AU5402490A - Therapeutic compounds, compositions and uses thereof - Google Patents

Description

THERAPEUTIC COMPOUNDS. COMPOSITIONS AMP USES THEREOF

Field of the Invention

This invention relates to the use of vasodilators and calcium antagonists in combination in treatment of deficiencies in cerebral blood supply and to pharmaceutical compositions containing them. In particular it relates to the use of CGRP and nimodipine in treatment of deficiences in cerebral blood supply and to

pharmaceutical compositions containing them.

Background to the Invention Calcium is an integral component of cell function. Systemic and coronary arteries and many other tissues in the body including cerebral tissue are influenced by the movement of calcium across cell membranes. For example, the contractile processes of cardiac and vascular smooth muscle depend upon the movement of extracellular calcium ions into these cells through specific ion channels in the cell membranes. Calcium channel blocking agents also referred to as slow channel blockers or calcium antagonists share the ability to inhibit the movement of calcium ions across the cell membrane.

Calcitonin gene-related peptide is a product of the calcitonin gene expression system. Alternative processing of RNA transcribed from the calcitonin gene leads to the production in neuronal tissue of CGRP, a 37 amino acid peptide. CGRP has been discovered in a number of species including rats, chickens and humans. The CGRPs are a very closely related group of compounds differing from each other by no more than a few amino acids. To date CGRP has been described as being principally of use in the treatment of

hypertension owing to its properties on the cardiovascular system where it has been found to cause vasodilatation and to lower blood pressure. CGRP has also been postulated to play a role in calcium regulation and gastric acid secretion. The cerebral blood supply may become deficient for a number of reasons including, for example, cerebrovascular spasm.

Cerebrovascular spasm of the carotid artery is the body's natural response to cerebral bleeding, cutting off the blood supply to the brain.

Cerebral haemorrhage such as subarachnoid haemorrhage has many causes including the rupture of weakened blood vessels within the brain and mechanical damage to the head (trauma). Unless the blood supply and hence oxygen supply to the brain is restored the cerebrovascular spasm normally leads to brain damage and sometimes to death.

The blood supply to the brain is also deficient in cases of stroke due either to infarction, i.e. occlusion of the cerebral blood vessel, or to rupturing of the blood vessel resulting in cerebral haemorrhage. The cerebral blood supply is also interrupted during a migraine attack and by restoring cerebral blood supply it is therefore possible to alleviate the symptoms of the migraine attack.

We have now found that a combination of a calcium antagonist and a vasodilator is useful in the treatment of deficiencies in the cerebral blood supply in human subjects.

Summary of the Invention

Accordingly in a first aspect the invention provides a vasodilator and a calcium antagonist for use in combination in the treatment of a deficiency in cerebrovascular blood supply. In order to be useful in the treatment of deficiencies in cerebral blood supply it is essential that the therapeutic agent is able to selectively affect the cerebrovascular bed, such that the blood supply is increased at the desired site. A further essential requirement is that the blood supply should be increased without substantially lowering the blood pressure. It is also desirable that the therapeutic agent achieves the desired effect without significantly raising the heart rate. Current therapeutic

strategies to reverse constriction of cerebral blood vessels are unsatisfactory because they also result in lowering of blood pressure, so exacerbating the original problem. Additionally some of the therapies currently available are associated with an unwanted increase in heart rate. Hitherto, therefore, there has been a real need for an effective treatment for restoring cerebral blood flow and/or reversing cerebral vasospasm which does not have the side effects associated with current therapies. We have found that it is possible to achieve both the required selectivity of site of action and the desired increase in cerebral blood supply without substantially affecting blood pressure or significantly raising the heart rate by administration in combination of an appropriate amount of a calcium antagonist and a vasodilator.

The use of a combination of the calcium antagonist nimodipine and the vasodilator CGRP results in a totally unexpected synergistic effect. The use of CGRP in treatment of deficiences in

cerebrovascular blood supply as described in published International Patent Application No. W089/03686, is commonly associated with a certain increase in heart rate which it would be desirable to reduce or eliminate. We have surprisingly found that use of a combination of CGRP and nimodipine appears to reduce or eliminate the

CGRP-related increase in heart rate. The expectation following standard pharmacological principles was that the CGRP effect on heart rate would be dominant and that use of CGRP in combination with nimodipine would still result in an increase in heart rate.

