WO2008058938A2

WO2008058938A2 - Hypericum and derivatives thereof as analgesic potentiating agents

Info

Publication number: WO2008058938A2
Application number: PCT/EP2007/062222
Authority: WO
Inventors: Enrica Bianchi; Nicoletta Galeotti; Carla Ghelardini; Massimo Guarna
Original assignee: Universita degli Studi di Siena
Current assignee: Universita degli Studi di Siena
Priority date: 2006-11-13
Filing date: 2007-11-12
Publication date: 2008-05-22
Anticipated expiration: 2009-05-13
Also published as: WO2008058938A3; ITRM20060616A1

Abstract

The use of hypericum or at least one derivative thereof for the preparation of a medicament potentiating the effect of an opiate analgesic, preferably morphine, is described. The invention provides also a pharmaceutical composition comprising a pharmaceutically acceptable and active amount of an opiate analgesic and of hypericum or at least one derivative thereof, either in separated or joined formulations.

Description

HYPERICUM AND DERIVATIVES THEREOF AS ANALGESIC POTENTIATING AGENTS

TECHNICAL FIELD OF THE INVENTION Morphine is an analgesic or hyperalgesic agent depending on the administered dosage. Even if the paradoxical effect of morphine is known for a long time, the molecular pathway of the hyperalgesic effect was only recently identified in murine animal model [Galeotti 2006, Fig. I].

The identification of the enzymes involved in the hyperalgesic pathway activated by morphine, administered at much lower doses than the analgesic ones, allows envisioning a therapeutic strategy to eliminate such effect by blocking responsible enzymes. The suppression of hyperalgesic effect potentiates morphine-induced analgesia in rodents [Galeotti 2006].

STATE OF THE ART

The enzymes of the hyperalgesic pathway, activated by low doses of morphine, are not exclusive to this pathway; they are also involved in other molecular pathways. Therefore, care has to be taken that the blockade of such enzymes does not interfere with other physiological functions not related to pain modulation. Hypericum is a genus of about 400 species of flowering plants in the family Clusiaceae, formerly often treated separately in their own family the Hypericaceae. The genus has a nearly world- wide distribution, missing only from tropical lowlands, deserts and arctic region. Hypericum extracts comprise naphtodiantronic derivatives such as hypericin, pseudohypericin and isohypericin [Greeson 2002]. It further comprises flavonoids, such as hyperoside, rutin, quercetin, quercitrin and essential oils. Hypericin results to be a powerful inhibitor of protein kinase C (PKC) by interacting with a domain regulating the enzyme [Takahashi 1989]. Recently, hypericum (also known as "St. John's wort") has been used for treating some forms of depression. It has a humour changing effect which appears after 2/3 weeks of regular administration at appropriated doses (generally 300 mg/die). Hypericum is active also in anxious-depressive forms and, in combination with Valeriana, it has an effect similar to that of a tricyclic anti-depressant drug. A series of recent double-blind studies, comparing the effects of hypericum extracts to those of placebo, have shown that hypericum is effective as anti-depressant, having also very few side effects. Among available opiates, codeine and morphine are the "first choice drugs" [WHO 1986] in treating acute and chronic pain syndromes. The use of morphine is exclusively reserved (and carefully regulated) in the specific field of high intensity pain treatment (myocardium infarcts, oncological pains, pain associated to serious trauma) and for treating strong postoperative pain [Project hospital without pain/ Toscan area]. The morphine analgesic activity is on two sides: -elevation of pain threshold and contemporary, -reduction in emotional response to pain itself, by eliminating the "emotional responses" accompanying pain, such as anxiety, panic, fear, prostration.

Morphine influences respiratory functions, by reducing it as a whole and by altering both respiratory rhythm and volume. Other morphine effects concern stomach and intestine muscles. Secretions and digestive processes are considerably reduced by morphine and intestinal muscle relaxation causes constipation. Furthermore, an increase in the contractile force of urethras and bladder is observed. These effects can be considered dose-dependent. In clinical practice, it is considered that the maximum tolerated dose by the patient should reflect the equilibrium between the quality of "pain relief obtained and the importance of side effects. At present, morphine has been associated with several compounds, however they do not result to potentiate morphine effect and to reduce its side effects. In high intensity pains, morphine can be associated with paracetamol and/or ketoralac. In this case, the effects of the associated drugs, that belong to a different class of compounds and have different action mechanisms, sum up; the morphine dose used remains equal to the one used in absence of paracetamol or ketorolac. Other associations propose the concomitant intake of morphine and ketamine [Richebe 2005]; in this way, however, the adrenergic system is activated. Antagonists of NMDA receptor induce a potentiation of morphine-induced analgesia in rats by blocking the glutamatergic system [Holtman 2005].

