Rectal insert

~l;23~ BACKGROUND _OF THE INVENTION The hemorrhoids, or piles, are swollen varicose veins-in the mucous membrane inside or just outside the rectum.

One common cause of piles is constipation and the straining to eliminate hard 3 dry stoolO The excessive pressure causes a fold of the membraneous rectal lining to slip down, thus pinching the veins and irritating them, Women during pregnancies are particularly subject to the hemorroidal problem because of the pressure in the veins in the lower body area.

Other causes are diseases of the digestive tract resulting in anal infection, and cirrhosis of the liver, which obstructs blood flow and puts increased pressure on the hemorrhoidal veins, Once the hemorrhoids are formed, they can further deteriorate or rupture by additional pressure during constipation and straining at stool~ or by external pressure by long sitting (particularly if the piles are prolapsed or external), The ruptured and bleeding piles are sensitive to~infection; the swelling caused by inflamation affects, in turn, the hemorrhoids by pressing the veins.

The hemorrhoidal problems are self-accelerating and the prevention of the progressive deterioration of the problem is the essential condition of a sucoessful treatment, The treatment methods range from warm bath through ointments and suppositories to surgery or an injection chemotherapy to control bleeding and to eliminate the varicose veins, O~ten several , .

2 ~23~7~ methods are combined to address various aspects of the disease.

One approach to the treatment is to relieve the pain and to diminish the swelling by cooling of the hemorrhoidal tissue. For instance Cowie in U.S.

Pat.

No. 969~134 suggested the use of hollow insert filled with crushed ice or another cooling medium which was refilled for every use.

More recently Harris in U.S.

Pat.

No. 3,939,842 suggested a plastic rectal insert with en~apsulated freezable liquid, preferrably water, equipped with a bulbous collapsible end. Both devices above have se~eral shortcomings in common:

1) The surface of the device may have very low ternperature so that it can cause frost-bites to the sensitive rectal tissue. The frost-bites occur when the intracellular liquid is frozen, rupturing the cell membrane. This may happen even at moderately sub-zero temperatures if the contact between device and tissue is intimate and heat transfer efficient, which is the case for both devices.

2) Neither of the devices is inherently disposable which can increase the risk of~ nfection. Although the Harris device is intended to be disposable, it lacks any features preventing its multiple use.

-~ Its presurnably higher cost, if compared with ointments or suppositories, may encourage its multiple use.

3) Both devices have one single functionj the cooling of the tissue in the rectal canal.~This treatment has to be combined with other means, such as ointments~ lubricants or suppositories etc., which support the treatment and the discomfort relief by delivering certain drugs, protective and lubricating layer onto the swollen tissue and by eventual softening the stool.

4) Neither device can be applied without a lubricant.

3 ~ 37~Ç~ Therefore, the freezable liquid encapsulated in a solid shell cannot utilize fully the beneficial cooling effect and introduces certain risks.

Suppositories cannot be used for the cooling effect because of their shape: the pressure of the sphincter squeezes them irnmediately from the rectal canal into bottom of the colon.

This holds even for hydrogel suppositories, as described e.g. by Byrne and ~ylott in U,S, Pat.

No. 4,292, 300, which could have otherwise sufficient heat capac,ity due to relatively high water content. The role of suppositories in general is drug delivery, and their cooling effect in the rectal canal was never suggested or anticipated.

Therefore, suppositories in general differ substantially from the rectal inserts described either in the prior art or in the present invention.

SUMMARY OF_T~IE INVENTION It has been found that the free water in a hydrogel containing more than 35% by weight of water can be readily frozen by reducing the temperature of its environment approximately below 0C, preferably below -5C. It has further been found that such a frozen rigid body has the interesting property that as soon as its surface is contacted with skin at or close to body heat a substantially non-frozen gel film is immediately formed between the skin and the frozen portion of the gelO This useful property may be,utilized in the treatment of hemorrhoids with or without the contemporaneous delivery of pharmaceutically active materials into the mucosa of the rectum, ~ 4 ~ ~23~7~ The present invention provides a rectal insert made of frozen hydrogel, a method of making same and a method of using the same.

