Studies suggest that kappa agonists (KA) and peripherally restricted kappa agonists (PRKAs) may affect thermoregulation. This pilot study has the aim to establish proof of concept regarding efficacy of an oral kappa agonist (KA) for the treatment of menopausal hot flashes.

To establish proof of concept regarding efficacy of an oral kappa agonist (KA), Pentazocine/ Naloxone 50/0.5 mg, for the treatment of menopausal hot flashes.

To gather data in support of a future proposal to study the safety and efficacy of a PRKA, a type of KA, for amelioration of menopausal hot flashes.

Inclusion Criteria:

1. Healthy women 45-60 years of age; 12 months amenorrhea
2. Documentation of > 8 moderate to severe, daily hot flashes during one week of baseline monitoring using daily diaries
3. Availability of a family member or friend to drive participant home following clinic visits

Exclusion Criteria:

1. Use of hormonal prescription medication or supplements for vasomotor symptoms (VMS)
2. Use of narcotics
3. Use of SSRI (selective serotonin reuptake inhibitor)/SNRI (serotonin-norepinephrine reuptake inhibitors), gabapentin, MAOI (monoamine oxidase inhibitor), anti-epileptics, sedatives
4. History of polycystic ovarian syndrome or hirsutism
5. Current history of depression
6. Any chronic or acute medical illnesses including renal, hepatic, pulmonary diseases, or seizures
7. Substance abuse
8. Severe corn allergy
9. Known allergic reaction to pentazocine or naloxone
10. Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient or the quality of the data
11. Hysterectomy
12. Use of anticholinergic medications
13. Lactating or pregnant