METHOD FOR INDUCING VAGINAL LUBRICATION

Abstract: Vaginal lubrication is induced in a female mammal by administration of the neuropeptide, vasoactive intestinal peptide.

Description: METHOD FOR INDUCING VAGINAL LUBRICATION TECHNICAL FIELD The present invention relates to the neuropeptide, vasoactive intestinal peptide. More particularly, the invention concerns the induction of vaginal lubrication by administration of the peptide. BACKGROUND OF THE INVENTION Vasoactive intestinal peptide, hereinafter referred to as VIP, is a 28-amino acid, carboxy-ter inal-amidated neuropeptide of animals, including fish, birds and mammals. The amino acid sequences of the VIP , s of numerous species, including human, are known. The sequence of human VIP is identical to that of bovine, porcine and rat VIPs. VIP is known to be involved in neurotrans ission associated with vasodilation, smooth muscle relaxation, and secretion in a number of tissues. VIP has also been implicated in various physiological processes related to sexual arousal. Systemic administration of VIP to females has been found to decrease uterine smooth muscle activity and increase vaginal blood flow. Ottesen et al., Eur. J. Clin. Invest. 13, 321-324 (1983). Insufficient vaginal lubricatory activity (i.e., secretion of fluids from the vaginal wall into the vaginal cavity resulting in vaginal lubrication) is a problem for many females, particularly post-menopausal females and those suffering from certain diseases, such as diabetes, which involve atherosclerosis or neuropathy. One consequence of insufficient vaginal lubricatory activity is increased susceptibility to various diseases of the female genital tract. Vaginal lubrication normally occurs during sexual arousal, and insufficient vaginal lubricatory activity can result in pain during sexual intercourse and generally unsatisfactory sexual relations. SUMMARY. OF THE INVENTION We have now discovered that administration of VIP to a female, either systemically as by intravenous injection, or locally to the vaginal wall, induces vaginal lubricatory activity and associated vaginal lubrication. Our invention thus provides methods for protecting against bacterial, fungal and other infections of the genital tract of a female associated with insufficient vaginal lubricatory activity. The invention further provides methods for increasing vaginal lubrication in a female during sexual arousal and intercourse. For a female who suffers from insufficient vaginal lubricatory activity during sexual arousal or intercourse, application of the methods of the invention to increase vaginal lubrication during sexual arousal or intercourse results in reduction of pain during intercourse and, associated therewith, generally improved sexual relations. DETAILED DESCRIPTION OF THE INVENTION The present invention entails a method for inducing vaginal lubricatory activity in a female, which comprises administering to said female an amount of a vasoactive intestinal peptide effective to induce vaginal lubricatory activity. The invention entails also compositions for carrying out the method of the invention. The invention is preferably applied to human females, although it can also be applied to females of other mammalian species, such as bovine, canine, equine, ovine and porcine females. The preferred vasoactive intestinal peptide for use in the method of the invention is the carboxy- terminal-amidated VIP of the species to which the neuropeptide is to be administered. However, other VIP's may also be employed, such as the VIP of a species other than the species to which the neuropeptide is to be administered. The VIP's for use in the method of the present invention are known and readily available in highly purified form. Administration of the VIP in accordance with the method of the invention can be systemic or local. Systemic administration is preferably by intravenous injection, although intraperitoneal, intramuscular or subcutaneous injection can also be employed. Continuous infusion may be used. Local administration is preferably to a portion of the wall of the female genital tract, most preferably to a portion of the inner wall of the vagina (i.e., the wall which defines the vaginal cavity) . Local administration can be accomplished by release of VIP by diffusion from a solution dispersed in a suitable support, such as a porous tampon or a suppository made with a composition comprising oleaginous base materials, or a suitable composition, such as an emulsion, cream, jelly, or tablet, placed in the vaginal cavity and in contact with the inner wall thereof. Upon contact of the diffusing VIP with the vaginal wall, it is absorbed thereby and taken up by cells therein, whereupon its vaginal lubricatory activity is effected. Alternatively, local administration can be by deposit of a volume of between about 1 ml and about 10 ml of a VIP-containing solution into the vaginal cavity in a manner whereby at least a portion of the vaginal wall is contacted with the solution. One convenient means for local administration of VIP in accordance with the invention is application of a volume of solution into the vagina using an applicator such as one used to self-administer contraceptive foam. In accordance with the invention, the VIP will be administered as part of a physiologically acceptable composition. Such a composition, especially suitable for systemic administration, can be a solution comprising