Oxytocin is a small six-amino acid peptide that functions as a hormone and signaling molecule. Oxytocin has been called the “love hormone” or “trust hormone” because of its association with relationships, whether romantic or social. Blood oxytocin levels increase during sexual arousal and orgasm and during childbirth. Oxytocin release helps partners connect, whether romantic partners or parents and children.

Oxytocin levels are increased during physical contact, sexual arousal, and orgasm in both men and women. Oxytocin increases the intensity of orgasm and feelings of commitment after sex. Oxytocin may also be involved in feelings of empathy and a sense of well-being.

Tadalafil (generic for Cialis) is a lower-cost option for Cialis that contains the same active ingredients. It works exactly the same way as the brand-name medication in your body. Tadalafil relaxes smooth muscle, allowing blood vessels to dilate, improving erectile function, and increasing arousal for men and women. Increased blood flow into the penis and clitoris increases arousal and orgasm frequency.

Hypoactive sexual desire disorder is not uncommon. It affects 8.9% of women between the ages of 18 and 44, 12.3% of women between the ages of 45 to 64, and 7.4% of women over the age of 65. Low sexual desire tends to increase with age, but distress associated with the disorder decreases, which means that the condition’s prevalence is consistent across ages. Low sexual desire is linked with lower health-related quality of life, lower overall happiness, and a higher risk of anxiety and depression. 

Female sexual dysfunction is a constellation of symptoms, including decreased desire, interest, arousal, orgasm, or pain with sex. Two large clinical trials demonstrated PT-141 safety and efficacy. Women using bremelanotide (PT-141) had a statistically significant improved sexual desire. Unlike previous treatment options, bremelanotide does not interact with alcohol.

PT-141 appears to act on melanocortin receptors 3 and 4 in the brain. It enhances sexual arousal and penile erections by releasing dopamine, a neurotransmitter in the brain.

In a double-blind placebo-controlled study, approximately 80% of men developed an erection satisfactory for intercourse after using PT-141 whether the cause of ED was physical or psychological, and 68% of men reported an increase in sexual desire.

Clinical trials are underway to further investigate PT-141; early results show that PT-141 is effective for men with diabetes and ED and for men who do not respond well to oral ED medications.

Oxytocin is produced in the hypothalamus in the brain. It has an effect on brain regions that regulate emotions (limbic system and amygdala). Oxytocin also acts on brain circuits that promote social bonding and affiliation with others.

Oxytocin is released from the pituitary gland in response to stress and acts as an anxiolytic. It decreases anxiety and the body’s response to stress.

Nitric oxide is a small molecule found throughout the body. It is released from nerve endings near the blood vessels in the corpus cavernosum of the penis after sexual stimulation. Nitric oxide triggers a chemical cascade that dilates blood vessels and increases blood flow into the penis, resulting in an erection. cGMP (another chemical in the cascade) levels must remain high to maintain the erection. Phosphodiesterase inactivates cGMP. When cGMP is deactivated, the smooth muscles in the walls of small blood vessels contract, reducing blood flow and ending the erection.

Oral ED medications, such as tadalafil, are phosphodiesterase inhibitors. By inhibiting phosphodiesterase, nitric oxide continues to trigger the cascade, and blood flow into the penis is maintained, meaning a firm erection that persists. Understanding this cascade led to the development and subsequent FDA approval of tadalafil in 2003.

PT-141 (bremelanotide) is a nonselective agonist of the melanocortin receptors type 3 and 4. It binds to these receptors and induces a similar effect to when natural peptides bind to these receptors. It is the active metabolite of Melanotan II.

In the brain, PT-141 influences sexual behavior by stimulating dopamine release from the medial preoptic area in the brain, an area of the brain associated with sexual behavior.