Midazolam, 8-chloro-6- (2'-fluorophenyl)-1-methyl-4H-imidazo [1. 5-a] [1,4]- benzodiazepine, is a short acting potent sedative hypnotic with anxiolytic properties. Midazolam has an excellent safety profile with minimal cardiovascular and respiratory side effects. The unique pharmacological profile of this agent makes it extremely useful for pre-operative sedation.

Conscious sedation techniques using midazolam alone or in combination with other agents are becoming increasingly popular for a wide variety of short surgical procedures. This important advancement avoids the use of general anaesthesia which is highly advantageous for health and economic reasons.

The pre-operative management of children is difficult. They are aware of separation from their parents and of the strange hospital environment. The use of pre-operative sedation helps to decrease patient anxiety and minimize psychologic trauma.

Midazolam is approved for intravenous or intramuscular injection in adults or oral administration as tablets. Oral administration is preferred over the injectable route as there is no pain and distress associated with the oral route.

However, the oral route suffers the disadvantages of presystemic metabolism and a longer onset of action compared with parenteral delivery. The oral route may also cause complications during surgery due to the presence of swallowed material in the gut.

Oral pre-medication is a popular sedative route in children. However, the onset of drugs taken orally is slow and so is the postoperative recovery. Many children tend to spit or even regurgitate oral pre-medication-others refuse to take the medication or may not be able to take it because of vomiting.

Aspiration is a real problem when giving drugs orally, because children may think that by taking oral medication, they are allowed to drink liquids. The nasal route has received a great deal of attention as a convenient and reliable alternative for pre-operative sedative administration. Following nasal administration, there is rapid entry into the brain tissue resulting in a rapid onset of action.

There is a need for a non-invasive safe and rapid acting form of midazolam which may be used in children and adults alike.

Midazolam is a basic drug due to the nitrogen atom in the imidazole ring fused to the benzodiazepine skeleton. The pKa value is reported to range between 5.5 and 6.2. The water solubility of midazolam is highly pH dependent, ranging from 2.357 mg/ml at pH 4.2 to 0.082 mg/ml at pH 6.39 (Andersin, R., Solubility and acid-base behaviour of midazolam in media of different pH. J. Pharm. Biomed. Anal. 1991,9,451-455). The increased solubility at low pH is due to ionization. At a pH of below 4, part of the drug in solution has an open benzepine ring bearing a highly ionizable primary amino group thus imparting water solubility. At a pH greater than 5, the whole of the drug is present in ring closed form and the lipid solubility is increased.

Transmucosal delivery of drugs via the oral or nasal cavities offers a means of avoiding the disadvantages of the orogastric route as the drug reaches the systemic circulation directly. The mucosal route of drug delivery is therefore a useful alternative to parenteral delivery where rapid therapeutic effect is desired.

Midazolam solution for injection at a concentration of 5mg/ml and pH of 3.2 has been used by several clinical investigators for intranasal, sublingual and rectal application (Karl, HW et al., Transmucosal Administration of Midazolam for Premedication of Pediatric Patients. Anesthesiology 1993,78,885-891, and references therein). The nasal route of administration results in satisfactory sedation within 10-15 minutes although intense burning, irritation and discomfort occurs (Lejus, C. et al, Midazolam for premedication in : Nasal vs. rectal administration. Eur. J. Anaesth. 1997,14,244-249). The irritation of the solution is attributed to the low pH of the solution (3.2 compared to nasal pH 5.5-6.5) required to maintain midazolam in solution. The nasal route of administration has therefore not been approved for clinical use of midazolam owing to the severe discomfort of the preparation. The sublingual route of midazolam administration results in sedation comparable with the intranasal route although very poor taste characteristics are encountered with the sublingual route. In order to achieve the required dosage of midazolam, relatively large volumes of the drug solution are required which result in the dose spreading into the oropharynx and ultimately being swallowed following nasal or oral transmucosal application. The portion of the dose swallowed will be subject to slow absorption and presystemic metabolism. In children, substantial sublingual dose may be lost by ejection due to the very bad taste of midazolam.

US Patent 4,950,664 to Rugby-Darby Group Companies, Inc. teaches the preparation of a solution of midazolam for intranasal administration containing midazolam hydrochloride at a pH of 3.62. Accordingly this preparation will suffer the same discomfort disadvantages such as severe irritation and pain, and contains midazolam in substantially ionized ring open form.