the VIP dissolved in a physiologically acceptable medium, such as physiological saline or phosphate-buffered saline, which may optionally include other physiologically acceptable substances, such as human serum albumin or the like, at physiologically acceptable concentrations, as understood in the art. Compositions more suitable for local administration can also be formulated by the skilled in the art. See, e. g., Okada et al., J. Pharmaceut. Sci. 71, 1367 - 1371 (1982) and 72, 75 - 78 (1983). Such compositions include those comprising, optionally dispersed in a suppository or cream of physiologically rm/r acceptable oleaginous substances (e.g., WITEPSOL-SSδ 4 -" sold by Dynamit Nobel AG, W. Germany) or a jelly of starch, carrageenan, xanthan gum, locust bean gum or the like, the VIP in an aqueous solution that is approximately isotonic with physiological saline, has a pH of about 2.5 to about 4.5, and comprises human serum albumin or the like (Preferably peptidase free) at about 0.01 - 1.0 %, a protease inhibitor such as aprotinin (e.g., sold as Trasylol™ by Bayer A. G. , Leverkusen, W. Germany) at 0 - 100 ϋ/ml, NaCl at about 0.9 %, and a polybasic acid, such as citric, succinic or the disodium or dipotassium salt of edetic, at 0.2 M to 0.5 M. The concentration of the VIP in the physiologically acceptable solution will be between about 0.1 μg and about 100 μg per ml. As the skilled will understand, the concentration will depend on the route of administration (e.g., local or intravenous), the total dose to be administered, and the time period over which the administration is to occur. A solution is prepared by simply dissolving under sterile conditions the purified, sterile VIP, to the desired concentration in sterilized, physiological acceptable medium. Then, if the solution is to be dispersed in a tampon, suppository, cream, jelly or the like to make a composition for local administration, the solution is combined with the desired substance, also under sterile conditions. The solution or other composition can be prepared at any time prior to use, including immediately prior thereto. If prepared more than a few hours prior to use, the solution may include physiologically acceptable, non-irritant preservatives, such as about 0.1% benzalkonium chloride. Similarly, solution, or composition for local application, if prepared more than a few hours prior to use, is preferably maintained at low temperature, preferably about 0 "C to about 4 β C. The dosage of VIP to be administered, and the rate of administration, will depend on the species, age, weight, and medical condition of the female to whom the neuropeptide is being administered, the route of administration, and the purpose of the administration. For purposes of inducing vaginal lubrication during sexual relations, a single intravenous injection of about 1 μg to about 100 μg (about 0.01 μg/kg body weight to about 1 μg/kg body weight) of VIP in 1 ml to 10 ml of solution may be administered between about 10 minutes and 1 minute prior to intercourse or a volume of between about 1 ml and 10 ml of solution, or solution-containing composition, with between about 10 μg and l mg of VIP may be delivered into the vaginal cavity, to bathe the inner vaginal wall, between about 10 minutes and about 1 minute prior to intercourse. For purposes of inducing vaginal lubrication to prevent, or reduce the risk of contracting, infections of the genital tract in a female who suffers from inadequate vaginal lubricatory activity, a continuous mode of administration may be employed. Suitable continuous modes of administration include continuous intravenous administration; percutaneous administration, as from a skin patch perfused with VIP in a physiologically acceptable carrier and applied to a body part suitable for absorption from the patch into the blood stream; or vaginal administration, as from a tampon or suppository perfused with a VIP solution and inserted into the vaginal cavity. Depending on the species, age, weight, and medical condition of the female, including the severity of the impairment of vaginal lubricatory activity and the nature of the infection or infections to be protected against, the rate of administration will be between about 10~ 7 gram and 10" "5 gram per kilogram body weight per hour over periods ranging from about 10 minutes to about 24 hoi'.rs,-interspersed with periods during which no VIP is administered. It is intended that VIP be administered in accordance with the invention under the guidance of a physician or veterinarian. For a particular female, the dosage, route and rate of administration of the VIP will be determined by the physician or veterinarian, taking into account the above-described factors (species, age, weight, degree of impairment (if any) of vaginal lubricatory activity, medical condition, purpose for administration of the VIP) as well as the known effects of the VIP on vasodilation, blood pressure, pulse rate and the like. For example, with human VIP employed with human females, concentrations of the neuropeptide in peripheral blood plasma in excess of 1 microgram per liter should be avoided due to the known effects of neuropeptide on the cardiovascular system. The invention will now be illustrated in the following examples. EXAMP.LE I Fourteen women (age 22-39 years, weight 55-65 kg, 0-4 pregnancies and 0-3 deliveries) , who were receiving no medication, including oral