EUROPEAN JOURNAL OF DRUG METABOLISM AND PHARMACOKINETICS, 1987, Vol. 12, No I, pp. 1-4

Bioavailability of dihydroergosine in healthy volunteers

POLONA CVELBAR*, J. CULIG**, Z. KOPITAR*, A. LENARDIC*, JANJA URBANCIC SMERKOLJ*,M. ZORZ** Research Institute Lek, Pharmaceutical and Chemical Works. Ljubljana. Yugoslavia** Department for Clinical Pharmacology. Clinical Hospital Center. Zagreb. Yugoslavia

Received for publication: June 6, 1985

Key words: Ergot alkaloids, dihydroergosine, pharmacokinetics, volunteers

SUMMARY

Eight healthy volunteers received an oral dose of 10 mg and an intravenous dose of 0.75 mg of dihydroergosine. Plasmaconcentrations were measured by HPLC method, and some pharmacokinetic parameters were calculated. The biologic half-life in theelimination phase was 8.35 ± 1.87 h after oral administration and 8.84± 3.64 h after intravenous administration. In both cases ofadministration a secondary rise in plasma concentrations of dihydroergosine was observed, which can be attributed to hepatic recycling.The calculated bioavailability of the drug was 9.80 ± 2.8 %.

INTRODUCTION

Dihydroergosine (DHESN) is a derivative ofpeptide ergot alkaloids, by its chemical structuresimilar to dihydroergotamineand dihydroergokryptine.DHESN is obtained from naturally occuring alpha­ergosine by hydrogenation of the indole ring inpositions 9 and 10. In the form of methanesul­phonate the substance is water soluble and suitablefor therapeutic administration. Its chemical structureis shown in Figure 1. The main pharmacodynamicaction of DHESN is its hypotensive effect, obtainedin acute and chronic experiments in unnarcotisednormal and SH rats. DHESN prevents the pressureeffect of noradrenaline and phenylephrine as well asin rats the arrhytmic action of adrenaline, nor­adrenaline and oubaine in guinea-pigs. The basicmechanism of action is supposed to be a strongantagonising effect on alpha 1 adrenoceptors. Itseems that the DHESN effect on DA receptors isincluded in its effect on blood pressure and heartrate (1, 2). These findings together with the pre­liminary investigations of acute and subacute toxicity

Send reprint requests to: Prof. Dr Zdravko Kopitar, LEKLjubljana, Research and Development, Celovska 135, 61000Ljubljana, Yugoslavia.

(3) and of its pharmacokinetic behaviour (4) indicateits possible usefulness in the treatment of hypertension.To better elucidate the pharmacokinetics of thesubstance and particularly to enable the determinationof appropriate dosing for future early phase clinicaltrials, the pharmacokinetics of DHESN in healthyvolunteers had to be carried out.

Fig. 1: Chemical structure of 9,1O-dihydroergosinemethanesulphonate.

METHODS

DHESN was prepared in the Lek Laboratoiresfor Synthesis, Pharmaceutical and Chemical works,Ljubljana.

2 European Journal of Drug Metabolism and Pharmacokinetics, 1987. No I

Volunteers

Eight healthy volunteers, males, aged from 19 to25 years and of body weight between 60 and 90 kg,were included in the trial. The volunteers wereacquainted with the purpose and the methods of thetrial, as well as with the related dangers andinconveniences.

Prior to the trial medical histories were in­vestigated in all volunteers, and clinicaland laboratoryexaminations were carried out. All the findings werewithin normal limits. (The values of endogenouscreatinine clearance were between 70 and 92mllmin.)

Course of the trial

In randomised, cross-over trial the volunteerswere given intravenously 0.75 mg (3 ml) or orally10 mg (40 ml) of DHESN solution at one weekintervals. The solution was taken on an emptystomach after overnight fasting. Four hours later,the volunteers were given standardised breakfast,

10 ml samples of venous blood were withdrawnimmediately before the administration of the drugand 10, 20, 40, 60, 80, 100 min and 2,3,6,8, 12and24 hours after the administration. Following in­travenous administration, an additional blood samplewas taken 5 minutes after administration. Theheparinized blood samples were centrifuged for 15minutes at 3000 rpm and the 'plasma stored at-18°C until the analysis was performed.

Analytical method

Plasma samples were analysed with HPLC andfluorescence detection after previous extraction. 5 mlof plasma were extracted with benzene: toluene:ethylacetate (3: I : I; v/vIv). The organic phase wasdried in vacuum. Then it was dissolved in the mobilephase and applied into the chromatograph.

Chromatographic conditions

The column was of dimensions 125)( 4 mm withthe stationary phase Lichrosorb Si 60, 5 um. Themobile phase was acetonitrile: methanol: cone.ammonia (1200: 100:0.8; v/v/v), with flow of 0.5mllmin.

Equipment

LDC-Constametric II G pump, Aminco-Bowmanspectrofluorimeter with 9 JJ1 flow cell (excitationwavelenght 285 nm, emission wavelenght 345 nm),

Valco 7000 PDL injector with 50 ul loop, ContronW +W 1100 recorder with chart speed 0.5 cm/min.The quantitation of plasma levels is based on the useof a calibration curve. The measure for the DHESNconcentration in plasma is given by the height of thecorresponding peak. Detection limit was 0.2 ng/mlof plasma.

Pharmacoklnetlc calculations

Areas under plasma concentration curves (AUC)were calculated according to the trapezoidal rule.Elimination constants (kel) were calculated from lin­log regression of plasma concentrations in timesfrom 3 to 12 hours. Bioavailability was estimatedfrom the ratio of AUC following oral and' in­travenous administration, corrected for the dose.TImes to reach maximal concentrations (!max) andmaximal concentrations (Cmax) were estimated fromthe experimental values. Volume of distribution (Vd)

was calculated accordingly to equation: Vd = ...!?....COp

D =dose, Cop =drug concentration at time O.