There are several methods known in the art to deliver drugs to the oral and nasal mucosae (see Chien, Y. W. ed., Novel Drug Delivery Systems, 2''d Edition, Marcel Dekker 1992, pp 183-188,244-249). These include buccal and sublingual tablets or lozenges, adhesive patches, gels, solutions or sprays (powder, liquid or aerosol) for the oral cavity, and solutions or sprays (powder, liquid or aerosol) for the nasal cavity.

Relatively few drugs are currently administered via the mucosal routes due to problems associated with poor transport of the drug across mucosal membranes. A given drug will partition between the lipid phase and the aqueous phase of the epithelium according to the lipophile/hydrophile balance of the drug molecule. According to pH partition theory, the permeation of an ionisable substance through biological membranes is dependent on the concentration of the un-ionise species.

Soluble midazolam at a pH less than 4.0 will be highly ionized and therefore poorly lipophilic resulting in sub-optimal membrane permeation.

Cyclodextrins and their derivatives have found extensive application as solubilizers and stabilizers due to their ability to form inclusion complexes with a wide variety of compounds (see (J. Szejtli, Cyclodextrin Technology, Kluwer Academic Press and J. Szejtli & K-H Fromming, Cyclodextrins in Pharmacy, Kluwer Academic Press). Cyclodextrins may improve nasal absorption of drugs (see (Merkus, F. W. et al., Pharmaceutical Research 1991,8,588-592 and Shao, Z. et al, Pharmaceutical Research 1992,9,1157-1163) and enhance absorption from sublingual administration of drug/cyclodextrin complexes (Behrouz, S. et al, Journal of Clinical Endocrinology and Metabolism. 1995,80, 3567-3575).

Cyclodextrins are water-soluble cone-shaped cyclic oligosaccharides containing 6,7 or 8 glucopyranose units. The interior or"cavity"of the cone is hydrophobic whilst the exterior is hydrophillic. The size of the cavity increases with increasing number of glucose units. Several cyclodextrin derivatives such as alkyl, hydroxyalkyl and sulfoalkyl ethers have been prepared with improved solubility (see J. Szejtli & K-H Fromming, Cyclodextrins in Pharmacy Kluwer Academic Press and Stella, V. J. et al Parmaceutical Research 1995,12 (9) S205).

There is a need for new pharmaceutical composition for the administration of midazolam.

SUMMARY OF THE INVENTION According to a first aspect of the invention there is provided a pharmaceutical composition for transmucosal delivery which comprises an aqueous solution of an inclusion complex of midazolam and a water-soluble substituted beta- cyclodextrin, the solution containing 2mg/ml or more of midazolam and having a pH of greater than or equal to 4.

The water-soluble substituted beta-cyclodextrin may be an alkylated beta- cyclodextrin, a hydroxyalkylated beta-cyclodextrin. or a sulfoalkylated beta- cyclodextrin. The cyclodextrin is preferably an alkylated beta-cyclodextrin, more preferably a randomly methylated beta-cyclodextrin (RAMEB), having an average degree of methyl substitution of 1.8 methyl groups per anhydrous glucopyranose unit.

The mass ratio of midazolam to the water-soluble substituted beta-cyclodextrin is preferably 1: 12 to 1: 40 inclusive, more preferably about 1: 20.

The aqueous solution must contain at least 2mg/ml of midazolam. The solution preferably contains from 2 to 20 milligrams inclusive per millilitre, more preferably from 7.5 to 15 milligrams inclusive per millilitre, most preferably about 10 milligrams per millilitre of midazolam.

The solution must have a pH of greater than or equal to 4. The solution preferably has a pH of from 4 to 7 inclusive. The pH of the solution may be controlled by the use of a pharmaceutically acceptable buffer such as a phosphate buffer or the like.

The pharmaceutical composition is adapted for transmucosal delivery. By "mucosa"or"mucosae"there is meant the epithelial membranes lining the oral or nasal cavities, and the terms"mucosal"and"transmucosal"have the same meaning.

The pharmaceutical composition may, for example, be designed for sublingual or buccal delivery, or for nasal delivery, preferably for nasal delivery.

According to a second aspect of the invention there is provided an inclusion complex of midazolam and a water-soluble substituted beta-cyclodextrin, as disclosed above.

Preferably, there is provided an inclusion complex of midazolam and a randomly methylated beta-cyclodextrin wherein the randomly methylated beta- cyclodextrin has an average degree of substitution of 1.8 methyl groups per glucopyranose unit.

The inclusion complex may be, for example, the inclusion complex which is the subject of Example 2.