SUMMARY OF THE INVENTION

The authors of the present invention have surprisingly found that hypericum or derivatives thereof as, for example, hypericin, potentiates morphine action. This effect allows to reduce morphine dosages to be administered while maintaining at least the same level of analgesia.

"Strong" opiates, such as morphine, are widely utilized for treating chronic from moderate to severe pain according to WHO indications. Such indications have been extended and adapted for the treatment of postoperative acute pain. In the last past years, the use of morphine has passed from end-of-life drug to elective drug in the treatment of moderate/serious pain. Therefore, the morphine/hypericin or morphine/hypericum combination is potentially of great use. Since the substances combined (morphine and hypericum or derivatives thereof) are available on the pharmaceutical market, the production of the combined preparation does not require investments to study and validate the single active principles. In the present invention, hypericum extract and one of the components thereof, hypericin, are shown to be ideal substances to potentiate morphine-induced analgesia. These substances induce the potentiation of morphine-induced analgesia by inhibiting the hyperalgesic pathway, since both block PKCγ action, one of the enzymes involved in the hyperalgesic pathway. The hypericum/hypericin dosages necessary to potentiate morphine- induced analgesia in an animal model are largely below the dosages used to induce the anti-depressant effect of such substances. The present studies performed on rodents, which have always been a good animal model for predicting morphine effects in humans, show that the morphine/hypericum or morphine/hypericin combination potentiates morphine- induced analgesia in a percentage of 35% and 67%, respectively. In practical terms, this means that, by using the morphine/hypericin combination, it could be sufficient to administer in human about 35% of the morphine dose usually administered to obtain the same analgesic effect. The potentiating effect is maintained over time and after repeated administrations. The side effects observed after morphine administration, such as intestinal constipation, nausea, vomiting and respiratory depression, are positively correlated with the administered dose and the repeated administrations. Morphine/hypericum and morphine/hypericin combinations change the value of the cost/benefit ratio by greatly reducing the cost (side effects) while increasing the benefits (analgesia). Furthermore, hypericum and hypericin are non-synthetic substances. The administration in pain therapy of a substance which is commonly defined as "natural" can facilitate approval of the patient who is sometimes unwilling to take medicaments considered as "drugs" in the common meaning. Therefore, it is an object of the present invention the use of hypericum or at least one derivative thereof for the preparation of a medicament potentiating the effect of an opiate analgesic.

It is another object of the invention the use of an opiate analgesic and hypericum or at least one derivative thereof for the preparation of a medicament for the treatment of pain.

Preferably the derivative of hypericum is hypericin. Still preferably the opiate analgesic is morphine.

It is a further object of the invention a pharmaceutical composition comprising a pharmaceutically acceptable and active amount of an opiate analgesic and of hypericum or at least one derivative thereof, either in separated or joined formulations.

Preferably, the pharmaceutically acceptable and active amount of the opiate analgesic is lower than the amount of the opiate analgesic needed to obtain the same analgesic effect when administered alone.

More preferably, the opiate analgesic is morphine. Still preferably the derivative of hypericum is hypericin.

In the context of the present invention pain comprises both acute and chronic pain. In particular the pain comprises oncological pain.

The present invention will be now described in non limitative examples, in particular referring to the following figures: Figure 1 : Molecular pathway of morphine-induced analgesia and hyperalgesia.

Figure 2: Effect of the hypericum/morphine combination on thermal analgesia.

Subcutaneous administration of the association. MF=morphine. *= significant statistical difference with respect to the administration of morphine alone (p<0,01). The reported values were obtained from at least 15 mice. Figure 3 : Effect of hypericin/morphine combination on thermal analgesia. Morphine was administered by subcutaneous route, hypericin by intracerebroventricular route.

MF=morphine. *= significant statistical difference with respect to the administration of morphine alone (p<0,01). The reported values were obtained from at least 15 mice.

Figure 4: Effect of hypericin/morphine combination on thermal analgesia after morphine chronic treatment. The animals were treated for 4 days according to the following scheme: at 9h00: hypericin by intracerebroventricular route; at lOhOO and 18h00: morphine by subcutaneous route, *= significant statistical difference with respect to the administration of morphine alone (p <0,01). The reported values were obtained from at least 15 mice. MATERIALS AND METHODS

The following substances were used: Morphine HCl (nor-NBI), hypericum (INDENA), hypericin (Sigma). The substances were dissolved in saline solution (NaCl 0.9%) immediately before use.

The behaviour test of the hot plate was used. The mice were placed into a steel container thermally set at a temperature of 52.5 ± 0.1⁰C (KW Mechanical Workshop, Siena, Italy). The reaction times (licking latency of the front or rear leg) was evaluated immediately before the administration of morphine or saline and after 15, 30 and 45 min. Each experiment was carried out in blind. The mice, which in the pre-test had a licking latency lower than 12 sec. and higher than 18, were discarded. All experiments were carried out at the same hour of the day (9h00-13h00). The mice were assigned to the respective groups randomly. At the end of the experiments, mice were anesthetized, brains were extracted and cut to verify the trace of the intracerebro ventricular injection. Only the data obtained from mice wherein the trace was placed within the ventricles were taken into consideration.