In i-ts simplest form the invention comprises a substantially cylindrical insert of frozen hydrogel having a substantially conical nose portion for insertion into the rectum. In a preferred embodiment a collar of substantially greater diameter tha-t the main portion of the insert is provided proximate to the rear end of the insert and acts as a block to possible inser-tion of the device entirely through the sphincter muscle.

This property permits application of reduced temperature to mos-t of the areas liable to be effected by hemorrhoids.

Numerous different embodiments of this invention are lS discussed in further detail hereinbelow including especially means for permi-t-ting the device to be held in position by the sphincter muscle itself after insertion and not expelled as would be the natural tendency of action of said sphincter muscle and its adjacen~ muscula-ture.

The device is provided in the form of a disposable "bubble type" package wherein the hydrogel is provided in gel form to the space provided by the bubble which is in the shape of the desired form of the rectal insert.

Prior to use tne entire package is cooled, suitably by placing it in the freezer compartment of a domestic freezer.

The package is then opened whereby, in the preferred embodiment -the two halves of the bubble pack are separated to provide the frozen insert. The insert is then removed and inserted into the rectum of the afflicted subject.

Where the simplest embodiment of the invention is utilized the muscle = ~ s 7~6 the insert unless the subject, after insertion, lies substantially flat on his stomach which would permit him to retain the device in place. The choice of the male pronoun is deliberate and not accidental since it has been found, surprisingly~ that while male test subjects are not able to retain the insert in a sitting position, i.e. on a toilet~ female test subjects have been able to do so without great difficulty. 1 The preferred embodiment having a further substantially frustro-conically shaped forward collar may be inserted while the subject is in the sitting position ~nd will be retained because. of the interaction of the rearward portion of the said collar wi.th the internal face of the sphincter muscle, The device is left in place for between 1 to 5 minutes after which time it may either be removed, or left in place until the combined action of body heat and pressure of the sphincter muscle dissolves that portion of the insert upon which it acts causing ` ~ 20 any undissolved portion of the insert, internal o~ the sphincter muscle to be retained and permitted to move up into the colon.

The hydrogels themselves which are utilized : in the formation of the rect,al insertions of ~he present invenci.on are entirely without physiological effect and the thus produced gels, sols.r or solutions thereof may be retained in the colon until the next.

bowel movement without any adverse physiological effect O 6 ~:3371~ BRIEF D~SCRIPTION OF THE DRAWINGS Figure 1 is a plan view of the preferred embodiment of the rectal insert of the present invention, Figure 2 is a plan view of a package for another embodiment of the present invention.

Figure 3 is a side cross-sectional elevational view of a package for the embodiment of figure 1.

Figure 4 is an axial cross-sectional view of the embodiment of figure 1 viewed'fromr4-4 showing a particular improvement thereon, Figure 5 is a simple embodiment of the rectal insert of the present invention.

Figure 6 is another embodiment of the rectal insert of the present invention especially suited for the use thereof for drug delivery.

Figure 7 is a perspective plan view of an embodiment of a present invention comprising a handle and collapsible insert filled with hydrogel.

Figure ~ is a plan view of a package comprising yet another embodiment of` the invention wherein the insert portion comprises the hydrogel segment and a substantially rigid combined carrier and blocking portion therefore.

~5~ DESCRIPTION OF T~]E PREFERRED EMBODIMENTS The rectal insert of the present invention ; ~ is preferably, but not solelyj,to be marketed as a blister type package having a blister of predetermined form in the form of the rectal insert itself, said blister being filled with a gel comprising a hydrogel polymer and water in proportions more ' particularly described hereinbelow.