According to a third aspect of the invention there is provided the use of an inclusion complex of midazolam and a water-soluble substituted beta- cyclodextrin in the manufacture of a medicament for use in a method of sedation of a patient.

According to a fourth aspect of the invention there is provided a method of sedating a patient comprising administration of an inclusion complex of midazolam and a water-soluble substituted beta-cyclodextrin.

The invention is of particular application where the patient is a child or a needle-shy adult.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of the effect of hydroxypropyl beta-cyclodextrin on midazolam solubility as a function of pH; and Figure 2 is a graph of the effect of RAMEB on midazolam solubility as a function of pH.

DESCRIPTION OF EMBODIMENTS The crux of the invention is a pharmaceutical composition for transmucosal delivery which comprises an aqueous solution of an inclusion complex of midazolam and a water-soluble substituted beta-cyclodextrin, the solution containing 2mg/ml or more of midazolam and having a pH of greater than or equal to 4.

A main advantage of the invention is to provide midazolam in a soluble lipophilic form for well-tolerated rapid mucosal permeation and uptake into the brain. The pharmaceutical composition of the invention may thus be advantageously used in children and needle-shy adult patients for rapid sedation, avoiding the disadvantages of the intravenous or oral routes.

The water-soluble substituted beta-cyclodextrin may be an alkylated, hydroxyalkylated or sulfoalkylated beta-cyclodextrin, preferably an alkylated beta-cyclodextrin, more preferably a randomly methylated beta-cyclodextrin (RAMEB) having a degree of substitution of 1.8 methyl groups per anhydrous glucopyranose unit.

From the results given in the examples, it can be seen that RAMEB is particularly effective in increasing the water solubility of midazolam, independent of pH. Solutions containing midazolam and RAMEB are substantially composed of midazolam in the lipophilic ring closed form included in the beta-cyclodextrin. The results are unexpected since the complexation of a given guest by related beta-cyclodextrin derivatives is generally similar.

The mass ratio of midazolam to beta-cyclodextrin is preferably 1: 12 to 1: 40, more preferably about 1: 20.

The solution must contain at least 2mg/ml of midazolam. The solution preferably contains 2 to 20mg/ml. more preferably 7.5 to 15mg/ml. most preferably about 10mg/ml of midazolam.

Effective intranasal or sublingual administration of liquid formulations requires the dose to be administered in relatively small volumes to avoid swallowing of a portion of the dose. Typical intranasal volumes of 0.1 to 0.4ml per nostril result in effective deposition of the dose on the absorptive surfaces of the nasal epithelium. Given that the effective dose of midazolam for pre-operative sedation is 0.2mg/kg, a pediatric patient of body weight 20kg would require 4mg midazolam. Using the pharmaceutical composition of the invention, the required dose may be conveniently administered in a total volume of 0.4ml, using a solution containing 10mg/ml midazolam at a physiologically acceptable pH.

The solution must have a pH of greater than or equal to 4. The solution preferably has a pH of from 4 to 7 inclusive.

The pH of the solution may be adjusted by the addition of alkali such as sodium hydroxide or the like or acid such as hydrochloric acid or the like. The final pH of the solution may be maintained by the use of a pharmaceutically acceptable buffer such as a phosphate buffer or the like The pharmaceutical composition may contain pharmaceutically acceptable excipients to modify osmolality such as sodium chloride, mannitol, sorbitol and the like. In order to improve the convenience of application and residence time of the composition, viscocity enahancing agents with bioadhesive properties such as cellulose ethers, cross linked polyacrylic acids, chitosan and its salts, polycarbophil and the like, may be employed at the intended pH of the composition. A composition intended for sublingual administration may optionally contain sweeteners and flavours. The pharmaceutical composition may be formulated as drops, spray or gel for buccal or sublingual administration according to methods known in the art.

Preferred excipients include viscosity modifying agents (e. g. hydroxypropylmethylcellulose, carbopol 974P, polycarbophils, water soluble chitosans, guar gum, alginates), flavours, preservatives (bronopol, benzalkonium chloride, EDTA, chlorhexidine gluconate), anti-oxidants (N- acetyl-cysteine, sodium sulfite, sodium metabisulfite) and sweeteners (aspartame, saccharin, cyclamate, sucrose and the like).