Additionally the use of CGRP in combination with nimodipine results in an improved blood flow to the internal carotid artery. The blood flow reaching a level greater than that seen when either agent is used singly and which is greater than the sum of the individual levels. This means that it is possible to achieve the desired therapeutic effect in the absence of unwanted side effects by using a

combination of CGRP and a calcium antagonist where each of the active ingredients is administered at a lower dose e.g. at a ten fold lower dose, than would be required to achieve the same effect if either compound were administered alone.

The use of a combination of a calcium antagonist and a vasodilator surprisingly does not produce any unwanted additive effect. For example, both CGRP and nimodipine will exert hypotensive effects if administered at a sufficiently high dose and it would have been predicted that the use of a combination of both would result in an additive hypotensive effect with the effect on blood pressure being observed at a dose at which use of either compound alone would not affect blood pressure. No such effect is, however, found. There are many classes of compounds which have calcium antagonist activity such as for example phenylalkylamines and derivatives thereof, e.g. verapamil; benzothiazepines and derivatives thereof, e.g. diltiazem; diphenylalkylamines and derivatives thereof, e.g. prenylamine; cinnamyl; diphenylmethyl piperazines and derivatives thereof e.g. cinnarizine and flunarizine and dihydropyridine derivatives as disclosed in British Patent No. 1173862, German Patent No, DE 2407115 and US Patent No. 3485847. The use of

dihydropyridine derivatives such as nifedipine

(1,4-dihydrc-2,6-dimethyl-4-(2-nitrophenyl)-3,5, pyridinedicarboxylic acid dimethyl ester), nicardipine

(1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid methyl 2-fmethyl(phenylmethyl)amino] ethyl ester) and nimodipine (1,4-dihydro-2, 6-dimethyl-4-(3-nitroρhenyl-3,5-pyridinedicarboxylic acid- isopropyl-(2-methoxy-ethyl)-ester) is preferred. We have found that nimodipine is especially useful and the use of nimodipine in combination with a vasodilator is especially

preferred. As used herein the term vasodilator denotes those compounds which produce vasodilatation and which do not directly block calcium channels and which when in combination with a calcium antagonist, preferentially act on the cerebrovascular bed to differentially increase cerebral blood supply without substantially affecting blood pressure.

The vasodilator for use according to the invention is preferably one which preferentially acts on the cerebrovascular bed to

differentially increase cerebral blood supply without substantially affecting blood pressure both in isolation and in combination with a calcium antagonist. Examples of such vasodilators showing the desired profile of activity include CGRP and as used herein the term CGRP, in addition to naturally occurring CGRPs, includes also biologically active fragments, analogues and derivatives thereof which have the characteristic cerebrovascular blood supply affecting properties of CGRP; i.e. which preferentially act on the

cerebrovascular bed to differentially increase cerebral blood supply without substantially affecting blood pressure such as for example those described in International Patent Application No. PCT/GB 89/01249 filed 20th October 1989. The CGRPs, fragments, analogues and derivatives may be naturally occurring or may be produced chemically e.g. by chemical modification, cleavage, or synthesis or they may be produced by employing recombinant DNA techniques. The fragments, analogues and derivatives may include non-peptide compounds as well as peptide compounds. The CGRP may comprise an animal CGRP, e.g. rat or chicken CGRP, though is preferably human calcitonin gene-related peptide (hCGRP). Human calcitonin gene-related peptide exists in at least two forms known as alpha hCGRP, for instance as described in US Patent No. 4549986, and beta hCGRP, for instance as described in published European Patent

Application No. EP 188400A. As used herein, the term 'hCGRP' is used to denote α- and β- hCGRP. The use of α- hCGRP is

especially preferred. The use of a combination of CGRP and nimodipine according to the invention is especially preferred. A combination of a vasodilator and a calcium antagonist is particularly useful in the treatment of deficiencies in cerebrovascular blood supply in human subjects such as are associated with subarachnoid haemorrhage, stroke, trauma and migraine.

According to a second aspect of the invention we provide a method of treatment of a human subject suffering from a deficiency in

cerebrovascular blood supply which comprises administering an effective amount of a calcium antagonist and a vasodilator to the subject.

