WO2010036878A1

WO2010036878A1 - Use of trpv1 receptor agonists in cervical pain and labor

Info

Publication number: WO2010036878A1
Application number: PCT/US2009/058357
Authority: WO
Inventors: Pamela Flood; Chuanyao Tong
Original assignee: The Trustees Of Columbia University In The City Of New York
Priority date: 2008-09-26
Filing date: 2009-09-25
Publication date: 2010-04-01

Abstract

The present invention relates to methods, compositions, and kits for decreasing cervical pain, promoting the onset of labor, or a combination of the two, by applying to the cervix a compound that is an agonist of the Transient Receptor Potential- 1 ("TRPV-I") receptor.

Description

USE OF TRPVl RECEPTOR AGONISTS IN CERVICAL PAIN AND LABOR

GRANT INFORMATION

This invention was made with government support under NIH grant numbers NS48065 and GM48085 awarded under the National Institutes of Health. The United States government has certain rights in the invention.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application Serial No. 61/100,518, filed September 26, 2008, which is hereby incorporated by reference in its entirety.

1. INTRODUCTION

2. BACKGROUND OF THE INVENTION Dilation of the cervix, as occurs in labor or during surgical procedures, results in cervical pain. Cervical dilation results in firing of the afferent hypogastric nerve, results in increased expression of cFos in the thoracolumbar spinal cord, and manifests as reflex abdominal muscle activity in experimental animals (Sandner- Kiesling et al., 2002, Pain 96:13-22; Tong et al., 2003, Anesthesiol. 99:205-211). In an animal model of cervical dilation, it was observed that the excitatory TRPV-I receptor was important in estrogen-induced sensitization of the cervix (Tong et al., 2006, Anesthesiol. 104:651-657; Tan et al., 2007, Anesth. Analg. 104:1246-1250). Indeed, in both rodent and human pregnancy, the uterine cervix is almost entirely innervated by C fibers, which both express and are activated by TRPV-I receptors. (Tong et al., 2006, Anesthesiol. 104:651 -657; Tingaker et al. 2008, Reproductive Biology and Endocrinology 6:8). Furthermore, a process known as "cervical ripening" occurs during pregnancy, beginning in the first trimester and progressing until term. "Cervical ripening" includes cervical thinning, and acute softening that facilitates effacement and dilatation during labor. Without being bound by theory, an inflammatory cascade, including cytokines such as TNF, interleukins, and bradykinins, is thought to be a key mediator of cervical ripening. The degradation of cervical collagen is the final step in the cascade. The release of Substance P and CGRP from cervical C fibers as a result of capsaicin application leads to neurogenic inflammation, which facilitates the release of the inflammatory cytokines necessary for cervical ripening. Aspects of labor that are frequently subject to medical intervention include the initiation of labor and the treatment of associated pain. It can be desirable to induce labor under circumstances where the pregnancy has progressed beyond full term, the mother is suffering from medical complications, or there is a problem with the fetus (e.g. irregular heart rate, infection in the amniotic sac, or the fetus has died). Labor can be induced by, for example, administering intravenous oxytocin (which promotes uterine contractions) and/or intravaginal prostaglandin (which promotes dilation of the cervix). Pain associated with labor is frequently treated with epidural anesthesia, where an anesthetic such as lidocaine, chloroprocaine, or bupivacaine is administered into the epidural space that is outside of the fluid-filled sac surrounding the spinal cord.

It is estimated that nearly 85% of women in labor nationwide choose to have pain reduction during labor (www.childbirth.org). Further, it is estimated that labor is induced in between 9.5 and 33.7% of all pregnancies annually (Tenore JL. Methods of cervical ripening and induction of labor. Am Fam Physician 2003;67:2123-8). Elective induction is rising more rapidly than clinically indicated induction. ( Zhang J, Yancey MK, Henderson CE. U.S. national trends in labor induction, 1989-1998. J Reprod Med 2002;47: 120-4). Induced labor is more painful than spontaneous labor (Conell-Price, J, Evans JB, Hong D, Shafer S and Flood P. Anesth Analg. 2008 May;106(5):1509-15). Accordingly, there is a need for an agent that both promotes the onset of labor and also diminishes the associated pain. Capsaicin, the active compound in chili peppers which acts through binding to the TRPV-I receptor, is used as a topical cream to treat arthritis and chronic pain states (e.g. post-herpetic neuralgia). The analgesic effect of capsaicin results from a rapid desensitization of TRPVl receptors after initial activation of the receptor elicits a burning sensation. Accordingly, the art has sought to develop compounds that act as antagonists of the TRPV-I receptor so as to produce anesthesia without an initial pain response (see, for example, United States Patent No. 6,723,730). In contrast, the instant invention relates to the use of TRPV-I receptor agonists, alone or in combination with an anesthetic, for reducing cervical pain, promoting the onset of labor, or a combination of the two.