The pharmaceutical composition may be formulated as a nasal spray or as nasal drops according to methods known in the art. Preferred excipients include muco-adhesive polymers to enhance residence time (e. g. carbomers, polycarbophils, chitosans), viscosity modifying agents (alkylcelluloses, hydroxyalkylcelluloses, hydroxypropylmethylcellulose, carbomers, polycarbophils, chitosans, guar gum, alginates, buffers (phosphate buffer, TRIS buffer), preservatives (bronopol, benzalkonium chloride, EDTA, chlorhexidine gluconate) and anti-oxidants (N-acetyl-cysteine, sodium sulfite, sodium metabisulfite).

The general principles of formulation and manufacture of sublingual. buccal and nasal pharmaceutical compositions may be found in The Pharmaceutical Codex 12"Edition, The Pharmaceutical Press; Remington's Pharmaceutical Sciences 18th Edition, Mack Publishing Company.

The pharmaceutical composition of the invention has improved galenical properties and thus enables safe, convenient and comfortable transmucosal administration of midazolam in a pre-operative clinical setting. The pharmaceutical composition of the invention enhances the penetration of midazolam through mucosal membranes facilitating a rapid onset of action which is highly desirable for therapeutic application to pre-operative sedation.

The pharmaceutical composition of the invention is of particular advantage for pre-operative sedation in children.

The second aspect of the invention is an inclusion complex of midazolam and a water-soluble substituted beta-cyclodextrin, in particular RAMEB with a degree of substitution of 1.8 methyl groups per anhydrous glucopyranose unit.

The third aspect of the invention is the use of an inclusion complex of midazolam and a water-soluble substituted beta-cyclodextrin in the manufacture of a medicament for use in a method of sedation of a patient.

The fourth aspect of the invention is a method of sedating a patient comprising administration of an inclusion complex of midazolam and a water-soluble beta- cyclodextrin.

Various examples of the invention will now be given.

Example 1 An excess of midazolam (as the base) is added to a series of aqueous phosphate buffer solutions at pH 4.0,5.8 and 7.0 containing from 0 to 200 mg/ml of either randomly methylated beta-cyclodextrin (RAMEB) with an average degree of substitution of 1.8 methyl groups per glucopyranose unit or 2-hydroxypropyl-beta-cyclodextrin (HPB) with an average degree of substitution of 5.1 hydroxypropyl groups per beta-cyclodextrin molecule. The mixtures are allowed to shake at room temperature for 24 hours and then filtered through a 0.45 m filter. The concentration of midazolam in the filtrate is determined spectrophotometrically at 220 nm. The solubility of midazolam as a function of pH is illustrated in Figures 1 and 2. The solubility of midazolam as a function of pH and cyclodextrin concentration is given in Table 1. Table 1. Midazolam solubility as a function of pH and cyclodextrin concentration Cyclodextrin Midazolam concentration (mg/ml) Concentration pH 4.0 pH 5.8 pH 7.0 (mg/ml) HPB (0) 0.55 0. 065 0.026 HPB (200) 3.64 2. 61 2.51 RAMEB (0) 0.55 0.065 0.026 RAMEB (200) 12. 38 12. 38 12. 71 Example 2 A solution at pH 7.0 containing 12.71 mg/ml midazolam with 200mg/ml RAMEB from Example 1, is freeze-dried and redissolved in deuterated water. The resulting solution is characterized by the two-dimensional ROESY spectrum.

The spectrum was acquired at 500 MHz with a probe temperature of 303K and a spin locking time of 150ms. The spectrum reveals multiple modes of inclusion complexation involving the chlorophenyl, fluorophenyl and imidazo ring structures consistent with higher order complexation suggested by the shape of the solubility curves.

Example 3 Methylated beta-cyclodextrin D. S. 1.8 (200 g) is dissolve in 900 ml purified deionised water buffered to pH 5.8 with phosphate buffer. Midazolam (10 g) is added to the solution with stirring until a clear solution is obtained.

Benzalkonium chloride (0.01 %) is added as preservative. The volume is adjusted to 1000ml by addition of phosphate buffer pH 5.8. The tonicity of the final solution is adjusted by addition of sodium chloride. The solution is filtered through a 0.45 im filter. Each 0.2 millilitre of solution contains 2 mg midazolam. The solution is well tolerated after intranasal administration by drops or spray.

Example 4 The solution obtained in Example 3 is filled into 2 mi amber glass bottles fitted with a nasal dropper calibrated to deliver 0.2 ml doses. With the head in a position such that the plane of the nostrils and ears is perpendicular to the vertical plane, the desired dose is delivered by inserting the dropper into each nostril and instilling the drops.

