Investigations on the pharmacokinetic properties of Harpagophytum extracts and their effects on eicosanoid biosynthesis in vitro and ex vivo.

PURPOSE: Harpagophytum extract and its marker substance harpagoside were shown to exert anti- inflammatory effects by interacting with the eicosanoid biosynthesis. In this study, different Harphagophytum extracts were tested with respect to inhibition of leukotriene and thromboxane biosynthesis in vitro and ex vivo. In addition, pharmacokinetic parameters of Harpagophytum extracts were investigated in vivo. METHODS AND SUBJECTS: Different fractions of Harpagophytum extracts were tested in vitro in human whole blood samples for effects on basal and ionophore A23187-stimulated cysteinyl-leukotriene (Cys-LT) and thromboxane synthesis. Furthermore, in 3 independent studies with different numbers of human male volunteers, a Harpagophytum extract was administered orally and tested in whole blood samples for Cys-LT and thromboxane B2 (TXB2) biosynthesis and for the determination of pharmacokinetic parameters of harpagoside. RESULTS: The special Harpagophytum extract WS1531 had a stronger inhibitory effect on ionophore A23187-stimulated Cys-LT levels compared with pure harpagoside or other extract fractions. Fractions without harpagoside had no pronounced inhibitory effect. When Cys-LT levels were measured after oral intake of Harpagophytum extract, a biphasic but dose-independent decrease of 28% and 58%, respectively, in basal Cys-LT formation was observed. Pharmacokinetic studies with the Harpagophytum extract WS1531 showed that the maximum levels of plasma harpagoside were reached after 1.3 to 2.5 hours. A linear relationship between dose and the first maximal concentration (Cmax) or area under the curve (AUC) (0-1)/AUC(0-infinity) was observed. CONCLUSIONS: Our observations strongly indicate a close relation between serum harpagoside levels and the inhibition of leukotriene biosynthesis.

Inhibition of noxious stimulus-induced spinal prostaglandin E2 release by flurbiprofen enantiomers: a microdialysis study.

Peripheral noxious stimuli have been shown to induce prostaglandin (PG) E2 release at the site of inflammation and in the spinal cord. The antiinflammatory and antinociceptive effects of cyclooxygenase-inhibiting drugs are thought to depend on the inhibition of PG synthesis. R-Flurbiprofen, however, does not inhibit cyclooxygenase activity in vitro but still produces antinociceptive effects. To find out whether R-flurbiprofen acts via inhibition of spinal PG release, concentrations of PGE2 and flurbiprofen in spinal cord tissue were assessed by microdialysis. The catheter was transversally implanted through the dorsal horns of the spinal cord at level L4. R- and S-flurbiprofen (9 and 27 mg kg(-1), respectively) were administered intravenously 10-15 min before subcutaneous injection of formalin into the dorsal surface of one hindpaw. Flurbiprofen was rapidly distributed into the spinal cord with maximal concentrations after 30-45 min. Baseline PGE2 dialysate concentrations were 100.6 +/- 6.4 pg ml(-1) (mean +/- SEM). After formalin injection they rose about threefold with a maximum of 299.4 +/- 68.4 pg ml(-1) at 7.5 min. After approximately 1 h PGE2 levels returned to baseline. Both flurbiprofen enantiomers completely prevented the formalin-induced increase of spinal PGE2 release and reduced PGE2 concentrations below basal levels. S- and R-flurbiprofen at 9 mg kg(-1) produced a minimum of 15.8 +/- 5.2 and 27.7 +/- 14.9 pg ml(-1), respectively, and 27 mg kg(-1) S- and R-flurbiprofen resulted in 11.7 +/- 1.7 and 9.3 +/- 4.7 pg ml(-1), respectively. PGE2 levels remained at the minimum up to the end of the observation period at 5 h. When 27 mg kg(-1) R-flurbiprofen was injected intravenously without subsequent formalin challenge, baseline immunoreactive PGE2 concentrations were not affected. S-Flurbiprofen (27 mg kg(-1)), however, led to a moderate reduction (approximately 40%). The data suggest that antinociception produced by R-flurbiprofen is mediated at least in part by inhibition of stimulated spinal PGE2 release and support the current view that increased spinal PGE2 release significantly contributes to nociceptive processing.

Measurement of the bioavailability of aescin-containing extracts.