3. SUMMARY OF THE INVENTION

The present invention relates to methods, compositions, and kits where a TRPV-I receptor agonist is used to treat cervical pain, promote the onset of labor, or a combination of the two.

The present invention provides a method of inhibiting pain arising from the cervix in a subject in need of such treatment comprising applying an effective amount of a TRPV-I receptor agonist to the cervix. In certain embodiments, the invention provides that, prior to application of the TRPV-I receptor agonist to inhibit cervical pain, an effective amount of a local anesthetic is administered to the subject.

In certain embodiments, the invention provides for the use of such methods to inhibit cervical pain when the subject is in labor. In certain embodiments, the present invention provides methods for promoting the onset of labor, in a subject in need of such treatment, by applying an effective amount of a TRPV-I receptor agonist to the cervix.

In certain embodiments, the invention provides that, prior to application of the TRPV-I receptor agonist to promote the onset of labor, an effective amount of a local anesthetic is administered to the subject.

In certain embodiments of the present invention, the TRPV-I receptor agonist is selected from the group consisting of capsaicin, resiniferatoxin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin. In certain embodiments of the present invention, the local anesthetic administered with the TRPV-I agonist is selected from the group consisting of lidocaine, benzocaine, procaine, benzocaine, bupivicaine, ropivicaine, and levobupivicaine. In certain embodiments, the invention provides for kits for inhibiting pain arising from the cervix, promoting the onset of labor, or a combination of the two, comprising a dosage form of local anesthetic and a dosage form of a TRPV-I receptor agonist. In certain embodiments, the invention provides for kits for inhibiting pain arising from the cervix, promoting the onset of labor, or a combination of the two wherein the TRPV-I receptor agonist is selected from the group consisting of capsaicin, resiniferatoxin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin. In certain embodiments, the invention provides for kits for inhibiting pain arising from the cervix, promoting the onset of labor, or a combination of the two, wherein the local anesthetic is selected from the group consisting of lidocaine, benzocaine, procaine, benzocaine, bupivicaine, ropivicaine, and levobupivicaine.

4. BRIEF DESCRIPTION QF THE DRAWINGS

Figure 1. Figure 1 illustrates the incidence (top) and duration (bottom) of behaviors indicative of labor pain (squashing and lateral contraction) in laboring rats treated with lidocaine alone (Lido) or lidocaine and capsaicin (Cap), as outlined in Example 2. The asterisk (*) indicates a statistically significant (p<0.05) decrease in incidence of lateral contraction in the population of rats treated with lidocaine and capsaicin as compared to the lidocaine control.

Figure 2. Figure 2 illustrates the incidence (top) and duration (bottom) of behaviors indicative of maternal attention (licking pups and eating placenta) in rats treated with lidocaine alone (Lidocaine) or lidocaine and capsaicin (Capsaicin), as outlined in Example 2. There is no statistically significant (p<0.05) increase or decrease in incidence of maternal attention in the population of rats treated with lidocaine and capsaicin as compared to the lidocaine control.

Figure 3. Figure 3 illustrates the incidence (top) and duration (bottom) of general activities (eating, drinking, rearing, and grooming) in rats treated with lidocaine alone (D) or lidocaine and capsaicin (B), as outlined in Example 2. The only statistically significant (p<0.05) difference is that the population of rats treated with lidocaine and capsaicin ate more than the lidocaine control. Figure 4. Figure 4 illustrates the demographic data (duration of labor, number of pups, and labor onset) in rats treated with lidocaine alone (Lidocaine) or lidocaine and capsaicin (Capsaicin) as outlined in Example 2. The only statistically significant (p<0.05) difference is that the onset of labor occurred earlier in the population of rats treated with lidocaine and capsaicin.