Typically the amount of the vasodilator and calcium antagonist used is an amount which in combination is effective to differentially increase cerebrovascular blood supply without substantially affecting blood pressure or significantly raising the heart rate.

In a third aspect the invention provides a pharmaceutical composition comprising a vasodilator and a calcium antagonist.

In a fourth aspect the invention provides a pharmaceutical composition in unit dosage form, each unit dose comprising an amount of a vasodilator and a calcium antagonist which acts to differentially increase cerebrovascular blood supply without substantially affecting blood pressure or significantly raising the heart rate in combination with a pharmaceutically acceptable carrier, excipient or diluent.

The pharmaceutical composition according to the fourth aspect of the invention preferably contains 0.01 to 1620μg CGRP, preferably

0.08μg to 1260μg CGRP, more preferably from 5 to 1260μg CGRP

and most preferably from 5 to 900yg CGRP; preferably 0.07 to 84mg of nimodipine, more preferably 0.35 to 4.2mg nimodipine and most preferably 0.7 to 3.0mg nimodipine. In a fifth aspect the invention provides a process for the production of a pharmaceutical composition according to the fourth aspect of the invention comprising bringing into association with a pharmaceutically acceptable carrier, excipient or diluent a vasodilator and a calcium antagonist. In one embodiment of the fifth aspect of the invention, the invention provides a process for the production of a pharmaceutical

composition in unit dosage form comprising bringing into association with a pharmaceutically acceptable carrier, excipient or diluent, aliquot amounts of a vasodilator and a calcium antagonist sufficient to differentially increase cerebrovascular blood supply without substantially affecting blood pressure or significantly raising the heart rate to provide unit doses.

In a sixth aspect the invention provides the use of a vasodilator in combination with a calcium antagonist for the manufacture of a medicament for the treatment of a deficiency in cerebrovascular blood supply.

In a seventh aspect the invention provides a drug for therapy of deficiencies in cerebral blood supply comprising a vasodilator in combination with a calcium antagonist as active ingredients.

In an eighth aspect, the invention provides a cerebral blood supply improver comprising a vasodilator in combination with a calcium antagonist.

In a ninth aspect, the invention provides a method for the treatment of deficiencies in cerebral blood supply which comprises

administering to a patient a vasodilator in combination with a calcium antagonist. It will be appreciated that there are a number of alternative ways of administering the vasodilator and calcium antagonist according to the method of invention. For example, the vasodilator and calcium antagonist may be administered sequentially in any order and with any time period in between each administration. Alternatively the vasodilator and calcium antagonist may be co-administered. As used herein the term co-administration covers the situation where the vasodilator and calcium antagonist are formulated together and administered in one pharmaceutical preparation, and also where the vasodilator and calcium antagonist are formulated separately and administered simultaneously. The vasodilator and calcium antagonist may be formulated differently, for example, one may be formulated for oral administration and the other for intravenous administration.

Preferably the vasodilator will be formulated for intravenous administration, and the calcium antagonist for oral administration, and most preferably both the vasodilator and the calcium antagonist will be formulated for intravenous administration.

Pharmaceutical compositions for use according to the present invention may be formulated in conventional manner, optionally with one or more physiologically acceptable carriers, diluents or excipients.

The vasodilator and calcium antagonists for use according to the present invention may be formulated for oral, buccal, parenteral or rectal administration or in a form suitable for nasal administration or administration by inhalation or insufflation.

For oral administration, the pharmaceutical compositions may take the form of, for example, tablets or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g. pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g. lactose, micro crystalline cellulose or calcium hydrogen phosphate); lubricants (e.g. magnesium stearate, talc or silica); disintegrants (e.g. potato starch or sodium glycollate); or wetting agents (e.g. sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents; emulsifying agents; non-aqueous vehicles; and preservatives. The preparations may also contain buffer salts, flavouring, colouring and sweetening agents as

appropriate.

Preparations for oral administration may be suitably formulated to give controlled release of the active compound.

For buccal administration the compositions may take the form of tablets or lozenges formulated in conventional manner.

The vasodilator and calcium antagonist may be formulated for

parenteral administration by injection e.g. by bolus injection or continuous infusion. Formulations for injection may be presented in unit dosage form. The compositions may take such forms as

suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilising and/or dispersing agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g. sterile pyrogen-free water, before use.