The type of blister pack chosen will depend upon commerclal considerations as well as the nature , 7 ~2337~ of the gel chosen. Gels having a water content of, say, 35-90% can be fairly shape sustaining and can be packed in packages having very little mold forming effect. Above 90% water the gels, at ambient temperature, are not form re taining. These gels can be retained either in a preformed substantially rigid blister pack made of, say, P~C or polystyrene.

Alternately, "soft" blister packs of polyethylene may be used into which the gel is injected under moderate ~ressure, if desired by softening the pack with heat.

Prior to use the package is cooled below the freezing point of water. A temperature reduction to -5C is ~enerally suitable though any domestic freezer, which has temperatures down to about -15C may also be employed.

It is an special advantage of the present invention that such further reduction in temperature carries no adverse effect such as frostbite during use.

This advantage arise from the special properties of water swellable polymers suitably hydrogels.

When ice is contacted with a warm surface, such as skin, the t.op surface is melted to water which on àpplication of pressure as will occur in the rectum,will be pushed away permitting the skin to contact the ice itself thus giving rise to frost~ bite. In contrast when a ge] is frozen there is a phase separation of ice and gel.

When the upper layer of ice lS melted t~he water thus liberated remains in the gel,forming a layer whose temperature will not fall below 0C and at the same time prevents contact with the inner frozen surface While the rectal insert could be either fluid or self form sustaining at ambient temperatures~ the discussions which follow are directed to a description thereof 37~6 in the fro2en form.

In the use of the rectal insert in the treatment of hemorrhoids, (to which use the device is by no means limited as will be discussed in further detail hereinbelow) it is important to maintain contact between the cooling surface and the hemorrhoidal tissue for âS long a period of time as possible. It has generally been accepted in the art that a minimum treatment time of 1 minute is essential while it would be desirable $o increase the contact time up to approximately 5 minutes or more.

It is an important consideration in this treatment that hemorrhoidal veins occur in the area of the rectum itself in and around the sphincter muscle and outside the sphincter muscle. A successful device must therefore maintain contact in all areas.

Thus, a device shaped in the form of a conventional suppository which will readily travel through the sphincter muscle and then up into the colon while satisfactory for chemical treatments of hemorrhoids is unsatisfactory for thermal treatment as the contact time is too short.

The simplest device is illustrated as insert 500 in Figure 5.

Rectal insert 500 comprises a substantially cylindrical central shaft portion - 510 having â substantially conical nose portion 512 and â stopper portion 530 having a f'orward surface 532.

The device is used by inserting nose section 512 through the sphincter muscle of the rectum up to the point where surface 532 contacts the outside of said sphincter muscle. The insert is left in place until either it rnelts completely or is removed after a sufficient length of time has passed.

9 ~23~7~ The ~eneral pressures generated by the sphincter muscle and adjacent muscles of the rectum when the subject is in the seated position tend to expel all inserted bodies. Thus, where the embodiment of figure 5 is employed it would be necessary to rnaintain constant inward pressure on the de~ice which may be considered inconvenient and somewhat unesthetic. Alternatively, the device maybe readily inserted and maintained in position when the subject is lying face down on a bed. Even in this situation there are esthetic disadvantages because of the neccessity of protecting the bed against the melting insert by towels and the like. Nevertheless, despite the foregoing disadvantages this simple embodiment is operative.

The preferred embodiment of the invention is that illustrated in figure 1 with the improvement illustrated in figure 4 This embodiment comprises, in the frozen state, a rectal insert lOO having a substantially cylindrical portion 110 provided with a substantially conical nose portion 112. Rearwardly of section 110 is provided a collar section 114 which, most desirably, is provided with a substantially frustro conical cross-sectioned forward face 114 to facilitate passage of the collar thru the sphincter muscle and a rearward face 113 to reduce the likelihood of the device, once inserted, being expelled outwardly through the sphincter. Rearwardly of collar 116 is substantially cylindrical mid_section 120 Rearward of this section 120 is provided a rearward collar 130 having a forward buffer face 132 and a rearward face 134. It is not essential that collar 130 entirely ~irdle the device since its sole purpose is to act as a stopper preventing the passage of lo ~3~'~6 the entire devlce through the sphincter muscle.