Figure 5. Figure 5 illustrates the labor and delivery behavior of mice treated with subcutaneous morphine, subcutaneous saline, or subcutaneous saline & cervically-applied capsaicin, as outlined in Example 3. The figure indicates the incidence per hour of several behaviors indicative of labor pain (squashing, lateral contraction, elongation, and pushing. The asterisk (*) indicates treatment with cervical capsaicin reduced elongation and pushing during labor in a statistically significant manner (p<0.05). Treatment with morphine resulted in a statistically significant reduction in squashing and lateral contractions during delivery.

5. DETAILED DESCRIPTION OF THE INVENTION

For clarity and not by way of limitation, this detailed description is divided into the following sub-portions: (i) TRPV-I receptor agonists; (ii) methods of treatment; (iii) compositions; and

(iv) kits.

5.1 TRPV l RECEPTOR AGONISTS

The present invention provides for the use of a TRPV-I receptor agonist for reducing cervical pain, promoting the onset of labor, or a combination of the two. Non-limiting examples of TRPV-I receptor agonists which can be used in accordance with the instant invention include capsaicin, resiniferatoxin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin.

Additional non-limiting examples of TRPV-I receptor agonists can be identified by employing in vitro assays, such as the assay described in detail in Example 1. Briefly, such assays can measure the ability of a candidate TRPV-I receptor agonist to activate and subsequently desensitize TRPV-I receptors by calculating the extent of TRPV-I receptor mediated calcium mobilization. Those candidate TRPV-I receptor agonists capable of effectively activating and subsequently desensitizing TRPV-I receptors are identified by their ability to elicit calcium mobilization at pharmaceutically acceptable concentrations.

5.2 METHODS OF TREATMENT

In certain embodiments, the present invention provides for a method of inhibiting pain arising from the uterine cervix. This method comprises applying an effective analgesic amount of a TRPV-I receptor agonist to the cervix. Pain arising from the cervix can, by way of example and not by way of limitation, be associated with labor, a surgical procedure requiring cervical dilatation (e.g. associated with curetage), a surgical procedure such as a biopsy, cervical cancer, or naturally occurring cervical dilation in the case of childbirth.

The present invention contemplates a variety of methods for the administration of a TRPV-I receptor agonist for the treatment of cervical pain. For example, and not by way of limitation, an effective analgesic amount of a TRPV-I receptor agonist can be applied to the surface of the cervix as a solution or cream or can be locally injected in order to inhibit cervical pain. Additional non-limiting examples include the administration of TRPV-I receptor agonists via vaginal suppositories or pessaries. In certain non-limiting embodiments, an effective analgesic amount of a TRPV-I receptor agonist reduces the amount of pain experienced but is not required to eliminate the pain entirely. In certain non-limiting embodiments of the invention, an effective analgesic amount is an amount of a TRPV-I receptor agonist that reduces the clinical symptoms of cervical pain. In other non-limiting embodiments, an effective analgesic amount of

TRPV-I receptor agonist can be correlated with the compound's ability to inhibit or reduce behavioral indicia of labor pain, in vivo, wherein a greater reduction in the behavioral indicia of labor pain at a lower concentration compared to a control subject that is not administered the compound is correlative with the compound's therapeutic efficacy. By way of example, and not of limitation, such an in vivo assay can comprise administering a TRPV-I receptor agonist to a test subject, for example, a mouse or rat, followed by an assay to determine the extent of behavioral indicia of labor pain (e.g., squashing, lateral contraction, elongation, and pushing) in the subject. The assay used to measure behavioral indicia of labor pain can be any assay known in the art, for example, behavioral assays such those detailed in Examples 2 and 3, below.

Where the TRPV-I receptor agonist is capsaicin, the effective analgesic amount can be, for example but not by way of limitation, between about 0.005 and 20 mg, preferably between about 0.025 and 10.0 mg, and more preferably between about 0.025 and 1 mg. Where the TRPV-I receptor agonist is resiniferatoxin, the effective analgesic amount can be, for example but not by way of limitation, between about 0.005 and 5 μg, preferably between about 0.05 and 1.0 μg, and more preferably between about 0.025 and 0.1 μg. Where the TRPV-I receptor agonist is an agonist other than capsaicin or resiniferatoxin, an effective analgesic amount of the TRPV-I receptor agonist can be determined by comparison of the activity of the agonist with the effective analgesic dosages of capsaicin or resiniferatoxin to identify a capsaicin-equivalent or resiniferatoxin-equivalent effective analgesic dosage.