The vasodilator and calcium antagonist may also be formulated in rectal compositions such as suppositories or retention enemas, e.g. containing conventional suppository bases such as cocoa butter or other glycerides. In addition to the formulations described previously, the vasodilator and calcium antagonist may also be formulated as a depot

preparation. Such long acting formulations may be administered by implantation or by intramuscular injection. For nasal administration or administration by inhalation the compounds for use according to the present invention are conveniently delivered in the form of an aerosol spray presentation from

pressurised packs or a nebuliser, with the use of a suitable propellent, e.g. dichlorodi-fluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas.

The compositions may, if desired, be presented in a pack or dispenser device which may contain one or more unit dosage forms containing the active ingredient. The pack or dispenser device may be accompanied by instructions for administration. In a preferred embodiment of the first to ninth aspects of the invention the calcium antagonist is preferably nimodipine and the vasodilator is preferably CGRP, more preferably human CGRP and most preferably human α-CGRP

The dose at which the combination of a calcium antagonist and vasodilator will be administered to man will be such that the cerebral blood supply is differentially increased and blood pressure is not substantially affected and there is no significant increase in heart rate. The precise dose of the vasodilator and the calcium antagonist trill depend upon the route of administration, the potency of the vasodilator and calcium antagonist and the body weight and pathology of the patient. The important factor is believed to be the concentration of the vasodilator and calcium antagonist which is present at the target vascular bed. On an individual patient basis the dose of the vasodilator and calcium antagonist which should be administered to cause the desired effect may be determined by administering a low dose of vasodilator in combination with a calcium antagonist for 10 to 20 minutes and then increasing the dose every 10 to 20 minutes until the desired effect is seen. A vasodilator such as CGRP may be administered to an average 70kg man by IV infusion at doses in the range 0.01 to 32ng/kg/min, preferably in the range 0.06 to 24ng/kg/min, more preferably in the range 2 to 24ng/kg/min, and most preferably in the range 2 to 16ng/kg/min. For example, α- CGRP and β-CGRP may be administered to an average 70kg man by IV infusion at doses in the range 2ng/kg/min to 16ng/kg/ min over a time period of 20 minutes. In some cases it may be desirable to infuse the patient with CGRP for longer time periods e.g. for up to or greater than 1 hour e.g. for 12 hours, or for more than 24 hours.

A calcium antagonist such as nimodipine may be administered to an average 70kg man by IV infusion at doses in the range 1-100μg/kg/h, preferably in the range 5-50μg/kg/h and most preferably in the range 10-35yg/kg/h.

For oral administration a calcium antagonist may be administered to an average 70kg man at doses in the range 0.05 to 20mg/kg preferably in the range 0.5 to 8mg/kg.

The calcium antagonist and non-calcium dependent vasodilator may be adminstered in combination as often as is required. For example, they may be administered more than once per day, e.g. 2 to 6 times per day. The duration of treatment may be for example from 20 minutes to 24 hours and the period of treatment may continue for, for example, up to 21 days. A calcium antagonist for use in the present invention may be obtained using standard chemical procedures. For example, nimodipine may be produced as described in British Patent No. 1173862;

nicardipine as described in German Patent No. DE 2407115 and nifedipine as described in US Patent No. 3485847. CGRP for use in the present invention may be obtained using

recombinant DNA technology as described in British Patent No.

2141430B and published European Patent Application No. EP-A-188400. Alternatively the CGRP may be produced by chemical synthesis using conventional techniques well known in the art, see for example published European Patent Application No. EP-A-188400.

CGRP in combination with a calcium antagonist such as nimodipine is particularly useful in the treatment of deficiencies in cerebral blood supply since it shows the desired profile of activity i.e. it selectively affects the cerebrovascular bed without substantially affecting blood pressure or significantly increasing heart rate.

The vasodilator and calcium antagonist may be tested for their ability to differentially increase cerebrovascular blood supply in animals and humans using the Doppler technique as described in the examples hereinafter. The effect of the vasodilator and calcium antagonist on blood pressure and heart rate may be measured using conventional techniques.