Nevertheless, it is both simple to provide for 130 to entirely girdle the device and furthermore, such construction substantially strengthens collar 130.

Rearward of stopper 130 is holding section 140 The presence of this additional section is a matter of mere convenience and is in no way essential to the operation of the device. Numerous conveniences can be incorporated thereon, if desired, ;for example, as illustrated in Fi~ure 4 9 two of the sides of 140 can be shaved to the substantially mutually parallel arrangements 142 illustrated which would make it easier to hold the device between two fingers when inserting the same or removing the same.

Similarly, a holding means of cloth, plastic, wood, or other materials may be incorporated into sector 140 and protruding theref`rom to provide a drier surface for handling during insertion or removaI.

Again these are a matter of convenience and do not affect the essential operation of the device.

It is contemplated that after insertion the frozen hydrogel will melt, thus reducing the external dimensions of the device including but not limited to, forward collar 116 to the point at which the device will either to auto-expelled by the sphincter muscle when the subject is in the sitting position or the dimensions will be so reduced that the device can readily be withdrawn outwardly through the sphincter ~uscle.

' , I 337~ Nevertheless, there are circumstances wherein it would be desirable to maintain the entire segment of the insert forward of sector 120 inside the rectum and, after substantial completion of the cooling ef'fect be permitted to travel up the colon in the manner of a conventional suppository, This embodiment is particularly preferred when the treatment calls for the additional delivery of a pharmaceutically acceptable amount of a rectally administrable pharmaceut~ically active com~ound, One form of this embodiment is illustrated in figure 6 which has some of the characteristics of figure 1 device and .some of those of figure 5 device, Particularly to be noted, however, in device 60Q of figure 6 is a very substantial narrowing of mid-section 620 so that its diameter is between : ~ 25 and '75% that of, say, forward shaft portion : ~: 110, ~eedless to say the sphincter will rest within ~ this indentation and exert excess.. -pres&ure.. thereon : ~ 20 to the point at which this segment will melt and : break prior to the melting of the forward segments of the insert causing the insert to be propelled up into the colon as mentioned hereinbefore, In an unillustrated modification of this embodiment forward coll~ar 614 is omitted~ ~ As mentioned heretofore at ambient temperatures : ~ ~ the device may be in a gel form.which is not or~ substantiaIly not self retentive of form.

Since it is convenient to package it in this manner and : 30 it is unnecessary to maintain a device in the frozen state except just prior to use, it: is convenient to employ any disposable type of blister packaging, : . It is 7 however, particularly advantageous to utilize heat formable sheets of therrno plastic materialO One modification of such packaging lS illustrated ::

~3~7~ in figures 2 and 3. The packaging 256 comprises a pair of pre-shaped blister sheets 254 and (no~ illustrated) 252. These are sealed around the edges thereof by thermal bead seal 256. In manufacture of the device the gel material is injected into space 210 by conventional means through orif`ice 250 after which the seal is completed~ In order to facilitate opening of the package there may, optionally, be provided assisting rneans such as notch 254';and score line 262. It,will be noted that as described above,the flat portion of package 256 is only sealed together at the edge.

While such otherwise unsealed contact is not an essential part of the invention and these flat portions may be sealed together, for example, by heat sealing, leaving them unsealed substantially facilitates opening of the device. Thus~ it will be clear to those skilled in the art that the actual location of the heat seal 256 although illustrated as a circumferential bead sea] may be located at other places on the packaging as long as it is circumferential to the location of the gel matter itself. Indeed as mentioned above where "soft" packaging is employed for a gel in substantially fluid form at arnbi~nt temperature, the circumferential seal should actually outline the shape of the insert.