In preferred, non-limiting embodiments, an effective amount of a local anesthetic is applied prior to or concurrent with administration of the TRPV-I receptor agonist to reduce the pain initially associated with TRPV-I receptor activation. In certain embodiments, the local anesthetic is not a TRPV-I receptor antagonist. In specific, non-limiting embodiments, the local anesthetic can be lidocaine, procaine, benzocaine, bupivicaine, ropivicaine, levobupivicaine etc. The local anesthetic can be applied to the surface of the cervix as a solution, gel or cream or can be locally injected. In specific, non-limiting embodiments, where the local anesthetic is lidocaine, the amount of lidocaine can be between about 2 and 500 mg. In further embodiments, the present invention provides for a method of promoting the onset of labor in a subject in need of such treatment. In certain embodiments such methods comprise applying, to the cervix of a pregnant subject, an effective labor-promoting amount of a TRPV-I receptor agonist. The TRPV-I receptor agonist can be applied to the surface of the cervix as a solution or cream or can be locally injected. "Promoting the onset of labor" means increasing the ripening of the cervix and/or shortening the interval before labor begins and/or enhancing the rate of cervical dilation or effacement or the efficacy of other treatments for labor induction. According to the invention, an effective labor-promoting amount is an amount of a TRPV-I receptor agonist that measurably promotes the onset of labor. For example, an effective labor-promoting amount is an amount of a TRPV-I receptor agonist that reduces the time to onset of labor by 10% in a subject. Where the TRPV-I receptor agonist is capsaicin, the effective labor- promoting amount to promote onset of labor can be, for example but not by way of limitation, between about 2.5 - 50 mg. Where the TRPV-I receptor agonist is resiniferatoxin, the effective amount to promote onset of labor can be, for example but not by way of limitation, between about 2.5 and 50 μg. Where the TRPV-I receptor agonist is an agonist other than capsaicin or resiniferatoxin, an effective labor- promoting amount of the TRPV-I receptor agonist can be determined by comparison of the activity of the agonist with the effective labor-promoting dosages of capsaicin or resiniferatoxin to identify a capsaicin-equivalent or resiniferatoxin-equivalent effective labor-promoting dosage. In still further embodiments, the present invention provides for a method of reducing pain in combination with promoting the onset of labor in a subject in need of such treatment. Such embodiments comprise applying, to the cervix of a pregnant subject, an effective amount of a TRPV-I receptor agonist. In such embodiments the TRPV-I receptor agonist can be applied to the surface of the cervix as a solution or cream or can be locally injected. Where the TRPV-I receptor agonist is capsaicin, the effective amount can be, for example but not by way of limitation, between about 2.5-20 mg. Where the TRPV-I receptor agonist is resiniferatoxin, the effective amount can be, for example but not by way of limitation, between about 2.5 and 20 μg. In preferred, non-limiting embodiments of the foregoing method of reducing cervical pain in combination with promoting the onset of labor, an effective amount of a local anesthetic is applied prior to or concurrent with administration of the TRPV-I receptor agonist. Application of the local anesthetic reduces the pain initially associated with TRPV-I receptor activation. In specific, non-limiting embodiments, the local anesthetic can be lidocaine, procaine, benzocaine, bupivicaine, ropivicaine, levobupivicaine etc. The local anesthetic can be applied to the surface of the cervix as a solution, gel or cream or can be locally injected. In specific, non-limiting embodiments, where the local anesthetic is lidocaine, the amount of lidocaine can be between about 2 and 500 mg. In further non-limiting embodiments, an effective analgesic and/or labor-promoting amount of a TRPV-I receptor agonist can be determined via an in vitro assay. By way of example, and not of limitation, such an assay can employ mammalian cell cultures recombinantly expressing human TRPV-I receptor and rely on a measurement of calcium mobilization in response to agonist administration to establish TRPV-I receptor activation and subsequent desensitization.