RESULTS

The experiments carried out in a mice model of acute thermal pain (test of the hot plate) show that the treatment with hypericum extract combined to the administration of analgesic doses of morphine induces a potentiation of the analgesic response (Figures 2-4).

The hypericum potentiating effect is dose-dependent, even if the administration of hypericum alone does not modify the hyperalgesic threshold. Among the substances composing hypericum, hypericin also potentiates morphine analgesic effect. This could be explained by its profile as a PKC inhibitor. Indeed, it was recently demonstrated, that the

PKCγ isoform of PKC, is one of the mediators of morphine anti-analgesic pathway [Figure

1, Galeotti 2006]. Therefore, the inhibition of PKCγ leads to morphine-induced analgesia potentiation. The present invention demonstrates that the administration of morphine at analgesic doses in animals treated with hypericin at sub-convulsant doses, induces both the potentiation and the prolongation of analgesia (Figures 3-4).

The present invention demonstrates that hypericum and hypericin are ideal substances to inhibit the hyperalgesic pathway activated by morphine, through blocking PKCγ. In animal model, the hypericum or hypericin doses necessary to potentiate the morphine-induced analgesia are largely below the doses used to induce the anti-depressant effect of such substances, therefore excluding a possible side effect.

The present studies carried out in rodents, which have always constituted a good animal model for predicting morphine effects in humans, show that the association of morphine with hypericin or substances containing it (hypericum) potentiate morphine-induced analgesia up to 67%. In addition, the analgesic potentiation is maintained over time. In practical terms, this means that it could be sufficient to administer in human about 35% of the morphine dose usually administered to obtain the same analgesic effect. Considering that the side effects are correlated with the dose of morphine administered and that, due to tolerance phenomenon during chronic treatment, increasing doses of morphine have to be administered, the morphine/hypericum or morphine/hypericin association is a promising alternative pain treatment. As a matter of facts, the combined treatment morphine/hypericum or morphine/hypericin changes the value of the cost/benefit ratio by greatly decreasing the cost (side effects), while increasing the benefits (analgesia). Furthermore, hypericum and its derivatives are not synthetic but naturals, therefore their use in combination with morphine for pain therapy may be more attractive and better accepted for patients.

CLINICAL MODELS Assay of analgesic efficacy in humans

Morphine vs. morphine/hypericum or morphine/hypericin

The assay evaluates the reproducibility in humans of the potentiation of morphine-induce analgesia by morphine/hypericin or morphine/hypericum combination, as already shown in murine model. The potentiation is tested in groups of healthy volunteers, each one made of at least 12 subjects. Each volunteer receives morphine at the analgesic doses reported in the protocols according to different administration routes; after a washout period, the subject receives morphine combined to hypericum or hypericin. Initially, the doses of hypericum are in the range of 600-1800mg/die p.o., starting from the lowest dose until reaching the maximum possible analgesic effect. The hypericin or hypericum dose is obtained by interspecies upscaling from the dose used in mice. The optimum administration route is determined by means of separate experiments. Cancer patients Cancer patients were also treated with a combination of hypericum extract and morphine. The combination results efficient against oncological pain.

BIBLIOGRAPHY

Galeotti N, et al, Pain 2006 ; 123, 294-305.

Greeson JM et al., Psychopharmacology (Berl) 2001; 153, 402-414.

Holtman JR., WaIa EP, Pain 2005; 114, 62-70.

Richebe P et al., Anesthesiology 2005; 102, 421-8.

Takahashi l et al., Biochem Biophys Res Commun. 1989; 165, 1207-12.

Claims

1- Use of hypericum or at least one derivative thereof for the preparation of a medicament potentiating the effect of an opiate analgesic.

2- Use of an opiate analgesic and hypericum or at least one derivative thereof for the preparation of a medicament for the treatment of pain.

3-Use according to claim 1 or 2 wherein the derivative of hypericum is hypericin.

4- Use according to claim 1 or 2 wherein the opiate analgesic is morphine.

5- A pharmaceutical composition comprising a pharmaceutically acceptable and active amount of an opiate analgesic and of hypericum or at least one derivative thereof, either in separated or joined formulations.

6- A pharmaceutical composition according to claim 5 wherein the pharmaceutically acceptable and active amount of the opiate analgesic is lower than the amount of the opiate analgesic needed to obtain the same analgesic effect when administered alone.

7- The pharmaceutical formulation according to claim 5 or 6, wherein the opiate analgesic is morphine.

8- The pharmaceutical formulation according to claim 5 to 7, wherein the derivative of hypericum is hypericin.