Brief Description of Drawings

The differential increase in cerebrovascular blood supply affected by CGRP and nimodipine has been demonstrated in rats using the Doppler technique as described below and, with reference to the accompanying Figures in which:

Figure 1 shows a graph of the effect in rats of a 30 minute

individual infusion of different concentrations of CGRP and nimodipine on heart rate, mean arterial pressure, and blood flow and blood velocity to the internal carotid artery where: 0.06nmol CGRP/h

0.6nmol CGRP/h

60nmol nimodipine/h

600nmol nimodipine/h

Figure 2 shows a graph of the effect in rats of a 30 minute combined infusion of 0.06nmol/h CGRP and 60nmol/h nimodipine on heart rate, mean arterial pressure and blood flow and blood velocity to the internal carotid artery.

Figure 3 shows a graphical representation of the cardiovascular

responses to human α-CGRP and/or nimodipine in conscious

Long Evans rats (n=8).

Left-hand panels: responses to a 30 min infusion of human α-CGRP ( , O.Oόnmol h^-1), or nimodipine ( , 60nmol h^-1) or human α-CGRP (O.Oδnmol h^-1) plus nimodipine (60nmol h^-1) ( ). Values are mean +

S.E.M.

Right hand panels: responses to a 30 min infusion of human α-CGRP ( , 0.6nmol h^-1), or nimodipine (

600nmol h^-1) or human α-CGRP (0.6nmol h^-1) plus nimodipine (600nmol h^-1) ( ). Values are mean + s.e.m. (n=8);

Decription of Specific Embodiments

Example 1

This series of experiments was designed to determine the effect on cerebral blood flow and blood pressure of administration of different doses of CGRP and nimodipine individually and in combination. Male long Evans rats (350-400g) were used (n=8)

Under sodium methohexitone anaesthesia (60mg/kg IP) the left external carotid artery was tied off (410 silk suture) and a miniature pulsed Doppler probe was sutured around the left common carotid artery (to monitor internal carotid flow).

7-10 days after probe implantation, animals were

re-anaesthetised (sodium methohexitone, 40 mg/kg IP) and catheters were implanted in the abdominal aorta (via the caudal artery) for BP recording, and in the right jugular vein for drug/peptide administration.

Experiments were run 1 and 2 days after catheter implantation with animals fully conscious and freely moving.

Day 1: Nimodipine vehicle

Nimodipine (60nmol/h)

Nimodipine (600nmol/h)

Day 2: CGRP (0.06nmol/h)

CGRP (0.6nmol/h)

CGRP (0.06nmol/h) plus Nimodipine (60nmol/h)

Infusions were given for 30 min at 0.3ml/h

At least 60 min was allowed between each infusion

Nimodipine vehicle consisted of:

969g polyethylene glycol 400

100g distilled water

60g glycerine All nimodipine solutions were made up in a dark room under yellow filters (approx. 550nm). Syringes and catheters used for administering nimodipine were protected from light by black shielding.

CGRP (human α) was dissolved in saline containing 1% bovine serum albumin. The results are shown in Table 1, Figure 1 and Figure 2.

Administration of CGRP 0.06nmol/h and nimodipine 60nmol/h in combination resulted in an increase in cerebral blood flow which was greater than that seen on administration of either compound alone and which was greater than the additive effect at these doses. This was achieved in the absence of an additive hypotensive effect.

Example 2

This series of experiments was designed to look at the effects of CGRP and nimodipine on the internal carotid blood vessel, on regional circulation, and on physiological parameters such as heart rate and blood pressure.

All studies were carried out on male, Long Evans rats (350-450g).

Animals were anaesthetized (sodium methohexitone, 60mg kg^-1 i.p., supplemented as required) and had one of the following procedures carried out:- a) implantation of a pulsed Doppler probe (Haywood et al., 1981) around the left common carotid artery after the external carotid artery on the same side had been ligated. This arrangement permitted assessment of flow through the patent internal carotid artery. b) implantation of pulsed Doppler probes around the left renal and superior mesenteric arteries and the distal abdominal aorta below the level of the ileocaecal artery (to monitor flow to the hindquarters).

Following 7-14 days recovery animals were briefly re-anaesthetized (βodium methohexitone, 40mg kg^-1) for the implantation of intravascular catheters for drug or peptide administrations (jugular vein) and the recording of instantaneous heart rate (HR) and blood pressures (BP) from the abdominal aorta (via the caudal artery). The experiments began on the next day and ran over 3 days.