In another non-limiting embodiment, an effective analgesic and/or labor-promoting amount of a TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity through activation and subsequent desensitization of the receptor, whereby the receptor is desensitized by at least about 5-10%, more preferably from at least about 10-20%, more preferably from at least about 20-30%, more preferably from at least about 30-40%, more preferably from at least about 40-50%, more preferably from at least about 50-60%, more preferably from at least about 60-70%, more preferably from at least about 70-80%, more preferably from at least about 80-90%, and more preferably from at least about 90-100%, when the compound is administered in an in vitro assay, such as the assay detailed in Example 1, wherein a greater level of TRPV-I receptor inhibition at a lower concentration in the in vitro assay is correlative with the TRPV-I receptor agonist's therapeutic efficacy. In a preferred non-limiting embodiment, an effective analgesic and/or labor-promoting amount of a TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 60% when the compound is administered at a concentration of 1 μM in the in vitro assay.

In other preferred non-limiting embodiments, an effective analgesic and/or labor-promoting amount of a TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 70% when the compound is administered at a concentration of lμM in the in vitro assay.

In other preferred non-limiting embodiments, an effective analgesic and/or labor-promoting amount of a TRPV-I receptor can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 80% when the compound is administered at a concentration of 1 μM in the in vitro assay.

In other preferred non-limiting embodiments, an effective analgesic and/or labor-promoting amount of a TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 90% when the compound is administered at a concentration of lμM in the in vitro assay.

In other preferred non-limiting embodiments, an analgesic and/or labor-promoting effective amount of a TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 95% when the compound is administered at a concentration of lμM in the in vitro assay.

In other preferred non-limiting embodiments, an effective analgesic and/or labor-promoting amount of a TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about 100% when the compound is administered at a concentration of lμM in the in vitro assay.

In another non-limiting embodiment, an effective analgesic and/or labor-promoting amount of a TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity through activation and subsequent desensitization of the receptor, whereby the receptor is desensitized by at least about 50% compared to a control that was not contacted with the candidate compound (i.e., IC₅₀), wherein the compound is tested in at concentrations of InM to lμM, preferably from at least about 1OnM to about 50OnM, and more preferably from at least about 1OnM to about 10OnM in an in vitro assay, such as the assay detailed in Example 1, wherein such inhibition of TRPV-I receptor activity at the above- described concentrations is correlative with the TRPV-I receptor agonist's therapeutic efficacy.

In other non-limiting embodiments, an effective analgesic and/or labor-promoting amount of a TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 50% when the compound is administered at a concentration of about lμM in the in vitro assay.

In other non-limiting embodiments, an effective analgesic and/or labor-promoting amount of TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 50% when the compound is administered at a concentration of 50OnM in the in vitro assay. In other non-limiting embodiments, an effective analgesic and/or labor-promoting amount of TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 50% when the compound is administered at a concentration of about 10OnM in the in vitro assay. In other non-limiting embodiments, an effective analgesic and/or labor-promoting amount of TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 50% when the compound is administered at a concentration of about 1OnM in the in vitro assay. In other non-limiting embodiments, an effective analgesic and/or labor-promoting amount of TRPV-I receptor agonist can be correlated with the compound's ability to inhibit TRPV-I receptor activity by about at least 50% when the compound is administered at a concentration of about InM in the in vitro assay.

5.3 COMPOSITIONS

The TRPV-I receptor agonist compounds and compositions of the invention can be formulated as pharmaceutical compositions by admixture with a pharmaceutically acceptable carrier or excipient. In certain non-limiting embodiments, the pharmaceutical composition can comprise an effective amount of a TRPV-I receptor agonist and a physiologically acceptable diluent or carrier. The pharmaceutical composition can further comprise a second drug, for example, but not by way of limitation, a local anesthetic.

The phrase "pharmaceutically acceptable" refers to molecular entities and compositions that are physiologically tolerable when administered to a subject. Preferably, but not by way of limitation, as used herein, the term "pharmaceutically acceptable" means approved by a regulatory agency of the federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in animals, and more particularly in humans. The term "carrier" refers to a diluent, adjuvant, excipient, or vehicle with which the compound is administered. Such pharmaceutical carriers can be sterile liquids, such as water and oils, or, for solid or semi-solid dosage forms, such as, but not limited to, vaginal suppositories, can be standard tabletting excipients. Water or aqueous solution saline solutions and aqueous dextrose and glycerol solutions are preferably employed as carriers, particularly for injectable solutions. Suitable pharmaceutical carriers are described in "Remington's Pharmaceutical Sciences" by E. W. Martin, 18th Edition, or other editions.