;

, ~33~7~.~ The embodiment of figure 7 comprises a handle portion 730 and a tubular portion 710 having a multi~ plicity of orifices 711 therein. The aforesaid combined article comprising segments 710 and 730 may be made of any soft collapsible material including but not limited to multiblock co-polymer hydrogel of acrylonitrile and acrylamide having an equilibrium swelling of 73% with water. Such a hydrogel polymer is recommended because of cheapness but other polymers or rubbers may also be employed.

This portion of the device is placed in a mold similar to that depicted in figures 2 and 3 and the hydrogel suitably a hydrogel comprising more than 90% by weight of water is injected into the mold so that entire section 710 is filled therewith.

~fter freezing in the usual manner, the device is inserted in the usual manner.

While the device of this embodiment may either be used in the subject face down position or else hand held for a subject in the sitting position, the form of th~- handle will tend to eliminate many of the esthetic problems of, say, the device of figure 5. As the inserted portion of the device becomes warmer the combination of melting and pressure of the rectal muscles will force the gel out of the orifices 711 and, after a predetermined time, 14 ~337~4~ the device can be withdrawn and discarded. This particularly form of device is well suited for the contemporaneous administration of pharmacologically active agents which are to be administered rectally~ and due to its design there is no possibility that an attempt would be made to recharge or re-use the remaining carrier portion after one employment.

~ igure 8 illustrates yet another e~lbodiment of the invention wherein the handling portion and the rearward collar portion are made of materlals other than hydrogel. In this ernbodiment the package comprises the usual blister pack 854/852 sealed by circumferential heat seal 856. Within the bubble there is provided a rearward portion comprising the handle segment 840 and the rearward collar section 830, For reasons of stability in use,a longitudinal protrusion 836 having a small bar or plug 835 attached thereto perpendicular to the longitudinal axis, serves to avoid the premature separation of the gel portion of the insert from the handle portion.

The hydrogel is introduced through orifice 850 in pack 854 which is subsequently sealed in the conventional mannerO While the embodiment of figure 8 does not illustrate a f`orward collar such as that shown as item 114 in figure 1, such a forward collar could readily be incorporated but would, suitably, be of frozen hydrogel. The insert of figure 8 ls utilized in a similar manner to that of figures 2,5 and 7.

The use of a non-hydrogel handle and rearward collar is more desirable esthetically but tends to raise the cost of the insert not only because o~ the cost of the materials involved but because of the necessity of several additional manufacturing steps including but not lirniting to the actual manufacture of the handle portion and its insertion into the package prior to the injection of the hydrogel.

~337~ The hydrogel rectal insertion of the present invention comprises a) an essentially cylindrical stem of diameter about 5 to 15 mm and~of length 35 to 1~5 mm, made of hydrogel having equilibrium water content higher than about 35% preferably over 90% most suitably 95-99% by weight and a substantial. part of the swelling water freezing between -1 and ~1 deg. C , which stem is to be inserted into the rectum in frozen state; and desirably, ~ b) a non-insertable end which adheres firmly to the said scem at least in its frozen state.

Whil~ this non-insertable end may, as described above, comprise a hydrogel collar, the invention is not so limited and it may be rnade of any rigid mat.erial such as wood, plastic or ca~dboa~d~ The hydrogel mentioned above ls a crosslinked or non-crosslinked polymer which swells in water to a certain equilibrium water content but is waterinsoluble at ambient or body temperatureO The equilibrium : water content at ambient temperature is at least 35% by weight, based on swollen hydrogel; and a substantial part of the swelling water is in a free state, being crystalliæable in the same manner as water itself Thus, an essential feature of the ~- hydrogel used in present invention is-its content of water in two states - hydration water (which does not freeze) and free water which freezes close to 0C. The hydrogels usable in our invention contain a substantial proportion of water crystallizable at near sub-zero(~temperatures, while the remaining part of the water serves to hydrates the polymer molecule. (for more details on free~ or mobile, and bound water phases in hydrogels see e.g~ Andronikashvili e~ al~: Biopolymers~ 1976~ 15, 1991).