contraceptives and intrauterine devices, volunteered for the study. The experiments were performed between the seventh and the sixteenth day of menstrual cycle, to insure that the measurements were made at the same time in the cycle for all of the women and that the women were not pregnant. All participants gave written informed consent after the study was approved by the local ethical committee of Copenhagen, Denmark. On the day of the experiment, the cubital vein on both arms was canulated for the infusion of drugs and physiological saline and collection of peripheral venous blood. Physiological saline (approximately 300 ml per hour) was infused continuously throughout the experiments Blood pressure and pulse frequency were monitored. The woman was lying on her back during the experiment. Sterile, synthetic carboxy-terminal-amidated human VIP (Peninsula Laboratories, Belmont, California, U.S.A.) was dissolved in physiological saline containing 1.5% human serum albumin. The solution was sterilized by filtration (pore diameter 0.22 μ) . The sterilized VIP solution was infused over a period of 30 minutes at a rate delivering 900 pmol VIP (i.e., 3 μg VIP) per kg body weight per hour using a perfusion pump. The VIP infusion was preceded and followed by control infusions of physiological saline over periods of 30 minutes each. The effect of VIP on local vaginal blood flow was measured with six of the women as described by Ottesen et al., supra. A seventh woman, to whom only physiological saline without VIP was administered, served as control for the vaginal blood flow measurements. The effect of VIP on vaginal lubrication was evaluated for six of the women. Vaginal transudate was measured by means of preweighed circular filter papers (12 mm diameter) arranged in layer and held inside a plastic suction capsule and in direct contact with the vaginal wall. Contact with the vaginal surface was assured with a light vacuum (20-30 mm Hg) . The area of vaginal surface from which fluid was collected was 1.13 cm 2 . The quantity of vaginal fluid was calculated from the weight gain of the filter papers during a certain period of time. Fresh filter papers and the suction capsule were applied every 30 minutes and weighed immediately after removal. Fluid released was, thus, measured during the period of infusion of VIP, during the 30 minutes immediately prior to the 30 minutes of infusion of the VIP, and during two successive 30 minute periods immediately after the infusion of the VIP. With a seventh woman, who served as control, only physiological saline without VIP was administered but vaginal transudate was measured in the same way as with the six women to whom the VIP was administered. Peripheral blood samples were collected every 30 minutes and, during VIP infusion, every 10 minutes, for measurement of VIP concentration by radioimmunoassay. (Fahrenkrug and Schaffalitzky de Muckadell, J. Lab. Clin. Med. 89, 1379 (1977)). Non-parametric statistics were applied using the Wilcoxon-test for paired observations. Differences resulting in p-values less than 0.05 were considered significant. The median peripheral blood plasma concentration of VIP during saline infusion prior to infusion of VIP was 22-23 pmol/1. At 10 minutes after the infusion of VIP (at 900 pmol x kg" 1 x h "1 ) had started, the median peripheral blood plasma concentration had increased to 200 pmol/1 (interquartile range: 130-240 pmol/1) ; at 20 minutes after the start of the VIP infusion, the median peripheral plasma concentration reached 290 pmol/1 (interquartile range: 190-380 pmol/1) ; at 30 minutes after the start of the infusion (i.e., at the time VIP infusion stopped), the median peripheral plasma concentration was 190 pmol/1 (interquartile range: 170-400 pmol/1) . By 30 minutes after infusion of VIP had stopped (but infusion of physiological saline continued) , the median peripheral plasma concentration of VIP had dropped to 30 pmol/1 (interquartile range: 20-40 pmol/1) ; 30 minutes later, the median concentration was 35 pmol/1. Additional data on peripheral blood plasma concentration of VIP, as a function of time after infusion and infusion rate, is provided in Ottesen et al., supra. The measurements of blood pressure, pulse, and change in vaginal blood flow with VIP infusion confirm the results reported by Ottesen et al., supra. Systolic blood pressure was not significantly affected by VIP administration at 900 pmol/kg/h as described here, presumably because of the accompanying rapid infusion of saline. Diastolic blood pressure was significantly reduced (from 70-80 to 50-55 mm Hg) and pulse rate significantly increased (from 60-80 to 95-110/min) during administration of the VIP; the effects on both diastolic blood pressure and pulse rate dissipated rapidly after VIP infusion was discontinued. All of the women to whom VIP was administered developed cutaneous flushing localized to the face and trunk; the flushing disappeared within minutes after VIP infusion stopped. Vaginal blood flow increased significantly in response to infusion of VIP and decreased to pre-infusion rates within fifteen minutes after VIP infusion was stopped. A significant increase in vaginal lubrication was observed with VIP-infusion, establishing that administration of VIP had induced vaginal lubricatory activity. The amounts of fluid absorbed by the filter papers, as described above, were as follows: Fluid Absorbed during Amount of Fluid