RESULTS

The plasma concentrations of DHESN followingintravenous and oral administration of 0.75 mg and10 mg DHESN, respectively, in healthy volunteersare presented. Mean values and standard deviationsof plasma concentrations can be seen in Fig. 2 and 3.

After intravenous administration there is a steepdecrease of plasma concentrations within first 10min, indicating a fast distribution phase. Theelimination phase is slow, with biological half-life(t Il2 ) = 8.84± 3.64 h. Approximately 2 h after ad­ministration, a small secondary rise of plasma con­centrations was observed.

Throughout the applied analytical method wewere able to follow DHESN plasma concentrationsup to 12 h in most volunteers, while at the lastsampling time (24 h) we could not detect DHESN inany volunteer.

After oral administration a very rapid absorptionof DHESN occured, leading quickly to maximalplasma concentrations: Cmax±:2.39± 0.55 ng/ml.The times to reach these concentrations were tmax == 0.25± 0.09 h. Between 1.5 and 3 h a secondaryrise in plasma concentrations was seen again. Afterthat, the drug was eliminated at nearly the same rateas observed after intravenous administration (t l /2 ==8.35± 1.87 h). In the case of oral administration

8

Polona eve/bar et al., Bioavailability of Dihydroergosine in volunteers 3

6

4

...J

%....C) 2z

Uz0 /u 0 I Lj

I I I I I I I IIt.. I I, I

0 2 4 6 8 10 12 14 22 24 TIME ( H)

Fig. 2: Plasma concentrations of dihydroergosine after i.v, application of 0.75 mg DHESN in volunteers (n =8, mean ± SD).

2.0

1.5

1.0...J

%....C)

z0.5

I I

It'u /Iz .r-«:0u 0.0 I I I I I I I I // i i

0 2 4 6 8 10 12 14 22 24 TIME (H)

Fig. 3: Plasma concentrations of dihydroergosine after p.o. application of 10 mg DHESN in volunteers (n = 8, mean ± SD).

DHESN in plasma could be detected in all volunteersat all sampling times, except the last one.

The absolute bioavailability of the solution afteroral administration, calculated from the ratio ofareas under the curves, was on the average 9.8± 2.8%,

SOme of the calculated pharmacokinetic para­meters are listed in Table I.

DISCUSSION

The comparison of the present results with thoseof the previous study, in which pharmacokinetics of3H-Iabelled DHESN was studied in rats, showssome differences in pharmacokinetic parameters,which were not unexpected. In the present study

4 European Journal of Drug Metabolism and Pharmacokinetics, 1987, No 1

Table I: Pharmacokinetic parameters of DHESN

only blood concentrations of unchanged DHESNwere followed, while previously all metabolites wereincluded. Consequently, biological half -lives inhuman volunteers are relatively short. In humans thevalue is 8.35 h, while in rats it is 13 h; and the timesto reach maximal concentrations are 0.4 h in ratsand 0.25 h in humans. Assuming dose independentpharmacokinetic of the drug, we compared maximalconcentrations of DHESN, corrected for doses, forhumans and rats. Maximal concentrations in humanswere approximately half lower than in rats (0.42nglml in rats against 0.24 nglml in humans).On the base of the above results it is not surprisingthat the bioavailability estimated in humans waslower too. In rats it was 31%, while in humans it was9.8 0/0.

In both cases of administration a secondary peakof DHESN in plasma was observed. This secondaryrise can be attributed to hepatic recycling, which isconfirmed also by the fact that it was much morepronounced after oral administration where inten­sive first pass effect is to be expected. This ob­servation is in agreement with the findings of Palmiand Segre (5) for related alkaloids. It is an establishedfact that peptide ergot alkaloids in general have avery low bioavailability (6-9) amounting from 1 to9%, due to limited absorption and even more toextensive first pass effect (10). In comparison withother peptide ergot alkaloids, DHESN bioavailabilityis at the upper level of this scale.

In comparing the DHESN plasma profiles withthose of dihydroergotoxine (11, 12) it can be con­cluded that peak plasma concentrations of DHESNare reached earlier than for dihydroergotoxine, whilebiological half-lives of DHESN are longer. Thecalculated percentage of absorption and the bio­availability, obtained in our study in healthy volun-

Parameter

k (h- I )

t 1/2 (h)AUC (ng.h/ml)

Cmax (ng/ml)

t max (h)

f (%)Vd (I)

Intravenousadministration

0.09±0.05

8.84± 3.6417.29 ± 3.33

61.90 ± 25.6

Oraladministration

0.09 ± 0.02

8.35 ± 1.87

1.64± 0.37

2.39± 0.55

0.25±0.099.80± 0.09

teers, will be a valuable guide for dose findings ineventual early phase clinical studies of the drug. Thepresent work deals with DHESN solution only.Possible changes of pharmacokinetic properties re­lated to pharmaceutical formulating will have to beresolved later.

REFERENCES

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II. Humbert H., Lavene M.F., Guillaume M.F., KiechelJ.R., (1981): Pharmacocinetique de deux derives ergotes:la dihydroergotoxine, et la dihydroergotamine. Biodispo­nibilite comparative de ditrerentes formulations par rap­port aux formes solutions. In: Premier congres europeende biopharmacie et pharmacocinetique, Clermont-Ferrand,pp. 334-340.

12 Vrhovac B. (1984): Bioequivalence study of ergoloidmesilates 1.0 mg oral tablet and Hydergine 1.0 mg oraltablet. Internal Report Lek for Food and Drug Ad­ministration, pp. 1- 138.