The protocols involved continuous recordings from conscious unrestrained animals of mean BP, HR and Doppler shifts from the implanted probes. Percentage changes in regional blood flows and vascular resistances were calculated as described elsewhere (Gardiner et al., (1989), Am. J.

Physiol. 256 R332-338). The following protocols were run:- Animals with internal carotid probes

1. Effects of human α-CGRP

Human α-CGRP (0.06 or 0.6nmol h^-1) was infused for 30 min.

Measurements were made before, during, and for 30 min after infusion.

2. Effects of nimodipine vehicle

Nimodipine vehicle (see below) was infused for 30 min. Measurements were made before, during, and for 30 min after infusion.

3. Effects of nimodipine Nimodipine (60 or 600nmol h^-1) was infused for 30 min. Measurements were made before, during and for 30 min after infusion.

4. Effects of human α-CGRP plus nimodipine

Human α-CGRP and nimodipine (0.06 and 60nmol h^-1 , respectively, or 0.6 and 600nmol h^-1, respectively) were infused concurrently for 30 min. Measurements were made before, during and for 30 min after infusi

Animals with renal, mesenteric and hindquarters probes

Protocols 1) - 4) above were run also in animals (n=8) with renal, mesenteric and hindquarters probes.

Drugs and Peptides Human α-CGRP (Celltech Ltd) was dissolved in isotonic saline containing 1% bovine serum albumin. Nimodipine (pure substance, Bayer, U.K.) was dissolved in a mixture of PEG400, sterile water and glycerine BP in the ratio 9.69: 1.00 : 0.6 (by weight). Nimodipine solutions were made up in a dark room under filtered light (wave length > 500nm) and all

catheters and syringes were masked to avoid exposure of the solutions to ambient lighting; the infusion rate was 0.4ml h^-1.

Statistics

All data were subjected to non-par nalysis of variance

(Friedman's test) with Wilcoxon's rank sum test, or the Mann-Whitney U test as appropriate. Results

Animals with internal carotid probes

1. Effects of human α-CGRP

Infusion of human α-CGRP at 0.06nmol h^-1 caused an increase in HR and a modest internal carotid hyperaemia, accompanied by a fall in vascular resistance (shown in Figure 3 and Table 2).

Human α-CGRP at 0.6nmol h^-1 caused tachycardia, hypotension and

marked hyperaemic vasodilation in the internal carotid vascular bed (shown in Figure 3 and Table 2).

2. Effects of nimodipine vehicle Infusion of nimodipine vehicle was associated with a significant

(P<0.05) fall in HR (-23±9 beats min at 30 min) and a slight rise in mean BP (+5±2mmHg at 30 min; P<0.05), but no change in internal carotid haemodynamics. 3. Effects of nimodipine

Nimodipine infused at 60nmol h^-1caused a transient increase in

internal carotid flow and fall in vascular resistance (Figure 3). The higher dose of nimodipine (600nmol h^-1) caused hypotension and

substantial hyperaemic vasodilatation in the internal carotid vascular bed. These effects persisted after the infusion was stopped, unlike those of human α-CGRP, (Figure 3).

4. Effects of human α-CGRP plus nimodipine

Infusion of human α-CGRP (0.06nmol h- )¹ together with nimodipine

(60nmol h^-1) caused significantly (P<0.05) greater increases in

internal carotid flow and falls in vascular resistance than seen with either compound alone (Figure 3 and Tables 2, 3 and 4). However, there were no significant changes in mean BP or HR (Figure 3).

Concurrent administration of human α-CGRP (0.6nmol h^-1) and

nimodipine (600nmol h^-1) did not enhance significantly the

vasodilatation seen with either compound alone (Figure 3). After infusion of human α-CGRP the vasodilatation did not persist whereas following infusion of nimodipine and human α-CGRP there was a

persistent vasodilatation (Figure 3). However, this effect was no greater than that seen with nimodipine alone (Figure 3).