Absorbed 30 Min. Period Ending: during Period mg/cm 2 (Median, with Interquartile Range) at. start of VIP infusion 27 (18-27) at end of VIP-infusion 53 (35-53) 30 min after end of VIP- infusion 18 (10-18) 60 min after end of VIP- infusion 19 (11-19) Thus, administration of VIP as described in this example induced and increased vaginal lubrication. Indeed, vaginal lubricatory activity, as measured by the rate of transudation of fluid to the inner vaginal wall, was increased by a factor of about 2 to 3. The vaginal transudate induced by VIP as described here corresponds approximately to the amount produced on the inner vaginal surface during sexual self-stimulation to orgasm. The test subjects in the present study reported that they felt the increase in heat rate and warmth, due to increased vaginal blood flow; but none of the subjects reported any sexual arousal. None of the effects observed with administration of VIP (on diastolic blood pressure, pulse rate, flushing of face and torso, vaginal blood flow, increased vaginal lubrication) was observed with the two women who served as controls. EXAMPLE II The effect of administration of VIP sub- epithelially to the inner wall of the vagina was studied as follows with 6 human volunteers. The volunteers ranged in age from 20 - 35 years, weighed 52 - 62 kg, had 0 - 3 pregnancies and 0 - 2 deliveries, and were receiving no medication, including oral contraceptives and intrauterine devices. With each volunteer, the experiment was performed between the seventh and sixteeenth day of the menstrual cycle. The volunteers had given written, informed consent after the study was approved by the local ethical committee of Copenhagen, Denmark. The volunteers were lying on their backs during the experiments. Blood pressure, pulse, and flushing of the face were monitored throughout the experiment with each volunteer. Following Ottesen et al., Eur. J. Clin. Invest. 13, 321 - 324 (1983), a measuring electrode was posi- tioned on the front wall of the vagina, about 5 cm up, to measure change in blood flow to the vagina. Then, 0.2 ml of sterilized physiological saline, warmed to 37 β C, was injected subepithelially at a depth of 2 mm at a site on the front wall of the vagina, about 3 cm up. 30 minutes after the injection of the saline solution, 0.2 ml of sterilized physiological saline containing 10 μg of filter-sterilized human VIP, also warmed to 37 β C, was injected subepithelially at a depth of 2 mm at about the same site as the injection of the saline without VIP. After the injections of saline without VIP, no increase in power consumption at the measuring electrode, no change in blood pressure and pulse, and no flushing were observed. After the injections of saline with VIP, a maximum increase in power consumption of 9.3 ± 2.6 W and an increase in pulse from 61 ± 1.5 to 79 ± 2.6/min were observed. Flushing was observed with 5 of the 6 women. No significant change in blood pressure was found. The increase in power consumption began at about 1 minute, reached a maximum at 2 - 5 minutes, and returned to zero at 13 ± 2.7 minutes after injection of the VIP solution. The observed increase in power consumption corresponds to that which accompanies an increase of vaginal lubricatory activity that is about the same as that observed with the systemic infusions of VIP solution described in Example I, i.e., about 2-fold to 3-fold. The fact that local, sub-epithelial injection of VIP results in increased vaginal lubricatory activity, as established in the experiment described in this Example, establishes that administration of VIP locally to the inner vaginal wall is a route of administration that is effective for increasing vagiwal lubricatory activity. Although the invention has been described with some specificity, the skilled will recognize variations and modifications within the spirit and scope of the invention. Such variations and modifications are also intended to be within the scope of the invention as described and claimed herein.

Claims: WHAT IS CLAIMED IS: 1. A method of inducing vaginal lubrication in a female mammal which comprises administering to the female a vaginal lubricatory activity-inducing-effective amount of a VIP in a physiologically acceptable solution. 2. A method according to Claim 1 wherein the VIP is the VIP which occurs naturally in the species of the female. 3. A method according to Claim 2 wherein the VIP solution is administered locally to the inner wall of the vagina. 4. A method according to Claim 2 wherein the VIP solution is administered systemically. 5. A method according to Claim 3 wherein a volume of between 1 ml and 10 ml of solution, containing between 100 μg and 1 mg of the VIP, is administered. 6. A method according to Claim 4 wherein the route of administration is intravenous. 7. A method according to Claim 6 wherein between 1 ml and 10 ml of fluid, containing between 0.1 μg and 1 mg of VIP, is administered in a single injection. 8. A method according to Claim 6 wherein the administration is by continuous infusion over a period of 10 minutes to 24 hours at the rate of 10~ 7 gram to 10~ 5 gram VIP per kilogram body weight of the female per hour. 9. A method according to any of Claims 1 - 8 wherein the female is human.

Inventors: FAHRENKRUG JAN, OTTESEN BENT, FAHRENKRUG, JAN, OTTESEN, BENT
Applicants: SENETEK PLC
Application year: 1987
Main classification: C07K7
IPC codes: A61K38, A61P13, A61P15