16 ~ 37~6 The mobile water phase has the following major funtions: it contributes substant:ially to heat capacity of the system and it assures that temperature of the molten outer layer of hydrogel is close to, but not below 0C.

The bound water plastizes the polymer which would otherwise be brittle (mixture of ice crystals and non-plasticized po].ymer would be as brittle as or even more brittle than i.ce itself~.

Although certain hydrogels can have as little as 35% of swelling water to be useful in the present invention, the hydrogels with water content over 70% of water are preferred. At this water content the mobile water distinctly prevails over the bound water even if the gel is homogeneous~ The mobile water consists of cage-like structures which cannot be fully developed if the pores or intermolecular spaces are smaller than about ~0 to 50.~.~.The percentage of such small spaces decreases with ~welling capacity, and at about 70b of water the volume of the large pores prevails even for hydrogels with large inherent binding capacity.

We have found that the freezing characteristics of some hydrogels with swelling capacity between 35 and about 70% of water depend, to some extent, on conditions of their preparation, thermal history, etc. The hydrogels with higher water content than about 70% are, on the other hand, only very slightly : sensitive to those factors.

Moreover, both heat capacity and thermal conductivity increase with increasing water content at a substantially exponential rather than linear rate, and above about 70% of water the cont:ri.bution of the moblle water to the thermodynamic characteristics starts to prevail over the contributions of the bound water and the polymer in readily predictable way~ 17 ~2337~ Basically any polymer with swelling capacity of over 70% o~ water can be used in the present invention.

Examples of such polymers are polymers and copolymers of acrylamide, methacrylamide and their N_ substituted derivatives; polymers and copolymers of acrylic, methacrylic, maleic and itaconic acids; polymers and copolymers o~ hydrophilic esters of acrylic and rnethacrylic acid, such as 2-hydroxyethylmethacrylate, glycerylacrylate and similarly; polymers ancl copolymers of vinyl pyrridine, or vinylpyrrolidone; polycondensates o~ polyethers, such as poly(ethylene) or poly~propylene)glycos and their graft or block copolymers; polysaccharides, such as starch; cellulose and its derivatives, such as methylcellulose; polypeptides, such as collagen or elastin or gelatin; and mixtures containing a substantial portion of such hydrophilic polymers.

The said hydrogels can be covalently cross-linked in the manner well known per se, e.g by copolymerization - 20 with bifunctional copolymers, by aldehydes or by irradiation, depending on the polymer type.

The non-crosslinked, though wat`er-insoluble hdyrogels are preferred because of their better processing characteristics in general.

Particularly preferred hydrogels are those derived from poly(acrylonitrile) and containing amidic and/or carboxylic funtional groups.

There are several classes o~ such hydrogels.

One of them contains block copolymers of acrylonitrile, as described 30 e.gO in U.SO P~t No. 4,337,327.

The other class are acrylonitrile-gra~ted and~ subsequen~lyihydrolyzed polysacharides, such as starchO This type of hydrogels has been described 18 ~2337~ ir numerous papers, such as MØ Weaver et al4, Journal of Applied Polymer Science, Vol. 15, pp~ 3015-3024(1971). Similar copolymers can be prepared by direct grafting of acrylamide onto starch~ as described eOg. by G.F.

Fanta et alO, Journal of Applied Polymer Science Vol. 16, 2835-2845 (1972).

The above mentioned hydrogels can form hydrogels with very low content of solids and with very high content of freezable water. The hydrogels are very soft in the molten state and they have lubricating properties.