The present invention provides for compositions for use in the methods described above, that comprise effective amounts of a TRPVl receptor agonist in a formulation suitable for cervical application. Such formulations include, but are not limited to, single-dose applicators containing between 1 and 20 ml of cream or gel comprising a TRPV-I receptor agonist. Such an applicator can be a single-dose disposable swab applicator. The present invention further provides for compositions comprising a

TRPV-I receptor agonist together with a local anesthetic. In specific non-limiting embodiments, the local anesthetic can be lidocaine, procaine, benzocaine, bupivicaine, ropivicaine, levobupivicaine etc.

The TRPV-I receptor agonist in the foregoing formulations can be comprised in a cream, a gel, a liquid, or a vaginal suppository. Without limitation, such compositions of TRPV-I receptor agonists and local anesthetic can be formulated into single dose applicators, such as disposable swab applicators.

In specific, non-limiting embodiments where the TRPV-I receptor agonist is capsaicin and the formulation is a liquid, gel or cream. In such embodiements, the capsaicin can be present at a concentration of between about 0.025 and 1 percent, between about 0.025 and 0.5 percent; between about 0.025 and 0.2 percent; between about 0.2 and 0.5 percent, or between about 0.5 and 1 percent (percentages are milligrams per 100 microliters of formulation). Where the TRPV-I receptor agonist is resiniferatoxin and the formulation is a liquid, gel or cream, the resiniferatoxin can be present at a concentration of between about 0.025 μg and 1 μg per 100 ml.

In specific, non-limiting embodiments where the local anesthetic is lidocaine and the formulation is a liquid, gel or cream, the lidocaine can be present at a concentration of between about 0.1 and 5 percent and preferably about 0.5 or 1 percent.

5.4 KITS

The present invention provides for kits useful for inhibiting pain arising from the cervix, promoting the onset of labor, or a combination of the two, comprising a dosage form of local anesthetic and a dosage form of a TRPV-I receptor agonist.

In non-limiting embodiments, the dosage form of local anesthetic comprises an effective amount of local anesthetic in injectable form or in the form of a liquid, gel or cream for application to the surface of the cervix. For example, but not by way of limitation, the local anesthetic can be contained in an ampule, tube, swab or other applicator.

In non-limiting embodiments, the dosage form of TRPV-I receptor agonist comprises an effective amount of TRPV-I receptor agonist in injectable form or in the form of a liquid, gel or cream for application to the surface of the cervix. For example, but not by way of limitation, the TRPV-I receptor agonist can be contained in an ampule, tube, swab, syringe-like applicator, cervical cap-like applicator, a suppository, or a pessary. In certain embodiments of the present invention the TRPV- 1 receptor agonist dosage forms are formatted for single-dose and in certain embodiments the dosage for is formatted for multi-dose release.

In certain specific, non-limiting, embodiments, the TRPV-I receptor agonist is capsaicin and the local anesthetic is lidocaine. In other specific, non- limiting, embodiments, the TRPV-I receptor agonist is resiniferatoxin and the local anesthetic is lidocaine. In additional non-limiting embodiments, the TRPV-I receptor agonist is selected from: capsaicin, resiniferatoxin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin; and the local anesthetic is selected from: lidocaine, procaine, benzocaine, bupivicaine, ropivicaine, levobupivicaine.

6. EXAMPLES

6.1 EXAMPLE l

The following in vitro assay can be used to monitor the response of TRPV-I receptors to candidate TRPV-I receptor agonists. The assay can also be used to predict the dosage of candidate TRPV-I receptor agonists effective to reduce the clinical symptoms of cervical pain, measurably promote the onset of labor, or combination of the two.

Mammalian cells are initially transfected with an expression vector carrying the coding sequence for the human TRPV-I receptor, thereby allowing for the expression of the human TRPV-I receptor. Such transfected cells are seeded and grown to 70-90% confluency in FALCON™ black-walled, clear-bottomed 96-well plates (#3904, BECTON-DICKINSON, Franklin Lakes, NJ). The culture media is emptied from the 96 well plates and FLUO-3 AM™ calcium sensitive dye (Molecular Probes, Eugene, OR) is added to each well (dye solution: 1 mg FLUO-3 AM™, 440 μL DMSO and 440 μl 20% pluronic acid in DMSO, diluted 1 :4, 50 μl diluted solution per well). Plates are covered with aluminum foil and incubated at 37°C for 1-2 hours in an environment containing 5% CO₂. After the incubation, the dye is emptied from the plates, and the cells are washed once with Krebs-Ringer HEPES (KRH) buffer (25 mM HEPES, 5 mM KCl, 0.96 mM NaH₂ PO₄, 1 MM MgSO₄, 2 rnM CaCl₂, 5 mM glucose, 1 mM probenecid, pH 7.4), and resuspended in KRH buffer.