Animals with renal, mesenteric and hindquarters probes

1. Effects of human α-CGRP

Infusion of human α-CGRP caused dose-dependent tachycardia, hypotension and reductions in renal and mesenteric flows, accompanied by increases in hindquarters flow (Table 2), although during infusion only the changes in hindquarters resistance were significant (Table 2). Following infusion of the higher dose there was a significant increase in mesenteric vascular resistance (Table 2). 2. Effects of nimodipine vehicle

Infusion of nimodipine vehicle was associated with an overall

bradycardia, but this was not significant at any specific time point. There were no changes in mean BP or regional blood flows. 3. Effects of nimodipine

Infusion of nimodipine at 60nmol h^-1 had no significant effects.

However, at an infusion rate of 600nmol h^-1 nimodipine caused

reductions in mean BP and renal flow accompanied by increases in HR and hindquarters flow, with no change in mesenteric flow (Table 3). During infusion there were falls in mesenteric and hindquarters resistances but a tendency for renal vascular resistance to rise. Indeed, after infusion a slight further increase in renal vascular resistance made the overall change significant (see Table 3).

When assessed from areas under curves all the cardiovascular effects of nimodipine (600nmol h^-1) were significantly (P<0.05) different from those of human α-CGRP (0.6nmol h^-1) .

4. Effects of human α-CGRP plus nimodipine

During infusion of human α-CGRP (0.06nmol h^-1) together with

nimodipine (60nmolh^-1) there was no significant tachycardia or change in renal or mesenteric haemodynamics, in contrast to the tachycardia and fall in mesenteric blo d flow seen with human α-CGRP alone. The hindquarters vasodilatation persisted throughout the infusion of human α-CGRP and nimodipine unlike the transient effect seen with human α-CGRP alone; in the former case there was also a delayed hindquarters vaβoconstriction following infusion. Concurrent infusion of human α-CGRP (0.6nmolh^-1) and nimodipine

(6.00nmol h^-1) had significantly (P<0.05) greater effects than human α-CGRP alone on all cardiovascular variables except HR and mesenteric flow. However, administration of human α-CGRP and nimodipine together did not enhance significantly the hypotension or mesenteric or

hindquarters vasodilatations seen with nimodipine alone (Tables 3 and 4) Nonetheless, combined administration of human α-CGRP and nimodipine caused a significantly greater reduction i renal blood flow and enhanced renal vasoconstriction than seen with ni ipine or human α-CGRP alone (Tables 3 and 4).

Conclusion

The results therefore show that low doses of human α-CGRP and

nimodipine exerted synergistic internal carotid vasodilator effects without compromising other regional circulation or causing systemic hypotension. Co-administration of high doses of human α-CGRP and nimodipine did not cause enhanced internal carotid vasodilatation compared to either compound alone or compared to the effects of

concurrent administration of low doses of human α-CGRP and nimodipine.

Claims (10)

Claims

1. A vasodilator and a calcium antagonist for use in combination in the treatment of a deficiency in cerebrovascular blood supply.

2. Calcitonin gene-related peptide and nimodipine for use in

combination in the treatment of a deficiency in cerebrovascular blood supply.

3. A method of treatment of a human subject suffering from a

deficiency in cerebrovascular blood supply which comprises administering an effective amount of a calcium antagonist and a vasodilator to the subject.

4. A pharmaceutical composition comprising a vasodilator and a calcium antagonist.

5. A pharmaceutical composition in unit dosage form each unit dose comprising an amount of a vasodilator and a calcium antagonist which acts to differentially increase cerebrovascular blood supply without

substantially affecting blood pressure or significantly raising the heart rate in combination with a pharmaceutically acceptable carrier, excipie on diluent.

6. A process for the production of a pharmaceutical composition according to claim 5 comprising bringing into association with a pharmaceutically acceptable carrier excipient or diluent a vasodilator and a calcium antagonist.

7. The use of a vasodilator in combination with a calcium antagonist for the manufacture of a medicament for the treatment of a deficiency in cerebrovascular blood supply.

8. A drug for therapy of deficiencies in cerebral blood supply comprising a vasodilator in combination with a calcium antagonist as active ingredients.

9. A cerebral blood supply improver comprising a vasodilator in combination with a calcium antagonist.

10. A method for the treatment of deficiencies in cerebral blood supply with comprises administering to a patient a vasodilator in combination with a calcium antagonsit.