Example 5 The solution obtained in Example 3 is filled into a nasal syringe device, such as for example Becton-Dickinson AccusprayTM. The volume fill of the syringe may vary between 0.2-1. Oml. The dose is conveniently administered by inserting the nozzle into each nostril and depressing the plunger to deliver the required dose.

Example 6 The solution obtained in Example 3 is filled into a metered dose nasal spray device such as for example a Valois Bi-doseTM device. The fill volume may be varied between 0.4-0.8 ml allowing the convenient delivery of two 0.2 ml doses or two 0.3 ml doses or two 0.4ml doses by inserting the nozzle into the nostril and actuating the device.

Example 7 Methylated beta-cyclodextrin D. S. 1.8 (200 g) is dissolved in 900 ml purified deionised water. Midazolam (10 g) is added to the solution with stirring until a clear solution is obtained. Carbopol 974P (0.5%) is added with stirring until a clear solution is obtained. Benzalkonium chloride (0.01 %) is added as preservative. Raspberry flavour concentrate (5mi) and saccharin (0.6g) are added with stirring. The pH of the solution is adjusted to 5.0 by addition of 1N NaOH. The volume is adjusted to 1000mi by addition of deionised water. The solution is stirred until constant viscosity is obtained. Each 0.2 millilitre of solution contains 2 mg midazolam. The solution is palatale and convenient for sublingual administration of small volumes containing an effective amount of midazolam.

Example 8 The solution obtained in Example 7 is filled into amber glass 2ml bottles fitted with a dropper device calibrated to deliver 0.2 ml-0. 8 ml doses. A single dose is conveniently administered by withdrawing the required volume of solution into the dropper, placing the dropper under the tongue and squeezing on the dropper to eject the dose.

Example 9 The solution obtained in Example 7 is filled into amber glass 2ml bottles. A conventional tuberculin syringe or the like is used to withdraw the required volume of solution. The solution is injected onto the sublingual cavity by depressing the plunger.

Example 10 Transfer 120 ml deionised water to a 200moi beaker. Slowly add 40.0 g RAMEB to the solution whilst stirring using a magnetic stirrer. Continue stirring until a clear solution is obtained. Acidify the RAMEB solution by addition of 10 ml of dilute hydrochloric acid solution. Slowly add 2.0 g midazolam base to the acidified RAMEB solution and stir for 10 minutes. Stir solution for 30 minutes.

Add 0.1 g EDTA and 8.33 ml benzalkonium chloride stock solution (2.4g/100ml) with stirring. Adjust the pH to 5.8 with 6.25M NaOH. Aseptically filter the solution thorugh a 0.22 micron filter into a clean sterile receptacle. Aseptically transfer 500mg presterilized Carbopol 971 P to a clean sterile beaker. Aseptically add the midazolam solution with stirring for 30 minutes. Record pH and adjust to pH 5.8 with either NaOH or HCI. Adjust volume to 200ml with sterile phosphate buffer pH 5.8.

Example 11 Twelve healthy subjects scheduled to undergo surgical removal of impacted wisdom teeth were enrolled in a randomized, two-way cross over pilot trial for identical dental procedures performed on two separate occasions. Subjects were treated with either the Reference medication (Dormicum injection, 5 mg/ml midazolam) or Test medication (10mg/ml midazolam prepared according to Example 3). Both Test and Reference solutions were packed in Becton Dickinson Accuspray devices. The Test product was dosed at 0.375ml in each nostril whereas the Reference product was dosed at 0.75 ml in each nostril. Test and Reference products were administered 10 minutes prior to infiltration of local anaesthetic. Vital signs were monitored before and after drug administration. Tolerability and efficacy was determined from objective and subjective measures.

There were no significant differences in blood pressure, pulse rates, respiratory rates and oxygen saturation levels. Anxiety and sedation levels were similar for Test and Reference products. Tolerability was assessed using a visual analog scale (0-10cm) described"no pain or discomfort"to'worst pain and discomfort imaginable". In the Test product group the mean VAS was 4.1 (SD 1.7) and in the Reference product group the mean VAS was 7.1 (SD 1.6) indicating a significantly better tolerability of the Test product compared with the Reference product All 12 cases receiving the Reference product complained of nasal burning, irritation, and bitter taste in the mouth. In the Test group only 5 patients complained of some form of nasal irritation but not to the degree of discomfort experienced after administration of the Reference product. The nasal mucosae of each patient was inspected at the end of the operation. In the Reference group all patients exhibited redness of the mucosae, resembling inflammation. In the Test group 4 patients had reddening of the nasal mucosae but not to the same extent as after the Reference product.