TRPV-I receptor agonist-induced calcium mobilization can monitored using either FLUOROSKAN ASCENT™ (Labsystems, Franklin, MA) or FLIPR™ (fluorometric imaging plate reader system, Molecular Devices, Sunnyvale, CA) instruments. Similarly, varying concentrations of the antagonists ruthenium red or capsazepine can be added to cells concurrently with the candidate TRPV-I receptor agonist to perform competition studies. For TRPV-I receptor agonist-induced calcium responses, data obtained between 30 and 60 seconds after candidate TRPV-I receptor agonist application are used to generate the EC_5O values. KALEID AGRAPH™ software (Synergy Software, Reading, PA) can be utilized to fit the data to the equation:

to determine the EC₅₀ for the response. In this equation, y is the maximum fluorescence signal, x is the concentration of the agonist or antagonist, a is the E_max, b corresponds to the EC_5O or IC₅₀ value, and finally, c is the Hill coefficient.

6.2 EXAMPLE 2

A rat model for gynecologic pain has been developed (Anesthesiology 2008; 108:1081-6) and was used in the instant study. Two groups of timed pregnant rats (at gestational day 21) were studied. The treatment group received vaginal lidocaine (0.5% solution) followed by capsaicin (0.05%) cream (n = 6) while the control group received vaginal lidocaine (0.5%) only (n = 6). Animals were placed into the observation chamber individually for a continuous video taping for up to 72 hours. By the end of the experiment (day 23), the video taping was stopped and the behavior of the maternal rats and pups were examined and recorded. The labor and delivery behavior was analyzed offline by specific software (Noduls Observation Pro 5.0) and an analysis strategy was developed to focus on general activities (eating, drinking, grooming, and vertical exploration), labor pain behavior (squashing, lateral contraction, licking and elongation), and maternal attention toward the pups (licking the pups, pushing, nesting, eating placenta). The frequency and duration of each behavior was analyzed in the timeline (2 hours before the birth of the first pup, the entire delivery period, and 30 minutes after the birth of the last pup). Outcome data analysis included the labor onset time and duration, the total number of pups, and the viability of the pups.

As illustrated in Figure 1 , vaginal capsaicin significantly decreased the appearance of pain behaviors compared to lidocaine control group. The lateral contraction incidence was 32.6 vs. 70.3, and the duration was 74.7 vs. 191.5 for capsaicin and lidocaine respectively, (p<0.05). In contrast, general activity, including behaviors of eating, drinking, rearing, and grooming, as well as maternal attention (licking pups and eating placenta) were not different between the two groups, except that rats treated with capsaicin ate more (see Figures 2 and 3). Finally, as outlined in Figure 4, there was no statistically significant difference in the number of newborn live pups, 12.8±3.4 in capsaicin and 10.8±l .6 in lidocaine, or the labor duration 83.8±27.8 min vs. 74.3±25.6 min (capsaicin vs. lidocaine). However, all animals that received capsaicin treatment gave birth on Day 22, while the majority of lidocaine treated rats gave birth at day 23.

These studies showed that (1) there was no difference between the two groups in general activities and the maternal attention towards newborn pups; (2) lateral contraction (a manifestation of severe pain) decreased by 50 percent in the group treated with vaginal capsaicin compared to lidocaine alone; (3) capsaicin- treated animals all gave birth on day 22, while lidocaine-only treated animals gave birth on either day 22 or 23 (with a mean of 22.7) consistent with an inductive effect of capsaicin on labor; and (4) there were no differences in labor duration between the groups. 6.3 EXAMPLE 3