We f`ound it advantageous if a major part of the insert is formed from a hydrogel with water content higher than 90% and preferably higher than 98% of water which has following properties:

1) it is strong enough in molten state between 0 and 50C to retain its integrity in a plastic wrapping foil, but it disintegrates under the pressure of the sphincter muscle, when molten, to a lubricating Jelly;

2) its swelling capacity in water stronglyincreases with temperature;

3) it can be molten in presence of water at a temperature between about 50 and 105C.

Examples of such hydrogels are multiblock copolymers of acrylonitrile-acrylamide with water content between about 95 and 99.7% of water; gelatine with water;

starch gels; and the mixtures thereof.

There are several advantages of the use of the hi~h-water content hydrogel collapsible by pressure.

Firstly, the collapsible hydrogel forms a lubricating (molten) layer on the surface of the frozen insert.

L9 ~ ~ 3 ~ Secondly, the collapse of the hydrogel by melting in rectum prevents its re~use on the one hand, and provides a protective and lubricating layer on the rectal tissue on the other.

Thirdly, the collapse of the molten layer improves heat transfer between the tissue and the f'rozen core of the insert.

Both the tissue and the core have roughly constant temperature and the collapse of the hydrogel ensures that the heat transfer is mediated by a hydrogel layer of constant heat conductivity and of constant thickness.

The increasing swelling capacity with temperature causes expulsion of certain amount of f'ree water during the melting.

The water and the excess of molten and disintegrated hydrogel are expulsed from rectal channel into the bottom of the colon, helping to soften excrements and protect the rectal tissue at stool.

The additional advantage of the collapsible hydrogels is that they stay in the rectum much longer than the insert itself. The cooling function of the insert lasts several minutes, while the lubricating and rnedicating function of hemorroidal suppositories has to last much longer to be effectiveD Hence, 2~ the use of the collapsible hydrogel enables us to combine functions of the cooling insert, suppository and ointment in single device.

While it is the principal purpose of the present invention to provide for the shrinking of hemarrhoids by reducing the temperature of their environment, it is within the scope of the present invention to utilize the devices disclosed and claimed herein as drug delivery systems both as an additional t~reatment for hemorrhoids or for any other desirable physiological effect in which there i5 incorporated in the rectal ~337~ insert a desired pharmaceutically acceptable amount of any predeiermined rectally administerabl,e pharmaceutically active.~compound.

When administered the medication can be either dissolved in the water phase or dispersed in the hydrogel, depending on its solubility in water, Particularly useful are drug.s causing symptomatic relief of inflamation and swelling such as Dexamethasone, Hydrocortisone, Phenylbutazone or Prednisolone;

local anesthetics, such as Phenazopyridine or Procaine;

tissue-shrinking drugs, such as Phenylpropanol amine;

antibiotics; natural substances used in hemorroidal ointments or suppositories, such as shark-liver oil, yiest cell derivatives and the like, The water-insoluble substances can be dissolved in oily substances (e.g, regular rectal ointment bases) which are subsequently dispersed in the hydrogel.

As long as a major part of hydrogel is used so that the dispersion is of oil-in-water type, the oily substances do not interfere with the freezing process.

On the other hand~ they further improve lubrication and the transport of the drugs into the tissue. The amount of medication th~n administeried both with respect to concentration and dosage amount ' is substantially similar to that employed in conventional suppositories using those medicaments i (see Physicians Desk Reference, U,S.

Pharmacopoea etc.). i I , , ', i .

, . .. . ` .

?1 ~2337~6 EXAMPLES 40 weight parts (w~w~ of 2-hydroxyethyl metha_ crylate monomer containing 0O7% of ethyleneglycol dimethacrylate was mixed with 60 parts (w/w) of water and 0.5 parts (w~w) of 30% hydrogen peroxide.

The mixture was polymerized at 65~C in a polyethylene mold. After the polymerization was finished~ the mold was opened and the polymerized article was washed thoroughly with water. The spongy hydro~el in the form depicted in Figure 5, having insertable stem 510 with rounded tip 512, and the enlarged non-insertable end portion 530, was packaged in heat-contractable plastic foil.

