions was unknown and was therefore examined in this study. STUDY METHODS: The 'experimental shelf lives' of ergometrine and methylergometrine tablets were examined by exposing the tablets to seven artificially controlled conditions. Samples were analysed by high performance liquid chromatography at nine different sampling times over a period of 1 year to determine the content of ergometrine and methylergometrine. RESULTS: Under refrigeration (test I), less than 90% of the stated amount of active ingredient was found in the tablets after 14 weeks in the case of ergometrine and 21 weeks in the case of methylergometrine. When stored in the dark at 40 degrees C and 75% relative humidity (test VI), the tablets fall outside accepted specification (= 90-110% of state amount of active ingredient) within 3 weeks in the case of ergometrine and 21 weeks in the case of coated methylergometrine tablets. The stability of uncoated ergometrine tablets was far less than that of coated methylergometrine tablets. Instability worsened under extreme humid conditions (test IV and VI), and hot conditions (test V), for both ergometrine and methylergometrine. From week 31 onwards the coating did not seem to protect the compound anymore, irrespective of the condition of exposure. CONCLUSIONS: Tropical conditions make the tablets unstable with humidity as the main adverse factor. The sugar-coated methylergometrine tablets are more stable under humid/hot conditions than the non-coated ergometrine tablets. Under all simulated conditions both oral ergometrine and methylergometrine tablets are unstable.

Pharmacokinetics and bioavailability of oral ergometrine in male volunteers.

The aim of this investigation was to assess the pharmacokinetics and bioavailability of ergometrine in six human male subjects after an oral dose of 0.200 mg and after an intravenous dose of 0.075 mg of ergometrine maleate. A large variation in bioavailability of between 34% and 117% in the six volunteers was observed. The lag time was also subject dependent and ranged between 0.0073 h (0.4 min) and 0.47 h (28 min). After intravenous administration, the pharmacokinetic profile can be described by a two-compartment model. The distribution half-life t1/2 alpha is 0.18 +/- 0.20 h, the elimination half-life t1/2 beta is 2.06 +/- 0.90 h, the total body clearance (CL) amounts to 35.9 +/- 13.4 l h-1 and the steady-state volume (Vss) of distribution is 73.4 +/- 22.01. After oral administration, the pharmacokinetic profile can be described by a one-compartment model. The absorption half-life t1/2 abs is 0.19 +/- 0.22 h, and the elimination half-life t1/2 beta 1.90 +/- 0.16 h. This study with oral ergometrine shows such a large interindividual variability in bioavailability that the oral route of administration does not seem not to be the most reliable means of accurate dosing in preventing post-partum haemorrhage.

High-performance liquid chromatography of ergometrine and preliminary pharmacokinetics in plasma of men.

An isocratic high-performance liquid chromatographic (HPLC) method with fluorescence detection has been developed for the measurement of ergometrine in human plasma. The quantitation limit in plasma was 75 pg/ml. An example of the plasma concentration-time curves obtained after both oral and intravenous administration of ergometrine in one volunteer is shown. This HPLC method makes it possible to describe the pharmacokinetic parameters of oral ergometrine.

[The mechanism of ergonovine-induced airway smooth muscle contraction].

There have been three articles in the clinical literature concerning ergonovine maleate-induced bronchospasm. The effect of this alkaloid on isolated canine tracheobronchial smooth muscle was analyzed to investigate the mechanism of ergonovine-induced airway smooth muscle contraction. Both ergonovine and serotonin (5-hydroxytryptamine, 5HT) contracted canine tracheal smooth muscle with EC50 1.4 X 10(-8) M and 5.1 X 10(-7) M, respectively. The maximal contractile response observed with ergonovine was approximately 30% less than that observed with 5HT. In diverse blockers such as methysergide, atropine, prazosin, propranolol, pyrilamine and cimetidine, only methysergide competitively blocked both ergonovine and 5HT responses with a similar calculated dissociation constant (pKB); 8.3 +/- 0.2 against ergonovine and 8.5 +/- 0.2 against 5HT (n = 6, p = 0.9). The relative affinity and efficacy of ergonovine and 5HT were determined by use of a partial irreversible antagonist, phenoxybenzamine. The calculated affinity of ergonovine was about 16 times higher than that of 5HT. The relative efficacy of EC100 for ergonovine was 0.2 but at EC10 it was 41.9 (5HT efficacy = 1). Ergonovine 10(-9) M or 10(-8) M shifted the 5HT dose-response curve to the right without reducing the maximal response, but the shift was nonparallel. Ergonovine and 5HT also contracted canine bronchial smooth muscle in a dose dependent manner with EC50 6.4 X 10(-8) M and 1.8 X 10(-7) M, respectively. The dose-responses curve of these two agonists were competitively blocked by methysergide 10(-6) M. These data indicate that ergonovine directly contracts canine tracheobronchial smooth muscle as a result of its combination with 5HT receptors. This effect may result in the precipitation of an asthmatic attack in susceptible individuals.