A mouse model for gynecologic pain has been developed and was used in the instant study. Three groups of timed pregnant mice (at gestational day 15) were studied. The treatment group received subcutaneous saline 0.5 microliters/hr followed by cervically-applied capsaicin 0.1 %, 0.1 ml (n=8) while a first control (negative) group received subcutaneous saline alone 0.5 microliters/hr (n=10) and a second control (positive) group received subcutaneous morphine alone 0.1mg/kg/hr (n=7). Animals were placed into an observation chamber for continuous video taping during labor (2 hours prior to delivery of first pub), delivery, and post-delivery (30 minutes after delivery of the final pup). At the end of the experiment, the video taping was stopped and the behavior of the maternal mice were examined and recorded. The labor and delivery behavior was analyzed offline and an analysis strategy was developed to focus on labor pain behavior (squashing, lateral contraction, elongation, and pushing). The incidence of each behavior was analyzed in the timeline (2 hours before the birth of the first pup, the entire delivery period, and 30 minutes after the birth of the last pup). As illustrated in Figure 5, treatment with cervical capsaicin significantly reduced elongation and pushing during labor (p<0.05).

6.4 EXAMPLE 4 The current protocol for labor induction after mid-trimester intrauterine fetal demise (IUFD) prior to 24 weeks gestational age includes intravaginal cytotec (misoprostol) 200 meg every 6 hours for up to 24 hours, occasionally followed by oxytocin infusion. When an IUFD occurs at 24 or greater weeks gestational age, labor is induced with cytotec 50 meg every 4 hours or oxytocin infusion. This protocol is associated with increased risk of cesarean section and elevated pain when compared to labor of spontaneous onset.

In order to facilitate cervical ripening and decrease the pain of labor induction, patients who present for cytotec induction of labor following the diagnosis of intrauterine fetal demise at 16 or greater weeks gestational age will be treated according to the following protocol. For all subjects, 20 ml of lidocaine gel (0.5% - 100 mg) first will be applied to the cervix, vagina and perineum. Patients will then have 1OmL of 0.5% capsaicin cream (10ml, 0.5% - 50mg) applied to the cervix at the time of the initial cytotec placement. Patients will be followed with hourly numerical analog scores for pain (NRS) and cervical examinations (station, dilation, effacement, position and consistency) at the time of all indicated cervical assessments.

* * *

The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and the accompanying figures. Such modifications are intended to fall within the scope of the appended claims.

Patents, patent applications, publications, product descriptions, and protocols are cited throughout this application, the disclosures of which are incorporated herein by reference in their entireties for all purpose.

Claims

WHAT IS CLAIMED IS:

I . A method of inhibiting pain arising from the cervix in a subject in need of such treatment comprising applying an effective analgesic amount of a Transient Receptor Potential- 1 receptor agonist to the cervix.

2. The method of claim 1, wherein, prior to application of the Transient

Receptor Potential- 1 receptor agonist, an effective amount of a local anesthetic is administered to the subject.

3. The method of claim 1, where the subject is in labor.

4. The method of claim 1, 2 or 3 where the Transient Receptor Potential- 1 receptor agonist is selected from the group consisting of capsaicin, resiniferatoxin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin.

5. The method of claim 2, wherein the local anesthetic is selected from the group consisting of lidocaine, benzocaine, procaine, benzocaine, bupivicaine, ropivicaine, and levobupivicaine.

6. A method of promoting the onset of labor in a subject in need of such treatment, comprising applying an effective labor-promoting amount of a Transient Receptor Potential- 1 receptor agonist to the cervix.

7. The method of claim 6, wherein, prior to application of the Transient Receptor Potential- 1 receptor agonist, an effective amount of a local anesthetic is administered to the subject.

8. The method of claim 6, where the subject is in labor.

9. The method of claim 6, 7 or 8 where the Transient Receptor Potential- 1 receptor agonist is selected from the group consisting of capsaicin and resiniferatoxin.

10. A kit for inhibiting pain arising from the cervix, promoting the onset of labor, or a combination of the two, comprising a dosage form of local anesthetic and a dosage form of a Transient Receptor Potential- 1 receptor agonist.

I 1. The kit of claim 10, wherein the Transient Receptor Potential- 1 receptor agonist is selected from the group consisting of capsaicin, resiniferatoxin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, and homocapsaicin. 12. The kit of claim 10, wherein the local anesthetic is selected from the group consisting of lidocaine, benzocaine, procaine, benzocaine, bupivicaine, ropivicaine, and levobupivicaine.