The hydrogel itself contained 60% of water~ of which about 20% of freezable water was contained in the microscopic pores.

Multiblock copolymer hydrogel consisting of acrylonitrile and acrylamide, having an equilibrium swelling 73% of water1 was injection-molded into a hollow tubular article 710 with multiple orifices 711 and end handle-like portion 732 as depicted in Figure 7.

1 part (w/w) of powdered~copolymer of starch grafted with acrylonitrile and subsequently hydrolyzed by sodium hydroxide~j was washed,~drièd and mixed with 5 parts (w/w) of potato starch and with 100 parts ~w~) of water. The paste was heated to 100C to liquify it.

The cavity 713 of the hydrogel article 710 was then filled with t~e hot liquified paste, which was subsequently gelified by cooling. ~ ` :

: : :

~ 22 ~3373!.~-3 The outer wall 715 o~ the hydrogel article 710 having a water content of 73% has lower thermal conductivity than the hydrogel with high water content inside, thus prolonging the cooling action. It simultaneously protects the weak gel inside during transport and handling.

The molten gel inside the device is disintegrated by rectal pressure and squeezed out of the jacket by the side and end orifices.

The outer hydrogel jacket is extracted from the anus after the inner gel becomes molten and is left behind as lubricant and, potentially, as a drug carrier.

~ le 3 Polyacrylonitrile of molecular weight 350,000 was dissolved in mi~ture of 71% nitric acid and 98% sulfuric acid (9:1 wJw) to form a viscous solution having 5% of solids (w/w). The solution was allowed to stand for 240 hours so that the nitrile groups were substantially all hydrolyzed, then the solution was poured into excess of cool wate~r so that the polyacrylonitrile hydrolyzate (PAN) coagulated.

The clear soft gel with equilibrium swelling over 95% o~ water was thoroughly washed, dried and ground to a fine powder.

7.5 parts (w~w) of the powdered PAN hydrolyzate was added to 990 parts (w/w) of water~and heated to boiling point until the powder dissolved.

The solution thus formed was gellified by cooling to ambient temperature to a clear, soft gel which could be disintegrated by a moderate pressureO lhe ~wo part mold is prepared from PVC foil 0~0~7511 thick as depicted in Figure 3.

The parts 352 and part 354 are assembled and their inner cavity filled by the hot solution described 23 ~.~33~7~6 above by injection thru inlet 350 ( not illustrated~ but similar inlet 250 in Eigure 2. The solution was cooled down in water bath and the injection inlet The resulting article comprising the PVC jacket (divisible to parti352 and part 354) and the soft hydrogel inside are cooled to a -15C before use.

After the hydrogel is frozen, the insert may be dipped briefly into warm water so that a thin layer of gel beneanth the PVC jacket melts, The parts 352 and 354 are separated and the insert inserted into the rectum of the!~pat~en~.

5 parts of rectal ointment, containing 3% of Liver Shark Oil; Live Yeist Cell Derivative~ supplying 2000 units Skin Respiratory Factor per ounce of the ointment; and 0.01% of Phenylmercuric nitrate (Preparation H, Whitehall Laboratories IncO, NOYork) were finely dispersed in 95 parts of the hot aqueous polymer solution from Example 3. The hot dispersion was filled into the two-part moldJcontainer from the Example 3 where it gelled to solid dispersion.

~e~ 1 part of procaine hydrochloride and 1 part of phenylbutazone were dissolved in 98 parts of 1% aqueous polymer solution (the polymer is the powerdered polymer described in the Example 3~.

The hot solution was injected into the mold/container 854 thru inlet 850~ so that the whole space 810 between the collar ~30 and the PVC foil container was filled by the medicated hydrogel. Then the container was closed by welding inlet 850.