OBJECTIVE: In horse chestnut seed extracts (HCSE), the triterpene saponin mixture aescin is considered the active principle. The bioavailability and pharmacokinetics of different HCSE preparations have been studied under single and repeated applications using a radioimmunological method (RIA) developed to identify beta-aescin, one of the pharmacologically active fractions of the saponin mixture. In this paper, the available pharmacokinetic data are reviewed and the observed heterogenicity between comparable studies is discussed. DATA SOURCES: Pharmacokinetic data from 5 single- and 4 multiple-dose bioequivalence studies with HCSE-containing products, were measured by the same analytical laboratory using the same RIA. EVALUATION: In studies where procedures were identical the pharmacokinetic data of beta-aescin show high variations. Even under steady-state conditions a considerable variability for the same HCSE product is obtained. CONCLUSION: Formal reasons like study design and medications can be ruled out as a source of pharmacokinetic variation. In extracts of herbal drugs like HCS, the relative concentration of the individual saponin fractions can considerably differ from batch to batch. For immunological methods, identification of such antigens with intermolecular variability, e.g., the structural aescin analogs, is of unknown validity. Therefore the shape of the concentration-time curve would only show an approximation of the time course but not for the absolute concentrations. A specific validation procedure for the RIA must be developed, otherwise a LC-MS/MS-method of sufficient sensitivity should be elaborated.

[The validity of radioimmunologic determination of bioavailability of beta-escin in horse chestnut extracts]. / Zur Validität radioimmunologisch bestimmter Bioverfügbarkeitsdaten von beta-Aescin in Rosskastaniensamenextrakten.

The bioavailability under steady state conditions of a standard, slow-release horse chestnut seed extract (HCSE)-containing product was compared with that of an analogous, fast-release test preparation (Noricaven novo) in a prospective, randomised, double-blind study in a double cross-over design. The serum concentration of beta-escin (CAS 6805-41-0) was measured by radioimmunoassay. In addition, the biopharmaceutical properties of the HCSEs present in the products were investigated, the amount and composition of the active ingredient, escin, being analysed with a validated HPLC method. The pharmacokinetics of this study were compared with the corresponding data of a similar investigation carried out under analogous conditions concerning study design, analytical methods and reference preparation. Comparison of the similar studies revealed differences in characteristic pharmakokinetic values of beta-escin in terms of a shift of the concentration time curves as could be demonstrated for the reference product. The total amounts of escin in the two products investigated did not differ significantly. However, quantitative and qualitative differences were detected in the constituents of the two different extract preparations. It is concluded that the high specificity of the validated beta-escin radioimmunoassay leads to analytical imprecision due to the variable constituents of the extract preparations used. It is necessary to test whether this problem can be solved using an analytical approach, which is specific for each extract.

Differences in the nyctohemeral secretion of TSH and PRL in healthy euthyroid men.

The circadian rhythm of TSH, PRL and cortisol was studied in 21 healthy euthyroid men in a normal sleep/wake cycle. Higher nyctohemeral (22.00 h till 6.00 h) levels of TSH as compared to diurnal (8.00 h till 22.00 h) levels were observed in 14 out of 21 men (Group A). In the remaining 7 volunteers the nyctohemeral and diurnal TSH-levels (Group B) were the same. In Group A, the nyctohemeral PRL-surge was also higher than in Group B (p < 0.01). The nyctohemeral area under the curve (AUC) of both TSH and PRL were significantly higher in Group A than in Group B (p < 0.05 and p < 0.001 respectively). The mean diurnal concentrations of TSH and PRL were, however, similar in both groups. Therefore, an impairment of the nyctohemeral TSH-surge can occur in healthy men usually combined with a reduced nyctohemeral PRL-surge. An impairment of nyctohemeral TSH-surge is thus not confined to patients with thyroid diseases.

The effects of a special Agnus castus extract (BP1095E1) on prolactin secretion in healthy male subjects.

The effects of three doses of a special Agnus castus extract (BP1095E1)--extracts from 120 mg, 240 mg and 480 mg of drug per day--were examined within the framework of a placebo-controlled clinical study of tolerance and prolactin secretion in 20 healthy male subjects during a period of 14 days. There was good tolerance during the study as regards the following: adverse effects, the effects on blood pressure and heart rate, blood count, Quick's test, clinical chemistry as well as testosterone, FSH and LH values. During each study phase the 24-hour prolactin secretion profile was measured from the penultimate to the final day, and the amount of prolactin release was monitored an hour after TRH stimulation on the last day. A significant increase in the 24-hour profile was registered with the lowest dose in comparison to placebo, the opposite being the case with the higher doses, i.e. a slight reduction. In contrast to the administration of placebo, the 1-hour AUC after TRH stimulation resulted in a significant increase with the lowest dose and a significant reduction with the highest dose. The results suggest effects of the special Agnus castus extract which are dependent on the dose administered and the initial level of prolactin concentration.